Re: sensors, megapixels and such part 3

Started 1 month ago | Questions thread
Mark Scott Abeln
Mark Scott Abeln Forum Pro • Posts: 15,307
Re: Sharpening...

Macro guy wrote:

So, it seems to me that there's no set formula per se.

Well, there is a logical basis for sharpening, and that's the scene you are photographing. Your camera, lens, and processing all soften the image to some degree, and I suppose you can compare the two and correct accordingly. For example, you could photograph targets with known properties, and use that to profile your camera and lens, and adjust your processing to correct for it as much as possible, or desirable.

As D Cox mentioned, some subjects don't do so well with sharpening, and so even if we develop an optimal sharpening baseline, very likely it will have to be tunable by amount, decreasing it as needed.

Sharpening is usually thought of as a process which adds perceptible sharpness to the very smallest level of detail, or equivalently, the highest frequencies in the image, and this is directly due to softening due to low megapixels, Bayer demosaicing, downsampling, and other processing. But lenses typically have poor response to high frequencies as well.  But in actuality, all frequencies are typically softened by lenses and so multifrequency boosts are desirable. This is the trend in software: Adobe's Texture, Clarity, and Dehaze features, which are all fairly recent, seem to boost middle and low frequencies. RawTherapee has a multifrequency sharpness adjustment, and Photoshop users doing portrait retouching have used frequency separation for years for smoothing skin without harming fine details.

The traditional solution to the sharpening problem is to use a lens with as high of an MTF curve as possible. Lenses that are typically considered sharp deliver good contrast at low and middle frequencies, and all that is needed is slight sharpening at the highest frequencies if you like to pixel-peep.

It's whatever looks sharp is fine as long as there are no artifacts scene at a given resolution/viewing distance print or monitor. Do I have that down?

Pretty much, I think. Often it helps to make an adjustment and not evaluate it right away. Often I find that I have to cut the sharpness amount in half

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