[Paul Carpenter]

Thanks again.

I’m running tests to the best of my ability, although I do not have studio space here.

I see what you mean about the luma key leaving a fringe which is an issue when overlapping. However, I waved an aluminium ladder around to simulate a chromed BMX performing stunts and the CHROMA key test couldn’t cope at all. I’ve since read that crews often use anti-shine sprays and the like on a ‘proper’ set. I guess this indicates the scale of this problem with metal surfaces and chroma screen?

I’m edging towards a luma shoot again now, with a view to compensating for the white fringe by avoiding high-contrast overlaps in the composite.

What I cannot test right now, is how well an AE luma key handles very dynamic motion such as a bike jumping off a half pipe ramp. Does anyone have experience applying a luma key to this type of footage?

I would also like to know if I can improve a luma key by shooting fast motion at our standard shutter speed of 1/50, thus introducting some edge blur, or if it would be better at a higher frame rate of, say 1/100 for sharper edges?

Many thanks again. This help is invaluable to me!

[Paul Carpenter]

Thanks for your reply. I guess I could patch any internal white holes (caused by blown highlights) by placing a white solid behind the problem area of the footage? I see what you mean about the edging issue though. Do you think the luma key will leave thick edges or very thin ones? Could I sort the edge with a feather?

[Paul Carpenter]

Thanks for the reply. Oh dear, that does not sound promising!

I was hoping to shoot against a long polar white paper roll, keyframe a feathered mask, apply a luma key and rely on any remaining thin white edges to blend with the white bg of my virtual set.