RAW histogram

[Ysarex]

A digitally displayed histogram by definition includes a software interpretation, so I'm not sure what you're really talking about when you say "a histogram prior to software interpretation."

I explained that. The camera processing software applies a tone curve to the data and then creates the histogram. Raw Digger allows us to examine the data without forcing that tone curve on us. The difference in the information that we can quickly garner can be striking. Here's an example:



All of the camera settings were neutral. On the left is the histogram in Photoshop for the camera processed JPEG. On the camera LCD I would have seen the RGB composite histogram as Photoshop is displaying it. The camera software tone curve has been applied to the data and that has resulted in a complete nuking of the red channel. Relying on the camera histogram when I took the photo would have been a mistake.

On the right is Raw Digger's histogram display for the raw file. It tells a different story. Raw Digger can display that data in different ways. But there is no way to get Raw Digger to display a red channel for this photo that indicates massive clipping. The OP and I would like to see the data on the right when we're out in the field. And since it's possible to do that, we think it's a reasonable request.

You're satisfied with the data on the left and happy using that to interpolate from experience what the data on the right probably looks like. Well, you're probably better at this than the I and the OP; I have a hard time mentally seeing the data on the right when I look at the data on the left. Fortunately when I took this photo I didn't look at the data on the left but instead relied on my work-around and used my camera meter. I got a pretty good exposure.

Joe

 

[Derrel]

SNIP...used my camera meter. I got a pretty good exposure.

Joe

Carefully using the camera meter is an old-fashioned way of working. It's the kind of thing people used to do when shooting on expensive film, and paying for processing on every shot, the good ones and the bad ones...

When done in combination with experience, and testing, and plenty of experience with a particular set-up, using the camera's metering system can actually give pretty good results.

Sekonic has a relatively new light meter,the L-758DR, one of their most-advanced models, that has software that allows the user to test his or her camera, and to test and calibrate their camera's dynamic range. I've read a couple reviews of it, but it has not really "caught on".

Sekonic Light Meter: L-758DR DigitalMaster Exposure Meter - Overview

I've been wondering about this product, off and on, over the past few years.

 

[Gavjenks]

Well, you're probably better at this than the I and the OP; I have a hard time mentally seeing the data on the right when I look at the data on the left.

Well no, I can't visualize it very well either. I'm not sure it's actually possible to fully visualize it from the histo alone (maybe intuitively from the histo + the image, but I am not skilled enough to do that personall).

What I actually do in practice is usually simply sacrifice some of the dynamic range I could have gotten and work with the range that happens to be covered by the LCD histo. Which is selling my camera short, I understand.

But if I did want to be more careful and use my full dynamic range available by exposing to the right of the full RAW, though, what I'm saying is not that I would somehow skillfully visualize the exact curve. Rather, what I would do in that case is the following:
1) Use rawdigger and your LCD histo together with a whole bunch of test shots and minor settings tweaks to figure out approximately what the actual difference is between the right side cutoff of your LCD histo and the rawdigger right side boundary, in terms of EVs. Maybe it's, let's say, 2.3 EVs, for example.
2) In the field, use some test shots and the LCD histo to get a perfectly ETTR image using the LCD histo alone (i.e. just barely not any or hardly not any pixels showing up as blown out on the LCD), as if that were the actual right side boundary.
3) Now take those settings, and add exactly +2.3 stops to them. Or maybe +2 stops if you want a little safety cushion.
4) Take the photo.

The LCD will show it as horribly blown out, and you'll have no idea what the actual precise shape of the histo is beyond the right side border of the LCD histo that you can't see. Yet you can still rest easy knowing that you should just barely be able to recover all of the data in RAW conversion later on, with an almost perfectly ETTR image in terms of the actual RAW data. There should be no reason why you would actually need to visually confirm it with a tethered computer. You should just be able to trust in the science, I think, unless there is some sort of significantly non-linear relationship between the shapes. Which there might be, but I can't think why.

 

[MatthewSimes]

It seems, on the rare occasions where this may or may not be a needed tool, that simply bracketing 3 or 5 shots at 1/3 stop intervals would've be much more productive.

 

[tschaaf]

Magic Lantern may be an option for raw histogram. Also, if you do not mind carrying a laptop, Kuuvik Capture offers RAW-based histogram and over/underexpo warnings. I can't tell how useful that is though.