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01-27-2013, 07:41 PM   #1
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Can K5 casue moire?

Can K5 cause moire?

I was playing with my new K5 and I see some "rainbow effect" on my daughter's hair.
This picture was taken with flash on. Is this because of flash light or is it moire?

Thanks

Edit: tried to correct title spelling, but I could not!

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01-27-2013, 07:48 PM   #2
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In this case I think it's because of the light being reflected, but to answer your question, yes, moire is possible with the K-5, though you're probably never going to see it. We were able to provoke it using a test chart when we did the K-5 IIs review, though.

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01-28-2013, 03:28 PM   #3
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Yes I've seen it a few times on suits with fine patterns on the K5.
01-29-2013, 11:19 AM   #4
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I think it's *diffraction* not moiré, whereby the microscopic structure of the hair shafts are acting like micro prisms,
reflecting the light of the flash at different wavelengths giving the rainbow effect.
As in Diffraction Grating: Diffraction grating - Wikipedia, the free encyclopedia
That's my theory and I am sticking to it! ;-)

01-29-2013, 12:48 PM   #5
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I agree. Same physical reason for the colour of many bird feathers such as hummingbird gorgets. Pure feather pigments other than black (melanin) and white are rare.
01-30-2013, 03:04 PM   #6
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With or without AA filter any camera can produce moire, and IMO your case is not moire.
02-05-2013, 06:06 AM   #7
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That isn't moire.

There is also an effect that is common in digital cameras and it is called false colour, it is really common with all cameras (not just ones without AA filters) - it usually occurs when there is an extremely sharp lens that provides detail but there aren't enough pixels to record it properly, so the demosaic algorithm just constructs the image with what information it has at its disposal and sometimes that construction is shall we say, less than accurate.

Another explanation is subsurface scattering, hair is at least partly translucent and light that strikes the surface also travels through it to some extent and in the process it gets scattered - like a tiny prism and the camera will pick up the scattered reflections. The colouration of bird feathers work by the use of Pigmentation or by the use of microscopic structures that create iridescence that are caused by naturally evolved diffraction gratings.
02-06-2013, 08:10 PM   #8
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I do think it is a digital artifact. I don't think that you would ever see that artifact in film. Pixels just don't have the resolution of film. They don't really do a good job on tiny specular highlights. The colors are really there, but the way the image is processed distorts what is actually there a bit. Same sort of thing that causes purple fringe.

02-06-2013, 08:44 PM   #9
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QuoteOriginally posted by gaweidert Quote
I do think it is a digital artifact. I don't think that you would ever see that artifact in film. Pixels just don't have the resolution of film. They don't really do a good job on tiny specular highlights. The colors are really there, but the way the image is processed distorts what is actually there a bit. Same sort of thing that causes purple fringe.
I have seen the kind of purple fringing as shown here (Wikipedia) many times on my K5. One reason may be that this is the highest resolution camera I ever owned (compared to K100D, Canon G2 etc) and I find myself doing a lot of pixel peeping now-a-days :-)
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