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I took the linked photo of a dime with a D5100 and a reversed lens combination lit by a table lamp. It is at 100 ISO where the D5100 shows no chroma noise. The burnished metal surface shows a weird effect that I think is like CA. However, I'm trying to decide if this is CA or some kind of effect from the irregularities in the burnished surface itself.

One Dime (2)

  • What is the goal of your question? If people here would tell you that it's CA, would you attempt to remove the effect? Maybe I'm not understanding your question correctly, but I think as long as the shot looks good in your opinion you should not worry if the effect is CA or some sort of reflection. – Saaru Lindestøkke Nov 11 '13 at 23:03
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    Hi, my intent is to understand the phenomenon. Also, practically, understanding the phenomenon better will lead me to understanding if I can improve the shot. If it is indeed due to the light as Frank suggests, I will try changing the angle of the light. If it is CA, it would suggest that this is a limitation of a setup using a reversed lens. I plan to test this both by changing the light as well as changing the subject. Thanks. – Kaushik Ghose Nov 11 '13 at 23:43
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The linked image to me looks like what one would see when putting a coin under a microscope and illuminating from a low angle from the side.

So, no chromatic aberration in my humble opinion.

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  • Ah, interesting. Would you hazard a guess as to the effect? Some kind of interference fringing, like from a soap film? – Kaushik Ghose Nov 11 '13 at 15:34
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    Maybe. The surface is quite rough on this scale and so the light hits the surface at all kinds of angles, may be even reflected more than once until it enters the lens. I can also imagine dust grains, or a thin film of grease (left by lust touching the coin with bare fingers) could add to the effect. – Frank Nov 11 '13 at 16:45
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    Burnished metal surfaces = anisotropic shading (or lighting) for which you can google and get representative images, and those will sometimes show rainbow diffraction patterns vaguely similar to what you're seeing. – Patrick Hughes Nov 12 '13 at 3:39
  • Thanks guys. I tried with a piece of printed paper and I can resolve individual ink specks on the rough fabric of the paper with no chromatic aberration. – Kaushik Ghose Nov 12 '13 at 5:32

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