Curves tool and layer blending modes

[Susan S.]

While using curves on greyscale images is straight forward, (more or less!) using them on coloured RGB images can produce some rather wild and unpredictable colour shifts - they can be useful for special effects but are rather difficult to control. I picked up a reference in the Adobe Mac photoshop forum to using Luminosity blending mode on the curves adjustment layer to (partially) get round this problem. And it works well. Am I correct in thinking that this is equivalent to splitting the luminosity and colour, using the curves on the luminosity and then recombining? And does anyone know of any other uses for different blending modes on any of the other adjustment layers? I am finding it hard to predict exactly what I would get using different modes on adjustment layers.
Susan S.

[Stephen M]

Hi Susan, for more on colour correcting separate channels via curves or levels, see this link to more links:

http://members.ozemail.com.au/~binar...V_links.html#C

Scroll down to the curves, levels and colour correction links...

Start with levels with the E. Tapp and then move onto the J. Kost and C. Lehan tutorials. Then read the S. Nelson primer on curves before reading and practicing the master work by D. Margulis. Then move onto the other general links. <g>

The basic key to colour correction is to set white/black/neutral and memory colour points where possible and with luck the image will fall into place. Global edits are done first, which often remove many isolated problems at the same time.


For blending modes - yes, using a fade after an edit or an adjustment layer can be useful. The luminance move is not the same as a true luminance edit, but for most RGB and CMYK edits this will be pretty good (same for color blend mode and hue or saturation blend modes).

For more info on blend modes, try this link:

http://www.retouchpro.com/forums/sho...blending+modes


Regards,

Stephen Marsh.

[Susan S.]

Thanks Stephen - while your links are interesting, and I've learnt from some of them (no - I'm not that quick a reader! - I bookmarked them on Friday night after one of your earlier posts!) I'm finding them tough going - as an Elements user I have to deal with channels in an entirely different way to full photoshop users - and some of the controls on the Big Brother just don't easily translate - "using a fade after an edit" doesn't compute! In Elements the only options I have are to set the adjustment layer to a particular blending mode. Is this the same as fading after an edit or are there some other subtleties involved?
Susan S.

[Stephen M]

Hi again Susan,

Photoshop has an ability to use the FADE command directly after an edit, with fade being found under the edit menu or the filter menu in earlier versions. It is the same as duping the layer, and changing blend mode or opacity and merging the layer into the original - all in one move. Sadly a layer mask breaks the fade command, which does not seem to be documented anywhere in Adobe literature.

I'm not sure about Elements, but simply having a duped layer or an adjustment layer set to a blend mode is the same thing and often more useful, although having the ability to fade lets you have the layer set to one blend while the edit is in another - which is very useful.

So yes, it is the same thing. <g>

Does Elements let you place fixed colour samplers (similar to eyedroppers) and view an info palette of the colour readings found in those sample points?


Stephen Marsh.

[Susan S.]

Thanks Stephen - that's really helpful in translating stuff I read which has been written for the full version. As far as I'm aware elements is limited to the eyedropper - I can't find any reference to colour samplers in any of the books I have - and I'm sure Richard Lynch would have used them if they were there as I reckon they would be useful for doing some of the stuff in his chapter on using curves to individually adjust the colour channels setting white, black and grey points. I'm still working through that bit of the book. Slowly. (I only do this stuff for fun, and as I only got Elements in November the learning curve is quite steep.)
Susan S.

[caseyJ]

Color sampler

Susan;
Click on the window tab at the top toolbar of elements and you will find the "info" pallette in the drop down menu. Click on "info" to open the pallette and then run your cursor around over your image. The info pallette will show the color values for where ever your cursor is at. You can change the info pallette color options from RGB to grayscale, web or HSB. You can have the info pallette open while in curves or at any other time to see the color values. I believe this is what Stephen is talking about. CaseyJ

[Susan S.]

Those I knew about! (It's what I meant by using the eyedropper - I was being insufficiently clear, sorry) - in the full version of PS you can put cute little markers that stay in the same place and display their colour values in that location. (I just tried it in the PS6 demo that I have).

Susan S.

[Stephen M]

Before v5, Photoshop did not have fixed samplers - which was a PITA.

You had to leave your mouse on the shadow point of the image while you used keycuts to edit the curve dialogs separate channels so that you could balance all the figures to read as 10 r 10 g 10 b or whatever.

When it comes to setting endpoints, the choices that the curves or levels eyedroppers make is often the same as what a human would make - so it can be very speedy to correct the hightlights and shadows via the curve/level eyedropper tools - which means that setting endpoints does not have to be hard even with no fixed colour sampler tools. I do not always agree with the neutral eyedropper and may make a different edit myself to set a gray point.

If I am going to keep entering these PE discussions - it might be wise if I d/loaded the demo so I knew what I was talking about. <g>


Stephen Marsh.

[Richard_Lynch]

Stephen,

The demo is a good place to start. There are also some free tools. But you really won't get the full crust-of-the-biscut till you have a look at the book and install the full set of tools.

Check out what they can do here:

http://hiddenelements.com

let me know if you have other questions