Mirror Lenses?

[disjecta]

Somebody explain to me exactly what these puppies are....

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=414112&is=DEMO&addedTroughType=search

I'm looking for a decent telephoto to use with a 35mm adapter and most of them are around the price of the DVX :) I'm looking for 600mm or greater....

These mirror lenses seem like a fantastic deal but, of course, I know there is a major catch....aside from it being a slow lens.

[Drew599]

Its a reflecting lens instead of a refracting. Which means that it has a parapolic mirror in the back of the lens, which sends the image to the black thing in the middle of the lens then back into the camera. I think the hubble uses something like this. I have never used one so I can't really help you with if there any good or not. They seem like a good idea and they're cheap.

[MattinSTL]

Lens designers noticed the ever increasing popularity of SCT (schmidt cassegrain telescopes) and the design advantages of them (larger surface area giving lower F for a given magnification in a shorter tube length) and they decided "why not apply this to camera lenses?"

The little black protrusion at the top of the lens is actually the secondary mirror... the image comes in around that and bounces off a precision ground parabolic mirror* in the bottom and is then focused on another precision ground mirror (the secondary) and is then focused through the exit pupil into the cam.

*Improvements in production processes are certainly raising lens quality and lowering costs... but in many cases mirror lenses are inferior to refractors. The differences are usually shown in absolute resolution... especially at the edges of the field.

For fair disclosure I'm not up on the very latest lenses and it's possible that they are finally offering designs with fantastic edge to edge sharpness in a mirror design... which would be great because you'd have all the power with half the weight of a similar power APO lens. (Still I doubt the glass industry has been sitting still over the years... so it's likely that APO flourite glass is still the resolution leader.)

[scharky]

From what I have seen with mirror lenses, is first, they are usually pretty slow "F8" or above, and they do have some abnormal visual properties, your bokeh looks much different and your lens flare looks like little rings. I have also found them to be visually inferior to most other lenses, but that is because the ones I have looked at have been the cheap ones, if I'm going to spend alot on a lens, I wouldn't get a refractor. By the way, which 35 adapter did you get.

[Petrus]

I used to have a Minolta 500mm F8 mirror lens. Short and light, but the only F-stop was 8, which is a slight problem. Mirror lenses picture out of focus points as rings, which shows clearly in bright out of focus light reflections, also OOF straight lines show as double lines.

For daytime shooting they are ok, especially with modern fast digital cameras, and why not video, too. For a normal dv camera 500mm is looooong...

[Don Tucci]

Good basic long lens .The problem is not fast ,no apature adjustment,no afs ,no vr .Long lenses dont allways focus all colors the same .The term appo and appochromat.Mirror lenses are usable but not easy.Don

[MattC]

I used to used these quite a bit for surveillance work. I don't think you'll be happy with them. As already stated, they're slow, combine that with the light lost due to the adapter and you now have an uber slow lens. Of course if you're shooting in broad daylight that might not be such a concern. The quality of the glass/lens never seemed to be that high as compared to regular high powered lenses. Sort of like hooking your camera up to a spotting scope.

This was the very reason I went with the XL2 - the ability to attach 35mm still photo lenses (with the EOS Adapter) to achieve high magnification. Now that said, if what you want is reach, is there anyway to fashion an adapter that would allow you to attach a regular camera lens to your DVX. Granted you won't get the DOF but for pure reach the 7.5 additional magnification really helps. You can put a reasonably priced 300mm lens on there and get the equivalent of a 2,250mm lens....

Matt

[MrBirdBoy]

They Are more an effect that a REAL lens choice. Like others have said, the highlights as rings are fun sometimes, but if you want a real lens they do cost alot. Try a 200 or 300 with a doubler. It will still be faster & sharper. But heaver.

I think we all should shoot at least 1000' of 16 just to see how great we have it with out little DVX's

[disjecta]

Thanks for the feedback guys. I have since done some research and seen examples and the bokeh is totally unacceptable for me to create useable footage. Oh well, back to the drawing board :)

Stefan, I'm considering the G35. I will also be testing Wayne Kinney's SG35 at the end of next month.