12 vs 14 bits raw files

Started 3 months ago | Discussions thread
beatboxa Veteran Member • Posts: 7,480
Re: 12 vs 14 bits raw files

plumberdp69 wrote:

beatboxa wrote:

I don't think that i understand this question. At base ISO, the camera has potential to capture the full tonality & range it is capable of. At 14-bit, a given range will have maximum tonality. At 12-bit the camera will retain the same range, but could have less tonality. All of these assume lossless compressed or uncompressed. Compression obviously changes many things when it comes to tonality & range.

When you move up from base ISO, for example 200, you are in essence clipping 1 stop out of the top. So you have the same tonality, but less range (a maximum half as much). In other words, you cannot expose as much. So by ISO 400, you have the same range & tonality at 12-bit and 14-bit for a given ADC.

This is true until you get to ISO 800--the second distinct ISO. Here, it will have more tonality than a simple software boost; but less than ISO 100, because again: the exposure range potential here is only 1/8th as much. Therefore, the practical tonality will be less than ISO 100 (if exposure at ISO100 is 8x as much). But again, because it is much less than the maximum tonality & range at ISO 100, 12-bit should likely be sufficient and indistinguishable from 14-bit here (and above) as well.

So 14-bit is really only practically different--and even then barely so--at ISO 100 & 200 on a Z6.

Noted and many thanks!

I was adding 1 + 2 and got 12! Ha. What are my 1 and 2?

1 - electronic ISO is via changing the signal amplification. High amplification leads to electronic noise (=noise in the image). I thought at base ISO, there is no or very little amplification.

2 - Because of no or little signal amplification, 14 bits then will give better data resolution, better image quality than 12 bits.

Guess my line of thought is irrational. Thanks for your clarification.

No worries. I think a better way to think about it:

There is almost no electronic noise today. Almost none. Almost all of the noise comes from photon noise. ie. the noise of photons not getting to the sensor uniformly. This occurs in shadows at low ISO and more-or-less everywhere at higher ISOs. In fact, forget ISO: your shutter speed and aperture alone will determine your noise. And then, the more you enlarge (or crop or zoom in) the more it becomes apparent.  And contrary to popular belief, ISO 800 has less electronic noise than ISO 100.  All other ISOs are the same as the lowest corresponding ISO because these are dual-gain ISO invariant (in-between dual gain) sensors in the Z6.  For the Z7, its ISO400, and for the Z5, its a single ISO(100).

Another way to think about it: imagine you had a can of spray paint.

Let's say you spray for the briefest time. You will see a lot of spots (noise). If you go far enough away, it will just look like a uniform color.

If you spray longer, it will saturate more. Regardless of ISO, the spray is what it is.

Bit depth has very little to do with it, except for tonality when you push or pull a LOT at very extremes. If you push shadows or pull back highlights 5 stops, you might see a difference. But how often do you do that; and if you do, chances are you have exposure problems, not ISO problems.

My take: ignore electronic noise nowadays. Even though it exists barely and there are 2 distinct levels (ISO 100 & 800), exposure noise will be the dominant one and follows the same patterns of noise vs exposure. So the only time it matters is near ISO 800: if you are using ISO 400 but will be brightening by 1 stop, use ISO 800 instead for the least noise (because electronic noise is less at the higher ISO800, while photon noise is the same). But even then, the difference is tiny. And regarding bit depth, it's one of those specs that doesn't really matter much in practice.

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