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GH4 with an external recorder vs Blackmagic for greenscreen?
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  • Not good enough to be called "as well as", which is the title of this thread. Likely "good enough" for most though.

    edit: there was no context given by the OP, it's a general question of whether A is as good as B. No, A is not as good as B. That's a simple fact.

    Now, is A just fine for local/regional commercials, for non-realistic weatherman style work? Sure. Fine. Neither the audience or anyone else would benefit from or could tell the difference between A and B in that scenario. Of course, in that context, any old camera is fine because we're establishing an audience that can't tell, doesn't care and a situation where it doesn't really matter anyway.

    Also, it also doesn't matter if the footage is being handled by someone dependent on "a few clicks" and who looks at the work like that. It doesn't matter what the footage is or where it came from if it's the magical keying tool that's going to be the deciding factor in how good the result is.

  • Interesting Test by Video Alchemy:

    Panasonic GH4 4K vs Blackmagic Cinema Camera Green Screen / Chroma Key Comparision

  • If I can help with my own experience here are things to keep in mind when doing a greenscreen: 1) try not to go under f8, you want a perfectly well defined subject in focus without depth of field. (This also means you gonna have to rent a lot of lights) 2) shutter speed above 1/100 because you do not want motion blur for greenscreen. You add it later in post if necessary. 3) lit well your scene and have a flat green surface. Also be sure that your greenscreen is a correct green one, I've received many shots which didn't use the official green which needed then to be corrected. Many green screen aren't good for chroma keying. Test your greenscrene before using it. 4) do not forget to denoise your shot before performing a chroma key.

    Also, I would suggest you to rather use nukex than after effects for compositing greenscreen. It has the same plugin (keylight & primatte) and many others useful tool that doesn't exist in AE and can sometimes be time saving when it comes to deal with complicated shots.

    And the more resolution, the better for greenscreen. It ain't so much about the color depth (this is useful but in particular cases when you have to deal with extreme shots that needs a very precise range of color)

  • @GeoffreyKenner

    Wow F/8 plus a shutter speed of 1/100 that will require some serious lighting no doubt. So just to recap what I read so far. It is suggested to use the sharpest most modern lens as possible plus using a the "correct" green screen. I have two at the moment a cloth backdrop and a paper backdrop from Savage 107" x 12yds Background Paper (#46 Tech Green) the ones that I have are really cheap do you have any recommended green screen backdrops?

    I have another question about the F stop. Since I am using the GH4/GH2/AF100 if I use F4 this is equivalent to an F/8 on a full frame will this suffice?

  • A strict f8 is not needed as long as your subject gets full focus on all edges. Many modern fast lenses have their sweet spot already at f5.6, some even at f4.

    And short exposure times for fast moving objects are critical, yes. Think martial arts or the like. You can add motion blur with RSMB in post and it even helps with image integration.

    To avoid green spill, your studio should ideally be black on all other walls. If it is not (or not even a studio), use large, painted black styro plates or the like on all light areas around your talent. Plus, put dark cloth in front of the actors as close to their feet as possible – never let them stand back with a lot of green in front of them.

    The latter applies to full body shots only, of course. in all other cases, avoid any green around your actors.