Quick Sharpening Question

[rickp1]

Hey guys,
quick question on sharpening and noise reduction. When you guys start your PPing do you sharpen your image first then reduce noise or the other way around? And also, do you run both unsharp mask and High pass of just one method?

R.

[OsmosisStudios]

Ive never actually done any serious noise removal. On occasion i'll try to dial it back in my RAW workflow, but other than that, it stays. I try to avoid it at all costs.

As for sharpening, that comes last, usually. I use the high pass filter for my sharpening, and it works very well.

[rickp1]

another point i forgot. The reason for the question is that sometimes after I apply the sharpening, the process generates a bit of noise. Is that normal or am I over doing something?

R.

[vsa]

I reduce noise before sharpening. Always.
Unless I want it to really exaggerate the noise then I'll add it after sharpening probably.

And usually just one type of sharpening is enough. Normally I use a sharpen filter that came with Topaz Vivacity but smart sharpen is probably equally good.

Sharpening shouldn't generate noise but if you have noise in the picture it will bring that out a bit. Also if you go overboard with the whole sharpen thing then you get halos around the places with most contrast.

[velvet4269]

Sounds like you're over-sharpening. I'm using CS4, and I do my noise reduction (color & luminence sliders) before doing anything with the other sliders - of course, that was also at the instruction of the "CS4 for Dummies" book.

The only other thing I can suggest is that you make sure you're zoomed in 100% (or larger) when you apply your sharpening. Also, if you hold the alt-key down when you click the sliders, it'll show you a greyscale image of what you're doing.

[OsmosisStudios]

Originally Posted by rickp1

another point i forgot. The reason for the question is that sometimes after I apply the sharpening, the process generates a bit of noise. Is that normal or am I over doing something?

R.

Sharpening in post is very simple: it accentuates the difference between 2 different coloured pixels. So if you have any kind of variation, it will be accentuated.

So even if you have one pixel that is (150, 100, 200) surrounded by (151, 99, 201) then you'll get some kind of accentuation between the two colours. When you're not examining the photos at a pixel level, it'll appear to be noise.

But it's not. And you'll never get rid of that.

[LeeR]

Originally Posted by rickp1

another point i forgot. The reason for the question is that sometimes after I apply the sharpening, the process generates a bit of noise. Is that normal or am I over doing something?

R.

You are right; sharpening can accentuate noise or even produce noise where there wasn't any if you aren't careful but I have a couple of suggestions that may help. First, if noise is a consideration use the High Pass filter, it tends to be a bit softer and tends to effect the edges primarily. (For this reason it is also the sharpening of choice for portraits.) USM is old technology and you would be better off using High Pass or Smart Sharpen but you shouldn't need both at the same time.
The rule of thumb is that you always do sharpening last. I usually try to get all my noise reduction done and then use sharpening to bring back some of the detail lost in noise process. Another thing you can do to avoid creating noise is apply sharpening selectively to the edges only. There are several techniques for doing this; the easiest is in ACR, but there are some tutorials on other techniques for doing the same thing in PS or GIMP on YouTube. Here is one I have used with success. By using the edge mask you can apply a great deal more sharpening where you want it without creating noise in broad flat areas where you don't want it. The technique is a bit cumbersome but the advantages of being able to have razor sharpness where you want it and smooth-as-silk gradients where you don't is well worth the effort.

[milosh]

As said, sharpening can easily accentuate noise if you have noise and you're not careful. Sharpening increases local contrast on edges and so can increase the contrast between normal pixels and noise pixels, making them more visible. In unsharp mask, you should pay attention to treshhold slider, along with the other two. If you want to read and learn in depth about sharpening, then read this: Sharpening in Photoshop -- Part I - Ron Bigelow
But I'm warning you, it is really detailed, there are 6 full pages on various sharpening techniques.

[LeeR]

Originally Posted by milosh

As said, sharpening can easily accentuate noise if you have noise and you're not careful. Sharpening increases local contrast on edges and so can increase the contrast between normal pixels and noise pixels, making them more visible. In unsharp mask, you should pay attention to treshhold slider, along with the other two. If you want to read and learn in depth about sharpening, then read this: Sharpening in Photoshop -- Part I - Ron Bigelow
But I'm warning you, it is really detailed, there are 6 full pages on various sharpening techniques.

Thanks for the great link on sharpening; one of the best explanations I have ever read. While I agree that it goes into a lot more depth than most people will want, the first page on why sharpening is needed should be required reading for all.

[milosh]

Originally Posted by LeeR

Thanks for the great link on sharpening; one of the best explanations I have ever read. While I agree that it goes into a lot more depth than most people will want, the first page on why sharpening is needed should be required reading for all.

You're welcome, I'm glad you like it. If you look at his other tutorials, aka articles, you'll find that almost all of them are detailed and extensive as the one on sharpening. Even the ones which are not about post-processing. I've read all of them.