Screencap science

[Joe Cain]

I hate to ask more of the insiders & the rest of the blu-ray.com support staff than they already contribute...

But considering the volume & intensity of various PQ discussions online fueled by screencaps---in many cases eliciting a wealth of opinions based exclusively on those captures---I think it would be helpful for this site to provide a clearinghouse of expert opinion on the validity of these kinds of analyses (a sticky, perhaps).

I know the topic has been addressed on multiple occasions, especially in Penton's thread, but considering the variety of terminology employed (grabs, captures, caps, w/ or w/o "screen" attached or in close proximity), attempting to create a de facto omnibus collection of such comments would require a pretty painful search process (particularly considering the sheer volume of posts involved).

It seems to me that well-intentioned and otherwise reasonably well-informed film fans (not to mention utter newbs) could be overwhelmed by the jargon involved, inferring expertise & experience where it doesn't truly exist, and altering their viewing and purchasing habits based on that information. It would be nice to have an easily-located collection of authoritative commentary on the subject, particularly since applied screencap science seems to be appearing in this forum more and more...

Thanks in advance for the consideration.

[jw]

What are you asking? Its kinda unclear

[Blaumann]

I can create BD screenshots myself and i can attest, that you have to know what they can tell about a transfer and what they can't. There is a rather "disturbing" trend to burn releases just on rather minor artefacts.

[Deciazulado]

Joe I wrote this as a screencap descriptor a long time ago:

Please note that this screenshot is not a a moving image but only a still image frame.. A still image screenshot of a moving image can show more - or less - artifacts due to the non-moving nature of the screenshot. A still image should not be used as the sole qualifier to conclude that a Blu-ray title features good or bad video quality, the Blu-ray Disc should be watched in full motion for that. Screenshots give the viewer a general idea of what a title will look like, and they may not be fully representative of the true quality that Blu-ray offers.

Elaborating a little further, when you look at a still picture it has more grain or noise than a moving picture because in motion, true grain is randomly changing position 24 times a second, so each individual grain is on just for 1/24th of a second and it's gone, and the eye/brain blends them more or less and tends to ignore them and focus on the the solid steady features, similar to what the ears do when you're in a noisy enviroment, in which after a while, they ignore the background noise and concentrate on the sounds that interests you. At the same time, moving objects in the still picture might be blurred from motion whch may not be as noticeable while viewing the moving picture because, your eye tracks the object as it moves and it's not stopping to examine the blurry edges, and in motion, they don't look as undefined as they should. Furthermore, you've heard of Super Resolution and all these methods of increasing detail and sharpness by having several different views (frames) examined and summed to find detail not present in a different adjacent frame. Well guess what, the brain does the same thing, it integrates and creates a world view that makes sense from all this data presented to it too (clever design, millions of years of upgrades) which a frozen frame prevents from doing. So if you have a good transfer you can check this out by alternating still view with play mode one after another and seeing how the grain kind of "DNRs" itself a litte going from still picture to movement and viceversa, while the underlying image remains and becomes a little more solid in playback. As I think I said in anorther post, this could be seen in home video since the days of the CAV laserdisc, and in moviolas, and home projectors, before that.

Also, on the other hand, some artificially added artifacts/patterns might not be visible in still mode but only show their ugly head in motion.

[owa]

Thanks for reiterating it. I guess I had missed that (whenever you posted it) and it would have come in handy several times.

[pro-bassoonist]

Originally Posted by Blaumann

I can create BD screenshots myself and i can attest, that you have to know what they can tell about a transfer and what they can't. There is a rather "disturbing" trend to burn releases just on rather minor artefacts.

I could not agree any more with you. Really!

Dr.A

[Monkey]

Originally Posted by Blaumann

I can create BD screenshots myself and i can attest, that you have to know what they can tell about a transfer and what they can't. There is a rather "disturbing" trend to burn releases just on rather minor artefacts.

From the group of HD DVD fans that are still bitter in defeat at AVS, yes that has been clear for some time..