Using Your SmartPhone to Measure Green Screen Lighting
May 11, 2015 by Jeff Foster
Regardless what kind of green screen setup you’re using or how you’re lighting it, you need to ensure that your screen is evenly-lit from the camera’s perspective. That means the screen behind your subject is all the same color and brightness. This can be harder than you may think, especially using a pop-up green screen and portable lights. But thankfully, with the advent of portable devices like smartphones and tablets, developers have been busy making useful tools to help you get a fantastic green screen lit, even before you set up your camera!
The Green Screener App
One of my favorite mobile apps is the Green Screener from Hollywood Camera Work that uses your smartphone or tablet’s camera to show you a live preview metering of the evenness of your green screen lighting. It will automatically adjust exposure from your lighting and give you a good idea of how even the lighting is and show you hot spots/shadows. This doesn’t replace a professional scope, however, but is a great tool I use in conjunction with a scope to dial in my shot, even on larger studio sets.
The Green Screener gives you live feedback on several sensitivity modes; Lo, Me and Hi – which splits up the number of bands of accuracy for each level. If you’re shooting higher definition in a professional studio, then you want to use at least Me/Hi to fine tune your lighting level.
If you’re shooting on a pop-up screen with portable lights, then you only have to light a smaller area behind your subject, it’s easier to define that space by moving your lights around to adjust for it. I’ve found that there’s a big difference between using traditional tungsten “hot lights” and using fluorescents or LEDs, which typically provide more even lighting, especially if they’re dimmable. LED light kits are getting more affordable for small businesses and corporate video departments that need to use them for interviews and product videos.
Here’s a demo video from Per Holmes, the developer of The Green Screener app, showing how it’s used and how the get the smoothest green screen lighting, while using this tool live:
Cine Meter / Cine Meter II
Another great tool which is useful for precise measurements on your iPhone is the *Cine Meter and Cine Meter II iOS *apps by Adam Wilt. Cine Meter will allow you to select your camera’s ISO, Shutter Speed and Aperture to get the most accurate reading and will display both the preview and the RGB Waveform in real time. This works even when your talent is in the shot or just a blank green screen.
The Cine Meter and Cine Meter II apps are great to keep with you if you’re shooting green screen or any other type of shot where you want to measure the RGB waveform of your lighting, or set the proper ISO/aperture on your camera.
One thing that Cine Meter does is give you very accurate RGB waveform data. This is really important when determining if your green screen material is appropriate for your shoot. As mentioned in other articles here, what you choose to use for your background material or paint can greatly impact how well your keyer can composite the foreground subject with the background. If there’s too much blue or red in the material, then it may have more noise in the video signal from the camera’s sensor.
In these examples below, you can see the difference between shooting with tungsten lights on a pop-up portable screen (top) and in a studio using a better quality material for the screen lit by compact fluorescent lamps (bottom).
Notice the RGB lines on the waveform of each example above. The blue and red are closer to the green line, which indicated a lesser-quality screen material, which isn’t true “green”. The example below shows greater separation of the blue and red from the green in an even form which makes a perfect green screen result.
I’ve used this app to determine what kind of materials or painted surfaces we will be working with on a job to see how best we can light it and still get usable results. Still, the best results are achieved with proper materials and lighting, which we cover in more detail in other articles here in the library.
The basic Cine Meter app (about $5) is available only for iOS devices (formatted for the iPhone) and you can get it in the iTunes App Store.
The Cine Meter II app (about $35) is also available only for iOS devices in the iTunes App Store.
If you’d like to see a comparison between the features of both Cine Meter and Cine Meter II, check out this fact sheet on Adam Wilt’s website:
I love all of these apps because I ALWAYS have them with me on my iPhone and can check lighting of any green screen or even studio shots no matter where I am!
More Green Screen tips by Jeff Foster:
- Incorporating Your Green Screen Talent Talent Into Virtual Sets
- Simple Green Screen Setups On A Budget
- Lighting Your Green Screen Subjects To Blend With The Intended Background
- Best Green Screen Materials Click here to learn more about Virtual Sets on TriCaster.
Portions of this article have been excerpted from The Green Screen Handbook, 2nd Edition (Focal Press, pub.) by Jeff Foster
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