Little Zooey
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Histograms and contrast
I made an interesting discovery last night. One of my images has a histogram that has no breaks at all and it touches both left and right. It tapers down to a point on the left and on the right it has the narrowest of lines for a short distance.
However, the image does lack contrast and Steven suggested I try again. First of all I tried adding a contrast layer of 20% feeling sure this would push the histogram off the sides, but it didn't. It did chop it up horribly though, so I didn't stick with this method.
Using the Convert B&W tool a second time worked better and I had more contrast with only 1 narrow break in the histogram.
I rarely use contrast on its own because I thought it would block the shadows and blow the highlights. I tend to use the shadows and highlights tool in Elements (just a little) and if necessary use the midtone contrast slider in there. That seems to add a bit of contrast without ruining the histogram.
Can anyone explain the differences between these different contrast tools please? If the midtone contrast tool is different to the standard contrast tool, then why doesn't the latter push a histogram beyond the boundaries? Also, how chopped up can a histogram be and you would still be happy with the image? Virtually all my histograms have no breaks at all. I daresay this is a sign that I haven't pushed them too far, but I'm clearly not doing enough 
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1/Sep/09, 10:47 am
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Bill Allsopp
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Re: Histograms and contrast
Hi
There is a lot in your wquestion, I'll answer what I can but am at work at the moment and out tonight, Bump it if I forget . 
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Bill Allsopp
Don't just look, see!
http://www.britishlandscapephotographs.co.uk
http://www.billallsopp.co.uk
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1/Sep/09, 11:08 am
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Bill Allsopp
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Re: Histograms and contrast
OK, this is not a technical answer, I don't have a technical background so it's just my experience for what that's worth and may well be contradicted by those that know better.
Chopped up histograms result from editing in 8 bit, if you edit a 16 bit image it is unusual to get breaks in the histo' and, if memory serves me right, there's a way of fixing that too but I won't look into that now.
The tool I use is dependant upon my mood at the time, the original image and what I am looking to get out of it. I hardly ever take notes as the I would not take the same image twice and want to process exactly the same result out of it. That's my excuse anyway 
I can only recommend that you experiment to get your style) and take notes if it helps).
I don't worry about small blocked areas or even tiny blown whites in the final image. Don't let it happen too early in the various stages of processing though as it will only multiply later and that will degrade the image.
The difference between the tools is only what suits your style and the image I'm afraid. I know, that is no help but in Photoshop (or any image editing software) there are usually many ways to get to the same end. Some are stated by the guru's as being more degrading and likely to result in artifcats etc than others but my experience show that working in 16 bit with a properly exposed original should not give any problems. Contras is a combination of sharpness and tonal values. The latter are obtained by using levels, curves, Brightness and contrast and any other tool you can lay your mouse on as well as the foundations of contrast grading and multi-RAW outputs.
To illustrate this I have put an example below. This was taken into the light in very contrasty conditions and is the result of blending two processings through my RAW processor. One for the field and one for the sky.
The common view that the ideal histogram should start at the bottom left (dark) and rise to the middle before falling to the bottom line at the far right (light) is in my experience tosh. This may well be fine in a colour image but our appreciation of those is dependant upon the colour tones and balance as well as the contrast. In mono we depend only upon the contrast and range of tones.
I find most images respond well to an almost flat histogram, as below. You can see it starts from full black on the left, has a big spike of dark areas (threes and tractor tyre tracks) and then is fairly flat (flat is relative here). In this image blown white would be quite a lot of the cloud fringes so I was careful not to let the histogram drift out to the right.
I hope this helps, happy monochrome editing.
Having typed all that I can find the pic, I'll edit again later 
found the blighter!
Last edited by Bill Allsopp, 2/Sep/09, 7:31 am
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Bill Allsopp
Don't just look, see!
http://www.britishlandscapephotographs.co.uk
http://www.billallsopp.co.uk
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2/Sep/09, 7:12 am
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Little Zooey
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Re: Histograms and contrast
My goodness, that's an awful lot to think about, so I'll have to find time to absorb it and have a play around. Thank you very much though. One question for the moment if I may, but you mention editing in 16 bit, but I have Elements 6 and I don't think I can. That is I seem to remember a lot of the tools are greyed out.
I started the South Bank image again from scratch last night and like you I seem to pick whatever tool works at the time. I have a general way of working, but I'm happy to throw in other things - none of them with much thought though. I added a contrast layer last night and because you suggested 20% for another image of mine I started with that. There were no breaks, but it was badly chopped along the top line. BUT... after doing a bit of contrast grading and bits and bobs, the histogram is nice and smooth again. I had to stop at the colour version when it got too late, but so far the tones and contrast look much better to my eyes. Thinking about it this morning I can see that a similar looking histogram could represent the same image, but one being very flat and the other having good local contrast. I'll stick a revised B&W version up when I'm done
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2/Sep/09, 9:09 am
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Bill Allsopp
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Re: Histograms and contrast
quote:
Little Zooey wrote:
... One question for the moment if I may, but you mention editing in 16 bit, but I have Elements 6 and I don't think I can. That is I seem to remember a lot of the tools are greyed out.
Sorry but I have no experience of anything but CS2 and no access to elements at the moment. My daughter may have it and I'll have a look and get back to you if/when I get the chance.
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Bill Allsopp
Don't just look, see!
http://www.britishlandscapephotographs.co.uk
http://www.billallsopp.co.uk
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2/Sep/09, 9:55 am
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Little Zooey
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Re: Histograms and contrast
Don't worry about it Bill! I used Elements 3 for ages and when I got the digital camera last year my husband looked around for something that could handle 16 bit. I upgraded to Elements 6, but then we found that all the colour related tools didn't work. I also didn't like the smaller files for my web site (jpg 2000?) so I decided to forget about 16 bit for a while. My scanner does 14 bit, which is even more confusing 
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2/Sep/09, 11:41 am
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gettingbetter
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Re: Histograms and contrast
I use Picture Windows Pro which has some interesting tools.
This article might give you some ideas on contrast control.
ftp2.bmtmicro.com/dlc/Multi-Zone_Adjustment.pdf
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26/Sep/09, 7:43 am
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Little Zooey
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Re: Histograms and contrast
Now that's very interesting. Thank you! I'll have to read it again when I'm not so tired
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26/Sep/09, 7:58 pm
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