Fill-Flash/Backlighting: what's it doing

[Dan Halbert]

Fill-Flash and Backlighting work well in a number of situations. I thought at first they were simple gamma adjustments that could be done in Levels, but they seem somewhat more sophisticated.

Do you have any inkling as to what they are doing exactly? Are they applying an S-shaped Curves curve, whose shape is determined by the sliders? Knowing what's happening would help know when to use them and when to go straight to Curves.

Thanks.

[pmarchant]

I guess by the number of replies no-one here knows the answer!

However, as an experiment I created a new image consisting of two spectrum layers with difference blending (create a spectrum gradient; simplify the layer; duplicate it; and set the blending mode). This gives you a black image. Plalying with the fill flash enhancement by moving the sliders seemed to only effect the red and blue components.

Using a black to white gradient gave expected (to me) results.

Cheers,
Paul.

[Richard_Lynch]

Actually, I somehow didn't see the question, and I'm a little tied up at the end of another book.

You are looking at something like a midtone mask: the highlights and shadows tend not to be effected. If you make a Blend Mask of the midtones (curve 100% black at 50% and 0% at 0 and 100), you can make the adjustment using the mask layer set to Luminosity and the Levels (perhaps rather than curves--I've not done enough testing to be sure, but I think I am looking more at a masked linear behavior than a non-linear one).

As I was not impressed with the saturation handling, I might do this all "manually" by making a Luminosity and Color separation and then using a Blend Mask for the midtones to use on the Luminosity -- but dropping the composite so the background is used as a fill source for the highlights. Perhaps a screen shot would help.

http://hiddenelements.com/files/Picture_51.pdf

This way, the midtone adjustment can be anything you want (Levels or Curves). The benefit of having the color separate is you can adjust that independently of the midtone adjustment, which it seems Adobe did not do.

That help?

[Stephen M]

For any full version users reading this thread...

I have a small article on similar masking techniques:

http://members.ozemail.com.au/~binaryfx/ST_utilitymasks.html

I termed this the 'Endpoint Mask' - as it protects the highlights/shadows while revealing the midtones (or opposite if you invert the mask). A solarizing curve is applied to a luminance mask (see attachment).

The layer option blend if sliders can also do this, without needing a mask!


Regards,

Stephen Marsh.

[Richard_Lynch]

Stephen,

There are limitation to access in the standard Elements interface, which includes Blend If. I created a work-around that I call Blend Mask, which is actually easier to implement, but has no direct access to the Blend If sliders.

I encourage you once again to have a look at the program and book...some of the technique is not just transferable to PS, but useful in it.

Hidden Power