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Filed under: Hardware •Post Production •Production •

Review: Panasonic BT-LH1760 17” LCD Monitor

Performance

The 1760 is a 720p-native display: 1280x720p signals fill the width of the screen, pixel-for-pixel, with just a tiny black band above and below the image (the panel is 1280x768). Standard-def images are scaled up to fit, while 1080-line images are scaled down. Interlaced images are converted to progressive using either field- or frame-based methods as described above. I have yet to find anything to complain about with either the scaling or the I-P conversion; the 1760 (like the 1700) does a great job displaying both panel-native and non-mative material.

The 1760 is capable of displaying just about every format out there, depending on the input connector used:

• NTSC and PAL;
• 480i and p;
• 576i and p;
• 720/50P, 59.94P, and 60P;
• 1035/59.94I and 60I;
• 1080/23.98P, 24P, 23.98PsF, 24PsF, 25P, 29.97P, 30P, 50I, 59.94I, 60I, 59.94P, and 60P!

On the RGB and DVI ports, it’ll also handle 640x400, 640x480, 800x600, 1024x768, 1280x768, and 1280x1024, at a variety of frame rates. [1]

The big news about the 1760 is its double-rate scanning: 100 Hz for 50 Hz inputs, and 120 Hz for 60 Hz inputs. When double-rate scanning is enabled (it can be turned on or off in the menus), the display is refreshed at twice the normal refresh rate, with dark frames or fields inserted in the extra scans. This scanning does two things: it improves motion resolution by cutting the “dwell time” of an image in half, and it reduces the overall light level, since the screen is dark half the time.

According to Panasonic’s Product Line Business Manager Steve Golub, the dark frame isn’t entirely black; it has “a certain level of luminance determined from the previous frame, thus it is not just simply half of the luminance at 120Hz mode compare to 60Hz. ... This is done so that the overall luminance level is

maintained.” While one might worry that a variable-level dark frame could cause fluctuations in contrast or black levels, in practice I saw no such issues: the 1760 appeared to hold blacks and contrast very consistently with inputs of widely varying average picture levels.

I set up the 1760 side-by-side with my 1700 to see how much of a difference there is between the two. I set both up for D65 white points, with chroma, contrast, and brightness at defaults, and I left the 1760 in double-rate scanning mode (the default). Both monitors were fed the same images via SDI. I photographed them using a Nikon D300 set to a fixed white balance of 6625K (the closest setting to D65), and did not fiddle with the color, nor dodge and burn the photos, before posting the pix below.

[Note: we’ve all seen the ads for TVs, always saying “simulated TV picture”. That’s not the case here: every one of these images shows the LCD screen unretouched. I may have tweaked overall exposure, and changed overall color balance in the beauty shots, but the pix show exactly what the Panasonic monitors displayed. In terms of overall exposure, evenness of illumination, and black levels, what you see is what I got.]

The 1760 is within 1/3 of a stop of the same brightness as the 1700, not bad when you consider that the 1760’s screen is dark (if not entirely black) 50% of the time. Presumably, if I turned off double-rate scanning, it would be almost twice as bright (I didn’t think to try this until after I’d returned the 1760). Panasonic claims the 1760 “consumes 50% less power in AC operation than prior models”, which correlates somewhat with my almost-as-bright-but-dark-half-the-time observation, but in fact the 1760 drew 46-48 watts (the former with an analog NTSC feed, the latter with a 1080i SDI feed with embedded audio) while my 1700 draws 48 watts all the time (as measured by a Kill-A-Watt meter).

Viewed on-axis, the two monitors match very closely in brightness, but the 1760 holds blacks a little bit better, and is not quite as green as the 1700.

Menus and color: 1760 (left) and 1700 (right)

As the most common complaint I hear about the 1700 is its slight green bias, the 1760’s color should please most folks.

Also note the menus: the 1760’s menu text is half the size of the 1700’s. Put another way, the overlay dot pitch on the 1760 is twice that of the 1700—and this translates to the waveform monitor, too. The 1760’s WFM appears to be twice the resolution of the 1700’s, both horizontally and vertically: while the 1700’s WFM is a fairly coarse “confidence monitor”, the 1760’s is fine enough to see subtleties and nuances; it’s good enough to light by. Mind you, it can’t overlay signal from two cameras at once, it can’t show chroma, and it doesn’t offer a parade display, so it’s not a replacement for the WFM in your engineering rack, but it’s a welcome improvement on the WFM in the 1700.

In off-axis viewing, the 1760 seems to have a slightly narrower “cone of imperceptible degradation”, but overall it holds both color and tone over a much wider viewing angle than the 1700.

A view from above: 1760 (left) and 1700 (right).

The 1700 rapidly degrades as one moves above or below the ideal viewing axis; its black lose density and there’s a decided greenish shift in color.

The 1760, by contrast, holds black levels and colors very accurately; it simply loses some brightness.

Side view: 1760 (left) and 1700 (right).

From the side, the differences are less pronounced. The 1700 goes greenish. The 1760, if anything, goes slightly cold, with a faint blue tint, but it’s minimal. Again, the 1760 holds its black levels very well, with perhaps some loss of shadow detail, but the change overall in shadow detail is much less than the 1700 shows.

Another view from above: 1760 (left) and 1700 (right).

The top view with a real image instead of bars again shows the difference between ‘em: which one would you prefer to make a critical color or exposure judgement on?

To look into what the double-rate scanning actually did to the image, I built a simple graphic of a vertical white stripe:

Swish-pan test image: 1760 (left) and 1700 (right)

I set my DSLR’s shutter to 1/5 sec, and shot swish-pans past the screens until I got the following image:

1/5 second swish-pan: 1760 (left) and 1700 (right)

Sure enough, there are 12 vertical refreshes of the image on the 1760, with dark fields inserted in between. This corresponds to 60 fields per second, plus 60 dark fields: 120 Hz updating. The tilt of the bars shows that the image is refreshed sequentially from the top down, just as on a CRT.

The 1700, by contrast, shows a mostly-undifferentiated smear of light, as its 100% duty-cycle display blurs one field or frame into the next. (The faint vertical striping in the 1700’s swish-pan may be a result of backlight pulsation; it appears to be flickering at around 200Hz. If you’ve got a better explanation, leave a comment!)

Looking at real-world, moving images, the 1760’s dark-frame insertion results in visibly less smear on fast-moving objects. It’s not quite as sharp as a CRT (where the duty cycle is on the order of 1%: the bright glow left on a television CRT by the scanning electron beam only lasts a few microseconds after the beam passes, though some small glow may remain for tens of milliseconds), but it’s noticeably “crisper” in motion rendering than the 1700 or similar, 100% duty-cycle LCDs.

(Of course, the reduced duty cycle also means that if you’re shooting a 1760 at a frame rate other than the display’s rate, such as a 24p shoot of a 60i image, you’ll need to pay attention to shutter angles / Synchro Scan / Clear Scan settings to avoid flicker and roll bars, just like when shooting a CRT!)

Overall, the picture is very pleasing. The high brightness of the image, and the 1760’s vastly improved accuracy in off-axis viewing, makes it suitable for use in the rough-and-tumble environment of field production. It’s even bright enough to use outdoors in open shade without a hood.

The Panasonic BT-LH1760 is bright enough to use outdoors.

Conclusion

The 1760 is a 17 inch 720p monitor; it’s small enough to be easily portable, yet large enough to view HD without getting eyestrain. It’s not 1080-native, but it has pixel-for-pixel monitoring when that level of detail is required. It’ll handle almost any video standard you throw at it, whether analog or digital, and it’ll accept computer connections, too. AC and DC powering makes it equally at home in the studio or in the field.

If it has the same durability as the 1700W, I’d expect the 1760 to rapidly infiltrate the rental community, as it’s a significant improvement over the popular 1700W in almost every respect. Only those of us who use Y/C connections for standard-def monitoring have anything to complain about (well, that, and the higher price, grin). But the 1760’s superior motion rendering, color, and off-axis viewing performance, along with the addition of DVI-D and headphone jacks, should serve to win over even whiners like me.

Pros

• Bright picture; very good color and tone.
• Minimal color and tonal errors when viewed off-axis; black levels well preserved.
• Excellent scaling and interlaced/progressive conversion.
• Pixel-for-pixel monitoring for critical 1080-line focusing.
• Double-rate scanning with dark-frame insertion for better-than-normal motion rendering.
• Detailed waveform monitor.
• Vectorscope, timecode, and audio level displays (SDI only).
• Full complement of composite, component, and digital inputs.
• Embedded SDI audio monitoring.
• Good user controls with plenty of customizability.
• More overlays, grids, safe action areas, etc. than you can shake a stick at.
• 100-240V AC and 11-17V DC powering.
• If it’s as robust as the 1700W, it’ll take a lot of abuse.

Cons

• No Y/C input.
• Silly fixed-position metal stand.
• Vectorscope, timecode, and audio level displays only work with SDI inputs.

Cautions

• Screen is neither truly glossy nor truly matte; if you need one or the other, you may want to keep looking.
• Non-glossy screen may cause washing out of blacks in certain lighting conditions.
• Even five function keys aren’t enough!
• Split-screen mode can’t show two live pictures, only one live plus a freeze-frame.
• Pricey for a 17 inch, 720p native monitor, but worth it if you need what it does.

When it came time to send the 1760 back to Panasonic, it occurred to me that the 1700W would fit in the box just as easily as the 1760, and if I were very, very lucky, no one would notice… but good sense took over and I returned the 1760 after all.

In summary, the BT-LH1760W is well worth putting on your short list if you’re looking for a bright, rugged LCD monitor with crisp images, a wide viewing angle, multiformat compatibility, and added features like audio monitoring, WFM/vectorscope, and overlay markers.

More Info

Specifications and operating manual here: http://catalog2.panasonic.com/webapp/wcs/stores/servlet/ModelDetail?displayTab=O&storeId=11201&catalogId=13051&itemId=243666&catGroupId=14625&surfModel=BT-LH1760

Wayne Cole’s review for Government Video.

[1] There’s no native support for British 405-line and French 819-line monochrome formats (both obsolete and off the air for decades), nor for Eureka 1250/50I (a defunct European analog HDTV standard), but if you can live without these, the 1760 should handle anything you throw at it. [2]

[2] Ok, it won’t help much with John Logie Baird’s 30-line and 240-line mechanical television formats, 441/50i and 441/60i, Baird triple-interlace and CBS frame-sequential color systems, and the like. Sorry. I meant any modern standard, say, one used within the past 20 years. OK?

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One thing not mentioned in the article is the inability to show waveform or vectorscope when in 1080p mode.

Will that maybe come in a firmwareupdate?
And how to get such a firmware update?

Posted by Christer Molander  on  12/17  at  01:44 AM

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I didn’t have any 1080p cameras to test with, only 1080PsF, so I’m not surprised I didn’t notice this!

Check with your dealer or local Panasonic rep regarding firmware updates. I haven’t heard of any but that doesn’t mean that none exist.

Posted by Adam Wilt  on  12/17  at  09:06 AM

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No that thing is not covered in the brochure either. Deep down in the manual it is.
We do most dramaproduction in 1080p/25.
I´ve come up with a workaround. Using for example an Aja IoHD you can put out a converted 720p signal on either of the SDI connectors (the monitor is as you said 720p) and that gave me the WFM.

Thanks for a good review.

/Christer

Posted by Christer Molander  on  12/17  at  03:33 PM

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