Photoshop idea: Subtract shaded version of a subject to simulate the sun-as-spotlight

Here’s an idea for exploring all of the lighting possibilities for a big object even when you don’t have any control over the “natural light.” (Thanks, Andrea Matranga.)

I’m kind of shocked at how well this works.

Readers: What do you think of the technique?

4 Comments

  1. lvl

    September 2, 2015 @ 1:57 pm

    1

    Very creative. I don’t have Photoshop anymore (LR only now) but I wonder how this would work when you can’t get the completely diffuse shot with total cloud cover. What happens if you use just a moderately more boring shot to subtract from/blend with semi-boring? Would it be somewhat akin to a polarizing filter?

  2. J. Peterson

    September 2, 2015 @ 4:26 pm

    2

    I like how she just assumes the clouds will cooperate before the sun moves significantly in order to get the diffuse image sample.

    If the clouds aren’t cooperating, another approach is to take a set of HDR photos, and use the tone-mapping controls to get a more dramatic result.

  3. Andrea Matranga

    September 3, 2015 @ 12:32 am

    3

    Hi, I’m the guy (yes, guy…. think Andrea Bocelli, Andrea Pirlo… ) who sent Phil the tip.
    LVL: in principle you don’t need perfectly diffuse lighting, it should work just as well with a light overcast. In practice, if the light isn’t different enough, the subtraction will result in a very dark image. Of course you can then apply curves to space out the histogram, but then you multiply noise. I think if you used RAW, really low ISO, or image stacking you could still get enough bits to play around with, but still trickier.

    I don’t assume the clouds will cooperate. You can usually get a good sense of what clouds will do by looking at them, so if there’s a solid overcast or no cloud in sight, no need to bother. In any case, you don’t need the sun to be in the same place for the overcast shot, the clouds scatter the light like a huge softbox ( I think my overcast shot was taken four or five hours after the direct sunlit shot).

    Thanks for the comments!

  4. jack crossfire

    September 5, 2015 @ 2:29 pm

    4

    It works because the change in lighting of the foreground is greater than the change in lighting of the sky. If the sky is blown out in 2 exposures of differing foreground light, it’ll appear completely black with only the foreground visible. If clouds in the sky move around, the foreground will sometimes be in shadow & sometimes in light while the sky will be relatively unchanged. A similar effect might be possible by photographing a nearby object with & without a flash, then shifting the white level of 1 image to make just enough difference in the sky to keep it from going black.

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