raw versus JPEG dynamic range?

petapixel.com/2024/02/27/picture-styles-and-losing-my-raw-religion/

4 to 5 stops seems a bit much to me.

Any comments?

I think it all depends on the camera. I've seen iPhone 8bit video bring blown out highlights to normal ranges. I've got old 8MB cameras that have half a stop at best jpeg range. I've got a lumix that I think 4 stops from a jpeg is feasible.

i shoot raw + jpeg for my studio work and 99% of the time jpeg is fine even though i process the raws. but the other day i was printing a young dancer that was wearing a fluro pink costume in a scene that i needed to lift the exposure of her, i had to print the 16 bit tiff to get the costume colour right without a blue-ish colour creeping in the costume.

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By "exposure latitude" I assume that he means some amount below clipping.

Now suppose there is a highlight in an sRGB JPEG, let's say it's 245/255, i.e. 10 levels of "head room". But between sRGB and raw there is approx 2.2 gamma.

So, all other things being equal, (245/255)^(2.2) = 0.916 of the raw saturation = an exposure latitude of -0.127 stops. However, the claim is that the raw latitude would be -4.127 to -5.127 stops. I suspect that the claim does not take gamma into account or that the claim is a really, really bad guess ...

Since he mentions a Sigma DP2 Merrill, I am tempted to find a Sigma raw shot and compare it with it's sRGB JPEG conversion.

I think you are asking the wrong question. For a good camera, the camera captures 4-5 stops more than you typically see when viewing an image on today's display devices. That is a fact that is well established.

The camera processes the raw image into a JPEG taking that into account. It doesn't simply throw away the bottom 4-5 stops of the dynamic range. Instead, it typically compresses the top 3 stops down to about 1 stop and may do something similar at the bottom end also. So the JPEG appears to show the full dynamic range of the original raw image, but, of course, inevitably some details present in the original have been lost.

However, it is not simply a matter of losing 4-5 stops of dynamic range. The process is much more subtle and sophisticated than that.

just did a test and 2 stops on the highlights is about right, so would imagine would be close on the bottom as well. mind you when do you ever shoot a scene with that much DR anyway without colour shift in the shadows. eg: skin tones.

I found a suitable Sigma DP2 Merrill shot and examined it's raw histogram:

Looks like the blue peaked at -1 stops (EV).

Then I converted the raw to an sRGB JPEG:

The blue peaked at 176/255 = 0.6902. Accounting for gamma that would be about -1.2 stops in the raw.

So next to no "exposure latititude" in the raw for the afore-mentioned camera model according to that test and certainly nowhere near the claimed 4-5 stops.

Half a stop?? Dynamic range?

I see. I didn't see where he related the dynamic range of raw or of JPEG to "today's display devices".

If that's what the OP meant (if he actually did) then I must agree ...

So Bill Claff measured my Sigma SD9 as about 9 EV but my monitor, permanently set to about 85 cd/m^2, is about 5 EV when I view it.

I ain't a math guy, but this Sony F828 has very little push and pull wiggle room when it comes to the jpegs it produces in the times I've played with them. The noise is bad at ISO64 and it just gets worse, so it's pretty limited on "acceptable" results right out of the gate. If your jpeg doesn't look good sooc, it's not gonna get better trying to edit it. Use the raws instead.

Sorry. Just seemed a bit low depending on what was meant by "a stop".

I have a camera with ISO only settable in the range 100-400 but I keep it super-glued to 100.

Half a stop or 4 stops of what? I don't think any camera tries to create an ISO setting where there will be less than 2.2 stops of headroom above metered middle grey. So what is the "half"? Half a stop more than 2.2 stops of headroom? "4" with the same definition would be tremendous headroom. You can't do that with any quality in the extra levels stuffed in, in a JPEG, because then whites would be dark grey. You can do it in a raw because where white lies within a raw is open to interpretation when converting to sRGB. If it is done by stuffing a couple of stops into just a few top sRGB values like 251 to 255, then if you try to pull those highlights down, you will have visible posterization, which often happens when you try to increase contrast in bright clouds in JPEGs,

As we should all know, "half a stop" is a ratio of 1.414 approx.

As to "of what" and with @OpenCube not being a technical guy, we could work with 8-bit data values. That would make the claim quite restrictive, I reckon. For example, a JPEG having highlights at exactly 255 would have a 'black level' of 180 and would look really silly on-screen or in the print. Or a JPEG having shadows at exactly 20 would have a 'white level' of about 28 and would look equally silly on-screen or in the print.

So, I'm not sure that "at best jpeg range" was really meant like it sounds.

It means if you try and push the shadows, highlights, or general exposure, even a very tiny amount, it becomes unusable to most standards of the eye with minimal adjustments. Modern jpegs I've made the mistake of messing with, seem to have much more range to be adjusted without suffering noise or other oddities.

Thanks for the clarification. I used to have a 6 MP Nikon D50. I'm tempted to go and measure some "JPEG ranges" ...

I found a D50 test JPEG and raised the "shadows" in Curves:

The result could be said to be usable:

Ignoring gamma, the JPEG "range" did change, not unexpectedly:

adj: 51-248 range log2(248/51) = 2.28 stops
orig: 29-244 range log2(244/29) = 3.07 stops

Posted for what it's worth ... could it be that our concept of "JPEG range" differs?

LOL ... Threadkiller Ted strikes again ...