Frequency Separation is evil

[Doug Nelson]

I've made no secret of my opinion of frequency separation during the RetouchPRO LIVE shows and here in the forums. I think it's a shortcut, and therefore a compromise. Good for assembly-line retouching of senior portraits maybe, but not so much if you're aiming for the cover of Vogue.

But I pride myself on my open-mindedness, so prove me wrong. Maybe it's not a crutch, I'd love to learn otherwise. Or perhaps you agree, maybe for different reasons. Feel free to chime in as well.

Of course, it's a tool, and like any tool can be effective or abused. I guess my primary objection is that it attracts abuse due to its promise of "ease" and "control". So "evil" in the sense of temptation away from best practices.

And "John Smith uses it and his work is in Vogue all the time" is not acceptable proof. Show me YOUR work and share YOUR experiences.

On a separate yet related subject, I'd love to learn of your examples using frequency separation for other types of retouching.

[skoobey]

Re: Frequency Separation is evil

I don't consider it to be a separation, but a blur and a sharpen.

So, yes you can paint in more precisely in the middle, and that will look super sharp.

And if you paint to replace a highlight with a midtone for example on the low, well you'll need to clone the texture to match. You would have to do the same with DNB. So it's really dealers choice.

[Jaalpari]

Re: Frequency Separation is evil

FS is the worse technique if you want to be a good retoucher.

[skoobey]

Re: Frequency Separation is evil

FS is the worse technique if you want to be a good retoucher.

Anything can be good or bad, it's about the artist, not the tools.

[shift studio]

Re: Frequency Separation is evil

You know, I don't feel like justifying/proving what I'm saying, but I say bullsh!t. Its a technique that I use all the time and it gets me the results I want. Use it to get what you want - why is that a problem?

And I use it in many many situations - not just skin retouching.

--shift studio.

[3pco]

Re: Frequency Separation is evil

I'm new here and an amateur who just discovered fs recently, so I'm not really aware of the debate. I don't do much glamor retouching, mostly restorations and landscape shots of my own. I've used fs on shots of boats, birds, etc., and I like using it to take the noise out of the high layer so I can replace it.

[Flashtones]

Re: Frequency Separation is evil

Doug, properly splitting an image has no visible effect. (Kinda like turning a layer into a smart object and then not touching it.)

If you have a problem with the technique it's in what's done after the split, so how 'bout you explain what that is that you don't like.

(My pet peeve is the way people throw the term FS out there without explaining what they even mean by it, let alone when, where and how they use it. And this applies to proponents and opponents.)

Just hating the tool is like hating any other tool in PS. It's like a person saying "I hate puppet warp". Ok, so they hate puppet warp, probably because they don't know when to use it or what they're doing with with it.

I don't use FS much, but it's come in very handy for some difficult situations, and I really doubt you'd know it was used. If you did then I did it wrong.

[klev]

Re: Frequency Separation is evil

Doug, properly splitting an image has no visible effect. (Kinda like turning a layer into a smart object and then not touching it.)

That's not entirely true. Okay so you start out with whatever level of precision stored at 8 or 16 bits per channel. The bits there are essentially a theoretical maximum and do not issue any kind of guarantee, especially with the overall complexity of color engines. You actually lose quite a bit of precision in signal processing alone, given that the values have to be quantized to some digital precision at the camera level, after which you not only have channel interpolation but a series of several mappings between color spaces before you're even in photoshop.

At that point you still lose information with every adjustment. It doesn't necessarily change at 16 bpc, but the step sizes are narrower. Even if the information is not always more accurate, it can be more aesthetically pleasing if banding does not occur.

The idea behind frequency domains is that if the range of a function is in fact bounded, we can measure how often it repeats itself and depict the two dimensional surface mapping as a sum of two or more of these functions. That is probably a horrible explanation, but it's not one of my stronger areas.

Anyway back to what I was saying, you do in fact have finite precision, and from my perspective you do have the potential for an unstable work space (potential for loss of detail over minor actions) in certain circumstances. 8 bits leaves you with too large of a step size, so I wouldn't suggest that. At 16 you do still have two significant adjustments, and you still have the potential for distinct haloing on both passes. If you go to 32 it will take care of the haloing. You could in theory have a more significant loss if recombining areas where the difference in values is very small, but if its eventual destination is 8 bit output, it's insignificant.

[HarmUdding]

Re: Frequency Separation is evil

Maybe you can show us what is going wrong when using FS?
Harm Udding

[Benny Profane]

Re: Frequency Separation is evil

Well, I'm a pro and use it a lot. So, lets separate (heh) this debate into two camps. Those that produce retouching under deadline for a living in a commercial enterprise, and those that talk about it.

"What's that? You have six model shots you want by next Tuesday. Hmmmm......awful skin. I guess you couldn't afford a better model, as usual, huh? I know, I know, we can always fix it in post. I'll see what I can do. Happy Holidays!"

[shift studio]

Re: Frequency Separation is evil

I want to add that frequency separation may not be appropriate for the cover of Vogue (still debatable), but a lot of work is being done that is not for the cover of Vogue.

I don't consider it to be a separation, but a blur and a sharpen.

If your radius is large, you can also think of FS as edges/texture and colour/shape - even more so if you've done an asymmetric split.
I'm not really talking about faces or skin here, but other things. Working image elements broken down this way can be beneficial.

--shift studio.

[Benny Profane]

Re: Frequency Separation is evil

I want to add that frequency separation may not be appropriate for the cover of Vogue (still debatable), but a lot of work is being done that is not for the cover of Vogue.



--shift studio.

And, of course, the dirty secret of most beauty retouching is that, the better quality of the model (and higher cost), the easier the retouching. There's really not much you have to do to some of those girls unless they were partying for two days before the shoot. Even then......
So, most Vogue covers, after the attention to detail given by the photographer, makeup artist, hair stylist, and others on set, are pretty easy to get right on the back end.

[Flashtones]

Re: Frequency Separation is evil

That's not entirely true. Okay so you start out with whatever level of precision stored at 8 or 16 bits per channel. The bits there are essentially a theoretical maximum and do not issue any kind of guarantee, especially with the overall complexity of color engines. You actually lose quite a bit of precision in signal processing alone, given that the values have to be quantized to some digital precision at the camera level, after which you not only have channel interpolation but a series of several mappings between color spaces before you're even in photoshop.

At that point you still lose information with every adjustment. It doesn't necessarily change at 16 bpc, but the step sizes are narrower. Even if the information is not always more accurate, it can be more aesthetically pleasing if banding does not occur.

The idea behind frequency domains is that if the range of a function is in fact bounded, we can measure how often it repeats itself and depict the two dimensional surface mapping as a sum of two or more of these functions. That is probably a horrible explanation, but it's not one of my stronger areas.

Anyway back to what I was saying, you do in fact have finite precision, and from my perspective you do have the potential for an unstable work space (potential for loss of detail over minor actions) in certain circumstances. 8 bits leaves you with too large of a step size, so I wouldn't suggest that. At 16 you do still have two significant adjustments, and you still have the potential for distinct haloing on both passes. If you go to 32 it will take care of the haloing. You could in theory have a more significant loss if recombining areas where the difference in values is very small, but if its eventual destination is 8 bit output, it's insignificant.

Klev, this is a visual field and I stand by my statement, that you will not see a difference in a properly split image at the moment of the split. Sure, one can screw things up afterward, but that's operator error.

It's like converting a 16bit image to 8bit. You don't see a change at the point of conversion, only if you mishandle it thereafter.

ETA: When I say "seeing it" I mean with the ocular nerve, as opposed to knowing there's an imperceptible mathematical difference.

[3pco]

Re: Frequency Separation is evil

Following this thread with interest, I realize I know very little about FS. All the tutorials I've found online limit themselves to a step-by-step approach, so I know how to do it but not why. Can someone point me to some material that explains what's going on und
er the hood here? Thanks!

[Flashtones]

Re: Frequency Separation is evil

Following this thread with interest, I realize I know very little about FS. All the tutorials I've found online limit themselves to a step-by-step approach, so I know how to do it but not why. Can someone point me to some material that explains what's going on und
er the hood here? Thanks!

http://www.modelmayhem.com/forums/post/439098