Green screen and HPX301

Cees Mutsaers

Cees Mutsaers

Veteran
For "green screen" work you should use the highest possible resolution (luma nad chroma) and turn all in-camera sharpening off (detail, vertical, skin). Off means at setting 0 right? Will this still give a sharp picture ? Which of the standard scene files are most suitable and what tweak would you suggest ????? thanks in advance :-)
 
Turn down sharpening, as you say; you can always re-sharpen after keying. Otherwise, just do the usual tricks to get a clean image. Drop the Master Pedestal to 0 or less if you can get away with it (can be an issue if there's black clothing in shot). Stay away from the wide and long ends of the lens, and stop down to f/4 or 5.6 to get the best performance out of the lens.

Beyond that, if you've got a well-lit screen and subject (much more important than camera settings), it should be pretty foolproof. This is where the HPX really shines, well-lit studio situations. I've pulled keys from 1080p/AVC-I 100, 720p/AVC-I 50 and 100, and even DVCPRO50 with great results, though obviously you should shoot the highest quality you can.
 
Cees:

Make sure that your screen is evenly lit by going over it with a light meter, it should stay within 1/4 stop all over. If it is not evenly lit, tweak the lighting until it is. Make sure that there is enough physical room to separate the talent from the green screen to avoid green spill and bounce from the green screen onto the talent. Make sure that your green screen exposure and the exposure levels on the talent are close, most compositers I work with like for the exposure to be within a stop or two.

I agree with Max, good green screen is all about lighting it and shooting it correctly. DVCPRO HD keys beautifully and AVC I keys even easier because it is a better quality signal.

Dan
 
Light meter? Dan, my friend, he's using an HPX300! Pop on the waveform monitor. Point the camera at the greenscreen and frame it wide. The waveform monitor should be the absolute straightest, thinnest line you can possibly get. If it's thick, that means you have uneven lighting. If it's angled or higher or lower, that means that your lighting is brighter or darker in those areas. Proper use of the waveform monitor can ensure you have a perfectly flat, perfectly evenly lit greenscren.
 
(and yes, a light meter is a perfectly valid way to do it too; I'm just pointing out that it's no longer the only way, and anyone with a waveform monitor now has a "free" tool to help them get perfectly even/flat results).
 
Good point Barry. I am old school, I still use mine but yes, my 170 has the waveform as well. I should be doing it that way.

Dan
 
Thanks for all the recommendations. I have never used the waveform yet. So to judge the waveform like you explain should I tilt the camera over the green screen surface or just frame the entire green screen and look at the waveform. Is the waveform more accurate than using the zebra's which look at the whole frame surface or does the waveform the same?

Barry_Green said:
Light meter? Dan, my friend, he's using an HPX300! Pop on the waveform monitor. Point the camera at the greenscreen and frame it wide. The waveform monitor should be the absolute straightest, thinnest line you can possibly get. If it's thick, that means you have uneven lighting. If it's angled or higher or lower, that means that your lighting is brighter or darker in those areas. Proper use of the waveform monitor can ensure you have a perfectly flat, perfectly evenly lit greenscren.
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No need to tilt around, just frame the whole greenscreen in one shot. The waveform is like having a hundred zebra settings all simultaneously.
 
If the wave form shows the green to be evenly lit side to side- in other words the WFM display of the screen is perfectly horizontal, but the WFM of the green screen is thick, that means the screen is not evenly lit top to bottom. As a quick comparison you can zoom in to a tighter frame of the screen and you will see the WFM display change from a thicker to thinner line as more of the uneven areas top and bottom are framed.
out by the zoom. Go back to your widest frame and tweak lighting to minimize the green screen thinness on the WFM by tweaking lighting, just as you would balance out side to side differences
 
thanks again you are all very helpfull :-)

is the vectorscope also of any help to evenly lit the GS (or is it just to pinpoint the green chroma?)
 
Waveform would be of much more use. The vectorsope would just tell you the shade of green you are using.

We want to see samples before and keyed when you shoot this thing. Green screen is easy when done correctly and a nightmare when done incorrectly.

Dan
 
The shoot in the GS studio is next Sunday March the 14th (yes Sunday !!). It is not a payed job I even have to pay all costs for the studio but it is for my portfolio and to get practical experiences.
 
Use Green Kino Flo bulbs if you can to light to green screen. Make sure the screen is perfect, no creases or wrinkles in the fabric. Use rear edge lights to reduce green spill on talent.
 
Thanks for you remarks, in fact there was a lot of spill but you are right making it B&W (which was decided already before we shot the video) concealed it a little but you can still see it when projecting it onto a big screen. I learned a lot in this green screen studio so next time I can do a better job. Just noticed on this site that the HPX370 is announced and after 10 years waiting and saving money before buying a cam and only having the HPX300 for just 4 months I have a bad taste in my mouth. Did not expect an update already after 1 year the cam is available in Europe.


GaryNattrass said:
Keying looks fine to me and making it black and white helps with any green fringing that you may have had.
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