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Old 28-04-2021, 04:29 PM
Mickoid (Michael)
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Join Date: Feb 2016
Location: Melbourne, Australia
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Quote:
Originally Posted by Sunfish View Post
Interesting. I have thought of it. I have my sons medium format camera lying around and some film. To reduce the cost of errors one could use BW film developed at home and RGB filters , then scan the film and combine. Problem is working out focus unless you have an identical digital body or can do knife edge focus on the film body.
I like your idea, should still work using that technique on a 35mm SLR provided there are some bright stars in the FOV to focus on. RGB filters are normally parfocal so once you've focused through one, usually the green filter because it's the brightest, the other two should be in focus, provided nothing moves in between exposures. I think from memory Ilford HP5 is 400 ISO but can be pushed in processing 3 stops if you calculate your exposure based on an ISO value of 3200. I shot the Carina nebula on Konica 3200 ISO colour film about 30 years ago and at f10, I needed an exposure of 30 minutes. You may need more time than this using HP5 B/W film and RGB filters, depending upon your working focal ratio. The blue filter will be the extra long exposure using film. Good luck!
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