JA Tadena Posted May 14, 2006 Share Posted May 14, 2006 (edited) Hi guys. Would anyone know what IRE rating should I place my blue screen and green screen at? I had a problem with a shoot with the F-950. I rated the camera at ASA 125 using the PRO 35 adaptor since you lose 1 1/3 a stop with the adaptor(setting my lens opening at F/2.0). I was shooting on blue chroma and getting the same f-stop reading in my incident light meter on my (person)subject and blue chroma. I usually underexpose my chroma by half a stop but in this case I thought that the blue was good enough. My HD technician was saying that my chroma was somewhere between 20-30 IRE and she thought that it was a bit low for a blue chroma. I checked the waveform and saw it but I didnt know what IRE the blue should be on. My talent(sublject) was pretty ok hitting 60-70IRE on the waveform. So I told her that I think I have to trust my meter since I wouldnt want light the blue screen stronger than my subject. Anyway Im sorry if i missed some threads on this. Edited May 14, 2006 by jatadena Link to comment Share on other sites More sharing options...
Premium Member Michael Nash Posted May 14, 2006 Premium Member Share Posted May 14, 2006 Forget the mathematics invloved with the Pro35, and forget what your meter tells you. What you see on a properly set-up waveform tells you what luminances you're recording. If you're recording a blue screen at 20-30 IRE then that's underexposed by more than your typical 1/2 stop (but it sounds like you knew that). Keying depends upon color saturation, and there is a "sweet spot" for most video cameras where they deliver the best color saturation for a green- or blue-screen. Usually this means 50 IRE or less; but if you go too low there is too much noise in the color to pull a clean matte. Link to comment Share on other sites More sharing options...
Premium Member Michael Nash Posted May 14, 2006 Premium Member Share Posted May 14, 2006 Forget the mathematics invloved with the Pro35, and forget what your meter tells you. What you see on a properly set-up waveform tells you what luminances you're recording. If you're recording a blue screen at 20-30 IRE then that's underexposed by more than your typical 1/2 stop (but it sounds like you knew that). Keying depends upon color saturation, and there is a "sweet spot" for most video cameras where they deliver the best color saturation for a green- or blue-screen. Usually this means 50 IRE or less; but if you go too low there is too much noise in the color to pull a clean matte. Link to comment Share on other sites More sharing options...
JA Tadena Posted May 14, 2006 Author Share Posted May 14, 2006 (edited) Thanks a lot. So you think 40-50IRE is what i should work at? How do I find out which is the best IRE setting for which camera i use? Thanks again. Edited May 14, 2006 by jatadena Link to comment Share on other sites More sharing options...
Premium Member Stephen Williams Posted May 14, 2006 Premium Member Share Posted May 14, 2006 Thanks a lot. So you think 40-50IRE is what i should work at? How do I find out which is the best IRE setting for which camera i use? Thanks again. Hi, Look at color bars, that will give you a good indication of the IRE value for different colours. Blue will be much lower than green. Stephen Link to comment Share on other sites More sharing options...
JA Tadena Posted May 14, 2006 Author Share Posted May 14, 2006 Oh yeah thats a great idea. Thanks a lot. Link to comment Share on other sites More sharing options...
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