note: This lesson will be useful for photo retouchers, who will be dealing with partially overexposed image, where important to see exactly where overexposed areas is. For example, if you need to get completely white background, etc.
Couple years ago we found that a histogram on the camera or different software’s don’t show overexposed areas correctly. Here is why: camera histogram will use JPEG to evaluate, even if you shoot RAW. So, it is inaccurate by definition.
When I’ve tried to find the answer in Internet, I get no luck, there are only tutorials and lessons how to fix this overexposed areas in Photoshop, but nothing about how to find these areas correctly.
So this tutorial about how to find and determine overexposed and underexposed areas using Photoshop.
Look at this image:
Some areas are overexposed here. Let’s check where are these areas:
Create new fill or adjustment layer -> Curves
Than drag the graph from the left lower corner to the right lower corner:
Your image become dark with few white spaces. This white areas are truly overexposed. Meaning you have no color information there (white, no details at all) , and it can’t be recovered.
Similar you can find truly underexposed areas on you image. Look at this image:
Here are plenty dark spaces. Do they underexposed? Yes. Can they be recovered? Let’s check.
Create again new fill or adjustment layer -> Curves.
And drag the graph from the right upper corner to the left upper corner:
What do we see? There are no underexposed areas on this picture. So, now you can create a pseudo HDR (HDR – like look from the one exposure, instead of several) image form it, and everything will look good, with some noise added on dark areas.
Here is another example with underexposed areas:
This black spots are real underexposed. There are no details and color information there, except black. There is no way you can fix such image. (if you find it should be fixed, of course:-)
If you know the better and faster way to find “truly” overexposed and underexposed areas on images, please share with me.
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