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Thread: Chroma key

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    Subscriber Member Jorgen Udvang's Avatar
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    Chroma key

    A potential new client needs to make studio shots where the subject (studio shots) will be placed in environments taken from available stock photos (nature scenes etc.). He mentioned "green screen" as a preferred method to achieve his goals (he has been using that before). I can see that there are advantages using a chroma key background compared to an all white one, I have no experience with this. What are the main advantages using this for still photography?

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    Re: Chroma key

    I've not done it but I have made a lot of masks and the advantage is one click selection based on color range in photoshop.

    HOwever its still not that easy- depending on how you light it and what you are masking on to things can look good or very bad, and so its not a substitute for everything.

    Hensel also makes a masking system where you shoot two frames in rapid succession and on the second frame the front light does not fire (shooting against white seamless)- this gives you (if you do it right) a black mask frame to use that is pretty much exactly the person if they don't move much (I think you can shoot the two frames on continuous low or something like that).

    Where it gets tricky is in hair, maintaining the right amount of transparency and feathering, inevitably you give people a "haircut" while masking. So that can look poor.

    I think it depends on output size- for web you can probably get away with anything but in print you'd need a good retoucher to make a nice mask.

    don't forget about dof issues- generally you'd want to shoot at smaller apertures to give a better edge to mask to, you can soften it later if you like- selecting out of focus hair is basically impossible.

    If the client is doing it then all of this is their worry.

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    Subscriber Member Jorgen Udvang's Avatar
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    Re: Chroma key

    Thank you, Robert, very useful post. Masking is exceptionally boring. I'm changing backgrounds on dozens of shots at the moment, and I really need to fight my lazy instincts. Luckily, all the people in that job wear helmets Unfortunately, that won't be the case for the possible upcoming job, which is an underwear thing (no, not the sexy stuff, sports underwear )

    The Hensel method sounds interesting. Might be worth a try.

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    Re: Chroma key

    I googled it its called hensel free mask and they advertise it for use almost exactly like you want to use it. Shooting on continuous high with a fast camera and the second flash is only a fraction behind the main- resulting in a perfect silo, or at least a great starting point.

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    Re: Chroma key

    evidently you can use a pocketwizard multimax on what is called "speed cycler" mode and it will trigger up to four sequential groups of flashes with a short delay, possibly it could do the "freemask" idea without having to buy the hensels.

    oh the internets!

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    Re: Chroma key

    Wouldn't it be possible to do it with hot lights on the background? For the subject lighting, most strobes won't recycle fast enough to fire on the second shot anyway, at least not if used at anything near full power.

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    Re: Chroma key

    I think you do need some wattage to make it work, and then you can't be at full pop on the back lights. But they have videos of it in action.

    Anyway you don't have to get to pure white in the silo anyway because that is a raw frame and you can push it in post several stops to get pure black and pure white. Also levels will do it.

    If you had tungsten on the back I think the problem might be it could bleed into the foreground- even with strobe you have to be careful of that.

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