RAW format histogram

[T.O.]

Hello photographers,

I noticed that the histogram I see in my 350D is not identical to the one I see in RSE and PS.

Generally, the in-camera histogram seems to display more rich tonalities and shows less highlights than RSE and PS. Similarly, the highlights blinking when looking at a picture in the camera are less than the highlights shown by the softwares in question.

All this regarding pictures in RAW format, I only shoot RAW.

What provokes these differences? Have you noticed the same difference in histograms?

Although the difference is small, is annoying to discover that a picture I thought perfectly exposed has some strong highlights that I could not see in the in-camera histogram.

curious about this,
T.O.

[EOSAddict]

I suspect the in-camera Histo is derived from the JPG data whereas the RAW histo ion RSE will show the full 12 bits of data. As for the clipping, RSE/RSP will highlight if any of the RGB channels are clipped, whereas the camera blinking is for full blownout highlights. See the RGB squares in the top left and right of the RSE histo to see which channels are under/over. As you move the sliders they go on/off as each channel goes into/out of clipping. Thats why sometimes when you hold CTRL down in RSE/RSP you get RED/BLUE highlights in strong colour areas - this is not necessarily a bad thing.

[nitsch]

I've noticed the same issue. Quite often a shot can appear well exposed based on the in camera luminosity histogram but on reviewing the image on the PC you discover that one of the channels (normally the red) is blown. I find the RGB histogram on the 30D gives far more useful info from this point of view, not that that helps you much!

[EOSAddict]

Nick,

I have switched to using the RGB version in camera for same reason - better spread of data than pure luminosity - and links better to what I see in RSP

[JMHPhotography]

First thing is... the histogram does not relate to the actual RAW file. It relates to a Jpeg representation of that RAW file. Even if you aren't shooting RAW+Jpeg the in camera display image is shown as Jpeg. I don't use RSE so I can not speak on that product, but in PS if you turn off the auto adjustments you might see the histogram look more like what you saw in camera. If not, why worry? You can make the histo look anyway you like when in RAW. :)

[T.O.]

Very enlighting answers, thank you!
T.O.

[Curtis N]

the histogram does not relate to the actual RAW file. It relates to a Jpeg representation of that RAW file.And because of that, the camera's luminosity histogram will be effected by the camera's parameter setting for contrast. The RGB histogram will be affected by the camera's setting for saturation.

So even though those parameter settings don't change the RAW data, it may be advantageous to use settings that resemble your intended post-processing.

[EOSAddict]

Good Call Curtis, I fell foul of this on my 30D when I set a Picture style with high contrast and thought I was underexposing my pics - then I looked in RSP and all was OK. Reset the Picture Style to Neutral and all is now well!

[nitsch]

And because of that, the camera's luminosity histogram will be effected by the camera's parameter setting for contrast. The RGB histogram will be affected by the camera's setting for saturation.

So even though those parameter settings don't change the RAW data, it may be advantageous to use settings that resemble your intended post-processing.

Yep great info Curtis. Thanks. :)

[Double Negative]

I suspect the in-camera Histo is derived from the JPG data...
Bingo.

[J Rabin]

All the above... about the camera histogram being a simple Luminosity brightness histogram, AND the histogram reflecting the JPG compression of tones as set in camera parameters, AND lastly, the Canon luminosity histogram is a histogram of the green color channel, partly because there are twice as many green pixels as red and blue, and partly because that's the way Canon did it.

So, I do not subscribe slavishly to the "shoot by histogram as light meter" approach. It's a guide, but you have to read it while looking at real tones in the real scene.
On newer models with the individual channel histograms, this green channel only histogram is a non-issue. Jack

[superdiver]

Is it derived from Jpeg, even if you are shooting in just RAW?

[J Rabin]

Is it derived from Jpeg, even if you are shooting in just RAW?
The in-camera histogram? Yes, it's just of the in camera compressed jpg, not the RAW data.

[Titus213]

I turned off in-camera sharpness long ago (thanks I believe to Curtis). It hasn't improved my photo taking abilities but I do get a better representation of my inabilities on the LCD.

[AJSJones]

Check out this thread http://luminous-landscape.com/forum/index.php?showtopic=10367

It basically suggests lowering the contrast setting for jpegs, this in turn affects the processing of the embedded jpeg and affects the derived histogram. By setting the contrast low, the histogram approaches that seen in the raw converter, so you can rely on the histogram more heavily once you've assessed your specific camera's in-camera processing.

[Jon]

Is it derived from Jpeg, even if you are shooting in just RAW?Yes, because even if you're shooting exclusively in RAW, there's an embedded JPEG contained within the RAW file. And all your in-camera parameter settings are applied to this JPEG.