Alpha Channel Masking

[Manfred M]

I'm looking at putting on a workshop on background replacement at one of the photo clubs in town where I teach.

The topic is using alpha channel masks (used in the attached image that are shot using a neutral background) and chromakeying (i.e. green screen) and was playing around with some concepts to use in the course itself.

I found that this creation is a bit amusing and thought I might use it rather than some of the more staid and proper materials. I thought a snowscape in the studio is a bit amusing...

[xpatUSA]

Excellent!

Will you be adding goose-bumps (pimples) ?

[Manfred M]

Excellent!

Will you be adding goose-bumps (pimples) ?

I had that problem during the shoot. The studio is adjacent to badminton courts and beside squash and raquetball courts (one can her the balls hitting the studio walls during a shoot), so the temperature in the studio tends to be on the cool side at the best of times. I had 2 or 3 space heaters going (just off camera on the left and right hand sides) to solve that issue.

[Evertking]

Nice.. Looks COLD.. i got a chill just looking at it.
Wow, so that is a composite? the cut out is VERY clean and the shadows sell it well. So what is this alpha channel thing?
It really does look good.. i couldnt tell for a second and probably would have not known.. i thought the sides were just flags for your softbox lol..

[Manfred M]

Nice.. Looks COLD.. i got a chill just looking at it.
Wow, so that is a composite? the cut out is VERY clean and the shadows sell it well. So what is this alpha channel thing?
It really does look good.. i couldnt tell for a second and probably would have not known.. i thought the sides were just flags for your softbox lol..

Thanks - I am planning to cool down the skin tones a bit to add to the "cold" feel. Alpha channel masking is viewed as an advanced Photoshop technique.


1. Original studio shot:






2. This is the background I used.





3. Here is the mask I created using the highest contrast channel. The channels are found in the Photoshop Channels palette. I selected the appropriate channel and then used a curves adjustment to turn it pretty well black and white. The gray areas on the mask are where I let some of the of the background through. These were added by painting on the mask after it was produced. I wanted to have shadows from the studio shot to help anchor the figures to the replaced background.






4. Of course, once the mask is built, it is fairly easy to throw other backgrounds in.

[Tom Barry]

Fascinating technique and well done, indeed.

[Antonio Correia]

Manfred, don't you think the mark is a tad too harsh ?