Anyone done any chroma key work before?

NorthernNikon · 12 Jul 2011

As per the title, has anyone done any chroma key work before? I've a shoot coming up where I'm going to have to superimpose a full length portrait onto a background. I'll be taking both elements specifically for the image and I was wondering if anyone had any hints, tips or experiences to share in terms of actually shooting?

I'm going to have to buy the chroma key background. I've found some muslin ones on eBay for about £40 which I presume will be okay. Am I right? I've read to avoid paper as it's too reflective, but also I'm looking for a background that will fold for storage.

Also, is it worth looking at some of the free Photoshop chroma key plug-ins or am I as well simply doing a 'colour range' selection to separate the subject from the background?

The23rdman · 12 Jul 2011

Might be worth dropping Daryl a pm, mate. He's done a lot of this work.

mercedes · 12 Jul 2011

For chroma key either blue or green is ok, evenly lit and stretched tight to avoid shadows.
Keep the subject far enough away to avoid light spill from the background, then light the subject to suit.

Once set up and tested - fire away.
If everything is lit properly PS will key out easily.

flossie · 12 Jul 2011

The choice of blue or green is very very technical (not really)

Well, some DoPs (or technical guides) will attempt to baffle you with bs about the relative sensitivities of particular mediums to certain frequencies of light that mean blue or green is the more appropriate choice for a particular shot...but ignore that.

Its down to picking a contesting colour with the subject. Not many people have green eyes or wear green clothes, but lots have blue eyes and wear blue jeans!

Theres a long story involving the development of blue screen technology for superman 2, which is even more stupid when you consider the costume colours...and how fake the flying effects look as a result...

You can chroma key off absolutely anything if there's enough contrast and you apply a rough mask - I've seen bored vision-mixers key off people's eyes and mix in flame effects...not on air, ofc!

The other important aspect is, as said on another thread, don't over light the background, your computer only needs a tiny hint of colour to work its chromakey magic on, and bounce light is a real problem to differentiate...

NorthernNikon · 13 Jul 2011

Thanks all. It will have to be green - the subjects strip contains blue so that's that decision made simple.

I'm torn between hiring a studio with a green screen available and buying a background and using Speedlight. Both have their pros and cons, but I suspect that the deciding factor will be a non photographic one.

Volusian · 17 Jul 2011

i recently bought a 3m x 6m green vinyl chromakey background from Bessel studio lighting ... got it all setup yesterday and had a quick practice in between decorating the new studio rooms out .... worked a treat in photoshop just using the colour range options ... the vinyl gives a much cleaner finish than muslin ..

Pity your not closer to Hull ..... you could have dropped in and had a freebie shoot with it ..

NorthernNikon · 18 Jul 2011

Volusian said:
i recently bought a 3m x 6m green vinyl chromakey background from Bessel studio lighting ... got it all setup yesterday and had a quick practice in between decorating the new studio rooms out .... worked a treat in photoshop just using the colour range options ... the vinyl gives a much cleaner finish than muslin ..

Interesting that you find vinyl better than muslin. Is it not shinier & therefore you get more spill from it?

Either way I'm going to be forced down the muslin front simply for being able to shoot on location with it.

Pity your not closer to Hull ..... you could have dropped in and had a freebie shoot with it ..

Thanks for the offer. If I had more time I'd be happy to drive across and take you up on it. My main concern with hiring a studio is getting no time to practice getting the lighting right.

Volusian · 18 Jul 2011

the vinyl chroma background i bought from Bessel has a fairly dull matt finish ... dont get much if any shine at all .... and any spill can be removed in PS fairly quickly ..

The hardest thing to watch is lighting angle of the subject in relation to the lighting taken in the digital background you are to use ... they have to be fairly similar or they can look a little odd ...

NorthernNikon · 18 Jul 2011

Volusian said:
The hardest thing to watch is lighting angle of the subject in relation to the lighting taken in the digital background you are to use ... they have to be fairly similar or they can look a little odd ...

Yes, I have that in mind which is why I'm shooting the background images too. I have a safer, easier shot as a back up where the sun will be directly behind me when I take the background and thus the subject lighting will be easier to manage.

The shot I really want to carry off is far far trickier though, but then that's part of the reason why I want to carry it off.