how to sharpen the Quattro files without causing noise

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mike earussi
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how to sharpen the Quattro files without causing noise
2 months ago

My thanks to Rick for providing me these raw files to work with.

As I mentioned to Rick earlier, a lot of the problems we've been having with properly evaluating the Quattro I find have been caused by Sigma's bad defaults in SPP. The first thing most of us discovered was that NR should be set to 0. Unfortunately, this had the side effect of increasing noise (the fine "sand" look) throughout the picture. This I found could also be eliminated by setting the sharpening slider to-2. But now, of course, the sharpening had to be applied in PS instead. But as PS allows for more fine control, that really isn't much of a problem.

But even with judicious sharpening there was still some residual sky noise left, so I asked Rick if he would mind shooting a series of four shots on a tripod of the same scene for a noise stacking experiment (along with a Merrill control shot). Stacking these four images did, not surprisingly, have the desired effect, allowing for even more aggressive sharpening without any noticeable increase in sky noise. Now, of course this technique doesn't work well if anything in the scene is moving, but for studio still life and many landscape shots this does help.

Here is the comparison:

I tried to match the color and contrast of the M to the Q as much as I could. The M has also been enlarged to match the Q.

and if you download this and enlarge you'll notice an even bigger difference. So this is definitely a technique I'd recommend to someone wishing to print beyond 100%.

(I also discovered that the magenta blotchiness in the sky was originating in the Green channel, but I don't know how to get rid of it yet, though the 4x stacking did cut it down.)

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