Histogram: is it good to follow or not

I dont think you should use the histogram as an absolute judge on whether your shot is good or not. I think it can be useful in terms of reviewing your overall exposure, but its not the be-all and end-all of whether a photo is good or not.

I think personally, that its useful in the context of a quick guage on whether you have exposed reasonably well on the photo ... as in ... is all the curve waaay to the left ( underexposed perhaps ) or waaaay to the right ( possibly over-exposed ) .... with emphasis on perhaps/possibly. .... but to me, thats all. I certainly wouldn't be looking to acheive a perfect bell curve by any means.

I'll take a shot, maybe glance at the histogram and see whether the bulk of the curve is in the middle and not at the edges, and if is OK i'll move on. If the curve is to the far left / right, i'll then factor that in against the actuall composition .... maybe i do want it to be dark or light ... and the histogram will confirm that.

So i wouldn't worry about it too much. Keep taking the shots, look at your shots later and where its gone obviously wrong in the photo, see if you can see that in the histograms. then from there you'll learn that if the histrogram is showing a particular shape, when you didn't really want it to, you can try and address that at the time of taking the shot.

but certainly dont worry about " oh no the curve aint bell shaped " .... just keep taking photos and have fun.

If you want to obtain the highest quality of capture, then the histogram is more important than the image displayed on your camera. Specially in low contrast scenes, where putting the histogram to the right means a general overexposure of your image, you should trust the histogram and not what the display looks like.

I give you an example:

This is the JPEG displayed on the camera:

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_GUI_ wrote in post #4460844
...
This is the RAW's histogram (pure RAW, not even white balance applied):

...

Dear GUI,
If you don't mind, what software are you using to get that display?

_GUI_ wrote in post #4460844
If you want to obtain the highest quality of capture, then the histogram is more important than the image displayed on your camera. Specially in low contrast scenes, where putting the histogram to the right means a general overexposure of your image, you should trust the histogram and not what the display looks like.

I give you an example:

This is the JPEG displayed on the camera:

[]http://img87.imageshac​k.us …805/mg9137thumb​kx7.jpg[/]

Is it nice? no it is not. Are the highlights blown? not at all. Was it a good exposure? not only good, it was almost perfect. This is the RAW's histogram (pure RAW, not even white balance applied):

[]http://img87.imageshac​k.us …/1197/mg9137his​rr2.gif[/]

Just 1/4 of f-stop before beginining to blow anything. After RAW development and a simple contrast curve:

[]http://img80.imageshac​k.us/img80/6665/mg9137​ib4.jpg[/]

The image resulted in the best possible signal to noise ratio (although this was not a problem here actually) and tonal richness.

If wanna play with the RAW file: namibia.cr2.

The problem of camera's histogram is that it does not represent exactly the information contained in the RAW file, but a processed version of it (JPEG) which has usually lost some information in the highlights that is intact in the RAW file. But even with this issue, camera's histogram is a must.

This is a good example of shooting to the right and then correcting the exosure during raw conversion or PP.

Guillermo:

Another request; what Canon body do you use, and what are your in-camera settings for Picture Style, and in particular the CONTRAST setting?

It has been stated by others on this forum that the setting for CONTRAST is critical for getting the JPEG Histogram to more closely indicat what the RAW file will look like.

Glenn

Hi all,

Robert:
- The display in the first picture was the JPEG embeded into my RAW file. I can extract it with the command dcraw -e of the program DCRAW (it's a free RAW developer).
- The log histogram was calculated with Histogrammar over a developed version of the RAW with no white balance applied. This can be done in DCRAW with the option -r 1 1 1 1
- The last picture was obtained in PS. The steps were:
1. Develop the RAW file with DCRAW and the -H 2 option which preserves the highlights (it never blows a pixel). This produces a 16-bit linear TIFF.
2. I opened the result in PS and assigned a linear version (gamma=1) of the AdobeRGB colour profile (the developed TIFF had no colour profile yet). This is not the most recommended way to proceed, but I don't have a linear colour profile for my camera yet.
3. I converted to sRGB so PS automatically applies the 2.2 gamma
4. I applied this curve for contrast control.

Good point Glenn, I have a Canon 350D with parameters set so that the JPEG histogram displayed in the camera becomes as close as possible to the RAW's histogram. So I set:
- Minimum contrast: -2 (this negative contrast is supposed to mean an inverted S-shaped curve applied to the image. That can prevent some highlights from blowing because of the white balance.
- Sharpness: 0 (not really important, but prefer not to create new unexising tones due to the unsharp mask)
- Saturation: 0 (saturated colours get closer to the right of the histogram in specific channels)
- Colour tone: 0

In this way the images in my display look really boring, but I don't care. I am insterested in the histogram.

Interesting idea – I think I’m going to look into that a bit further before changing my custom settings, but I like the idea of having the histogram in the camera come close to the histogram in Lightroom.

_GUI_ wrote in post #4463199
Hi all,

Robert:
- The display in the first picture was the JPEG embeded into my RAW file. I can extract it with the command dcraw -e of the program DCRAW (it's a free RAW developer).
- The log histogram was calculated with Histogrammar over a developed version of the RAW with no white balance applied. This can be done in DCRAW with the option -r 1 1 1 1
- The last picture was obtained in PS. The steps were:
1. Develop the RAW file with DCRAW and the -H 2 option which preserves the highlights (it never blows a pixel). This produces a 16-bit linear TIFF.
2. I opened the result in PS and assigned a linear version (gamma=1) of the AdobeRGB colour profile (the developed TIFF had no colour profile yet). This is not the most recommended way to proceed, but I don't have a linear colour profile for my camera yet.
3. I converted to sRGB so PS automatically applies the 2.2 gamma
4. I applied this curve for contrast control.
...
-

Thanks, GUI, I think I have gathered together all of the needed tools and tutorials. This ought to be interesting!

Off track somewhat, but what is the significance of wave amplitude in the cameras histogram or in your PP software?

chauncey wrote in post #4464012
Off track somewhat, but what is the significance of wave amplitude in the cameras histogram or in your PP software?

Nothing at all.

If you take a picture of a single colour object, you'll notice that one or more channels will go beyond the upper edge of the histogram. Nothing is being clipped as it would be if it went beyond the left or right edges.

I have a pic of a red flower - up close - nothing else in the image.

The histogram is pretty well all red, and it goes well beyond the top edge in Lightroom. Nothing is missing - but picture is sure red.

Of course for colours that are actually a combination of the three RGB channels, things are more complex. Magenta, yellow, orange, etc will contain at least two colour channels.

_GUI_ wrote in post #4463199
Hi all,

Good point Glenn, I have a Canon 350D with parameters set so that the JPEG histogram displayed in the camera becomes as close as possible to the RAW's histogram. So I set:
- Minimum contrast: -2 (this negative contrast is supposed to mean an inverted S-shaped curve applied to the image. That can prevent some highlights from blowing because of the white balance.
- Sharpness: 0 (not really important, but prefer not to create new unexising tones due to the unsharp mask)
- Saturation: 0 (saturated colours get closer to the right of the histogram)
- Colour tone: 0

In this way the images in my display look really boring, but I don't care. I am insterested in the histogram.


-

Thanks for the reply - I've been trying out a negative CONTRAST setting of -2, but I think it still needs some tweaking. Too bad that the RGB histogram doesn't reflect the RAW profile, but that would require more in camera processing which would be different than if the desired output was JPG files.

Glenn

Glenn NK wrote in post #4464117
Thanks for the reply - I've been trying out a negative CONTRAST setting of -2, but I think it still needs some tweaking. Too bad that the RGB histogram doesn't reflect the RAW profile, but that would require more in camera processing which would be different than if the desired output was JPG files.

Glenn

I don't think it's difficult to display the RAW histogram (I mean the true RAW linear histogram, before white balance, before gamma correction and even before demosaicing). Camera manufacturers don't do this as it is a very advanced feature that can appear not very intuitive. Look at my previous histogram:

HTTP response: NOT FOUND | MIME changed to 'image/png'

_GUI_ wrote in post #4464428
I don't think it's difficult to display the RAW histogram (I mean the true RAW linear histogram, before white balance, before gamma correction and even before demosaicing). Camera manufacturers don't do this as it is a very advanced feature that can appear not very intuitive. Look at my previous histogram:

http://img87.imageshac​k.us/img87/1197/mg9137​hisrr2.gif

I would love to have that in my camera; but if it would be there Canon should explain photographers how the hell a desert red landscape produces a histogram where the G channel rules over the B and specially the R channel.

It's the same as an "Expose to the right mode": if a camera can analyse the scene's histogram before shooting (some compact cameras even plot a real-time histogram), why don't implement a special exposure mode which will automatically calculate the aperture or speed value, not to locate the light metering in the middle gray, but exactly to the right of the histogram before blowing the highlights?

All these things are possible, they simple haven't come yet.

Hopefully, Canon can come up with what you are suggesting since they are already doing the opposite, i.e. "shooting a stop to the left", with their Highlight Tone Priority setting.

Well, this is all very interesting and informative.

Thanks to Guillermo and Leo for this enlightening discourse; not the first time Guillermo showed us a thing or two. I recall a thread about blown highlights a while back.

Glenn

Maybe because some highlights aren't important & saving them would just underexpose the important areas of the shot? Which is why I usually use this to keep the important whites white: Need an exposure crutch?