Green screens are an essential tool used in video production, photography, and other visual media. They allow editors to digitally remove the green background and composite in other footage or images. This technique is also known as chroma key compositing. When it comes to green screens, there is an ongoing debate over whether blue or green backgrounds work best for chroma keying. In this comprehensive guide, we’ll examine the pros and cons of both colors and help you determine which is better for your particular needs.
How Green Screens Work
Green screen technology is based on color keying principles. The screen is a single, bright color that contrasts with the subject being filmed. During post-production, editing software analyzes the footage pixel-by-pixel. It removes areas of the key color, making them transparent. Other visuals are then overlaid in those transparent spaces.
For this process to work effectively, the key color must be very different from the colors of the foreground subject. Green and blue work well because they differ distinctly from skin tones and other common colors in video production. The editing software can easily discern and cut out the solid backdrop.
Factors in Choosing Blue or Green
There are several important factors to consider when deciding between blue and green screens:
- Color spill – Reflected light from the background tinting the subject
- Contrast with the subject – How distinctly the key color differs from the foreground
- Availability of screen materials – Formats the colors are available in
- Software algorithm – How well the editing program keys out each color
- Cost – Relative pricing of the different colored screens
We’ll look at how blue and green compare for each of these criteria.
Blue Screens vs Green Screens
Color Spill
Color spill occurs when light reflects off the background, slightly tinting the color of the foreground subject. This can make it more difficult for the software to separate the subject cleanly. Green is more prone to color spilling onto skin tones. Blue reflects less, producing better separation.
Contrast
Both blue and green differ substantially from common colors in video production. Green provides a high contrast from skin tones, with no similar hues. Blue has slightly less inherent contrast. However, the contrast depends on the specific shade used. Bright blue and green are both very high contrast.
Screen Availability
Green screens have traditionally been much more widely available than blue. More fabric and paint colors were manufactured in green. Recently blue screens have become more popular. Major brands like Elgato and Lastolite now offer collapsible blue backgrounds. But green still has a larger selection of materials and prebuilt stand options.
Software Algorithms
The chroma keying algorithms built into editing programs are calibrated for both blue and green screens. However, software developers put more focus on green because it has been the traditional key color. Sophisticated tools like Adobe After Effects have advanced settings to finely tune blue screen keys. But basic and older software works better with green.
Cost
Green screen materials and paint tend to be priced lower than blue options. Again, this is likely because green has been the standard for many years. The supply is higher, bringing costs down. As blue gets more popular, the pricing difference may diminish.
Blue vs Green Comparison
| Blue | Green | |
|---|---|---|
| Color Spill | Less spill onto subject | More spill, green tint |
| Contrast | High contrast from most colors | Very high contrast from skin tones |
| Availability | Growing selection | Very widely available |
| Software | Works well in advanced programs | Better in basic/older software |
| Cost | Tends to be pricier | Lower prices typically |
Should You Choose Blue or Green?
With their relative pros and cons, green and blue both have their merits for green screen use. Here are some guidelines on choosing between them:
- For professional productions using sophisticated software, blue often provides better keying results.
- For basic DIY videos or projects using cheaper editing programs, green may work better.
- If minimizing color spill is crucial, blue will spill less onto the foreground.
- If cost is a primary concern, green screens are generally cheaper.
- If you need a very large background, green will have more prebuilt stand options.
- For a collapsible portable screen, blue and green are both widely available now.
There are always exceptions based on the individual shooting conditions and software used in each case. Testing out each color if possible is the best way to determine which works best for your particular production.
Tips for Shooting Green Screen
Follow these tips when setting up and shooting with either a blue or green screen to get the best possible footage for chroma keying:
- Use the brightest version of the color – Deeper blues and greens are harder to key out cleanly.
- Illuminate the screen evenly – Make sure there are no hot spots or shadows on the background.
- Light the subject separately – Add accent lighting just on the foreground subjects.
- Allow maximum distance from the screen – Subjects further away help minimize color spill issues.
- Avoid matching colors – Don’t wear clothes or use props that are blue or green.
- Watch for reflections – Glossy surfaces can reflect the background color onto the subject.
Sample Blue and Green Screen Shots
Here are some example shots using blue and green screens. These show the raw footage, before chroma key compositing is applied.
Blue Screen Sample
Photo Credit: needpix.com
This blue screen provides a solid, non-reflective background. The bright blue will key out easily. While there is some subtle blue spill on the model, it should not cause issues isolating him in post.
Green Screen Sample
Photo Credit: Pixabay
The model here has excellent separation from the bright green background. Notice the subtle green spill on her skin and clothing. The spill is minimal and should still allow effective keying.
Advanced Green Screen Techniques
As you gain experience with chroma keying, there are some advanced techniques that can help take your results to the next level:
Lighting and Materials
- Backlight the subject for separation from the background
- Use collapsible reflector screens to control spill light
- Construct curved screens to avoid shadows
- Hang an additional backdrop behind the main screen
Shooting and Planning
- Camera settings like white balance and exposure affect keying
- Plan actor’s wardrobe, makeup, and props to avoid the screen color
- Allow more space for subjects to move for multi-camera shoots
- Use tracking markers on the screen for compositing CGI elements
Compositing and Effects
- Use garbage mattes for sections the software keys imperfectly
- Apply subtle effects like color correction to match the foreground and background lighting
- Use rotoscoping to manually isolate complex foreground elements
- Add cgi shadows, reflections, or atmospherics to blend the layers
As you refine your green screen techniques, your composites will look increasingly realistic.
Conclusion
Green screens have been the norm for many years, but blue screens offer some advantages that make them worth considering. Blue backgrounds spill less onto the subject and provide cleaner keys, especially when using sophisticated editing software. However, green remains widely available and affordable. There is no universally superior choice. The best option for any video or photography project depends on the specific conditions and tools involved.
With either color, following best practices for setup, lighting, and filming will ensure you capture quality footage for effective chroma keying. As you gain experience with compositing techniques, you can produce seamless, professional-looking results. Just take care to choose the screen color that meets your needs and works best with your process.
