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DVD Shooters & The Peril of Small-Format HD

Apr 13, 2006 4:39 PM, Barry Braverman

The advent of small-format HD camcorders like the Sony HVR-Z1U, Canon XL H1, Panasonic HVX200 and JVC HD100u should by all indications be a blessing for DVD shooters and producers. After all, the increased resolution of the latest generation 1/3-in. HD/HDV cameras provides considerable additional fineness up to 1440 horizontal pixels, which infuses nicely into standard definition DVD compliant MPEG-2.

So what is there to complain about? It turns out quite a bit as many of us are grumbling now about the new HD/HDV cameras' dismal low-light performance particularly in underlit shadow areas. This rampant noise is wreaking havoc in our encoded DVD files; the aggravated noise issue (and not workflow) being in my opinion the number one challenge facing small format HD shooters today.

Ironically, it was we shooters looking ahead to improving the look of standard definition DVDs who most anxiously awaited the increased native resolution offered by 1/3-in. HD camcorders. Few of us anticipated this nagging noise issue, however, a logical consequence of cramming too many pixels into a 1/3-in. CCD (actually 1/4-in. in diameter) imager.

The tinier pixels like fine grain film may have enabled higher resolution images but at the price of dramatically lower light sensitivity, a condition leading to significantly increased noise in broad underlit shadow areas. Such noise especially apparent in night scenes can be highly problematic to the DVD MPEG-2 encoder; the encoder being unable to distinguish the single-pixel noise in the shadows it doesn't want from the fine picture detail it most certainly does.

In my book VIDEO SHOOTER (CMP Books, 2006) I describe the loss of contrast in detailed scenes such as landscapes as the imager approaches the limits of its native resolution. While loss of contrast is inevitable as fine lines converge at higher resolutions, say, at 1440 pixels, there is no comparable reduction in contrast at the 720-line SD resolution cutoff. Thus HD cameras offer shooters a major advantage over SD models when capturing images for ultimate release in standard definition. The effect is similar to shooting 35mm film for release on VHS; the quality of the outputted VHS image from 35mm is considerably better than shooting VHS in the first place.

KEEPING THE NOISE DOWN

While moving to a larger pixel (i.e. lower resolution) imager will almost certainly improve low-light performance, this would appear to subvert the reason for shooting "HD" in the first place. Indeed, Panasonic was widely excoriated earlier this year after it disclosed the native 960 X 540 resolution of the HVX200 imager.

Never mind that this gave the camera a nearly two-stop advantage in low light with better highlight latitude when compared to competing HDV models. Like clock speed on a computer, some shooters simply can't transcend the numbers associated with native resolution. Fact is, regardless of camcorder model, abundant shadow noise will always tend to be a problem in any HD or HDV camcorder with a relatively miniscule 1/3-in. imager.

To forestall ugly happenings in the MPEG-2 encoder, the DVD shooter of small-format HD must take care to minimize noise in the original image capture. The use of adequate camera fill is therefore imperative, a top-mounted light like the LitePanel Mini providing both daylight and tungsten fill with a surprising amount of punch. Of course a passive fill such as a white showcard or silver reflector can also be used successfully; both methods of returning light into a scene are routinely used to strengthen anemic shadows that are the source of so much angst.

Another technique gaining rapid acceptance among small-format HD shooters is raising the coring detail in the camera setup menus. This option found in camcorders such as the Panasonic HVX200 and Sony HVR-Z1U scours the shadows (located close to the baseline in the waveform) for suspicious single-pixel artifacts. Noise identified in this manner is either removed or defocused, rendering it much more benign for the onerous MPEG-2 processing and compression that lies ahead.

While overall camera detail should be routinely reduced a click or two in most shooting environments, coring detail should be conversely increased one or two increments or the equivalent of roughly 25-percent in low-light conditions. That's how I usually set up my HVX200 for night shoots or to capture severely under-illuminated scenes as I find the shadow integrity to be considerably improved.

The use of the appropriate glass camera filter can also help reinforce underlit shadows and reduce noise. When shooting at night I generally use a 1/4 Tiffen Ulta Contrast or 1/8 Schneider Digicon, which helps considerably in the expansive dark areas of the frame.

The filter works by redistributing surplus values from the image highlights to the struggling shadows. Professional camera filters of the ultra contrast type are generally not available in round or screw-in sizes so a matte box (always a good idea anyway) with appropriate size holders is required.

Whatever approach you adopt to reduce noise, an effective strategy is essential in order to take proper, practical advantage of today's small-format HD camcorders. Rampant noise in low light is a serious and growing risk for the new generation DVD shooter, and so it's vital as much as feasible to minimize or eliminate such debilitating artifacts in the original image capture.

© 2008 Penton Media, Inc.