Frequent questions for Green Screen Photography.

We receive as many questions about setting up a chromakey studio as we do about working with our Primatte chromakey software. This page is devoted to Q & A about screens, lighting, staging, and other general questions.

• How does Primatte get rid of the hot spots in my photo?
• Primatte doesn't remove the screen's wrinkles.
• Primatte doesn't remove the shadow behind my model.
• What is color spill?
• What screen color should I use?
• How do I hang chromakey material?
• The pros & cons of going chromakey.

Don't see the answer you need? Contact us with this Request Form. You can also go to our Anarchy Underground forum to post a question.

How does Primatte get rid of the hot spots in my photo?

• My background has bright spots from the lights that I set up. I think that uneven tone is causing the Primatte mask to be incorrect. How do I compensate for this?
• Unfortunately, Primatte cannot fix bad lighting. Like all photography, chromakey photos need good lighting. If the photo is too dark or bright, if your subject is not well-lit or the lighting is uneven, then Primatte will have difficulty creating a good mask. The background color is too uneven, for instance, for Primatte to distinguish its bright spots from the light colors in your subject (like teeth and eyes). Alternately, your subject is not clearly defined from the background if there are uneven shadows falling along the screen and the model. Read about how to light properly.
  
  
  

Primatte doesn't remove the screen's wrinkles.

• Primatte isn't removing the wrinkles in the screen, where the folds cast shadows.
• Unfortunately, Primatte cannot fix wrinkles. Wrinkles and folds can easily creep into the back screen if you aren't paying attention to how it lays. This causes uneven tones and makes it difficult for Primatte to define the range of color that it needs to remove. Primatte can't tell the difference between the dark wrinkle colors and the dark colors of your subject (like folds of clothing). Read about working with a screen.
  
  
  

Primatte doesn't remove the shadow behind my model.

• Primatte isn't removing the very dark areas behind my model, where she was sitting near the chromakey screen. How can I get rid of this shadow?
• Unfortunately, Primatte cannot fix shadows. After your photoshoot, you may notice a deep shadow cast along the backing screen. This shadow generally happens from the subject being placed too close to the chromakey screen. Problem is, Primatte can't tell the difference between those dark shadow colors and the dark colors in your subject (like folds of clothing). Ideally, your subject should be positioned at least 4-6 feet away from the screen and preferably up to 10 feet. If your subject is sitting only 1-2 feet away from the green screen then unwanted shadows will occur. Read about working with a screen.

What is color spill?

• What is color spill? Why should I worry about it?
• After you have created a mask in Primatte, you may see a colored tinge around the foreground image. This fringe is called 'color spill'. Color spill describes areas of your foreground subject that have absorbed or reflected color from the background. This often happens during the shooting process and needs to be corrected afterwards. Spill is especially noticeable (and difficult to remove!) in semi-transparent areas like blonde hair.
  
  
  
  Any color tinge will be especially noticeable in semi-transparent areas, like wispy hair and materials such as glass and water. You need to remove spill in order to create a natural looking composite or your composite will look 'cutout' and fake. During the removal process, you want to be conscious of any tradeoff between removing spill versus maintaining color fidelity. Primatte gives you a many ways to remove this spill without losing details that you need to keep.

What screen color should I use?

• Is there a particular shade of Blue or Green that should be used as the background. I want to get the best possible results when using Primatte Chromakey software. Can I use other colors?
• One of the great aspects of Primatte Chromakey software is that you can use any color, not just green or blue. Blue and green are the most commonly used because they contrast with flesh tones. What's most important, actually, is good lighting and staging. As with anything digital, the better your source image, the better your result. Read more.
  
  You want to make sure that the color of your screen is not in the colors of your subject/object. Also, black, gray, and white are not great screen colors because you find them in the shadows and highlights of most subjects.

How do I hang chromakey material?

• I have 12 yards of chromakey fabric and some chromakey tape to fill in the seams. My question is: How do I hang up the material? I have three pieces of fabric that I somehow need to join together. Should I just staple it to the wall? Should I use "stick-back" tape? My intention is to have this up as a permanent backdrop, so I want it to be as seamless and straight and stable as possible.
• Well... we use duct tape. :-) But that's mostly because we just shoot test shots and don't have the fabric permanently installed. Not really being a handyman myself, take my opinions for what they're worth. Personally, I'd first try stapling the fabric because it is an easy, cheap solution. But I'd also recommend consulting with someone who does interior construction to get their thoughts.
  
  
  • If you can find a good seamstress, many folks have the fabric sewn together. If done right, this becomes _almost_ seamless.
  • You don't want to use tape if you can avoid it. It will be a different color than the fabric, which is a potential small headache.
  • Stapling should work if done right. Make sure to keep everything taunt. The downside to this is the risk that the fabric will tear, and you will probably have to re-staple everything occasionally as the fabric stretches/shrinks over time.
  • I've attached c-clamps to the fabric, with a rail running through the c-clamps, and then pulled the fabric taunt along the rail.
  • You could possibly build a wood frame, wrap the fabric around the frame like a painting canvas, and staple gun the fabric to the frame.
  
  See our forum post for a longer discussion of this topic. (You won't have to sign in.)

Pros & cons of going chromakey.

• I am going fully digital and I'm considering setting up a chromakey studio. What are the pros and cons of the technique?
• The advantage that Chromakey software has over, let's say, just using Adobe Photoshop is that it's made specifically for power use in a certain kind of scenario. Chromakey software is designed to get rid of a single color background (it can be any color, not just blue or green) and then help you color correct that single color out of the object being keyed.
  
  It's a bit of a one trick pony, in that it only works on single color backgrounds, so it's not a generic masking tool. But any Chromakeyer should do its one trick really, really well. For example, hair and transparent areas are very difficult to remove from a photograph normally. Most chromakeyers have tools to color correct hair and to adjust the alpha channel to make those transparent areas look transparent.
  
  If the green / blue screen is properly lit and set up, you can pull off a key of a very complex object or person in a couple minutes. No hand work in Photoshop. This is the main advantage, but blue / green screen photography is not something that's instantly intuitive. There's a fair amount of set up involved to make sure the subject keys out correctly once you're in front of Photoshop.
  
  See our forum post for a longer discussion of this topic. (You won't have to sign in.)

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