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Testing Film Stocks & Filtration


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#1 Matt Smith

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Posted 21 June 2010 - 01:34 PM

Hey guys.

I'm getting down in the trenches I guess in working with film and I wanted to try and get a better understanding of the relationships between various film stocks and filters. I've shot a couple projects using mostly Kodak 7219 and some 7205. I understand basic color conversion filters like the 85 & 80A and NDs, but where I get lost is the "other" filters. So I want to do some simple tests with the Kodak 7219 and 7207 stocks and various filters. Any recommendations on what types of filters I should test? Which types of filters would I find handy on most sets? What types produce specialized effects? Is there any protocol I should follow in the actual testing? Thanks in advance!
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#2 Adrian Sierkowski

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Posted 21 June 2010 - 01:41 PM

I'd look into Diffusion filters. Try testing all their grades and makes and what i"d do would be your standard over/under exposure tests as well as highlight flare tests, with different types of highlights at variable over/unders. So I'd go candles +1 stop/+2 stops etc.. and then practical lamps, fresnels, sun.
I would also test out against varying types of skin and makeup-- though that is getting a little bit specific. I find the filters I use most on set, aside from the typical CCs are diffusion.
Also see if you can test 'em out on film as well as on some HD cameras, as I'd say on the HD/DCinema beasts that's where you'll use 'em the most.
Also, test them out at different ratios, 2:1 4:1 etc.
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#3 Rob Vogt

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Posted 21 June 2010 - 01:49 PM

When you say other filters, if you mean like Chocolate- or Amber, Most people wouldn't do exposure compensation just make sure you have a properly dense negative and a higher printer light by overexposing by 1/3 or 2/3s stop and you should get the filter's intended affect. If you wanted to do a diffusion filter test you should also test them at varying focal lengths. As for your question about which is most handy on set- that has more to do with the camera/stock and story.
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#4 Matt Smith

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Posted 21 June 2010 - 09:45 PM

Nice. Thanks for the replies guys. I definitly plan on testing the diffusion filters, and thanks for the tip about testing it under practical and sunlight lighting. The only thing I was lost on was the ratios. Were you talking key/fill ratios or something else?

Also, one more question...would filters have any type of noticable variant effect due to distance from the lens? Like would a twist on filter respond differently to one placed in a matte box? Might sound silly, but it popped in my head.
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#5 Adrian Sierkowski

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Posted 22 June 2010 - 02:57 AM

Yes Key to Fill for the ratios, and also There probably will be a difference, especially on smaller format cameras (which have generally deeper DoF) especially on diffusion filters the further they are from the lens. I can't say I've ever used screw ons on a cine-camera, though, aside from the UV/Haze I keep on my EX1 just to keep the lens safe from dust/scratches. I doubt you'll really notice a problem too close to the lens (though as you stop down you'll start to have some issues on some diffusion filters if you're on a wide lens).
Another thing to look into as well with diffusion filters is how they effect objects at varying differences and shot sizes for the grade (e.g. 1/4 v 1/2 v 1 ). Perhaps do something like 50mm @5ft/10ft/30ft (move person back) , then Wide shot/Mid Shot/Close Shot (move camera). Repeat for a few lenses you tend to go towards a lot (in my case it's be an 18mm, 35mm (maybe a 50.. depending on the day), and 75mm, for 35mm (9.5/16/50 for S16mm).)
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