The vibrating sensor would be a temporal version of the old spatial trick of pixel-shifting in 3-chip camcorders.

All this gave me an idea. Most cameras have a "clean sensor" feature that vibrates the sensor. It seems to me that you could increase effective resolution by shifting the sensor between captures. It would be sort of like HD photo techniques, except applied to effective resolution rather than DR. It could be great for landscape/architectural images, etc... Integrating the images would require some new widget, though.

"RED is doing it to some degree to extend DR with their HDRx™. They sample every cell with a shorter exposure time and then continue until a longer one is reached. You'll get two tracks, one exposed for the blacks and one for the highlights, which you can mix later in RCX or DaVinci Resolve to your liking."

This sounds fairly similar to VK's idea.

Sure! Temporal oversampling. But I don' see how this can be applied to film in that manner.

RED is doing it to some degree to extend DR with their HDRx™. They sample every cell with a shorter exposure time and then continue until a longer one is reached. You'll get two tracks, one exposed for the blacks and one for the highlights, which you can mix later in RCX or DaVinci Resolve to your liking.

If they license this, one day a GH5, -6 or -7 might have this too ;-)

Oops, sorry, double post…

@nomad

I was under the impression that Nyquist/Shannon applied to any kind of analog sampling in any domain. At least that what it means from an information theory standpoint. I guess conventional use of the term has been restricted - too bad, that just means that things are made more complicated for no good reason.

Wouldn't the black frame require the use of a shutter even if not all the time? I doubt the GH2 can fire it fast enough to not end up interrupting video. I assume the Red uses a shutter?

Chris

@VK

Clever way to get around the 8-bit issue. Double the bitrate and increase usable DR by at least 2 stops (theoretically, even more) - pretty nice!

Chris

The black frame trick I was alluding to is used to subtract noise that results from the sensor heating up over time - like with long shutter speeds, or constant capturing. It has to be done separately for each shot and in close proximity, and using the same capture time as the image. I can see where one could do this as long as shutter speeds are faster than 2x the frame rate. Or, maybe they can do it faster?

I doubt the GH2 can do this because it requires using a shutter during capture - maybe the GH3 will?

Chris

@nomad

You're right about the pixel count, of course - I was mistaken (stuck in the old 3 sensor days). Thanks for the correction.

The nyquist limit does apply because the A/D converters are 12-bit (I believe), which makes the roundoff error insignificant in this discussion. So, we are close to the simple mathematical error introduced when pixel values are mapped into the 8-bit space. From an image gradation fidelity standpoint the principle is the same.

Chris

One way cameras get better DR is to use tricks like combining multiple image captures when low shutter speeds are used (this can be very effective and can greatly raise DR). This is not HD photography because the images are all captured the same way - rather the images are combined to effectively counter the effects of noise. Another trick is to capture an image and then a black frame (with shutter closed) - the black frame is used to subtract sensor noise. Unfortunately, none of this works with video.

Chris

@qwerty123

I've been away for a while so I haven't had time to work on film modes. They are extremely complicated and elusive so I haven't been able to make much progress on that front. There is an unfortunate trade-off with film modes. If DR is increased, posterization will result because of the 8-bits of data per channel.

As for the 9.5 stops. I suspect that for the GH2 that's pretty much the practical limit - again because of the 8-bits per channel. JPEG and H.264 images will never be able to handle the full raw range and still look good in most cases. Even my big Nikon cameras limit DR to 9 or so stops with JPEG in most cases. Raw, of course has much higher DR; but raw is 14-bits per channel.

Chris

@danyyyel

The problem with many of these tests is that signal to noise ratios are often not considered, and that results in being able to claim better DR. True, the darkest pixel vs the brightest one might be a wide spread, but if you look at details you will notice that low level details are swamped with noise. If you consider S/N ratios the D7000 comes to about 9-10 stops of usable dynamic range. Even Nikon admits that the D3x cannot resolve low level detail as well as the D3/D700 - but you have to save in 14 bit lossless mode (which is not the camera's default) to see the difference. Canon, for example, actually lowered the pixel count in the G11 because of how bad the low level detail looked with the G10 (which had a higher pixel count). My hat's off to them for that because at long last they listened to their engineers instead of simply going for a higher pixel count (as marketing people would suggest).

It's not strictly the pixel density that needs to be considered - it's the pixel well size that actually matters. One advancement has been to connect sensor elements more efficiently (back-light sensors) so that a higher percentage of of the sensor space is actually sensor wells - resulting in bigger individual wells, and that helps. With a camera that is strictly video the pixel count can be much lower (2 megapixels for HD 1080) - also resulting in bigger wells.

APS-C is a bigger sensor than 4/3 (1.5x vs 2x), so one would expect better performance.

I realize that incremental advancements have been made. However, there is a limit to how effectively low level detail can theoretically be captured simply based on the physics of how many photons can be gathered within a given time within a certain space.

By the way, virtually nobody supports these high DR values with JPEG because quantization gets ugly. With JPEG, DR is typically degraded 2-5 stops. H.264 is similar to JPEG when it comes to compression, so video performance is also limited by the 8 bits per channel. 8 bits can only completely correctly represent 7 stops of data (because of the nyquist limit) - if a higher DR is rendered, gradation steps will be skipped and the total range is mapped into only 8 discreet steps. This is why S/N ratio is so important - if the dark detail has a lot of noise then you are effectively stuck with 6-7 bits of usable data per channel. Raise ISO too high and you lose another stop or two. It can get pretty bad.

Of course all this can be obfuscated depending on how you develop specifications - which would explain why some cameras look better than others even with "lower" specs.

Chris

@qwerty123 there has been renewed discussion on P-V regarding issues with higher than 9.5 stops- notably the issue present in the C300- (using 8 bit to describe 12-14 stops) - so until it has been concluded that 8 bits can actually safely contain higher stops- then this is not really going to be a game changer.