Wavelet sharpening?

[TonyW]

There was a passing remark about wavelet sharpening by Donald in a recent post. Since then, I have been doing some Google research and wavelet sharpening seems to offer something worthwhile.

Is there a general view about this? Is it better than Photoshop's smart sharpening? I think I understand how the unsharp mask works, or doesn't work depending on the circumstances, but have no idea about "smart sharpening.

In my professional years, the theory of wavelets passed me by but when I look at the mathematics behind them now they seem to have potential in this application.

Is it possible to get a wavelet plug-in for Photoshop that works on a Mac?

[IzzieK]

I can't answer your question, Tony but it will be nice to know the answer to this...but is it worth having it?

[Black Pearl]

New one on me too.

I suppose the real question should be what issues are you having with sharpening your images now and what have you tried to remedy it. With the experience here I'd wager someone will be able to help get your output files correctly sharpened without the need for an esoteric route.

[John 2]

Looks like it's a GIMP only plug-in and from one of the Google references, seems to work in a similar way to Unsharp mask - but I'm no expert.

[tclune]

Looks like it's a GIMP only plug-in and from one of the Google references, seems to work in a similar way to Unsharp mask - but I'm no expert.

I got the impression that it was more like microcontrast than unsharp masking from what I read. But I may well be wrong.

[Donald]

I got the impression that it was more like microcontrast than unsharp masking from what I read. But I may well be wrong.

It's neither one nor the other and it's a bit of both. The difficulty is in trying to define it in relation to what folk have knowledge of and currently use; i.e. USM, Local Contrast Enhancment (LCE). It's 'different'. But as I wrote elsewhere, I do all output sharpening with it. Before I started using DxO to process RAW files and the NIK suite of software to make my images, I used the Wavelet Sharpening tool for all phases of sharpening (Capture, Creative & Output) ... at different settings of course.

It is a GIMP plug-in.

[dje]

I've never come across this either so it's interesting to hear about it. It almost makes me want to play with Gimp !

The other sharpening tool often talked about is de-convolution sharpening. Some say it's used in Smart Sharpen and ACR/Lightroom sharpening when the Detail slider is set towards the top end but it's difficult to find much definitive information on this from Adobe. It is availble in RawTherapee.

Dave

[Richard Lundberg]

Focus Magic is a deconvolver and motion blur remover. It even has a forensics mode. Reasonable price, easy to use. There's another app somewhat like it I believe, can't remember the name, but Google is your friend.

[tclune]

Focus Magic is a deconvolver and motion blur remover. It even has a forensics mode. Reasonable price, easy to use. There's another app somewhat like it I believe, can't remember the name, but Google is your friend.

Topaz InFocus is another deconvolution sharpener. I have both, but find Focus Magic massively easier to use. OTOH, Topaz is considerably more flexible if you can ever figure out how to control it. FWIW

[Richard Lundberg]

Blurity is a deconvolver also. Its sample images show considerable ringing, possibly due to their FFT process. it costs twice as much as Focus Magic. I agree about Focus Magic ease of use. I have InFocus but have only used it once or twice. Images Plus is another app, and there is something called Sharpen Smarter or whatever that was mentioned in another forum that I can't find right away.

[TonyW]

Richard, can you explain what you mean by ringing?

Deconvolution sharpening is something else I had not heard of before either. With the help of our friend Google, I understand the basic idea of it but I would have thought there are traps in its application. The blurring of the image due to out of focus lens, Bayer filter, etc, is somewhat analogous to a diffusion process and reversing that is like solving a diffusion equation backwards in time, which is unstable and not guaranteed a solution.

[revi]

Ringing is an artifact after Fourier transformation caused by sharp edges in the original data. In short: Fourier transformation tries to describe the data as the sum of sine and cosine functions. Sharp edges cannot be described this way with a finite number of such functions, so we get artifacts.

See http://en.wikipedia.org/wiki/Ringing_artifacts for a more in-depth description.

One disadvantage of deconvolution sharpening (and I guess with wavelet sharpening) is the amount of computation involved, which makes those techniques slow relative to USM. But they can (at least in theory) increase the amount of detail in the image, which USM cannot do.

Images can look a bit soft after deconvolution sharpening and similar, as those techniques do not increase the edge contrast (contrary to USM).

[TonyW]

Thanks for that, Remco. I understand about Fourier series/transforms - I just did not know this terminology.

When you look at the effect of USM sharpening in detail, i.e. by pixel peeping, you see that for with small radius there is something like genuine sharpening but with larger radiuses, there are artefacts that give an illusion of sharpening but do not produce what I would call genuine sharpening.

[dje]

Hi Tony

I've been fiddling with the Slanted Edge method of measuring sharpness in recent times. These plots from a test image may be of interest. They show the effects of various levels of sharpening in ACR. The labels such as ACR 100/0.5/25/20 refer to the ACR settings Amount, Radius, Detail and Masking respectively. This is not Unsharp Mask but the results give a feel for what sharpening actually does to an edge. You can see how increasing Amount and Radius increase overshoot and ringing.

I used to sharpen a lot of my landscapes with a radius of 4 but over time I've come to the view that radii around the 0.7 to 1 are better to get cleaner sharpening. Higher radii can give more "pop" but this is doing more than just sharpening edges and, as you say, can give some undesirable effects.

Dave