Chroma Key

[rubens_t_vora]

<p>Dear,<br>

After reading some posts I decided to aply a Chroma key color into a studio background. For a test I asked a Coral Paint dealer do mix a Pantone color code 354 for green and 2735 for Blue. But, it fails!<br>

Photoshop could really not extract hair with his best tools. <br>

So, is possible do it with pantone codes otherwise I must look for Rosco?<br>

Thanks, Rubens </p>

[charlesheckel]

<p>You can do a chroma key technique with essentially any color that isn't included in your subject--the tricky part is getting even illumination on the background. There's an article in the latest issue of Photoshop User that talks about getting a good extraction from any color of background using the Add and Multiply blend modes. You might look into that.</p>

[Charles_Webster]

<p>You probably had the subject too close to the background and the light reflecting from the background onto the subject spoiled the extraction.</p>

<p>Keep the subject at least 5-8 feet in front of the background, and make sure the background is evenly lit as Charles H indicates.</p>

<p><Chas><br /></p>

[martijn_houtman]

<p>Post an example and we can probably tell you what went wrong.</p>

<p>I am quite sure that the uneven lighting is not that big of a problem, it is usually the subject being too close to the background.</p>

<p>On a technical note (I wrote chroma-keying software myself), lots of software tries to do it in RGB color space, while I find that HSV/HSL or YCbCr color spaces seem to work a lot better. In PS you can try it manually in LAB color space.</p>

[rubens_t_vora]

<p>Hi Charles and Martjn,<br /> <br /> Your teses are very helpfull. In fact I tried also in LAB mode that improved but not get solved<br /> <br /> Here is one picture and I put some red balls were definetelly you can see green casts. Even without those points I encountered a line fringing all over the hair.<br /> <br /> <br /> <br /> Thanks for you time, analisys and help. Rubens</p>

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[peter_ferling]

<p>When shooting chroma's, you need distance separation and three lighting sets. One for subject, one for backdrop, and a third for controlling spill. Unless using a white backdrop where you blow it out by 2 stops over the subject, you just want even and continuous illumination, or very little fall off for green. The backdrop material itself must be smooth, non-textured, non-shiney and free from sags. Such will cause shadows and affect the mask. The brighter your backdrop, the worse your spill. Edges and intruding setups can be masked in post.</p>

<p>To control spill and bleed when using objects in which no amount of distance will help (glass, leather, hair, etc), you can use a third lighting source, a spill light, coming from the backdrop to either overpower, or with a correction gel, to change the spill to white.</p>

<p>The link below will give you an example of such a setup. However it was for video, and you'll note that my "spill" light was greatly overdone on purpose for the final edgy look. A little diffuse will help in your case. In regards to the example: The cars interior was a haven for spill, and I put a softbox right over the open sunroof to flood fill the interior and kill the spill. Note the effect on the actors hair. Also note the heavy edge on his arm from the direct spill light. I think a soft diffuse hair light will do well for spill. Experiment with that next time.</p>

<p>http://www.flickr.com/photos/ferling/sets/72157602654703774/</p>

<p>In regards to your current images, you need a dedicated plugin or software such as After Effects to deal with fine hairs. Such software will provide edge, spill or blending tools to deal with that. The other issue is just pure grunt work, or doing fine painting on the pixel level where software and setup fails, (welcome to my world...).</p>

[garry_jones1]

<p>I think <a href="http://www.photostudiosupplies.com/green-muslin-screen-5-7.php?cat=270&page=1">Chromakey Green Screen 5*7 Backdrop</a> is best to used</p>

[andrew_smith35]

<p>I found this website interesting related to chroma key <a href="http://www.photostudiosupplies.com/chromakey-green-screen.php">www.photostudiosupplies.com/chromakey-green-screen.php</a></p>