Is this Moire?

Started Feb 27, 2013 | Discussions thread
boardsy
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Re: Is this Moire?
In reply to Jokica, Feb 28, 2013

Jokica wrote:

Thank you all for clarify that to me!

To be clear: subject I was shooting has no such thing visible by naked eye. And to prove it, I shoot different subject. (Picture below). If this phenomenon is related to lens sharpness, can it be used fort testing purpose, i.e. if the lens is more prone to moire that other, can I conclude that it is sharper?

Regards

Test subject

100% crop

Moire is produced by a pattern resolved/focused at a finer level than the sensor's pixel pattern (above its Nyquist frequency to be technical). Your example is possibly moire, only if you are sure the pattern isn't "really" there - and some pattern must be there to produce moire in the first place! The lens/sensor may be more sensitive to a print pattern or texture than the naked eye. I'm not sure what your test shot above demonstrates?

This is a more common moire pattern:



On her jeans over the back pocket you  see false colour moire - the denim weave  focused by the lens (Minolta MC Rokkor PG 50/1.4) is resolved at a closer/higher-frequency level than the pixels of the sensor, thereby confusing it to render false colours that aren't really there. So I can conclude that the lens resolving  more detail than the sensor can handle.

NB the same thing happens in digital audio where false frequencies are generated - I happened to heard this yesterday on the radio, in Will.I.Am featuring Britney Spears' "Scream and Shout" - the synth riff where he sings "Aw yeah" has been down-sampled with the result that its higher-frequency components have given way to a high-frequency fuzzy "noise" along with the "real" notes - the audio analogue of the moire patterns above. NB I do not endorse Will.I.Am or Britney, b*tch!

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