Stunning Good Looks
Cinematographer Art Adams has worked in the film industry for 25 years. He shoots spots as well as corporate marketing, visual effects, web and interactive/mobile projects. He also consults for a variety of motion picture equipment vendors in the areas of usability and interface design, equipment training, and scientific comparative testing of products.
Art likes to write articles that explore the hidden side of the tools and techniques many take for granted. He's been published in HD Video Pro, American Cinematographer, Australian Cinematogra...
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By Art Adams | June 17, 2008
Equipment doesn't make the image; people do. I proved this on a music video recently where we had more people than equipment.
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Will a printer that does only one thing save my sanity?
By Art Adams | May 22, 2008
For quite a while I've used an Epson R320 printer to label my showreel DVDs, but the end of that era has come. I now own a Dymo Discpainter.
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Written by a complete post idiot, these RED tips may make your life slightly easier
By Art Adams | May 12, 2008
This is by no means a definitive manual on how to post RED footage. Rather, this is how I managed to work with R3D footage while creating a spec spot using the RED. Your mileage may vary. I expect to be flamed repeatedly regarding my handling of this shoot's post process, but from the ashes I hope to extract some knowledge as to how to do it all better next time.We did not record any sound on the shoot, so that part of the post process is not addressed. Yay!For behind-the-scenes action, see Adam Wilt's post on the shoot itself.
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By Art Adams | May 10, 2008
Wii Spec Spot, 1k version
Here it is, finally finished. Phew! Now I know why I'm not in post production. I'll write a blog entry on my stupid post mistakes later; for now, enjoy!Details that may be interesting to the reader:Shot 4k 2:1Edited in 2k on Final Cut ProRedcode 36Color correction applied to RedLog-exported footage from RedCine, using ColoristaZeiss Ultra Primes, mostly at T2Schneider True-Cut IR filter used on every shot except for the TV (16mm Ultra Prime saw some off-angle cyan vignetting)All shots daylight- or 4500k-balanced (the TV had to be shot under a daylight balance, for proper color, so I shot everything else daylight for consistency) except for the ceiling shot, which was done at 3200k to keep the light bulbs from going too warmThere's one shot that was done on a Lensbaby. See if you can pick it out.More soon.
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By Art Adams | April 29, 2008
I'm a bit late in writing this, but there are some NAB wonders that I want to blog about. I had all of one day to see the show, but I did see some pretty cool things. How can you not at NAB?I spent Sunday through Tuesday working in the Element Labs (elementlabs.com) booth. I've been consulting on their lights for a little over a year now, helping them develop a broad-spectrum LED light for the motion picture industry. Most LED lights are made of single LEDs that appear to be white (although many skew slightly green) but if you look at the spectrum you'll see a very sharp spike: they don't emit much of the color spectrum. As you only get accurate color reproduction if you hit an object with light containing its color, you won't get very accurate color from a narrow band light source.Element Labs uses six LED (three each in two packages, alternating across the fixture) to create broad spectrum light. The mixture of LED colors provides for more accurate color response, and it also allows the fixture to change color temperature. The current spec allows for 2200k to 6500k, and it's a very pretty quality of light.Last year I worked with Element Labs to create a process shot in the booth. Their original product line consisted of large video wall displays, and several DP's have used those video wall products to create traveling light for process shots. The idea is that you can hang the panels above a car on a green screen stage, and then play your background plate back across the video wall to create interactive lighting between the plate, which will be added in post, and the actors on the set. Last year we did exactly that, by creating a video wall that reflected in a Shelby Cobra that was parked in the booth. The model in the car was lit with earlier versions of the LED light that we've been developing, and the display was a huge hit. This year we scaled down to a motorcycle without a model, so the display was a bit less dramatic but it was still fairly pretty.The great thing about working a booth for several days is that people come find you. I got visits from a lot of people I know through CML (cinematography.net) as well as a Panavision rep and the president of my IA local.My free day was reasonably well planned out. My first stop was over at Schneider Optics, to visit Bob Zupka and see their new IR cut filter for the RED. We had a long talk about the complexities of filtering, which once again proved to me that I frequently have no idea how much I don't know, and then he gave me a prototype of the IR filter for testing. Bob has a theory that IR reduction in the RED may improve the overall MTF of the system, increasing resolution noticeably. Adam Wilt and I are going to do that test on Thursday.I then visited a local producer, Luke Seerveld (seerveldmedia.com) who was working a booth for a company called Prompter People (http://www.prompterpeople.com/). They specialize in making cheap but useable gear for the production industry. Is a $500 tripod a good buy? In this case, yes--it's not an O'Connor or a Sachtler but it was darned good for a cheap tripod. They make LED lighting units that are decent--not great, they're a bit green and spiky, but decent--for very little money. Add 1/4 minus green and your good to go for most purposes. They're probably not great on color rendition but they'll work for a number of less critical applications.I stopped off at a couple of other locations before making my way to Tiffen to see their IR filter. I spoke with one person who was in sales and didn't know much about the IR filter, but she pointed out the gentleman I should talk to and I waited patiently while he helped someone who was obviously new to the business understand the basics of filters. He recognized my name from an article draft I'd recently sent over (I wrote an article on HD filtration for a future issue of HD Video Pro that I sent over to Tiffen for vetting) but continued to spend a lot of time demonstrating consumer camera support tools to the person ahead of me. After waiting 20-30 minutes I gave up and left.I met up with fellow DP and rental house owner John Chater (chatercamera.com) at the Tiffen booth and we walked over to BandPro (http://www.bandprodigital.com) to see the Sony F35. I really like the external design of the camera, and I was amazed at the latitude I saw in the image. Looking across the aisle into the Sony booth I was able to see deeper into shadows than I could by eye.I've learned that a good way to analyze a camera's limitations is to look at highlights, as well as bokeh, to see what happens when the sensor and optics are pushed to their limits. In this case I noticed two things:(1) Highlights flare vertically, much like an IT chip would, but much softer. It's not a nasty streak, but a soft and visible flare--almost like anamorphic flare, only not predominantly blue and not horizontal. The design of the chip is rather interesting: instead of a Bayer pattern or three chips around a prism, the pixels are laid out in stripes: two stripes of red, of green, and of blue, repeating left-to-right across the sensor. In post the pixel strips are shifted over on top of each other for full color. When I first heard of this scheme I was worried that horizontal resolution would be compromised, but it's not--apparently the chip is over-populated with pixels by something like 40% more than it needs.
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By Art Adams | April 12, 2008
I just received my April copy of HD Video Pro magazine, and there on page 54 is my write-up of Element Labs LED lighting technology for the film industry. When I'm not writing here, or shooting somewhere, I'm writing for HD Video Pro. It's turning out to be a great magazine, and I'm quite pleased to be a regular contributor. I'm losing track of what's running when these days, but future issues will see articles I've written on the Lensbaby 3GPL (Lensbabies.com), the Sony EX-1, and a truly massive article on diffusion filters for use in HD (thanks to Ira Tiffen, formerly of Tiffen, Inc., and Bob Zupka of Schneider Optics.)I'm in the Element Labs booth from Sunday through Tuesday (elementlabs.com/nab.html) giving product demos and such, but Wednesday I'll be off on my own. I'm definitely planning on visiting Iridas, the subject of one of my earlier articles, to see their new color grading system for raw Bayer-pattern workflows, and Schneider Optics, to see their new-for-HD UV and IR cutting filter. Beyond that... well, I'll just try to see as many cool things as I can before I have to jump on a plane Wednesday night.I'll be at the Digital Cinema Society Party Monday night, and the Cinematography Mailing List Party Tuesday night, so look for an incredibly handsome man with impeccable hair and the fashion sense of a Vanderbilt. I'll be the squat graying guy just behind him.Meanwhile, stay tuned to PVC for lots of NAB action. I don't know that I'll be able to post much while I'm working the booth, but I hope to have a few things to report from my jaunt on Wednesday.
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By Art Adams | April 12, 2008
For a bit over a year now I've been consulting on a new broad-spectrum LED light for the motion picture industry. The idea is that this light, with six different LEDs, can change color temperate with a simple turn of a knob and dim without changing color temperature. The spectrum on this light is much better than current LED lighting products that use only one LED.In order to see an object's color accurately you have to light it with light containing that same color. Single LED lights typically use phosphor-based LEDs, which have a little spectral spread to them but not much. They only produce a very narrow range of colored light, so they are good an illuminating but not good at all for color reproduction. The Element Labs Kelvin Tile (the product I've been working on) has one phosphor and five dye LEDs mixed together, creating a much broader color palette.I'll be working the Element Labs booth at NAB, so come find me if you have a chance. Sunday I'll be setting up, and Monday/Tuesday I'll be giving product demos and showing off the new Kelvin Tile "paintbox" control system. Wednesday I'll be wandering NAB in search of juicy new products.Here's where I'll be:http://elementlabs.com/nab.htmlCome on by and say hi!
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By Art Adams | April 11, 2008
RED ONE Build 15 EI Test
The idea behind this test was to underexpose a neutral reference and see at what point the RED's noise becomes too much of an issue. Using Colorista in Final Cut Pro, I put 18% gray at 50 units on the waveform monitor for each exposure, effectively "printing up" each exposure to see how much "grain" (noise) showed up. Some of this is exaggerated by compression artifacts, but I think you can get a good feel for what's going on.I'm not sure how this would look on a film out, but to me there isn't a ton of difference between noise levels at 320 and 640, although I think I'm more comfortable rating the camera at 320. I start seeing reduced contrast at EI 1280, which I really wouldn't want to try on a paid job.Compressed via FCP Compressor, H.264.
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By Art Adams | April 10, 2008
A while back, while browsing Reduser.net, I saw that someone had done an IR test and discovered that RED has a weakness when it comes to IR filtering. I did my own tests and here are the results:First shot: RED Build 15, Redcode 36, processed in Red Alert (contrast +.7, brightness +3.0, Kelvin 5130k, all else at presets)Filtration: Schneider Optics ND .30:Second shot: same as above, but filtration increased to ND .9 plus ND 1.2--a total of seven stops of ND:(left to right: PVC's own HD guru Adam Wilt, and DIT/video engineer Jay Farrington of Chater Camera, San Francisco)The theory is that when ND filters cut visible light to the point where the ratio between visible light and IR light is very low, the IR shows up much more dramatically than it would otherwise. Normally IR effects are overwhelmed by visible light.I was a bit confused by this image. The darkest object in the shot--the filter pouch--is made of synthetic fibers and is bright magenta, making me think that the magenta cast in the second picture is an IR issue. But the picture has a magenta cast overall while not everything in the image is radiating the same amount of IR.I've been interviewing Ira Tiffen, formerly of Tiffen, Inc. and a world-renowned expert in the creation and manufacturing of filters, for a magazine article on HD filtration that I'm writing for HD Video Pro magazine. I sent him the pictures above and asked for his expert opinion. This is what he had to say:-------------------------------------------------------------I am making certain assumptions which are commonly encountered. The camera has a built-in IR reduction filter. It is essentially clear to the eye, transmitting most of the light between 400nm and 680nm, which is the visible spectrum, minus the part between 680nm and 700nm. Once it reaches 680nm, the filter begins to reduce light. From 680nm to 700nm, there is a little red lost (which is why this type of filter has a very pale green cast to it), but further above 700nm there is a quickly diminishing transmission of light, all in the IR region. But there IS some transmission from, say 700nm to 730nm, causing a small 'leak' in IR. At some higher point, say 900nm, it may start to transmit more light again, but the camera isn't sensitive to it.We have to remember that the chip is generally going to have more sensitivity to light in the IR than film does. So a small 'leak' in light just above 700nm can be picked up as red by the camera, but with the ND 0.3 filter, at only one stop of light absorption, there is still an abundance of visible light to overpower any leak of near IR getting through the IR filter.If the camera did not have the built-in IR filter, there would be a much greater amount of near IR light, enough to show a reddish cast on objects (usually black or dark gray) that tend to reflect more IR (remember that dark objects get hotter in the sun than lighter objects- this heat is the excess of reflected IR) and proportionately less visible light. This is why the effect appears even without ND filters when there is no IR filter in the camera.Here's what happened in the scene with the ND 2.1 (7 stops, 0.8% transmission) filter combination. All organic-dyed ND filters I have seen, including Schneider's, begin transmitting an increasing amount of light from about 680nm and up. When there is no ND filter, or a ND filter not much denser than, say, ND 0.9, the amount of additional light in the far red (680nm-700nm) is proportionately too small to be seen among the much greater amount of visible light.However, with the ND 2.1, the amount of visible light is brought down to less than 1% of the original. The small amount of near red is not affected as much because the filter dyes do not function well in that region. This is the key. So the small amount of far red that gets through is now much greater in proportion to the overall, including the visible, and so a reddish cast is created. Now Schneider ND's tend to be cooler (read a bit bluer) which is an increase of light transmission just above 400nm, which acts to minimize the reddish cast that would otherwise show up throughoutthe image. In the ND 2.1 filtered image, there is an overall addition of blue in the areas that do not reflect much IR, like the bricks, the silver car, and most other areas. However, in the black filter case, and the gray jacket and sweatshirt, there is a greater amount of light in the far red and IR being reflected, so the reddish cast on those objects becomes enough to overpower the addition of blue that neutralized the red everywhere else.To recap, without an IR filter the camera would suffer from an excess of red especially in objects that reflect a large amount of IR light. Even without a ND filter.With just the IR filter, there will generally be a good balance between the visible and the near IR, so that color rendition is normal. The small amount of far red and near IR is overpowered by the large amount of visible light.With an organically dyed ND filter that is not much denser than a ND 0.9, there is still enough visible light to counterbalance the excess amounts of far red and near IR.With a much denser ND filter, the overall amount of visible light is reduced enough in proportion to the amount of far red and near IR getting through that there can be a reddish cast through the whole image. With a cooler ND, with some addition of blue, the color can appear normal for objects that do not reflect excessive IR. However, for those objects that do, the amount of IR is enough to still cause a reddish cast because it is then proportionately greater in amount than either the visible light or the increase in blue that worked to counteract it for parts of the scene that do not reflect much IR.-Ira Tiffen-------------------------------------------------------------I'm extremely thankful to be able to publish this incredibly in-depth explanation of what was going on in the images above. It just shows that no matter how long one works in the industry one can never say, "Now I know it all." There's always more. I just love that."Now I've seen it all" is a completely different matter.Ira Tiffen is currently working on a book about filtration. He has a publisher but no firm release date. Let's hope it comes out in the next year or two. I, for one, am dying to read it.I'm told by Bob Zupka, of Schneider Optics, that they have a filter, called the 486, that was designed for early digital still cameras that didn't have any effective IR filtering and were extremely sensitive to IR. This filter has a pale pink cast, much like a UV/haze filter, and cuts the spectrum like a knife above 680nm. The cast is easily eliminated by white balancing or basic color correction. Expect to see some HD-size 486 samples at the Schneider Optics booth at NAB. I'm hoping to test one with Adam Wilt shortly thereafter. Stay tuned!
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By Art Adams | April 09, 2008
RED ONE Build 15 Flesh Tone Latitude Tests (tungsten)
In my quest to figure out just how much overexposure latitude I can get out of a RED under tungsten light, I decided to do a test with a flesh tone reference and a RED with build 15 loaded. It turned out to be almost a completely different camera.Previously I was only able to see two stops of overexposure latitude on a Kodak 18% gray card under tungsten light. That was using build 14. This build seems to yield 3 stops of latitude before clipping flesh tone, which already has more red in it than a gray card. Also, instead of the red channel clipping and causing highlights to turn cyan until the other channels clipped, I see no indication of that at all now. The clipped highlight is very clean and holds color a lot longer than I expected.On top of that, the DRX highlight recovery tool in Red Alert now seems to cause more problems than it solves. When I used DRX on these clips they turned green, the exact opposite of what they're supposed to do--which is to take red channel clips that have turned cyan and use the other two unclipped color channels to rebuild detail in the clipped channel, while using the white balance meta data to blend all of that into a neutral highlight.I don't know what they did to keep the highlights so clean, but I'd be willing to take this camera into a real world situation now. The only thing that bugs me is that the red channel, which used to be the cleanest color channel by far, now seems very noisy. Maybe that's a side effect of whatever was done to clean up the highlights.
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By Art Adams | March 31, 2008
Hi all- I apologize, but I've been swamped with work of one sort or another, and when I tried to sit down and start sorting through the latest RED test footage today I couldn't finish it. I took a nap instead. I must be getting old!I've got three days of shooting this week, and hopefully I'll be able to pull the footage together and post it by the end of the week. If I were to speculate wildly about the results of the latest round of RED testing, I'd say the following:The RED definitely has an infrared problem, as previously seen on Reduser.net. We put 7 stops of ND on the lens and saw very severe magenta color shifts on black cloth due to IR contamination. Apparently if the ratio of visible light to infrared becomes too low the RED sees the IR quite easily. I understand that at least one filter manufacturer is currently working on the problem.We tested build 15, which seems very different to build 14. On build 14 we saw severe problems with red clipping under tungsten light that turned highlights cyan and required highlight recovery work in REDCine and REDAlert to bring back highlight detail. On build 15 it seems that a lot has been done internally to eliminate this problem: the camera seems to hold highlights vastly better under tungsten light, and highlight recovery actually seems to make things slightly worse. There's obviously something different going on in the camera with this build.I think there's some additional processing going on in there, particularly with the red channel. It's interesting to note that build 14 saw the red channel being the quietest, with green second and blue the noisiest. Now green is the quietest (although still fairly noisy), with red being noisier and blue about the same. Something seems to have happened to the red gain. Also, preliminary histogram examination shows red rolling off around clip instead of hard clipping, which is interesting.It's a completely different camera now. I hope to post some build 14 and 15 comparisons and more data later in the week. Stay tuned.Thanks, as always, to camera guru Adam Wilt for his help and photos. Also thanks to DP Alan Hereford, DP-in-training Ted Allen, and video engineer/co-owner Jay Farrington of Chater Camera (chatercamera.com).I've also got a new showreel coming together, so I suspect I'll have a lot to say about that process at some point.
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By Art Adams | March 25, 2008
I've now had independent confirmation from a couple of people who watched my RED build 14 exposure tests and have had great luck treating their RED as a daylight film stock. Apparently clipped highlights are significantly less of a problem and noise in the shadows drops way down. It's a much smoother look.If you haven't had a chance to test your RED before shooting to see how well you can recover clipped highlights, it might be a good idea to go HMI or daylight if at all possible. I'm hoping to test recovering clipped highlights and blue filtration by the end of the week, so stay tuned.Meanwhile, look back a couple of posts in this blog if you need to learn how to recover clipped highlights in Red Alert, and remember that the same control in Red Cine, called "highlight," does work--but you need to "jiggle" or double-click another control before the new value takes effect. That is slated to be corrected in the next build.
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If I'm not tweaking color I can't screw up as badly
By Art Adams | March 22, 2008
Like a lot of people with Final Cut Pro or After Effects, I'm trying to become a crack colorist in the privacy of my own home. It's unlikely to happen anytime soon as I just don't have the training or the time to take on a second full time career. But--that doesn't mean I can't do a little bit of damage to my own footage when I want to experiment. Or when I'm too cheap to hire someone else to do it.There's been much discussion on the Cinematography Mailing List about rookie colorists and why it's a bad idea to try to do these things yourself on a wing and a prayer, but I figure the more I work on my footage the more I'll learn about giving others the kinds of images that they can improve on my behalf in the future. I've done the same thing editing my own footage, and I've learned a hell of a lot not just about shooting for editors but also how to fix the kinds of mistakes that just happen on sets when we're working against time and budget.I don't have a color critical monitor, and as much as I've tried to calibrate my Apple Cinema Displays to look something like what I might find on a badly tuned TV set in a third world nation, I can't quite get close enough to feel comfortable. If I'm working with a piece of footage that's been horribly screwed up in post by someone else (I once shot some jeans spots where the client decided the whole thing should have a blue cast because, well, jeans are blue, and isn't that a good enough reason?) I can bring it back to normal, but creating rich sophisticated looks on a questionably-calibrated computer LCD is a little frustrating.The one thing I can't screw up too much is luminance, and the single most beneficial thing I can do to my 8-bit HD footage is to pop in a Power Window and reduce bright unclipped areas that I couldn't control during shooting. This is super simple in a telecine suite on someone else's dime, but where I live and work HD footage is made on the set and never touched again. That's fine, we do good work anyway, but it's nice to have the opportunity to take footage to the next level. And since I'm only affecting brightness, which I can judge reasonably well on a computer screen and via waveform, I've got a lot more confidence controlling luminance alone than if I decided to cool the shadows and warm the highlights with any degree of finesse.I've got Digital Film Tools 55mm, Apple's Color, and Magic Bullet's Colorista, and all can do vignettes (frequently called Power Windows because that's they're designated on a high-end Da Vinci color corrector). So far, for ease of use, Colorista wins hands down. It's incredibly simple to quickly create a Power Window.In this shot, from a Microsoft Zune spot shot on a Varicam (with a Pro35, Zeiss Super Speeds, and while riding a Steadicam operated by Tim Bellen) I've always been bugged by not being able to cut the laptop brightness down a bit. We were shooting in a cafe in Santa Cruz, and our morning ritual saw the crew standing around on top of a train trestle for two hours waiting to shoot the first shot while the day's creative was re-written. As a result we ended up in this cafe shooting day/interiors after the sun went down. It ended up being a 17 hour day, and at some point our mission became doing the best we could before the poor Steadicam operator went numb from the waist down. (Every single shot for two days was a Steadicam shot. Every. Single. Shot.)In this case the ambient light was established by erecting a couple of 12x12 gryffs in front of the windows on one side of the restaurant and bouncing PARs off them to recreate the daylight look. After that it became fairly simple to wheel around some Kino Flo Image 80's to quickly shape whatever area we were shooting in. In this case we propped an Image 80, with 216 on it, on a table in front of our actress and started rolling. She looked great; the laptop looked hot but it wasn't horrible, and my hope was that the viewer would be more interested in her than the laptop.These stills are a little deceptive because the laptop looks better here than it does on DVCProHD, but take my word for it--the brightness competes a bit with the actress's face. Not a lot, but enough that I wanted to try to focus a little more attention on her.Colorista's controls are very simple: you pick a vignette shape (ellipse or rectangle), place a top point and bottom point, set a width using a slider, feather, and done. You can see the vignette as a shape alone or as a red mask on top of your footage. Tracking is done in the usual way in Final Cut Pro, by plotting key frames on a timeline. (I have After Effects but haven't learned it yet. Who has time???)I'm going to go through all of this Zune footage and look for opportunities to focus attention by darkening corners and edges. I used to have this done to film all the time but I've yet to get any of my HD footage in front of a professional colorist. I've got great DIT's who paint my cameras phenomenally well, but being able to dodge-and-burn HD images after the fact is a wonderful, wonderful thing. It will only ever end up being seen on my reel... but that's where it counts.(I'm in the process of reading "The Art and Technique of Digital Color Correction," by Steve Hullfish. It's a great primer on the art and craft of coloring. Highly recommended.)
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By Art Adams | March 18, 2008
New from RED: how to correct those bothersome clipped highlights I've been freaking out about for the last few days. Currently the procedure only seems to work in RED Alert using the DRX slider. This process is intended to work within REDCine using the "highlight" function but at the moment neither Adam Wilt nor I can get it to work (Intel Mac, build 90). That's being looked into right now.DRX works to reconstruct highlights in a clipped channel using information from the other channels. It then blends the reconstructed pixels and the original pixels together to create the most natural-looking effect.When shooting, try not to clip more than one color channel at a time if you can avoid it. One channel isn't hard to reconstruct. Two make it more difficult. It's pointed out to me that two channels will rarely clip at the same time, so for part of the image only one channel will be repaired, and in other parts of the image two will be repaired (although the quality may suffer when two channels are clipped).In RED Alert, open the R3D of the shot in question and look at the histogram. If you've got at least one channel that isn't clipping, you're in reasonable shape. If you have two channels that aren't clipping, even better.Using the exposure slider, back the exposure down until the curves are just touching the right side of the histogram. Then dial in the DRX slider until things look right. Make sure the matrix is turned ON with your desired white balance in place before using DRX, otherwise the algorithm won't know what white balance you want and won't know how to reconstruct the channel(s).That's it. It's that easy. The hard part will be keeping an eye on the camera histogram when shooting to protect the quality of the highlights. It's a strange new world, this land of RAW, and waveform and vectorscopes aren't the only tools with which we need be familiar. The histogram is our new best friend, as that will be what tells us the quality of the data we are capturing.A huge "thank you" to Graeme Nattress of RED for his help in solving this issue. I hope we'll be able to bring you more info on this subject, and others, soon.
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Wherein I investigate whether the RED ONE's 5000k chip loses effective latitude in tungsten-lit environments
By Art Adams | March 17, 2008
RED ONE Build 14 Latitude Tests
My goal was to see if RED's 5000k chip is limited in exposure latitude under tungsten lighting conditions due to a tendency for the red channel to clip early. This seems to be the case, but I'm told there's a post fix for this problem that I hope to learn about in the near future.Here's what I did:-Shot a Kodak 18% gray card, with some texture to it, at different exposures to see where the camera clipped and to see where significant underexposure noise occurred.-Shot two tests, one under tungsten light and one under tungsten + full CTB, to see how the camera did under both kinds of light.-Originally set exposure by setting gray at 50 units using the camera's Rec 709 output, which turned out to be a stop slower than REDLog would have me believe. Zone 4 on Rec 709 turned out to be Zone 5 in REDLog. (The ASA appears to be a true 320.)-Took the darkest three tones for each lighting situation and boosted them to 18% gray value to better see noise; also isolated each color channel to see where the noise was coming from.-Included histograms for each clip from Red Alert.-Captured in RedCode28, 4K 2:1, 23.98 fps and 1/48 shutter.I wasn't able to check underexposure latitude as far down as I wanted because of the ambient light in the test location.The process was: open .R3D in Red Alert and export clip; then reset white balance to 5600k and capture the histogram to see what the daylight-balanced chip was doing in each situation. The clip was scaled and output as a ProRes HQ Quicktime, 1280x720, and assembled on a ProRes HQ timeline in Final Cut Pro 2. It was then output via Compressor using H.264 VBR encoding at 1k/sec. bit rate, where I tried to keep the file size down without letting the noise get lost or exaggerated by the compression process.Enjoy!
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I never knew how much processing cameras did for me, until I used a camera that didn't do any.
By Art Adams | March 17, 2008
My quest for digital truth took me to a little known corner of the world, a private spot where there are three mountains known as The Gains. The middle one, Green Gain, is considered the most stable, and that was where I sought the Guru of all Digital Media.After a long hike through windy prairies and along steep cliffs I found myself at his abode. At the annointed hour I let myself in and took a seat on the floor opposite the guru's prayer matte. And then I waited.An hour later, after discovering that Zen Monthly was simply a magazine designed to help you fill the moments of your life (2,505,600 ideas just for February alone), and realizing that the centerfold model of New Solipsist was actually the editor, I was startled by a voice."Sorry I'm late. Take my advice, never buy a British car."I half jumped out of my skin. "Where did you come from?"The Guru pointed to his green robes. "They key very nicely, even in reality. Sorry to sneak up on you like that." He took his seat across from me. "Tell me, son, what brings you to my retreat."I steeled myself, thinking of all the trouble and turmoil that brought me to this point. "It's very simple," I said. "I've been trying to wrap my mind around this whole 'RED' thing and it's really perplexing. For a long time we've all been looking forward to an affordable, raw 4k camera for the masses, and now that we have it... I don't think we know what to do with it. For myself, I'm learning that there's an incredible amount that goes into making a digital camera work--and if I'm to make the RED work for me I have to learn how to do in post what other cameras have been doing for me automatically all along."The Great Teacher looked sedate, eyes closed, a faint smile on his lips. After a few moments he started. "Ah, sorry about that. Miles away. I do love the Bahamas."He leaned closer to me, as if trying to determine whether I could handle the Great Truth he was about to unleash upon me. "Tell me more about these troubles you so desperately wished for.""Well, I thought I wanted a camera without any processing built-in," I whined. "But now I'm learning about all the things that cameras do for me every day that I took for granted. For example, color clipping. I've learned that the RED creates these interesting cyan highlights if you shoot under tungsten light, with the RED's daylight-balanced chip, if you clip the red channel--something that's easier to do under tungsten light because of the large red component of the spectrum. Apparently it's not terribly hard to fix and I'm talking with RED about how to accomplish that, after which I hope to publish the solution as a tip on my blog (see 'Self-Promotion 101,' New Solipsist, February 2008). But I never knew that this was a common problem solved by the knee circuits in all the other cameras that I use. I know I wished for a raw camera, but now I'm discovering that someone has to take care of all these problems later, and supposedly they can do it better than it can be done in camera--but I'm not sure who that's going to be. No one knows who will be converting the footage into dailies: is that the rental house that furnished the camera, a post house, an editor who fancies himself a colorist? Will someone do a final color correction pass or will dailies be it? There are so many questions.""Ah, grasshopper." The Guru smiled, seeing a grasshopper nearby. "Now you know why you must be careful what you wish for. Yes, having a camera that dumps a pile of steaming raw data onto your plate, for you to do with what you will, seems attractive at first. THEN you find out how much has been done for you all along without your ever knowing it was happening, and suddenly there's a new learning curve: it's not about delivering a pretty picture anymore, it's delivering footage and making sure someone else turns it into the pretty picture you intended it to be."It's very similar to the problems my old friend, the Film Guru, used to hear all the time. His followers eventually figured it all out, and so will you. I see him less and less these days. I think he's getting ready to retire. I guess all his silver reclamation schemes paid off."The Guru of All Digital Media stood, adjusted his robes, and smiled. "Let me know how things go with RED. I like them, after a fashion. It'll be interesting to see what evolves."Now, if you'll excuse me, I'm late for a meeting with Sony. I'm trying to talk them out of another prism camera and I'm already overdue. You know, for a guy who's always supposed to 'be here now', I'm always late!"He slowly started to fade away, his green robe disappearing against the background of reality. "Be careful what you wish for, young man," he said. "Take my advice and skip the Monkey's Paw concession on your way out."And he was gone.
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RED doesn't like fluorescents, and after this clip you won't either.
By Art Adams | March 16, 2008
Rolling_Green_Bars500.mov
I was shooting some exposure tests with a RED and I turned my tungsten reference light off to look at something on the camera. I noticed green roll bars crawling up the monitor, and quickly figured out that it was the rolling shutter interacting with the overhead cool white Ace Hardware fluorescents in the shop. The problem was completely eliminated by going to 1/40th/sec. on the camera shutter at 23.98 fps.This was build 14. I understand build 15 will introduce shutter angle control in degrees, so it's probably good to know that the equivalent to 1/40th is 217 degrees.1/48th at 24 fps is right on the edge of the 60hz flicker-free window, so I habitually shoot with other cameras at 1/40th or 217 degrees just to avoid flicker issues with house power or odd discharge lights in the background. It looks to me like this practice might be mandatory with this camera. Any additional motion blur is minimal.Notice how green the image is. Most other cameras (three chip CCD's) don't see the green spike in the average uncorrected hardware store fluorescent fixture. This camera sees it almost as strongly as film would. Very interesting.
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Rolling shutters and noise: why do we tolerate CMOS sensors?
By Art Adams | March 15, 2008
The other day I found Harry, the Civil Toaster ("civil" not as in kind, but because he was in the civil service) in the driveway tossing corn chips."Harry... dare I ask what you're doing?""It's very simple, white bread," he said. (Are toasters naturally rude, or is it something they develop over time?) "I read that CMOS chips have a rolling shudder, so I'm trying to find one by rolling chips and seeing if I can induce a seizure. If a chip starts shuddering, I'm halfway toward making my own camera!""Harry, you're smart for a toaster. Which means if you heat up when you're plugged in you're already at the median for toaster intelligence, so I'm not saying much."What I think you're talking about is that CMOS chips have a rolling shutter. CCD chips generally grab data in one fell swoop, after which the data is read out of the chip, the chip is blanked, and it's then ready for another exposure."CMOS chips expose one horizontal line at a time, from the top of the frame to the bottom, and while they do it very quickly it's not unusual to see artifacts from this type of scanning. Generally this shows up as slanted verticals when a camera is panned quickly. That's because a vertical line will appear to be in one spot when the scan starts at the top of the frame, but will appear in different spots as the camera continues to pan and the shutter moves down and exposes successive lines."They can also be a bit noisy. CMOS sensors tend to have a lot of blue noise in the shadows.""Huh," said Harry, taking his bag of chips into the shadow of the garage and looking for any that exhibit blue speckles. "So why use CMOS chips, then?""Well, they tend to require less power than CCD chips do. The Sony EX1, for example, would run extremely hot if it used CCD chips instead of CMOS. It deals with noise by putting the analog-to-digital (A/D) converter, which converts the chip's analog signals to digital, right on the chip. Traditionally the A/D converter is separate from the chip and connected by wires, which can act like antennas and pick up transient signals from inside the camera and make the noise problem worse. By putting the A/D converter right on the chip the noise floor is reduced dramatically. There are solutions developing for these issues, and I'm sure we'll see huge advancements in the near future.""I'm going to beat them all," said Harry. "All I need to do is find a corn chip with low noise on the floor and I'll be way ahead of the game." And so he set out to find a quiet chip, snapping them one at a time while laying in the shade of the garage door."By the way," he said, "from now on I'm changing my name. I'm going to be Harry the Video Toaster. Once I build my camera I'll be famous, and everyone will shiver and quake at my name! I'm even considering joining the ‘League of Unlikely Media Superheroes.'***""Harry," I said, shaking my head, "you're twenty years too late. The original Video Toaster has long gone"Harry looked me straight in the eye: "The Toaster will rise again!" I couldn't tell if he was serious or if I was the victim of what he calls his "rye humor."***Foreshadowing alert. The reader is informed that this will pay off in time.
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Does the RED ONE's 5000k balanced chip reduce latitude under tungsten light?
By Art Adams | March 13, 2008
Life isn't easy when one lives with overly intelligent appliances. In my case, my home is "enriched" by Harry the Civil Toaster ("civil" not as in kind, but because he used to be in civil service), an appliance who frequently makes life more interesting than it needs to be.Yesterday I got home from work to find a pile of potato chips in the middle of the kitchen floor, and Harry in the middle sorting through them one at a time."What the heck, Harry!" I said. "What are you doing now?""Keep your crust on," he replied. "I'm in the midst of a great scientific experiment. I read that the RED ONE's chip is daylight balanced, and I figure if I can find a daylight balanced chip I can probably make my own camera and sell it cheaper!"Problem is, I don't know what a daylight balanced chip looks like. I found one that was really, really dark, and my suspicion is that it's only good for infra-red. I want to start with a full spectrum chip before I get into the esoteric stuff." He bit into a chip. "Maybe I'm going down the wrong track. Would a daylight chip be corn-based?"Harry is a highly intelligent toaster. That's not saying much; any toaster that doesn't burn Wonder Bread is considered to have an above-average IQ."Harry, a chip is a silicon wafer that's sensitive to light. That's it. It's not made of potato or corn. It's basically melted sand."And you can't tell if a chip is daylight balanced just by looking at it. Most chips are probably balanced for 3200k, as we add an 85 filter when we go outside. What that means is that under 3200k light the chip response in all three color channels (red, green and blue) is relatively equal, resulting in a combination of colors that's very easy to ‘balance' so that colors render properly. When shooting under daylight conditions an 85 filter is added because daylight is bluer than tungsten light--and without removing some of that blue, the blue channel will clip long before the other channels do, making it very difficult to white balance.""So you're saying I should be looking for a tungsten chip?" asked Harry, testing another chip. "This one is really salty but it could be hiding a slight metallic taste...""Harry," I said, "you should stick to sourdough. You're out of your league. You can't tell what light a chip is optimized for just by taste!""Ah, so you've tried?""No, but...""Just keep jabbering, butter boy." Harry opened a bag of dip chips and dumped them on the floor. "Maybe the ruffles, with their greater surface area, will give me greater sensitivity and resolution."I don't know why I bother, but I do. "Look," I told him, "I'm not totally sure it makes a difference. There are cameras that can handle daylight situations without an 85 filter. The Sony DXC-D50, for example, has an "electronic" 85 filter that you can turn on for exteriors, but I suspect all it's doing is reducing the blue gain to bring it in line with the others."That seems like a reasonable trick if you can pull it off, but it worries me. My gut says I'll get better results using an 85 filter, so that's what I try to do. Fortunately most of the cameras I use have 85 filters built in.""Yeah, and luckily they're all smarter than you are," said Harry. "Hey, this chip is pretty big. Does that mean it's higher resolution? I could make a 65mm version of the RED and clean up!'"You will be cleaning up," I said, looking at Harry's chip plant situated on my floor, "but not by selling cameras. And the interesting thing about the RED is that I'm told it's a 5000k chip. I'm not sure what that means yet.""I think it means that it's manly enough to kick your ass, white bread." Harry can be very rude sometimes. "Who cares how a chip is balanced anyway? None of these balance very well at all." He showed me by putting a chip on one finger and trying to balance it. "At best it's a pale yellow balance, except for the dark ones. Did I say that I think those are infra-red?""Yes, you did. The issue with a 5000k chip is that it's going to get used under tungsten light a lot, which means that the red channel is going to be more saturated than the others. Potentially it will clip sooner than the other channels, and if it does it will severely limit exposure latitude under tungsten light. "Normally this would be compensated for by reducing the red gain... but the RED is a ‘raw' camera, and doesn't have any gain controls. It also doesn't have a knee circuit to smooth out and desaturate highlights."I don't know this for a fact, but I'm going to test it soon. I've already played with someone else's footage and I've noticed that flesh tones do tend to clip sooner than I expect under tungsten light. I can solve the problem by desaturating the image in REDCine, but I don't always want to be stuck doing that for most tungsten situations."It'll be an interesting test. I'm also curious if I'll run into problems in the other direction, for example if I shoot a test under skylight at 8000-10,000k. Will the blue clip sooner than the other colors?""Beats me," said Harry. "Maybe a single chip isn't the answer. Maybe I need an array of three chips. Small chips, like Fritos. Yeah, that's it. I'm going to the store to get some corn chips.""Okay, Harry, and while you're at it get some bean dip. You're going to need an A/D converter."Harry stopped at the door. "Hey, you're not so stupid after all, white bread. Maybe I'll get some guacamole, too. After all, most of the luminance info comes from the green channel... hmmm."He spent most of the next hour trying to get his jacket on. Even the simplest task is difficult for a toaster. No opposable thumbs.
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