(Page 1 of 5 pages for this article  1 2 3 >  Last »)

Filed under: Cameras •Production •Tips •Training •

Diffusion Confusion

Digital filters are awesome for post image manipulation if you have enough bits to throw away. Glass filters, though, work at the highest resolution possible, in the camera head itself, and you’ll never have a better image to tweak than that.

A year ago I had the pleasure to interview Ira Tiffen, formerly of Tiffen, Inc., and Bob Zupka, currently of Schneider Optics, for a magazine article. Here, with a few tweaks and updates, is that article.

THE BASICS


The class of filter most often spoken of, and yet the least understood, is that of diffusion. Twenty years ago, Ira Tiffen sought to formulate a methodology of classifying diffusion filters to make it easier for cinematographers to understand what a particular diffusion filter was doing, and to make it possible to guesstimate what another filter would do based on knowledge of a particular filter’s effects. He proposed numbering the three components that a diffusion filter affected, on a scale from zero to ten, and using those numbers as part of the filter name. The three components were contrast, resolution and flare.

Filters that reduce resolution are said to affect “high frequency detail.” To those of us who got A’s in English and D’s in Physics, that means areas of the image that contain fine detail are affected more than areas that contain coarse detail. Wrinkles are a fine detail, lips and eyes are a coarse detail. How much fine detail is removed depends on the strength of the filter used.

Flare can also be thought of as halation, or “halos.” Flare causes highlights to scatter, and the quality of that scatter determines a lot about how the filter is used. For example, a Tiffen Pro-Mist may only scatter highlights a short distance across the filter so the highlight appears to glow. A Schneider Fog filter would create highlights that spread a great distance, effectively distributing the halation across the entire image and creating an overall “fog” effect.

Contrast filters affect—wait for it!—contrast. These work off flare as well, but instead of creating halation in the scene they scatter the light into the shadows, revealing details in the darkest tones that might not otherwise be visible.

Tiffen’s system would have designated each filter with a three digit sequence that told how much of each effect was present in the filter. If, for example, a 1/2 White Pro-Mist had a score of 2 for reducing high frequency detail, 3 for contrast, and 5 for halation, it would be relatively simple to find a filter that provided roughly the same effect but without the halation (a Soft F/X filter, for example). While the system itself never caught on, the thought behind it did.

On page 2: the three aspects of diffusion…

(Page 1 of 5 pages for this article  1 2 3 >  Last »)

                   

 

Are Two Copies Really Better Than One? Mary Yurkovic | 03/12 Either way, will that help preserve them forever? This recent NY Times article made me think of all of the books, videos, photos and other physical items that I have donated, recycled or tossed. Some of those items I wish I would have kept, though others I intentionally destroyed.

Apple Launches New iPad PVC News Staff | 03/08 New iPad Features Retina Display, A5X Chip, 5 Megapixel iSight Camera & Ultrafast 4G LTE Apple® has introduced the new iPad®, the third generation of its category defining mobile device, featuring a stunning new Retina™ display, Apple’s new A5X chip with quad-core graphics and a 5 megapixel iSight® camera with advanced optics for capturing amazing photos and 1080p HD video.

LIGHTING STRATEGIES: Exploiting a Single Light Source Art Adams | 01/28 Sometimes all it takes to make a beautiful picture is placing one light—as long as it’s the proper light source. This still photo shows an example of one style of soft lighting that’s been in use for centuries, and for good reason: it works. There are few things more elegant than lighting a shot with a single light source. It doesn’t always work, but when it does—it’s magical.

You must be registered to comment. This is an effort to reduce spam. Please REGISTER HERE.

Tremendous explanation regarding the arcania of Lens Filters.I spent the first ten years of my Grip career wondering what these cats were doing putting extra glass, pantyhose, and or facial grease in front of perfectly good lenses.

Posted by mitch reeves  on  06/29  at  08:05 AM

---

Glad you liked it. There are so many ways to affect the image that don’t have obvious explanations, and it’s wonderful when a couple of people come along who can make it seem so clear and simple.

Posted by Art Adams  on  06/29  at  08:44 AM

---

What exactly is the difference between the Digicon and Ultra Contrast filters? The UCs are marketed to increase shadow detail, but after having tested them they certainly reduce the highlight levels as well.
Thanks for another great article- I swear I’ve learned more from your articles in the last 2 days than I have in the last year.

Posted by .(JavaScript must be enabled to view this email address)  on  07/10  at  02:46 PM

---

Name:

Email:

Location:

URL:

Smileys

Remember my personal information

Notify me of follow-up comments?

Submit the word you see below: