ACK -- I've been asked to shoot a wedding

Started Feb 25, 2011 | Discussions thread
Victor Engel
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Re: Post-wedding
In reply to PenguinPhotoCo, Apr 3, 2011

PenguinPhotoCo wrote:

Both ceremony pics they're skin tones are off and in the second about the only diff I see is the dress is a bit whiter -whether that's from your WB or added flash (exposure more than light color).

I figured out how to crack the mixed lighting nut (see below).

Go for skin tone first and the dress second - she bought a white dress (i'm assuming) and expects it to be so in the pics.

It turns out, she paid $10 for the dress at a thrift store.

OK. Here's how to solve the mixed lighting issue. The technique works on the assumption that the flash is bluer than the ambient light. The technique will need to be amended slightly for another scenario.

  • First, process the image twice, once for custom white balance set for ambient light. Let's call this image Pcustom. The second image will be processed from raw using flash color balance. Let's call this image Pflash.

  • Convert these images to HSB (HSL might work better, but I haven't tried it yet). Current versions of Photoshop don't include ability to convert to HSB or HSL. That's OK, you can download the legacy plug-ins (including 64 bit versions) from Adobe. What we want is the hue channel of each image. These get converted to the R channel using the plugin.

  • Split the channels for Pcustom and Pflash after converting to HSB, and using only the R channels. Let's call these PcustomR and PflashR.

  • Paste PflashR onto PcustomR and use the Subtract blend mode.

  • Flatten this image and call is Pmask.

  • Close everything except for Pmask.

  • Reopen Pcustom and Pflash.

  • Just as before, paste Pflash on top of Pcustom.

  • Create a mask, and paste Pmask onto it.

  • Use normal blend mode at about 50%.

Here are the results of my first test.

These steps are straightforward enough that it should be relatively simply to create an action to do all the work.
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