Photo Compositing - - selection issue

imann08 · #1 07-15-2006, 10:22 PM

I originally thought this would be a fairly easy selection using luminosity masks and some blending. It appears I was mistaken. No matter what channel I use it seems as though it conflicts with something I don't want to include in the selection. Due to this image's detail in the flowers and edges of some of the leaves, I was trying to avoid grabbing a paint tool. Am I right that I have no other option or am I totally missing something?

mistermonday · #2 07-15-2006, 11:13 PM

Isaac, LAB works well for magenta / green selections. If you duplicate the A and B channels and auto level them, you can bulid a selection from the combination of the two. The attached is a 5 min effort. With a little more time you can make a precise selection. BTW, this one has been feathered.
Regards, Murray

imann08 · #3 07-15-2006, 11:38 PM

Thanks a bunch Murray. As much as I go over this stuff you'd think it would stick eventually. Not a chance. I'll give this one a try and then come back to complain that I still can't figure it out. At least that's how it usually works.

imann08 · #4 07-16-2006, 02:05 AM

Ok Murray, as planned I am back. Regarding your recommendations, I went directly for the LAB seeing the color of the plant. I used auto levels as well. Also, feathering selections is pretty standard process for me so I did that as well. The problem is that I could not separate the green of the plant from the ground beneath it and the bushes in the background enough. A painting tool was necessary to the extent that 5 minutes wasn't going to be possible. You evidently did it though. Could you elaborate? Thanks.

mistermonday · #5 07-16-2006, 07:26 PM

Isaac, I duplicated the A channel and Auto Leveled it to boost the contrast. You will notice that the magentas are bright, the greens are dark and most evertything else is near neutral. I used the magic wand with a tolerance of 10 and made two clicks - one on the magentas and one on the leaves (uncheck contiguous). This left me with Snap shot 1. I then dod Select>Modify>Smooth and chose 8 pixels. That filled in most of the voids and left me with snap shot 2 (composite image shown). The selection did capture some green in the top background as well as the small area on the lower left. But if select the composite image and hit Q (quick mask), you can masks those off in a few seconds.
I suggest you experiment a little with the A channel copy channel. If you apply it to itself in various blending modes you will see even easier ways to make a selection. You can build your mask or selection increments by choosing the same selection channel each time you save a selection and just choose Add to Selection or Subtract from Selection in the options dialog box.
Regards, Murray