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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

16-bit linear vs 10-bit log?

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Hi Guys,

Just a question. I was reading through the DALSA specs and was quite surprised by the 16-bit linear RAW output from it's sensor. What real-world difference does this make in comparison to the 10-bit log we will get from the Red?

What was the reasoning behind not going to 16-bit with the Mysterium? Does it have to do with the fact the DALSA sensor is a CCD and the Mysterium is CMOS?

Rich
 
You can also record 12-bit linear from the Red. It's not a huge difference to 10-bit log - because the log curve puts the bits in the right places.

I think the rationale behind Red's 12-bit recording would be that when you get to a certain point, superior bit depth is not necessary because all you'll be recording is noise... there's a law of diminishing returns there, versus putting resources into another part of the sensor / data pipeline. It's very similar to audio recording - 8 bit vs 16 bit is a huge difference, 16 bit vs 24 is noticeable but not as huge. People don't go beyond 24 for now because the money is better invested in mics / preamps / etc...

Of course, the Dalsa sensor is very clean and from the tests I've seen them show, the images are really great. Maybe their sensor is a little bit cleaner than the Red's and they felt it needed a couple more bits to be absolutely sure of storing everything it captured?

On the other hand, the Red stuff that Jim's been posting recently seems to be able to be pushed quite a few stops without quantization. Of course, we need to see full-frame moving images to tell...

Bruce Allen
www.boacinema.com
 
I've not seen noise specs from Dalsa that would indicate that 16bits is necessary to record it's dynamic range. The good thing of recording lots of bits is you're certain to get all the range of the sensor, but the bad thing is that if you record too many bits you waste bandwidth and disk space. If you "nail" the number correctly, you get both the full range of the sensor and you don't waste space or bandwidth.

Graeme
 
I've noticed that all the cameras i've seen with dalsa sensors have 16 bit outputs. The digital hasselblad backs, the origin, and that huge seitz 6x17 digital panoramic camera. It made me wonder if thats just how dalsa likes to roll, or if its really necessary.
 
10 bits per pixel is like having 1.07 billion crayons to color your picture with: (Two to the tenth power, for green) times (two to the tenth, for blue) times (two to the tenth, for red).

16 bits is 281.5 trillion. That's a lot more, but the human eye cannot see the difference. Plus, you could only hold 11 minutes on a 320 GB drive.

Plus, when you put your movie on DVD, it doesn't matter, because the DVD guy is going to copy your picture with his set of only 16.8 million crayons (8-bit).

The advantage of more bits in your original is for stretching the picture in post. For example, if you brighten your picture something crazy like to ISO 4000, like Red has done in another forum post, it decreases the overall palette. In this case, I think, from 12 bit to 8 bit.

This is because you are basically saying, "Okay, I am going to redraw the original, but for each color, I am going to instead switch to the crayon four shades brighter. So, for orange in the original, you redraw with your light, light, light, light orange. For dark orange, you switch to light, light, light orange. For dark, dark orange -- light, light orange. And so on. . . . The turning point comes when you get to four shades below your white crayon. It is replaced with white. So is the color three steps below white, the color two steps, the color one step, and white itself. They all become white. So, a decrease in the total breadth of your palette.

Eight bits is still acceptable for distribution, but at ISO 4000 and above, other limits creep in, like the noise floor of the sensor. My point is, unless you regularly need to push your picture six or seven F-stops, and all of the other advantages of Red over Dalsa don't matter (portability, modularity, cost), then maybe Dalsa is the one for you. Otherwise, it would be a waste.
 
combatentropy,
good analogy, i'll probably reference it to explain color space transfers in the future. You do gain a benefit by having a high bit-depth besides pushing and brightening. If your going for a complicated look, like in saving private ryan or something like 300, where you are actually only looking at a few small sections of the original color space, your resulting image will look much cleaner with less pasteurization if you master in higher bit-depth.
 
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Thanks guys, that helps. So I take it there actually is going to be no noticeable difference in the end if the scene you are shooting is lit correctly for the exposure (no need to under or over expose at all). All the image information you need (and more) will be captured to hard disk even at 10 or 12-bit.

The explanation of pixel size is also helpful, especially when it comes to understanding photodiode/lenslet and fill factor.
 
4K Hub said:
So I take it there actually is going to be no noticeable difference
Click to expand...

This rectangle is actually two squares beside each other. The right square is one shade away from the left, using the next step available in the 8-bit color space.

2100_1184695994.png


Can you tell whether it is one step lighter or one step darker?

With 10-bit, you will have six more shades between these two.

With 12-bit, you will have 14 more.

Eight bit is about the threshold for the human eye, which I think is why distribution formats like DVD and your computer monitor have adopted it. More is invisible.
 
i see banding all the time on dvds..mostly in scenes with a subtle dégradée.
try the same in greys and i think you'll see it
 
betty schaefer said:
i see banding all the time on dvds
Click to expand...

Sometimes you will see blotchy color in DVDs, digital cable, and photographs on a computer. That is due to compressing the image with 30-to-1 ratio with MPEG-2 or JPEG. Uncompressed 8-bit does not have such banding.

Redcode is compressed, but it is less (only about 12-to-one) and of a newer, better kind (wavelet instead discrete cosine transfer).

big lebowski said:
It's one step bluer. :sarcasm:
Click to expand...
You cheated.

In this example, the right square is 3 steps brighter (using only the 8-bit color scale) than the square on the left.

2100_1184698126.png


10-bit would have 12 shades, instead of three, between these two squares.

12-bit would have 48.
 
Eight bit is about the threshold for the human eye, which I think is why distribution formats like DVD and your computer monitor have adopted it. More is invisible.
Click to expand...
8-bit (with video gamma, normal gamut) is good enough in (the vast?) majority of situations. This is likely evidenced by the fact that LCD manufacturers almost get away with 6-bit panels.

In lab situations, we can see better than 8-bit.

>At the same time, 8 bits per channel is well below the human threshold >of color-difference perception

While this may be a commonly held belief, it does not hold up to rigorous testing.

In October 03, we (under request from DCI) did a comprehensive discrimination threshold test using theatrically projected images - at 40, 4, and 0.4 cd/m^2 using a gamma of 2.6. These were projected images on a 45' screen at the DCL in Hollywood. We tested approximately 75 subjects, from both "expert viewers" and non experts. The test patterns created steps in luminance corresponding to 1 count in 8,9,10,11 and 12 bits. The viewer was asked to identify the orientation of the test pattern, to verify if he really saw the steps.

The results of the experiment will be published in the September 04 SMPTE journal, but can be summarized by the following :

* Gamma 2.6 best follows the threshold of human perceptual discrimination
for luminance at cinema levels
* All viewers could see 8 bits all the time
* Almost all observers could see steps at 10 bits
* Some observers (40%) could see steps at 11 bits
* Essentially no observers (1%) could see steps at 12 bits.
* Observers learned to see steps and became more sensitive with repeated viewing

These differences calculated to very small DeltaE* - in the smallest case, the threshold of discrimination was 0.05 DE* (if I remember correctly), much smaller than previously thought to be visible.

This was the experiment that caused DCI to adopt a 12 bit (gamma 2.6) recommendation.

If the display does not exhibit contouring at 8 bits, this will be caused by several factors :

* Noise - (either in source or display) dithering will hide contours very effectively

* Environment - environmental contamination of the display (e.g. lights on around display)

Note that if you translate this into linear space, it requires a lot more bits.

Matt Cowan
Click to expand...
http://www.cinematography.net/Pages DW/ColorBitDepth.htm

2- In the grey example above, you can see the difference if you zoomed in or if the patches were bigger. The noise in that image helps obscure things though. Visual angle makes a difference... sensitivity goes up for larger angles.

3- There's a difference between 12-bit linear and 12-bit gamma of 2.6 in DCI. (12 bits linear does not give a "perfect" 12-bit gamma/2.6 signal; Small amounts of noise might smooth things out to give visually perfect results perhaps.) Though in practice I wouldn't worry about it.
 
Performance envelope blown to bits

Performance envelope blown to bits

Good thread. The Mysterium sensor (as described) is a significant achievement but it is not the "perfect imager" or the holy grail. Some future sensor, probably combined with a 16 bit pipeline will smash all the performance benchmarks of the RedOne system (as described). I even buy the premise that the Dalsa Origin can outperform the RedOne in meaningful areas of image quality.

Of course back here in the real world the image quality that all tests to date indicate we can expect from the RedOne is legitimately "state of the art" - in a compact package, with a post pipeline that runs on commodity hardware and sensitivity/signal to noise capabilities that match or exceed any other motion imaging option I am aware of at any price.

Did I mention the plethora of operational and workflow advantages the RedOne has? That I agree wholeheartedly with Graeme's post about the 12 bit linear / 10 bit log choice as just right for sane bandwidth management without significant impact on the finished image - even for theatrical. How about the best implementation of wavelet compression I have ever seen, by a noticeable margin.

Oh yeah, I almost forgot - it hardly matters what kind of images you can acquire with a camera if you can not realistically acquire the camera in question. The day the RedOne ships (assuming they hit their schedule) it will change the price to performance benchmark of the industry by a full order of magnitude.
 
combatentropy said:
10 bits per pixel is like having 1.07 billion crayons to color your picture with: (Two to the tenth power, for green) times (two to the tenth, for blue) times (two to the tenth, for red).

16 bits is 281.5 trillion. That's a lot more, but the human eye cannot see the difference. Plus, you could only hold 11 minutes on a 320 GB drive.

Plus, when you put your movie on DVD, it doesn't matter, because the DVD guy is going to copy your picture with his set of only 16.8 million crayons (8-bit).
Click to expand...
The differences you pointed out between the bit-depth is accurate and helpful for comparison when everything else is equal, however the topic was querying linear vs. log in addition to the bit-depth. In this case, the numbers are vastly different.
 
combatentropy said:
Sometimes you will see blotchy color in DVDs, digital cable, and photographs on a computer. That is due to compressing the image with 30-to-1 ratio with MPEG-2 or JPEG. Uncompressed 8-bit does not have such banding.
Click to expand...
Unless you apply dither 8 bit can very well have banding with critical gradients, uncompressed or compressed.
 
This is a perfect example of getting lost in the specs. What does the image look like? Dalsa makes a great image but I don't recall any features being shot on that camera... not sure why. I do know that Peter Jackson compared the RED image to 65mm film, and that is with our 5.4 micron pixels. That seems good enough to me for a $17,500 camera that you can actually own. We have 4 features in the works and these will all be shot with prototypes. Getting into 16bit vs. 12 bit debate seems like an interesting discussion, but it just might lead to the wrong conclusion.

Jim
 
Right on Jim ! You can't make it any more clear than that. I suspect Red is going to make the current generation of Dalsa into a very short term player.
Aloha
-A
 
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