Calculations???

[Mike Kalcevic]

Unless I'm off base, I remember reading somewhere about using the Calculations command when retouching skin, but I can't really find any good explanation as to how and why...

Anyone feel like giving me the 10 cent tour on this, or at least point me in a direction to good tutorials on using Calculations for skin retouching??

[Daviskw]

Hi Mike...I'm sure Chris will be alone soon with some much better advice. I often use apply image when making masks. Calculations does essentially the same thing except it saves you steps by allowing you to use two channels and output the result to a third channel.

Dan Margulis often uses and explains calculations in his books.

Butch

[cricket1961]

Hey Mike

Calculations would be a bit difficult to use for retouching skin. It would be a blending of different channels to even out blemishes and then incorporate that into the existing channel/s. For someone not familiar with Calculations it can be time consuming figuring out the best combo's and blend mode to use.

But it could be done. : )

But a 10¢ tour would be a bit short on providing the answers you are looking for. It really depends a lot on the skin coloring, brown, white, tan, etc. And then fixing shadows etc would involve a bit more.

In PS David, it went like this:

calculations - to apply image - to channel mixer.

experience to newbie (not necessarily powerwise, just familiarity)

Chris

[Mike Kalcevic]

Thanks Chris,

Do you have any book recommendations that I can check out to learn this better?

[cricket1961]

There hasn't really been any improvement on the offerings in that area since ChoPs. Kelby put out a lower level book that might help you out, and I believe Katrin's masking book might delve into it a bit. I haven't had the ambition to do it.

Check out Margulis's books. Just keep an open mind and take what you need from them.

Chris

[vapour]

Is ChoPs how you learned Chris or did you learn by trial and error?

[smak]

I thought the invention of layers made a lot of the Chops book obsolete.

[cricket1961]

I do have the ChoPs book, but I only got it because I admired Bert Monroy's work very much and wanted his autograph. That was a LONG time ago. When he signed I told him I was going to be doing a book on calculations also. He just had this look in his eyes. I should have noticed it more and strayed away altogether.

I am self taught with the use of Calculations and Apply image. I actually learned Apply first and then discovered Calculations by accident. Back then it had another blend mode that was magic for compositing.

And still learning. I have not done it in years except for advise to Katrin but am now starting to dive into it for a second dvd.

Chris

[Markzebra]

Still got a lot to learn about that area. Seem to remember the CHoPs book floating around in a studio I once worked, and dipping into it, should have borrowed it I guess. Apart from masking what I do use calculations for is to create a good Luminosity channel, where digital noise is a factor, and its been extremely successful.

Its probably true to say that layers have made these channel operations less necessary- by this I mean the use of layer blending where its possible to switch channels off and use opacity and blend modes, can accomplish much of the same thing. Knowing how to extract channels from this is of course still important.

I've been asking them for years to improve calculations and apply dialogs - at one point I asked for dynamic layer masks, where the mask or channel would update on the fly. I see now in CS4 they have now implemented this, beginning with Color Range (always my first tool for channel based selections anyway) - so its looking that in some future version the whole business of channel ops might become more "discoverable"

[cricket1961]

Mark

Certainly a bunch can be done in layers and blend modes combined with turning channels off and blend if. It is almost the same but I still cannot combine two channels through a third to achieve what I might need to be done.
Fixing the digital noise is a cool way of using Calculations. Love to hear how you go about it.
Unfortunately, I don't think that the calculations or apply image are going to change anytime in the near future. Like you I have been asking for man, well over a decade to get these updated. I've put in a feature request on every build since version 3 and it has gotten nowhere. Not that I expect them to jump just because I asked. But a LOT more high profile people than I am have been asking since the mid-90's for an upgrade to no avail. They're not a consumer/prosumer tool and are rarely if ever tweaked. As a matter of fact I have to go report a bug with calculations when I am done viewing this board.

They did do a pretty good overhaul of Color Range and you get MUCH better masks with it.
It is not quite as dynamic as I think you might be thinking, but it is possible to change an existing layer mask with it. I'll dig up a quick tutorial on it that I posted on the Beta board and stick it up here when CS4 is released.

Mark, I know you are over the pond and all, but if you can't find the ChoPs book let me know. You can borrow mine. Although it really doesn't get into the stuff that I do with it. You might just as well do a search for kai's chops online, the book is VERY similar to what he wrote about so long ago.

Chris

[Markzebra]

Thanks Chris - all interesting stuff as usual. Yes I've seen the Kai stuff online, been through it all a few times, each time understanding more and more - maybe its time for another bash. Thanks for the offer of the book too! I really don't want to inconvenience you though - pity that books not available on Bit Torrent. Interested to hear what kind of things are you using Calculations for then apart from the masking?

The noise thing for me is just a question of first of all identifying where the noise IS - this can be in the color or Luminosity information, a quick switch to LAB can help here. Smooting Luminosity noise (the most visually distruptive) is just a question of multiplying a new channel sometimes from red and green - not always, but very often leaving blue out because this is usually the most nasty. Then using it in Luminosity blend over the file in RGB with a curve. Color noise is more difficult, and I have experimented with this by isolating using Calculations or Levels where damaged pixels are and finding a curve to bring them into line.

"They're not a consumer/prosumer tool and are rarely if ever tweaked". Yes, well you hit the nail on the head there about the current decision making at Adobe when it comes to new feature development; First of all they underestimate the user base, and increasingly, we see old stuff revamped and passed as "new" - functional improvements are few and far between.

Color range sounds good, its going to be a while before I move towards CS4, its still using LAB to calculate selected areas I assume? I saw that its possible with click and drag to do a kind of quick select with continous areas and that looks interesting, but in what way are the masks better?

[Daviskw]

Very interesting Markzebra...I grasp the idea anyway if not the nuts and bolts. Do you use this procedure on most of your projects...or just when standard procedures will not return satisfactory results.

Do you find a dramatic increase in quality over standard noise reduction plug-ins at least in luminosity noise?

If you get a chance maybe you can write a tutorial on this procedure..love to learn more and give it a try.

Butch

[cricket1961]

The CR masks that happen now are more along the lines of a true grayscale image instead of the chunky broken up bits of Black and white. Much smoother and capable of showing more of the subtleties going on in the image.

CHris

[Markzebra]

Daviskw - Ive never really used the third part noise reducers, think I tried Noise Ninja once but thought, no thanks - as for Photoshop's reduce noise plug in, its got its uses but they are limited. And no its only used as a rescue, and the new backs are much better, this is old stuff going back to the beginnings of digital really, but its still useful when you have rubbish source material to work from, or low light. And Chris I'm not so sure the improvement in Color Range quality-wise didn't come a few versions ago, one workaround was to convert a duplicate to 16 bit and run it on there.

[cricket1961]

I think you'll be pleasantly surprised at what it is capable of doing Mark.

Chris

[Markzebra]

Been trialing CS4, and Chris is right, one big improvement worth paying the upgrade for - Color Range. Seems to perform completely differently with "localised" checked. Its almost as if its using a different method completely with this option. Other than that its nice in CS4 to be able to rotate the view, and navigation is quicker now they are using the graphics card.

They kind of messed up with Adjustments panel if you ask me. Curves in particular is a more of a pain now they screwed with the shortcuts. Luckily its still possible to still get the old modal dialog up if you know how.

[MacBurg]

And how exactly do we do that?

[pixelzombie]

i'd also like to know how to get the old dialog to work in cs4 as they really did a number with the curves/eye dropper shortcuts...

[Markzebra]

You'll be glad to discover that the old shortcuts including command key to place points and 'reset' are still available using this technique. They have shifted the channel numbers two places to the right though.

There's two ways to achieve the old dialog…

You can now design your own photoshop panels using a new 'Configurator' application.. John Knack posted a Configurator panel that will either open an existing curve or create a new curve. http://blogs.adobe.com/jnack/2008/11...r_is_live.html. The new curve option does bring up the annoying initial blending Options dialog though, although there's probably a way to tailor this so that it doesn't happen.

Another, in my opinion better way, is to use CS3 to create an action step. In CS3 record an action step "Set current adjustment layer to Curves" - This is recordable in actions by double clicking, and opening an existing arbitary curves adjustment layer, and resetting the values to zero. You then have to save this action down and read it into CS4. Triggering this action will now edit or create (depending on how you've set it up) a Curves adjustment, this triggering can also now be done with Mr Knacks new Configurator, although F keys is probably the pro way to go on it.

[MacBurg]

Thanks Mark, still getting used to and making errors with the new channel keys, and the new adjustment palette thing just pisses me off, somethings are best left as they are.

[Markzebra]

Yeah, the argument in favour of the new adjustments set up, is that you can now alter the opacity and blend mode, while still editing your values. But that's really learning level stuff, when you move on you appreciate that there's not much use for any of that really, certainl not in an experimental way. That and they now provided nice little adjustment buttons for people too stupid to prepare their workflow with actions. They are really trying to make everything more accessible to beginners, at the cost of professional workflow its a pain