Why no histograms based on RAW on LCD of camera?

Hello,

when I shoot things like waterfalls and have a lot of contrast I often expose to the right as much as possible. 
What's annoying is that the histogram on the back of the 1DX (and as far as I know most other DSLRs) are based on some JPEG the camera generates based on settings for saturation, etc.
If the camera can already convert the RAW file why not at least offer the option to base the histogram on the RAW file?
Even when the JPEG is blinking like crazy it is often possible that the RAW file is perfectly fine and no highlights are blown when seen in Lightroom.
No problems with waterfalls, I just make several stops until the jpeg is completely ruined and with some experience you know how far you can go.

I am just curious. This should all be possible just by software and as a programmer myself I find it hard to understand why there isn't at least an option for this. 


Markus

I agree with your sentiment. I know I can push my 5D3 about 1/3-2/3 of a stop (Depending on scene) past blown highlights without actually blowing pixels. It sure would be nice if the histogram read off the raw file to give an accurate representation of capture.

Hi Markus,

I agree. But while on the internet one reads the histogram is based on the jpeg, it makes little sense from a software engineering standpoint. For example, why code a lossy jpeg and then decode it just to get a histogram? That would just take more resources and slow down the system (decoding jpegs).

More likely is the tone map is applied and the data converted to 8-bit. Then the histogram is computed. Histograms are compute expensive, so it is faster do it on byte data, rather than 16-bit data. Further, to speed things up, they might even sub-sample the image so it is even easier to computer the histogram. The jpeg is then computed from the same 8-bit data that went into the histogram.

But with all the push for speed (frames per second), it would be nice to have a camera function to slow down and get better data, e.g. slower high fidelity 16-bit A/D with much expanded dynamic range for landscapes or wherever one didn't need the speed. For example, even a second or two for readout. Many scientific sensors work with slow readouts, sometimes as much as a minute to read a few megapixels. With all that time, there would be more time to generate a better histogram.

And how about a log scale on the histogram so one can see the highlights and shadows better, or maybe just a vertical scale expansion to see the low counts in the histogram.

Roger

D810 has a flat picture style which applies no tone curve and as a result gives you an accurate representation of the RAW file.

E.J. Peiker wrote:D810 has a flat picture style which applies no tone curve and as a result gives you an accurate representation of the RAW file.

Do you know if Canon bodies read any of their picture styles (faithful) the same way?  I did a quick search but didn't find anything. 

I did find this...

Looks like setting the contrast all the way down may give the most accurate histogram representation.

http://www.luminous-landscape.com/tutor ... ista.shtml

crw816 wrote:

E.J. Peiker wrote:D810 has a flat picture style which applies no tone curve and as a result gives you an accurate representation of the RAW file.

Do you know if Canon bodies read any of their picture styles (faithful) the same way?  I did a quick search but didn't find anything. 

You should be able to setup a custom picture style with zero contrast and saturation and come pretty close.  That's what I do.

DOglesby wrote:

crw816 wrote:

E.J. Peiker wrote:D810 has a flat picture style which applies no tone curve and as a result gives you an accurate representation of the RAW file.

Do you know if Canon bodies read any of their picture styles (faithful) the same way?  I did a quick search but didn't find anything. 

You should be able to setup a custom picture style with zero contrast and saturation and come pretty close.  That's what I do.

No that's not the same thing.  All zeros still applies a tone curve.  Canon does not currently have a flat picture style and yes Canon also reads the picture style applied curve and uses that in the display of the histogram and blinking highlights.  Nikon has added this primarily for film making in the D810 but a benefit to the still shooter is that you get a display with no tone curve applied.

E.J. Peiker wrote: No that's not the same thing.  All zeros still applies a tone curve.  Canon does not currently have a flat picture style and yes Canon also reads the picture style applied curve and uses that in the display of the histogram and blinking highlights.  Nikon has added this primarily for film making in the D810 but a benefit to the still shooter is that you get a display with no tone curve applied.

If I am understanding it correctly, the examples and graphs shown here make it look like the "Flat" picture control is just a flatter tone curve than "Neutral"  :

http://imaging.nikon.com/lineup/microsi ... e/flat.htm

If so, wouldn’t this be fairly similar to what you would get using Neutral with contrast and saturation turned down to the minimum?

Also, if I am interpreting the graph correctly, it looks like there would be very little difference between Flat and Neutral once you get above a mid-tone?

I have both my Canon bodies (30D and 5DII) set to minus three for Contrast. No other changes.
This has been on the 'net for several years (first saw it on DPR several years ago at least).

Glenn

E.J. Peiker wrote:D810 has a flat picture style which applies no tone curve and as a result gives you an accurate representation of the RAW file.

If this is true, then the displayed data are linear, the image would appear mostly black on the LCD, and the histogram would be bunched up on the left side.  The standard tone curve is a variable gamma function that shoves most of the data range scrunched up at the high end and the low end gets multiplied by 10 (in a 16-bit range).  Perhaps it is a reduced tone curve, but probably has some gamma function to it???

edit: moving the 10x factor from the 16-bit output file back to an in camera 8-bit value, it would be a 2.5x increase at the low end.  That helps bring dark parts of the image further to the right where it can be seen.

Roger

I believe most digital images have 2 different curves applied to them. There's a basic gamma curve, then there's a tone curve applied on top of that for effect. Certainly Canon picture styles each appear to have a different tone curve (the latter type) on them to produce the different looks, or at least this is how the similar effects have been simulated by the Adobe DNG profiles that attempt to mimic each of the Canon picture styles. You can open the DNG profiles in Adobe's DNG profile editor tool and see the tone curve.

But I presume all the of Canon picture styles apply on top of the same basic gamma curve. Even the flattest picture style you can apply (which has a linear tone curve in the associated Adobe DNG profile) still doesn't look like an actual linear RAW conversion, which would be extremely dark with a histogram pushed way to the left, as Roger describes.

I adjusted my contrast all the way down and took some test shots. It is far better then just "faithful" and the histogram is remarkably close to what LR displays. Even if it is not actually reading from the RAW file, this "quick fix" seems to produce acceptably accurate histogram display. From my test shots one would have to split hairs to argue that it was not accurate, however my test shots certainly do not represent a variety of diverse images.

There is a 'technique' call UniWB which was all the rage a while back - a search in dpreview.com will yield gobs-o-hits.
Basically a its method to determine a true null tone curve and then use that in camera to calculate the jpegs.  Yielding a histogram that reflects what's in the RAW file. It worked for me on a D600, but I found that once I use a particular camera for a while I have a good feel for how much the jpeg histograms are off.  Thus, I have not bothered with my D800.
russell

Thanks for all the replies. As always very helpful and I am learning something new!

I agree with Roger. Would be nice to have the option for "slow" shots like landscapes, macro.

I understand that the 1DX (or a D4s) does a lot of optimizations for clearing the buffer, AF speed, 12fps and this is probably some highly optimized C code (maybe with some assembler) but why not let the photographer choose?
When I shoot at 12fps I of course don't check the histogram for each shot but it would be nice for landscapes.

I now know what I can do with jpegs and I also played with the picture styles in the past. It's just annoying that one has to waste time with this instead of just heaving an entry in the menu.

Markus

What Royce wrote is correct. Think of Nikon's Flat something more akin to SLOG2 in video parlance which is about as flat as you are going to get after accounting for the linear nature of digital capture itself. But even in picture styles like "Camera Neutral" there is a tone curve applied on top of that. Yes you can get closer to it by turning down the contrast setting on the "Neutral" picture style but this is very rough and not the same as "Flat"

Or you can build a Flat "tone curve" and upload it to the camera. The camera will still apply the Gamma curve but no Tone curve adjustment.