Moiré disaster on the E-5

Started Jul 10, 2013 | Discussions thread
Airmel
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This is normal behavior
In reply to Barry Stewart, Jul 11, 2013

Barry Stewart wrote:

Stacey_K wrote:

OK try this.

I opened the original in CS2 at 100% I see nothing, at 33% I see the issue. If I bicubic downsample to 33% of the original size, it's not there either. This is a problem with soft previewing, not final image downsampling or the image itself.

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Stacey

Stacey, I'm coming to appreciate what you're saying... though I could make the grain show up at a variety of (de)magnifications from 100%.

My worry was that what I was seeing would turn up for my friend when he went to put his image on the company website — or even before that, when he was choosing which pose to use.

Surely he could/would see the same problem, if I sent shots via e-mail for him to preview. No?

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Barry

Barry,

As has been mentioned by several others, your original photo does not appear to contain a significant amount of aliasing artifacts (which are the actual cause of visible moire). Your photo does contain somewhat higher frequency content that you would see shooting something other than fabrics, but there is nothing wrong with this.

The aliasing artifacts which you find disturbing are created by sampling (downsizing) your photo without appropriate anti-aliasing first. The sampling theorem requires that inappropriate high frequency content be removed before the sampling act occurs in order that alias artifacts not be produced by the sampling process.

This effect is occurring post E-5 and has nothing to do with your camera. It is all about the viewing feature in your PC, iPad, Software, Dpreview web site, etc. When you make a change in viewing size, obviously your software must re-sample the photo, but in many cases it won't bother to anti-alias the data first because this takes time and CPU cycles.

On the other hand, when you re-sample your photo to a smaller permanent size (using Photoshop for example), the photo will certainly be anti-aliased before re-sampling and these disturbing artifacts won't be produced.

In short, don't assume that view resizing is the same as re-sampling to a smaller permanent file. These are often very different processes.

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AirMel

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