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10-18-2010, 10:56 AM   #1
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Spot histogram trick on Pentax cameras

I don't know if some of you more experienced folks might be familiar with this, but it's something I just dreamed up today and it's a fudge that does seem to work.

I was looking through some histogram stuff online trying to find out more about the RGB channels that you can see, and how to use them effectively, and I saw that Canons allow you to see crops of the full live view into its own histo. Which I thought was rather neat, especially for metering for selected highlights, shadows etc.

Anyhow, then I realised that actually you can do something similarish and it's unbelievably simple. If you need a histo of a small part of your final image, all you do is make the pic, then use the editing options to make a tiny crop of the pic, and then you can see a histo of just that crop. Which is kind of neat I think, now that I've worked this out I'll definitely use it.

Anyhow, this might be so obvious that it's like teaching grandma to boil eggs but hopefully it might be of some use to someone.

10-18-2010, 11:18 AM   #2
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I didn't know that, Nass, but I don't spend a lot of time looking at histograms.
I did know it shows a histogram on a cropped images after they've been cropped, but are you saying it show the histogram on the crop area before you actually crop it?
If so, I agree that could be useful.
10-18-2010, 01:10 PM   #3
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I rarely use them hence I thought I'd better read up and see what they could usefully bring to the party =). No, it's not before you crop it. You have to generate an incam cropped image - then like any image it has a histo showing. But you can make a pretty small crop using the incam crop tool so actually it's like having the centre focus point area having its own histo or so. As I said, not sure if it's of any use to anyone, YMMV =)
10-18-2010, 04:53 PM   #4
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I use histograms occasionally, and the "blinking" overexposed areas often. I can't think of when I would use a histogram of only part of an image, I want to check the entire frame.

Perhaps this is because I usually have a Tamron 18-200 SuperZoom attached so can frame just what I will keep. If I had a short focal length prime then I could imagine keeping just a small area of the FOV.

I'll keep the trick in mind.


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