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Benefits of frequency separation?

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  #1  
Old 12-25-2011, 04:40 AM
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Der_W Der_W is offline
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Benefits of frequency separation?

In another thread RetouchPRO Member kav said, he could do everything that FS enables you to do in a more simple manner and with a smaller file size.

Since this forum is all about learning from each other, I thought why not give this a try and see how different methods compare and also try to lay out potential pitfalls, pros and cons of them :-).

For my first test image I'd like to split some hair.
Since many retouchers don't like retouching hair, I thought it might be a good idea to test the possible benefits of FS and maybe find a better approach here.
The image I used to do this test is this one here by the photographer Grant Thomas: http://dl.dropbox.com/u/7124285/Fore...omas%20PRE.jpg
And here's what I came up with after maybe 0.5h (for the split I used a combination of Median 7px and Gaussian Blur 6px): http://dl.dropbox.com/u/7124285/Fore...homas%20FS.jpg
If you want to see the PSD file, you can download it here: http://dl.dropbox.com/u/7124285/Fore...t%20Thomas.psd (I mainly worked with the clone stamp/spot healing brush on the high frequency layer though, so I doubt it'd be very interesting)

The benefits that I've encountered during the work were that I didn't need to watch out for tonal transitions, but only for the hair detail. This is a huge benefit for me because this way I can work more freely and don't have to double-check all my brushwork.
I also noticed, that some of the really tiny stray hairs can be easily removed by using the Spot Healing Brush in "Content Aware" mode on the high frequency layer only, so this way I didn't even have to sample a new area.
To retouch the back of the hair I first copied a large area of low frequency detail, pasted and rotated it into place.
Next it was a piece of cake to clone some new stray hairs over this area. Again, no need to match tonal transitions because I already did this on my low pass layer.

Now for the cons. Obviously the file size doubled because I now have two layers to work with. Also near edges you have to be careful not to create any smudging, even when using the clone stamp. To avoid this, you'll have to work along the edges and not towards them.
Also you have to make sure that you're sampling the current layer only, otherwise it'll look really crappy.
Apart from that I haven't noticed any disadvantages, but I might be biased as I use this technique on a regular basis.


Now of course it'd be nice if some of you could come up with other examples of how and when FS works better/worse than other methods for you in you retouching workflow .
Hopefully this thread will be a great source of information and inspiration to everyone .

Edit: Techniques I previously tried were cloning in "Darken" mode on a new layer (set to "Darken" mode as well) and sometimes even smudging hair (only works well with low quality originals).

Edit #2: I was just thinking. I don't know if it really helps to know how long it took me to get to the results you see here, since everybody has a different working speed, so you might be faster with your approach while I would take longer with the same approach.
Maybe we should just exchange some methods and let everyone decide for themselves which one to use and where the disadvantages are bigger than the advantages?

Last edited by Der_W; 12-25-2011 at 06:02 AM.
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Old 12-25-2011, 03:38 PM
kav kav is offline
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Re: Benefits of frequency separation?

Give me a day or two. I have to run out today and only came on here to mention that.
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Old 12-26-2011, 09:19 AM
KTG KTG is offline
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Re: Benefits of frequency separation?

Jonas,
Would you mind explaining further your choice of both Median and Gaussian Blur filter for the split? And why did you choose 7 and 6 pixels respectively?

I use this method for hairs also, but I notice that sometimes I have to go over the low freq layer also. Would asymetric split be preferred for this?

k
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Old 12-26-2011, 09:56 AM
Caravaggio Caravaggio is offline
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Re: Benefits of frequency separation?

I like using frequency separation but have noticed a tendency for it to introduce banding on areas that are flat and have very smooth transitions like architectural walls. The banding is more extreme in files that are only 8 bits, but still present in 16 bit files as well.

I am generally doing the separation with a low gaussian blur (of about 3) on the LF layer partly to try to minimize the amount of banding introduced. The more times I do a frequency separation on the same file, the worse the banding problem becomes. When the banding is present, it is visible on the low frequency layer when the high frequency layer is turned off.

For me then frequency separation becomes a trade off between the ease of cloning on the separated layers and having to fix the banding that is introduced.
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Old 12-26-2011, 02:29 PM
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Der_W Der_W is offline
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Re: Benefits of frequency separation?

I used a combination of Median and Gaussian blur in order to preserve the edges a little better than I could with Gaussian blur alone. The Median filter was used to get rid of most hair detail, the remaining detail was then blurred away with the Gaussian blur. Gaussian blur alone sometimes results in too soft edges and is therefore harder to work with.
The asymmetric split has nothing to do with working on the low pass or high pass, it's just used to preserve all the unblurred color detail on the low pass layer, so if you intend to work on it and use the asymmetric method, you might end up with color bleeding depending on what you do to it.

I actually never had the problem with banding although I've heard quite a few people are having trouble with this.
However I use one split for the whole image, if necessary I'll just blur different areas differently, that way I keep my file size small and don't get into too much problems.
Banding on the low pass however might be pretty standard depending on the level of blur you used for your initial split. However the high pass should help there (working on the low pass in those areas will probably make things worse though, good hint!).
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Old 12-26-2011, 03:36 PM
Caravaggio Caravaggio is offline
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Re: Benefits of frequency separation?

The banding is mild but I notice it and for that reason as you suggested, I try not to blur too much when making the separation and minimize the number of splits that are done on one file.

I often am able to fix the banding by painting it out. I turn off the high frequency layer and paint on a separate blank layer in between the high and the low. I don't paint directly on the low frequency layer incase I mess up.
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Old 01-08-2012, 03:22 AM
HarmUdding HarmUdding is offline
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Re: Benefits of frequency separation?

KAV,
You wrote: "Give me a day or two..."
I would like to see your results.

Harm
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Old 01-08-2012, 05:52 AM
skoobey skoobey is offline
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Newbie Re: Benefits of frequency separation?

It is much faster, yet I can still see ghosting on most of the hairs you healed(of course it wouldn't be so noticable if i steped away or zoomed out).

Overall, given the amount of time, I think you've got a pretty decent results, yet I would avoid doing things this way as part of a regular work flow, as it is neither accurate enough not fast enough.

I do have a question about cloning in darken mode, or cloning in general.

What I do is set up a new empty layer just for the hair cloning, and then clone in darken and lighten mode (ALt+shift+G Alt+shift+K to switch between the modes, not that when you use those shortcuts with selection tools you actually change the blending mode of the layer, not the effect).

The downside to this way of doing things i s that I get A LOT of repeted patern, so I zig-zag my way trying to get it to be less noticable.

ANY ADVICE ON THE PLACEMENT OF THE BRUSH WHEN SAMPLING AND/OR CLONING IN THE HAIR?

Many say that doing the upper half, and then the bottom half of the hair strand is the right approach, yet it's given me much trouble in practise, as I get two repeated patterns, as opposed to only one when zig-zaging.
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Old 01-08-2012, 08:12 AM
kav kav is offline
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Re: Benefits of frequency separation?

Quote:
Originally Posted by HarmUdding View Post
KAV,
You wrote: "Give me a day or two..."
I would like to see your results.

Harm
I've been bogged down with other things. I just need to open it up and do the damn thing. The one posted from that technique had trails left which aggravates me, but it's literally just going to be rebuilding whatever I can, then shading the result to match, and cloning once I get to the smallest parts. It's pretty simple, and done correctly you don't see trails.
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Old 01-08-2012, 03:48 PM
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Der_W Der_W is offline
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Re: Benefits of frequency separation?

skooby, kav, you're both right, there's a lot of ghosting on that retouch, looks like I did a pretty sloppy job there :-).
I'm looking forward to seeing what you come up to, kav, please don't feel like you need to rush anything. This thread is for learning purposes and although you specifically said you would show us a better technique, there's no reason why anybody else shouldn't jump in and show us there way if they feel it's better or give another example of what they like about FS, which maybe again can be improved so at the end we're left with some really great methods of retouching.
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