Look at these copy lenses? This could work?
http://www.rolyn.com/html/page_3__v..._CMSprod__companyid_64329__lineid_1016__.html
I'm waiting for your comments.
Bye.
Tonga
http://www.rolyn.com/html/page_3__v..._CMSprod__companyid_64329__lineid_1016__.html
I'm waiting for your comments.
Bye.
Tonga
http://www.apogeeinc.com/optics.html
i found this site a while ago, they have some copy type lenses near the bottom of the page,
hope someone find this usefull
i found this site a while ago, they have some copy type lenses near the bottom of the page,
hope someone find this usefull
Guys the enlarger lenses are the most likely to work with the DIY projects we have. The projection lenses on those sites are for projecting small 35mm film or something close to that in size.
the f4.5/500 mm is perfect for a 15 inch LCD as it will give a better projection distance size ratio.
The 240 will work well with a 7 inch lilliput and the 300 will be good for 10 - 13 inch LCD's.
Those lenses are wide aperture so they will gather and project a lot of light.
Because they were designed for enlarging don't think they are'nt good lenses. For DIY projectors we want copy type or enlarging type or large format photography lenses.
Hezz
the f4.5/500 mm is perfect for a 15 inch LCD as it will give a better projection distance size ratio.
The 240 will work well with a 7 inch lilliput and the 300 will be good for 10 - 13 inch LCD's.
Those lenses are wide aperture so they will gather and project a lot of light.
Because they were designed for enlarging don't think they are'nt good lenses. For DIY projectors we want copy type or enlarging type or large format photography lenses.
Hezz
Don't get me wrong - I'm sure copy lenses are fine if the price is right, but if you're ordering new, surely a long FL projection lens designed for a higher object / image ratio would be better.
Copy lenses are optimised for maximum edge to edge sharpness and minimum geometric distortion - expensive, and not the most important factors for video (unless you're projecting text, etc). IMHO, the money's better spent on a large (say f/1.8) aperture.
OTOH, there are a lot of scrapped process cameras out there since digital became the norm in printing, which have superb quality lenses. I've seen them going for free (and some have xenon arc lamps...)
Copy lenses are optimised for maximum edge to edge sharpness and minimum geometric distortion - expensive, and not the most important factors for video (unless you're projecting text, etc). IMHO, the money's better spent on a large (say f/1.8) aperture.
OTOH, there are a lot of scrapped process cameras out there since digital became the norm in printing, which have superb quality lenses. I've seen them going for free (and some have xenon arc lamps...)
dnsey,
I can see your point but unfortunately the lenses you are talking about do not exist for large format projection. Having one custom made would cost thousands of dollars.
Also the sharp wide angle field of view is exactly what we want for our projectors.
I have only occasionaly seen a used large format process lens so my feeling is that they are not so easy to find.
Hezz
I can see your point but unfortunately the lenses you are talking about do not exist for large format projection. Having one custom made would cost thousands of dollars.
Also the sharp wide angle field of view is exactly what we want for our projectors.
I have only occasionaly seen a used large format process lens so my feeling is that they are not so easy to find.
Hezz
Hi Hezz,
I beg to differ - large circle of illumination lenses are made for industrial projectors, episcopes, etc at fairly reasonable prices.
Edge sharpness, is, of course, relative, but TV camera lenses are not particularly good in this respect, on the basis that there's rarely any object of interest in the peripheral field. There's no point in trying to resolve what's not present in the source material. Try testing the average commercial projection lens, and you'll see what I mean!
Try printing equipment dealers for cheap process lenses - they sometimes have to take away cameras as part of clearance deals, and there's virtually no resale market any more. There's also a good chance that your local printer has one stored away somewhere which they don't use any more, and would be glad to sell for a nominal sum.
I beg to differ - large circle of illumination lenses are made for industrial projectors, episcopes, etc at fairly reasonable prices.
Edge sharpness, is, of course, relative, but TV camera lenses are not particularly good in this respect, on the basis that there's rarely any object of interest in the peripheral field. There's no point in trying to resolve what's not present in the source material. Try testing the average commercial projection lens, and you'll see what I mean!
Try printing equipment dealers for cheap process lenses - they sometimes have to take away cameras as part of clearance deals, and there's virtually no resale market any more. There's also a good chance that your local printer has one stored away somewhere which they don't use any more, and would be glad to sell for a nominal sum.
Hello dnsey,
Forgive my ignorance but I'm not entirely shore which lenses you prefer. Surely a lens that can focus the entire LCD would be much more natural than one that can only focus the centre.
I have to agree with Hezz on this one. Most projection lenses are designed to work well with the object they are focusing on, in this case film. If you look at the size of the lens compared to the size of the film, the lens is generally larger than the film. In this situation you are correct in saying that the peripheral field is not important. When we try to focus on an object that is larger than the lens, a LCD, the peripheral field is very important.
That’s what I reckon anyway.
DJ
I'm not suggesting using a lens which can't focus on the periphery of the object - just that correction of abberations in that area is not, IMO, a high priority for this application. In fact, in the scheme of things, resolving power is not too important anyway, as anything but the very worst lenses will have a resolution orders greater than a video screen.
I'm not sure what you mean by the 'size' of the lens compared with the object - if you mean focal length, then I agree (roughly) that a focal length comparable with the diagonal of the object is required. (Actually, it's not quite that simple - lenses of the same FL can have very different circles of illumination). Not a problem - projection lenses come in a wide range of FLs (as a simple example, OHP objectives - not that I'd suggest using one of these).
In an ideal world, I'd prefer to use a properly designed projection lens of appropriate focal length and wide aperture. Perhaps not quite so easy to find second hand or surplus, but worth the search.
As an economical and easily obtained alternative, a process lens is intended to work at similar object / image distances and magnifications to most DIY LCD projectors, but will generally have a smaller aperture than a proj lens.
Copier lenses are usually corrected for small enlargement / reduction ratios, and have a fairly small aperture, so I don't believe that they are ideal for the job. The site suggested appears to sell new copy lenses, which are not cheap compared with surplus lenses which I think would be more suitable.
However, each to his own
I'm not sure what you mean by the 'size' of the lens compared with the object - if you mean focal length, then I agree (roughly) that a focal length comparable with the diagonal of the object is required. (Actually, it's not quite that simple - lenses of the same FL can have very different circles of illumination). Not a problem - projection lenses come in a wide range of FLs (as a simple example, OHP objectives - not that I'd suggest using one of these).
In an ideal world, I'd prefer to use a properly designed projection lens of appropriate focal length and wide aperture. Perhaps not quite so easy to find second hand or surplus, but worth the search.
As an economical and easily obtained alternative, a process lens is intended to work at similar object / image distances and magnifications to most DIY LCD projectors, but will generally have a smaller aperture than a proj lens.
Copier lenses are usually corrected for small enlargement / reduction ratios, and have a fairly small aperture, so I don't believe that they are ideal for the job. The site suggested appears to sell new copy lenses, which are not cheap compared with surplus lenses which I think would be more suitable.
However, each to his own
dnsey,
According to my rough estimates we should need between 27 to 35 degrees of a field of view depending on FL and LCD size. This is total field of view accounting for both sides of optical axis.
The enlarger lenses should be designed for about 30 - 40 degrees field of view. Lenses with a wider field of view would be much more costly and the ones I looked at on the above website don't look like they are designed for really wide field of view.
I have spent 2 years looking for the right 500 mm lens and I have given up and the above is the closeset thing that I have seen to an ideal triplet that I optimized in software.
Hezz
According to my rough estimates we should need between 27 to 35 degrees of a field of view depending on FL and LCD size. This is total field of view accounting for both sides of optical axis.
The enlarger lenses should be designed for about 30 - 40 degrees field of view. Lenses with a wider field of view would be much more costly and the ones I looked at on the above website don't look like they are designed for really wide field of view.
I have spent 2 years looking for the right 500 mm lens and I have given up and the above is the closeset thing that I have seen to an ideal triplet that I optimized in software.
Hezz
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