Creating a White Background with a Channel Mask

One question that I get asked more than most is “How can I make my white backgrounds white?” Well, where as most photographers are looking for a one click answer, I am sorry to say there isn’t one. But, this screencast comes pretty close as I delve into the world of the alpha channel mask by sneakily using image calculations, and the dodge and burn tools at 100%.

Creating a mask can be tedious to say the least, so I hope the techniques I show you in the screencast above will help you not only to keep your backgrounds nice and white, but will also get used with future compositing articles and screencasts that I have in the pipeline.

The shot above was taken as part of The Big Picture training series and I always did promise that I would demonstrate an effective way of cleaning up a background and make it pure white.

Lighting

Now, as you can see I used a Nikon SB28 speed-light aimed at the wall to light the background and at the time I was actually going for a vignette of white through to the soft cream from the wall colour. The light on the subject is coming from a Bowens Esprit 250w with a 1m Square Softbox and in terms of exposure the main light was about 2/3rds of a stop under-exposed and the background light was 2 stops over but with an 50mm zoom setting on the Nikon SB28 speed-light to focus it for the vignette. This was very much a manual setup and fly by the seat of your pants judgement call by looking at the histogram in the back of the camera. In hindsight, I should have done a few shots that blew the background completely to white and I also wished I had a C-Stand and Boom Arm attachment so that I could have got underneath the light. But hindsight is a great thing!

Photoshop

If you want to keep as much hair detail as possible in your mask for compositing then this technique is one to practice until perfected. Its my go to guy for composites and you will be seeing a lot more of it in other situations much more complicated than cleaning up a white background. But for now lets all walk before we can run and I bet there’s a few of you out there just saved a few hours in front of the computer!

Note the little hairs retained along the bottom of the camera right of the hair and on the neck line camera left. Try get that with a lasso tool or even with extract if you still have it installed! Pretty Cool eh! Well, one final word to the wise. Once you have cranked up both the Dodge (O) and Burn (O) tools remember to right click on both their tool icons on the top left of the options bar after your done. Then choose the “Reset Tool”, that way you won’t blow up your next image.

Finally…

If you want to learn about the retouching involved in the image above, then don’t forget to check out The Big Picture. It’s got over 180 HD video tutorials and all the “behind the scenes” from this and 5 other shoots. >

Related screencasts & articles.

• What Don't You Want in Photoshop CS6? Wed 18 Aug 2010
• 5 Techniques for Enhancing Contrast in Digital Images Wed 11 Aug 2010
• Picture Package with Smart Objects Sat 05 Jun 2010

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