View Full Version : How to replace a black background?


buso23
01-15-2006, 04:09 PM
Hi,

I am aware of couple of techniques of replacing a background and I think that the best one is to use the pen tool, but it's time consuming. I have some photos shot against black background and I would like to change it into white. No matter how hard I try there's always some bleeding from the black background and it is easily detectable in the new background. So I'd like to know if there's an easier way to replace a black background with a white one. I'd really hate to use the pen tool. Thanks in advance, and regards from Macedonia.

Here's a photo shot against black background:

http://www.shutterstock.com/pic-161776.html

Chance_1
01-15-2006, 05:04 PM
Check out this tutorial, on advanced masking to delete backgrounds : http://av.adobe.com/russellbrown/AdvancedMasking.mov

Chance

OnlinePhotoDoc
01-15-2006, 06:48 PM
For a background so contrasted from the foreground like this, using the Threshold tool usually works well for me. Duplicate the image, apply threshold to the value chanel, and adjust until the foreground looks completely white (completely selected). Change the layer to a layer mask and clean up the mask if necessary with the paintbrush.

Mig
01-16-2006, 12:22 AM
By the looks of the picture of the flower from the site, I think what you're getting at is a problem with there being a dark or black fringe and you want to get rid of that. For the flower example, you first have to select that, and you can use whatever method you know how how at this moment - it doesn't have to be the pen tool. Then copy/paste the selected flower to a new layer and we'll call this 'flower layer', and then add an empty layer below it and fill it with white (or whatever light bg you're using). You'll see the problems on the fringe of the flower immediately.
Return to the 'flower layer' and Ctrl+click this layer to select its contents, then go to taskbar and to Select>Modify>Contract and enter something like 1 pixel, or perhaps 2, which will reduce the selection size of the flower by one or two pixels. Then there's several things you can do from here - but what I'd suggest is feathering the selection by 1 pixel, then adding a layer mask and see what happens - and then play around with the layer mask. If you're not familiar with layer masks, just invert the selection and carefully erase the black pixels.

Mig

Flora
01-16-2006, 03:16 AM
Hi,

... and Welcome to RetouchPRO to buso23 and OnlinePhotoDoc! :pleased:

Great tips here!!

A picture with a plain coloured background and presenting such a high contrast between background and subject is, in my opinion, one of the easiest for a mask/selection ....

Working in RGB Mode, I usually duplicate the Channel with the highest contrast between background and subject (in most cases either Red or Blue Channel) but for this picture I chose the Green channel...
I run the Levels on the duplicate Channel to strongly increase contrast, refine the mask and invert it whenever necessary .... I described this technique step-by-step in this Tutorial (http://retouchpro.com/tutorials/?m=show&id=120).

Since writing the Tutorial, I read about an additional step for refining the mask and that is:

after running the Levels on your duplicate channel, select a semisoft edge brush (Opacity 30-70%), set the brush to Overlay first and Normal later, and carefully paint white on the grey areas that are to be lightened, and black on the grey areas that are to be darkened...

After this you can either follow Mig's excellent tip for removing the 'fringe around the edges (I usually also use a very light feathering for that), or you can follow Doug's also excellent 'Levels on the mask' tip described in my Tutorial...

As the daisy's petals are white, I decided against a white background, but rather went for a coloured one, but i could also post a version with a white background ...

Attachment 2 show the mask obtained with this procedure..

Hope this helps ...

aztek1020
01-16-2006, 03:27 AM
hi,

you can use the magic eraser or extract to clear the background in photoshop.

Gary Richardson
01-16-2006, 08:02 AM
For such a high contrast subject, you are really swamped with choices.

Try the extraction tool, this took about 1 min to do. A little time spent cleaning up would improve it.