Narrow Histogram.

[JockoT]

Some images produce a narrow histogram. Is there anything I can do to stretch the histogram, either in capturing the image or in post processing? Should I be trying to stretch the histogram in post processing?
I enjoy the post processing aspect but I am not that great at it, though I am learning and hope to learn more now I have joined your forum.

[Manfred M]

Welcome to CiC, John.

"Stretching the histogram" as you put it is is something I do in virtually every image I work on. It's technically called "setting the black point and setting the white point", but of course this assumes that the image has these.

Showing us an example of an image with what you are asking about would be quite helpful. That way the members would all be looking at the same thing during the discussions. The other thing that would be useful is to know which piece of editing software you are using.

[DanK]

A narrow histogram means that the tonal range (dark to light) is limited. Assuming that you have not under- or overexposed, it is a function of the illumination of the image.

Re postprocessing: yes, this is something you can adjust in any postprocessing software, although the tools differ among them.

I suggest you start with the excellent tutorials on this site, specifically a few on this page: https://www.cambridgeincolour.com/ph...-tutorials.htm. Read the two on histograms, the one on the levels tool, and the one on the curves tool. That will give you a better explanation than anything one of us quickly types. Then post again with any questions you have after reading those.

[xpatUSA]

Some images produce a narrow histogram. Is there anything I can do to stretch the histogram, either in capturing the image or in post processing? Should I be trying to stretch the histogram in post processing?
I enjoy the post processing aspect but I am not that great at it, though I am learning and hope to learn more now I have joined your forum.

Hello John,

If your editor has Levels, that would be the simplest way to do it. So, if a histogram shows no 'counts' below, say, 64 and none above, say, 192, you move the black slider upward (to the right) to 64 and the white slider downward (to the left) until it meets 192. In this example there were originally 192-64+1 levels. Those levels will be expanded to 0-255 or maybe 1-255 giving you mucho contrast . . BUT . . .

Since the number of levels or tones got stretched out, there might be some posterization in skies, e.g., depending on how the editor handles the expansion.

A bit like zooming in with viewers that smooth or don't smooth the resulting pixelation.

P.S. others were typing at the same time as me, so pardon any duplicated information.

P.P.S "stretching the histogram" during image capture is less easy and is completely scene-dependent. Basically, you have to alter the lighting! For example, take a street scene: on an overcast misty winter's morning (lots of those where you live ) the shot will lack contrast and thus the resulting histogram will be narrow; on the other hand, in bright sunlight with consequent dark shadows the shot will probably have more contrast than you would like and the resulting histogram could even be maxed out (brick-walled) at both ends with slim chances of recovery.

[JockoT]

This is the image that prompted my question. I am learning Lightroom 6 and I was trying to improve the image with that software. With Photoshop I don't use Levels, usually preferring to set my end points with Curves but I don't know how to set end points in Lightroom. Not yet anyway.

[Manfred M]

That image definitely has a limited tonal range. The haze doesn't help at all and neither does the overcast conditions.

There's an old saying "You can't make a silk purse out of a sow's ear", and while you can make some improvements in post, the conditions you were shooting under limit what you can achieve. Photography is all about light and when the lighting conditions are marginal, your images are going to suffer too.

[jcuknz]

Another thing to appreciate and it applies to this shot is that while adjusting B&W points can be the first step one should watch the effect on the image. In this case I also used the ability of my editor to only apply adjustments to a selected area* ... in this case the sky where I used two adjustment layer/curves ... first for the whole picture and then secondly for the sky.
There are usually more than one way to treat images so I just point the above as a way and the way I approached the matter.

Also note my use of an adjustment layer which if I make a mistake I can cancel and start again or even start another AL and toggle between them to compare treatments ... one of the advantages of working with a 'proper' editor with layers as we both do and Manfred tells us he does too.

*sometimes applying different adjustments to different segment of the curve's line can produce the required effect .... it is worth playing with the curves tool as it is a very power tool.
As a simple example I raised the black point end of the line to the top and dragged the mid point down to just above the display and go this interesting[?] result.... psuedo solarisation effect.

A sketch of the AL/Curve


Sometimes I play with dud shots to see if I can make a silk purse out of a sows ear

[DanK]

With Photoshop I don't use Levels, usually preferring to set my end points with Curves but I don't know how to set end points in Lightroom.

There is a curves tool in Lightroom. It's the second box in the right panel, below "Basic".

You need to learn the Basic panel. Google "lightroom basic panel" without the quotes and you will get gobs of explanations and videos. For example, here's one I picked more or less randomly from the top page in the google search: http://www.slrlounge.com/school/tips...nel-lightroom/. You'll see that the tonality controls in Lightroom work somewhat differently from a levels tool, but it's the same basic idea: you can use the sliders (or the tone curve below it) to stretch or compress the histogram.

Again, if you run into specific things that you can't figure out from these, post specific questions.

[xpatUSA]

This is the image that prompted my question. I am learning Lightroom 6 and I was trying to improve the image with that software. With Photoshop I don't use Levels, usually preferring to set my end points with Curves but I don't know how to set end points in Lightroom. Not yet anyway.

I don't have Lightroom and, with my primary computer dead yet again, I don't even have RawTherapee or the GIMP, just FastStone Viewer. But I still couldn't resist a quick go with just Levels, re-sizing and final sharpening:



The black and the white levels were set to 51 and 188; the mid-range slider was moved to taste at 0.85

Unsharp masking was applied at 2.1px and an amount 9. Then again at 0.3px and an amount of 23.

Re-sampled to 960px wide in honor of CiC's new forum format (just kidding, Manfred).

To be honest, I am struggling to understand why Curves would be useful on this kind of image.

[JockoT]

Thanks, Ted. I am not saying Curves would be any more useful. It is just that when I started to learn Photoshop, the book I used advocated using Curves, instead of Levels, and I just went along with it. I would use Threshold to mark the darkest and lightest areas of the image, then the Eye Dropper tools in Curves to make these points 0 and 255. Since originally posting the image I think I have found out how to set the end points in Lightroom 6 as well.

[JockoT]

Like what you have done with the image. Unfortunately photographers in Scotland have to make the best of "overcast conditions", and the use of a long lens didn't help. A boat would have made for a better image.

[JockoT]

Now I am getting a handle on Lightroom, here is my processed image.

[IzzieK]

I do not have Lightroom but your edit is almost as good as Ted's. Welcome to CiC.

[JockoT]

Thanks.

[DragomirNikolov]

This image also can look like in this order. I think that aperture f/5.6 is too low for this image. I will choose f/13
[IMG][/IMG]

Drago

[Timar]

This is a good example of an image where the new dehaze filter from Lightroom 6 works wonders, as the lack of contrast is due to the atmospheric haze on the sea. Here's what I made out of the JPEG:



First I corrected the overall exposure by +1 EV, then I played a bit around with both clarity and the dehaze slider to find the best combination, and settled at +50 for both. Finally I adjusted the black (-40) and white (+20) sliders and applied some sharpening. Moreoever, I used the structure at the center of the platform as a grey card to get rid of a slight purple color cast. As you may notice, both dehaze and clarity tend to emphasize vignetting in the image, so it is important to properly correct for the vignetting first. Straightening the horizon and applying proper sharpening is also crucial for this image.

You can see that there are much more details to the sky and sea than in yours and Teds rendition.
As usually the case in post-processing, it is important to exercise restraint and not to carry the use of filters and tonal adjustments to the extreme in order to maintain a natural look and the atmosphere of the image. Simply expanding the histogram to the maximum wouldn't work here. However, I see that both of you did a good job in that regard and I couldn't have done better without the dehaze tool.

[Timar]

I think that aperture f/5.6 is too low for this image. I will choose f/13
Drago

Why would f/5.6 be too low? The focus distance is so far that choosing a smaller aperture wouldn't have gained any significant depth of field. f/13 is excessive even for a full frame camera, as diffraction will significantly reduce sharpness at this apperture. In general, apertures smaller than f/7.1 (4/3") f/8 (APS-C) or f/11 (full frame) should only be used for macro photography or in situations where a large depth of field combined with a close subject distance is an absolute priority.

See: https://www.cambridgeincolour.com/tu...hotography.htm

[Timar]

*sometimes applying different adjustments to different segment of the curve's line can produce the required effect .... it is worth playing with the curves tool as it is a very power tool.
As a simple example I raised the black point end of the line to the top and dragged the mid point down to just above the display and go this interesting[?] result.... psuedo solarisation effect.

Manually adjusting the curves is a dangerous thing to do with an image with such a severely limited dynamic range. The less tonal range you have to work with, the sooner you run into problems like introducing solarisation effects. I'd try to stick to the basic panel (and the dehaze filter, if necessary) for such images, as those settings give much better results with a limited DR.

Anyway, you can of course still make creative use of the curves. Tonally flat images are always tempting to create extensive solarisation effects. This is what I once did with a similary hazy image:

[xpatUSA]

This is a good example of an image where the new dehaze filter from Lightroom 6 works wonders, as the lack of contrast is due to the atmospheric haze on the sea. Here's what I made out of the JPEG:



First I corrected the overall exposure by +1 EV, then I played a bit around with both clarity and the dehaze slider to find the best combination, and settled at +50 for both. Finally I adjusted the black (-40) and white (+20) sliders and applied some sharpening. Moreoever, I used the structure at the center of the platform as a grey card to get rid of a slight purple color cast. As you may notice, both dehaze and clarity tend to emphasize vignetting in the image, so it is important to properly correct for the vignetting first. Straightening the horizon and applying proper sharpening is also crucial for this image.

You can see that there are much more details to the sky and sea than in yours and Teds rendition.
As usually the case in post-processing, it is important to exercise restraint and not to carry the use of filters and tonal adjustments to the extreme in order to maintain a natural look and the atmosphere of the image. Simply expanding the histogram to the maximum wouldn't work here. However, I see that both of you did a good job in that regard and I couldn't have done better without the dehaze tool.

Thanks for the compliment

Your image became a bit noisy in the vignetted area. I don't use LR but wondered whether the de-hazing did it or the sharpening/clarity?

[Timar]

Your image became a bit noisy in the vignetted area. I don't use LR but wondered whether the de-hazing did it or the sharpening/clarity?

The combination of all three. Extracting all this detail from a very limited tonal range inevitably brings up at lot of noise, even if the image has been shot at a low ISO. Any residual vignetting gets amplified for the same reason. Aggressive sharpening of course aggrevates this kind of noise. I guess I should have choosen a higher value for masking, but I normally wouldn't do this kind of heavy processing without having a RAW file with proper lens correction anyway, which would have yielded much better results.

This is the most extreme case of a limited tonal range image I found in my catalogue. There was a lot of mist and snow grains in the air at that day, and one could barely see from one hilltop to the other. Notwithstanding, in some kind of desperate defiance, I took this tele shot (SOOTC, only cropped):



As you can imagine, my first impulse after seing this on the monitor was to hit the delete key. But given that I hardly took any usable photos on this misty day, I decided to take it as a challenge in post-processing instead. This is what finally came out of it:



Noise and vignetting were my greatest enemies in achieving this result. Lightroom's automatic vignetting correction wasn't precise enough for such an extreme case, so I ad to manually correct it. I also had to mask the sky with the adjustment brush as otherwise there would have been an unpleasant amount of noise visible in the sky (the remaining noise in the trees is much less bothering, even enhancing their apparent detail). This was in the days before dehaze, which might have made it a bit easier.