cheapest basic 8X10 lens
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cheapest basic 8X10 lens
I am building a right angled camera obscura thing at work on thursday, basically it will be as follows:
square wood box
pin hole in the 'front' side
mirror internally at 45deg
opaque perspex (ground glass effectively) top
the idea being you point it at your subject, stick a bit of paper on the top and a dark cloth over your head and you can copy the scene onto your paper. it has to be quite portable.
I guess the internal optical length will be about 20-30cm so I'm looking for a cheap lens in that kind of length to substitute for the pin hole to give me a brighter image.
any suggestions, the budget is very limited, they are moaning at £10 for the mirror I'm wondering about things like tescos reading glasses or trying to blag a single lens from specsavers in town etc (I think i need about a +4 dioptre lens).
any help or suggestions?
square wood box
pin hole in the 'front' side
mirror internally at 45deg
opaque perspex (ground glass effectively) top
the idea being you point it at your subject, stick a bit of paper on the top and a dark cloth over your head and you can copy the scene onto your paper. it has to be quite portable.
I guess the internal optical length will be about 20-30cm so I'm looking for a cheap lens in that kind of length to substitute for the pin hole to give me a brighter image.
any suggestions, the budget is very limited, they are moaning at £10 for the mirror I'm wondering about things like tescos reading glasses or trying to blag a single lens from specsavers in town etc (I think i need about a +4 dioptre lens).
any help or suggestions?
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Re: cheapest basic 8X10 lens
I'm thinking big magnifying glass. Or even one of those fresnel sheets - they come in A4 size for a couple of quid: http://www.ebay.co.uk/itm/Fresnel-Page- ... 2eb6511c20
Neil
Neil
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Re: cheapest basic 8X10 lens
not sure how well the fresnel sheet would work, but I like your thinking.
Your certainly in the right area budget wise I've tried a couple of cheap magnifying glasses and most seem to have too shorter focal length at around 150mm, hence my thought at a lens from some reading glasses.
Your certainly in the right area budget wise I've tried a couple of cheap magnifying glasses and most seem to have too shorter focal length at around 150mm, hence my thought at a lens from some reading glasses.
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Re: cheapest basic 8X10 lens
It will have to be tracing paper on top? Have you read the Hockney book on the old masters useage of lenses & mirrors - can't remember the title? Sounds similar. Dennis
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Re: cheapest basic 8X10 lens
Just tried a smaller 3.5" * 4.5" fresnel I have lying around (from the same supplier I pointed to) and it's focal length is also about six or seven inches. It's a very bright image, though...
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Re: cheapest basic 8X10 lens
Hi Bill
magnifying glasses are the way to go - having said that I've only seen published images on a 4x5, however
now if you're after interesting unusual good quality glass, then the Surplus Shed is well worth checking out - here's the link - http://www.surplusshed.com/
regards
andrew
magnifying glasses are the way to go - having said that I've only seen published images on a 4x5, however
now if you're after interesting unusual good quality glass, then the Surplus Shed is well worth checking out - here's the link - http://www.surplusshed.com/
regards
andrew