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Justin, I agree... I'm tired of repeating myself.
Andre, you are saying that if you put 37mm wide angle lens on 37mm cam there will be no change. how about 54mm wide angle.. how about 250mm? you are saying that there will be no difference between having those different lens. arguments like "Only powerfull raytracing programs can show exactly what happens " or "Convertor lenses are not designed to change lux ratings." no one said they are designed for that, that doesn't mean it does not happen either.... |
Yes George, once the convertor lens is "large enough", this means just shows no vignetting at the wide position of yr camera optics, the lens diameter doesn't make any difference. So you can put a 250mm diameter convertor in front of yr 37 mm camera optics... only a small central part of the convertor will be "seen" by the CCD(s). By "not designed for.." I mean that the optical challenges for convertor design are avoiding field distortion and field curvature while keeping good resolution specs. Most of the time this ends up in some lightloss. With raytracing programs one can verify and optimize those parameters. One could also easely verify how much light would be wasted with the 250 mm lens on a 37 mm cam.
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Andre, I didn't want to go into this but.... see.. the light collected by a lens is determined by it's surface area (the higher the angle - the more surface, the higher the diameter - the more surface again)
if the lens is doing what it is supposed to do then that light will be transfered to the original lens. maybe 250mm was a bit too much, but this (85mm) can and was used by someone, on dv953: http://www.fortvir.net/albums/tom-s-photo-album/deep_curvature.sized.jpg and I was wondering IF the extra collected light by the lens was enough to make a difference after considering the light loss of aditional light-direction correction trough the extra lens(es). the fact of the increased (amount of) light collected is beyond contestation, I was wondering how much after the additional loss is left and if it makes visible difference. anyway... we are going no where like this. when I get my cam, I'll make the tests and post the results. |
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I might just have to reconsider a 37mm and 43mm wide angle for that extra LUX. |
Frank I think I answered this question some time ago =)
The only miniDV cam I have available now is not my personal cam and it's canon XL1. If I could I would have done it and not even talked about that in a forum. Maybe Andre can use the "raytracing programs" and tell us the results when we use this: http://www.fortvir.net/albums/tom-s-...ture.sized.jpg on dv953 ps. do you want to know my background too? ps2.how about considering the 85mm? http://www.fortvir.net/albums/tom-s-...ture.sized.jpg |
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a program like this should be able to report the net-change of the light falling on the CCD after you put the 85mm wide-angle adaptor.
you know what.. enough is enough... i'm out of here... =) |
Frank, he's funny eh?
BTW, no, a ray tracing program does not report such information. |
Well, I don't know anything about this program. That's why I asked about it; and I don't have a broadcast engineering background like Andre. Though I hope he can do some scientific LUX measurement tests for us with the PV-DV953 (or GS500, or XL1, etc) and a wide angle lens. I'm looking forward to his results. It should be good reading.
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Well Bob I am not shure if you ever used a raytracing program because you then should know that those programs do a lot mors than just show how the rays are bend...
Setting up a project for raytracing for convertor lens principles is beyond the targets of this forum I think...and takes some time. Two further remarks: 1.I just verified my VX2000 (in full manual mode with and without the Canon WD58 at 50IRE for the central image part. Result: no measurable change in IRE levels. I hope some body else will do the test too...for the non-believers. 2 George. it's not allways easy to "explain" how optical components believe, but I will give it a try: A wide angle convertor lens is in it's basic form a large positive lens and a smaller negative lens at a distance (like 1") well within the focal distance of the positive lens. Both lenses have the same power but with opposite sign. The positive lens "collects" (bundles) the incoming light on an area much larger than the negative lens area. So only part of that collected light is being used for further transmission through the negative lens. Why this "loss"? Well off axis image points have still to shed enough light on the negative lens in order to avoid off axis light fall-off. In optical terms this means that the image field area at the negative lens plane is much larger than the lens area. Still questions? |
Yes. When I was with SGI and Pixar I wrote ray tracing programs.
The problem is he wants visual proof and not "talk". |
Bob, I do know those companies and there research in raytracing and radiosity for synthetic image rendering, but "raytracing" in the geometric optics (lens design) world is not at all related to that. Download e.g. the free "Winlens" program and you will see what it is all about raytracing in optics.
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Thanx Andre =)
(finally someone who knows what he's talking about Rob) Andre, actually I was wondering if there is actual improvement after pieces like Aspheron 85mm http://www.fortvir.net/albums/tom-s-...ture.sized.jpg I know that there are imperfections, but as a whole what would the net effect be? So I was asking for someone to test it if he can, that is. Thank you. |
George, I'am happy I could give you a feeling about that stuff. Unfortunately, I can't help you any further on the Aspheron product. I suppose it contains aspherical lens elements like most wide convertors do. It used to be difficult and expensive to manufacture aspheric lens elements but since acrylic lens production technology is well mastered, most consumer cam optics (not only the convertors)contain internal aspherical components. This is much cheaper than using a bunch of different refractive index glass components to fight all kinds of aberations and distortions. If I would buy such a convertor I would first screw it on my cam and see what happens, because depending on your own optics (mainly wide properties) you could end up in vignetting, and/or excessive brightness fall-of in the corners.
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Thanx Andre, I was planing to do the same thing =)
I'll have to wait to get the gs400 cam first =/ |
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