[TIPS] Processing sharpening after noise reduction

Orio · Expire: 2012-12-04

I think many of you have experienced this problem with digital cameras: you take a high ISO picture, and want to reduce the noise, because alas, even if the technology has made progresses, the digital noise still looks worse than the film noise.
So you apply the noise reduction as first thing, like it must be done. Then you want to do the sharpening, because all Beyer sensor images need sharpening. But there comes the problem, because when you do sharpen a picture that has been de-noized, you notice those strange artifacts especially on the flat color areas.
The problem is not of easy solution. Yes one could mask out the flat looking areas, but this is not a practical solution.
I think I have found a way to reduce the problem.
First you apply the de-noise, taking take to disable possible sharpening passes that your denoizer may include (Noise Ninja does for instance, this is the program I use).
Then you open the photoshop filter "smart sharpen" (I think it's called this way but I'm not sure, I have Italian Photoshop) and apply a sharpen value to a very small range, usually below 0,5. This will leave most of flat color areas alone and sharpen the edges and higher contrast areas only - those areas where you must notice the sharpness of an image. Apply a SMALL value!!! This is not the final sharpening, unless you plan to print the image full size. If instead you plan to publish to the internet, resize the image now using a plain bicubic method (NOT bicubic sharpen) or even better Genuine Fractals if you have it.
Finally, you apply a light pass of Photoshop's "Unsharp Mask" or of the sharpening plugin you use. Apply lightly, because you already did presharpen with the "smart sharpen" filter!
I find this combination to work well for me to "save" pictures of 400 ISO or higher and give them a little sharpening as well.
This is a picture I took this evening of a flowering Yucca in the city park. I think it is Yucca elephantipes but I am not 100% sure. Anyway, I applied the above processing to it and I am happy with the result:

direct link:
http://img352.imageshack.us/img352/4690/yuccareddz2.jpg

Orio · Expire: 2012-12-04

Oh I was forgetting the specs!
400 ISO EOS 5D Zeiss Planar 1.4/50mm

Attila · Expire: 2025-11-18

Thank you Orio this very useful lesson. Please continue to share your Photoshop knowledge!

Orio · Expire: 2012-12-04

This is a 100% crop detail of the image before and after treatment:

direct link:
http://img365.imageshack.us/img365/9871/denoisesharpbeforeafterem6.jpg

As you can see, I have been able to denoize, then sharpen, but you don't see the artifacts!!

Of course here there is only the smart sharpen pass, not the final sharpen pass because I did not resize image.
In the resized image above, you have also the final sharpening pass applied (very lightly, as I do as little sharpening as possible)

LucisPictor · Expire: 2013-12-03

Very well done, Orio!

I know this process and have used a very similar one several times.

But in your first example picture the sharpening went - in my eyes - a little too far, since we can see the telltale "stairs" at the blades of the plant.
Of course, this is a matter of taste and use.

Carsten

Orio · Expire: 2012-12-04

LucisPictor · Expire: 2013-12-03

Yes, I did download the picture and looked at it using a photo viewer.

If you look at the tips of the blades, you can see little "stairs" at their edges.
It is not bad, but I always try to avoid those.

Carsten

Orio · Expire: 2012-12-04

LucisPictor · Expire: 2013-12-03

That's right. Compression or Sharpening are the main causes for that.

I just mentioned it, because this is the only part we have to be careful when we follow your excellent idea of how to sharpen a picture.

Carsten

P.S.: In the last test my eyes achieved a 120%. Yes, I have good eyes. Wink

Jigt · Joined: 16 Mar 2007 Posts: 412 Location: Belgium

My experience is sharpening is the very last thing you do.

If you sharp a 6mpixel and then rduce the size you will end up with terrible artefarcts.

In stead of setting your iso to 800 you better make a picture in raw at 200 and the make it lighter. works splendid with Pentax photolaboratory.

The best sharpening you get this way.

Set your pic in the modus "lab colour" open the channell toolbox choose the channel that gives the B/W image, do the sharpening and then get the colours back. After sharpening you go back to the RGB modus. Works perfect!!

Guido