question about frequency separation method

[Caravaggio]

I like the frequency separation technique and am starting to use it and get more familiar with it. The only problem I have is where areas of extremely strong contrast meet or "edges". If I clone over those areas on the high frequency layer, it introduces a tonal change into the image when all I wanted was the texture because some of the tonal and color information is also stored on that layer. Generally I just avoid those areas as it creates a mess and do them separately on another layer above the split that doesn't have a frequency separation. I have tried sampling a color and painting it in on the low frequency area in the problematic areas, but that doesn't seem to give me good results and often makes it worse.

Does anyone have any advice or suggestions for dealing with areas of high contrast on a frequency separated image?

[mistermonday]

Re: question about frequency separation method

Caravaggio, try posting a sample of that specific area. It may be that you need to chose a different separation radius. In fact in most retouches, a single separation radius is not suitable to do the entire image. Also depending on the image, you may want to use an asymetric frequency separation where the color is completely separated on the LF layer and the HF layer has texture but absolutely no color.
Regards, Murray

[Caravaggio]

Re: question about frequency separation method

Here is an area that would cause problems because of the change from the pink object to the blue wall and the shifts in tonal value. The original is a very high res, 16 bit image.

I don't know how to do an asymetric frequency separation. Can you point me in the right direction? Thanks.

[mistermonday]

Re: question about frequency separation method

To make a frequency separation in which the color is completely separated from the HF layer as well, do the following:
- Create 3 copies of layer to be separated and name them LowFreq, Color, HighFreq (bottom to top).
- To the bottom copy (LF), desaturate the layer (Image>Adj>Desat or Crtl+Shift+U), and then immediately go Edit > Fade Desaturation and change the Blend Mode from Normal to Hue.
- Next to this same layer apply the Gaussian Blur as you normally would.
- Now select the top layer (HF). Change blend mode to Linear Light. Once again, Desaturate the layer and Edit > Fade Deasaturation and change the Blend Mode to Hue.
- Next do Image > Apply Image using the LF layer as the source as the source just as you do in a normal freq separation.
- Finally, select the middle copy (Color) Layer and change its blend mode to Color and hit Ctrl+E to merge it down onto the LF layer.
Your separation is now complete.
You can experiment by sampling texture with the healing brush and stamoing it on another area. You will heal with texture only. You still need to choose your Radius of separation wisely because you can still make a mess if you are not careful.
Regards, Murray

[chillin]

Re: question about frequency separation method

Could you be more specific as to what you intend to do with the posted sample?

[Caravaggio]

Re: question about frequency separation method

Could you be more specific as to what you intend to do with the posted sample?

Its part of a product shop, more or less already finished. I just posted it because it seemed to be a good illustration of the type of area I was having trouble with using frequency separation, areas where there is a sudden large shift in either color or luminosity or both.

Murray, I am liking the asymetric separation. Thanks a lot for the detailed explanation. I am playing around with it now and getting better results although sometimes it doesn't always work right so I assume I am not always choosing the right radius.

[Aladdin]

Re: question about frequency separation method

What radius you guys talking about, the Gaussian blur?

[Caravaggio]

Re: question about frequency separation method

What radius you guys talking about, the Gaussian blur?

Yes, the gaussian blur radius.

[ashphotoart]

Re: question about frequency separation method

Murray, its very helpful post from you. nice technique to sepereate the colors from textrure. Even if we use small radius in standard seperation, some color (little) remains on HF Layer. now its very neat processing of texture with Asymetric Seperation.

[Der_W]

Re: question about frequency separation method

Just to make sure I'm getting the problem right: when you're doing a Gaussian blur based separation to fix problem areas in your image, once you work on areas of high contrast, you run into problems?

The first thing I'd try then would be to use something different from Gaussian blur to create the separation.
E.g. the "Filter"-"Noise"-"Median" preserves (especially round) edges pretty well. Or you could try the "Filter"-"Blur"-"Surface Blur". Possibilities are nearly endless :-)!

But if the asymmetric separation works, that's great as well, I just thought this could give you even more flexibility :-).

[Caravaggio]

Re: question about frequency separation method

Just to make sure I'm getting the problem right: when you're doing a Gaussian blur based separation to fix problem areas in your image, once you work on areas of high contrast, you run into problems?

The first thing I'd try then would be to use something different from Gaussian blur to create the separation.
E.g. the "Filter"-"Noise"-"Median" preserves (especially round) edges pretty well. Or you could try the "Filter"-"Blur"-"Surface Blur". Possibilities are nearly endless :-)!

But if the asymmetric separation works, that's great as well, I just thought this could give you even more flexibility :-).

Yes, Jonas. I was finding that gaussian blur spread the color and luminosity too much on the low frequency layer in areas where there is a strong sudden shift in color and or luminosity. Imagine for example an image of a red apple set against a blue background. A normal, non-asymmetrical split is applied. If you clone on the high frequency layer in the area where the wall meets the apple, the cloning will not look good because both the wall and apple colors are contaminated by each other.

I will try your suggestions to use surface blur or median filter. Thanks.

[JoeFotosiamo]

Re: question about frequency separation method

Yes, Jonas. I was finding that gaussian blur spread the color and luminosity too much on the low frequency layer in areas where there is a strong sudden shift in color and or luminosity. Imagine for example an image of a red apple set against a blue background. A normal, non-asymmetrical split is applied. If you clone on the high frequency layer in the area where the wall meets the apple, the cloning will not look good because both the wall and apple colors are contaminated by each other.

I will try your suggestions to use surface blur or median filter. Thanks.

I totally agree with the problem with Gaussian Blur in the low frequency layer. I've switched to Dust and Scratches under the Noise filter for a cleaner low freq layer. It takes a lot less time than Surface Blur to render also.

I'll have to test out the difference between dust and scratches vs surface blur vs median filter, though

[JoeFotosiamo]

Re: question about frequency separation method

Just love this technique! I do find that having a totally HF layer without color contamination easier to work with.

I don't use Gaussian Blur on the LF layer anymore because of the smearing effect. Dust and Scratches under Noise seems to be better. Will have to experiment with Median filter and Surface Blur, though.

To make a frequency separation in which the color is completely separated from the HF layer as well, do the following:
- Create 3 copies of layer to be separated and name them LowFreq, Color, HighFreq (bottom to top).
- To the bottom copy (LF), desaturate the layer (Image>Adj>Desat or Crtl+Shift+U), and then immediately go Edit > Fade Desaturation and change the Blend Mode from Normal to Hue.
- Next to this same layer apply the Gaussian Blur as you normally would.
- Now select the top layer (HF). Change blend mode to Linear Light. Once again, Desaturate the layer and Edit > Fade Deasaturation and change the Blend Mode to Hue.
- Next do Image > Apply Image using the LF layer as the source as the source just as you do in a normal freq separation.
- Finally, select the middle copy (Color) Layer and change its blend mode to Color and hit Ctrl+E to merge it down onto the LF layer.
Your separation is now complete.
You can experiment by sampling texture with the healing brush and stamoing it on another area. You will heal with texture only. You still need to choose your Radius of separation wisely because you can still make a mess if you are not careful.
Regards, Murray