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Archive 2012 · Histogram - What is it really telling me?
  
 
svassh
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p.1 #1 · Histogram - What is it really telling me?


So I thought I understood the histogram when shooting and previewing the image on camera I adjust iso, speed and aperature to try to achieve a bell curve look.

However, if I let the camera select auto iso, and speed and I just select the aperature the shot often looks much better but the histogram is largely left or right based.

Adjusting the exposure in LR to make a bell curve again really messes up the look.

So I guess I really have a couple questions:

1. What is the histogram telling me?
2. Is a bell curve exposure histogram always correct?
3. If a bell curve histogram is not correct when should I adjust?

Attached are 2 shots examples, the first is really SOC, the second is if I try to approximate a bell curve in LR by adjusting the exposure, shadows, highlights etc.

Thanks for any advice.





SOC







My Horrid Bell Curve adjustment




Dec 16, 2012 at 03:46 PM
James_N
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p.1 #2 · Histogram - What is it really telling me?


Hard to say what the histogram is telling you without actually seeing it but here's an excellent explanation of the histogram: http://www.cambridgeincolour.com/tutorials/histograms1.htm


Dec 16, 2012 at 03:51 PM
svassh
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p.1 #3 · Histogram - What is it really telling me?


James_N wrote:
Hard to say what the histogram is telling you without actually seeing it but here's an excellent explanation of the histogram: http://www.cambridgeincolour.com/tutorials/histograms1.htm


Great tutorial, thanks for the link



Dec 16, 2012 at 04:00 PM
dwerther
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p.1 #4 · Histogram - What is it really telling me?


James - thanks for the link. Very informative and a great reminder!


Dec 16, 2012 at 04:07 PM
Peter Figen
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p.1 #5 · Histogram - What is it really telling me?


The ONLY thing a histogram is, is a graph of the number and distribution of pixels in your image, or within a selection if you have one. The histogram tool in Photoshop will tell you exactly how many pixels there are at each level from dark to light. That may or may not be useful to you. There's never a right or wrong look to the histogram but there's certainly a right or wrong look to an image. The histogram is very useful when shooting a digital image in helping determine clipping, but very little else. It's also helpful in scanning black and white negs in the same way, but again, there's never a right or wrong look to them. They are what they are.


Dec 16, 2012 at 05:45 PM
 

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svassh
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p.1 #6 · Histogram - What is it really telling me?


Thanks went thru the tutorial and I think I get it now. I understood it for clipping and mistakenly thought that the bell curve was always right. There is also a useful tutorial on that sight for calibrating your monitor. I did that and wow what a difference that made on my laptop LCD.


Dec 16, 2012 at 06:29 PM
Alan321
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p.1 #7 · Histogram - What is it really telling me?


Peter Figen wrote:
... The histogram tool in Photoshop will tell you exactly how many pixels there are at each level from dark to light. ...



Trouble is, it doesn't tell you how dark or how light because there is no brightness scale. The middle of the scale is almost linear but the ends are so highly compressed as to be almost useless. In effect it covers about 5 or 6 stops out of the dozen or so that a raw file can capture, and those extra few stops are represented by just a few pixels on the horizontal scale of the histogram.

Don't blame just Adobe for that - the camera manufacturers and most other photo programs do it that way too.




Dec 18, 2012 at 05:32 PM
Peter Figen
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p.1 #8 · Histogram - What is it really telling me?


The histogram isn't meant to tell you the brightness of the image, only the distribution of pixels. You're reading more into it than is there. I don't see how it's compressed at either end of the tonal range either. Move your cursor over the graph and it will read out each level and give you the number of pixels at each level from zero to two fifty five. Pretty linear to me. Now, it's true that it only reads in 8 bit numbers, but for most applications that should be more than sufficient.


Dec 18, 2012 at 06:36 PM
jstaylor
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p.1 #9 · Histogram - What is it really telling me?


Basic, but i like this Sekonic doc on histograms and meters.

http://www.sekonic.com/images/files/HistogramsLightmetersWorkTogether.pdf



Dec 20, 2012 at 06:39 AM
Peter Figen
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p.1 #10 · Histogram - What is it really telling me?


Yep, pretty much everything I've already said here. It's a freaking graph and nothing more. It's up to you (or whomever) to figure out whether it helps you or not.


Dec 20, 2012 at 07:53 AM





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