500mm mirror lens on dSLR?

[puttick]

Hi

has anyone tried a 500mm (usually f8 ) mirror lens on their 1.6x crop factor SLR? I was wondering about the effect of the smaller frame size in relation to the image circle of the lens, given that it is a catadioptric lens with a central obstruction.

For example, Tamron 500/8 adaptall II lenses can have an EOS adapter, and also the Russian MTO 500/8 in 42mm fitting can be used with an adapter.

Thanks
Nigel

[Sicily1918]

I have not, but I would think that it would not make much difference -- after all if it's not in the way of a full-frame, which uses more of the glass, I would presume that it wouldn't do anything to a crop...

Now I'm curious... :?

[formula4speed]

I have a cheap 500mm lens I got many years ago as a gift, cost $99 from the back of some catalog (you get what you pay for). I'm not exactly sure what it is you want to know, I mean it technically works but the picture quality is well below par. It does make a nice spotting scope tho.

[CyberDyneSystems]

The examples I have seen have been no better or worse than what you'd get with ful frame,. ie: yes,. you still get donuts..

Anyone I know who has purchased one of these lenses has sold it immediately thereafter.

[FlyingPete]

The examples I have seen have been no better or worse than what you'd get with ful frame,. ie: yes,. you still get donuts..

Anyone I know who has purchased one of these lenses has sold it immediately thereafter.

Hmmm donut bokeh, makes me hungry, then it is lunch time here!

[yellow_belly]

Hi, I actually have the Tamron 500 SP f8 and I think its a T2 mount ???. I tried this on my Canon 300D without much success, nothing wrong with the image I just found manual focus soooooooooooo hard to get right with the shallow depth of field. The oof doughnuts can be a little off putting. I now have a Canon 20D but have not tried this combination yet, I should do as I now also have an 'Angle Finder C' which should make manual focusing much more precise as you can set it to magnify the image in the viewfinder a little.

I personally would not spend much money on one of these lens but it is probably ok just for the odd time when you need a little further reach.

Terry

[Gday3]

I have a cheap 500mm f8 for the 20D, made some test shots:

1) Focusing is not easy because of the viewfinder not haveing a split field

2) Image quality is not comparable to a normal lens but I am going on an Africa trip and want to use it only for extreme situations so it was a matter of use to money ratio for me, I just don't want to miss a shot and take a bit lousier quality in account.

3) Next time I would by a Beroflex lens, also cheap but better image quality

4) Use of a sturdy tripod absolutly necessary makes 800mm on the 20D, every shot even in bright sunlight without tripod was shaken.

Best wishes

Christian

[crazy rose]

hi!!!!!!!!!

wow great link...

Thankx

[Perfect_10]

... Anyone I know who has purchased one of these lenses has sold it immediately thereafter.
I agree .. I had one for my FD camera .. never liked it and sold it when I went to EOS

[puttick]

There is no reason why a mirror lens cannot be of excellent quality - indeed as the optical surfaces are reflecting rather than refracting there will be less risk of chromatic aberration, and less loss of resolution due to wavefront diffraction at each air/glass interface. This is the case for reflecting astronomical telescopes - it is easier to make an excellent Newtonian reflector than an equivalent refractor. However the central obstruction (due to the secondary mirror, in this case the silvered spot on the inside of the corrector plate) causes a problem at the eyepiece of such a telescope - if the exit pupil of the eyepiece is small, you get a floating dark spot in the centre which affects your view. I was thinking the the smaller sensor size of the 300/350/10/20 Canons would have the same effect - in other words, compared to full frame the central obstruction could reduce image brightness, and possibly resolving power as all the image circle of the lens is not being used.

So the real question again is - has anyone got any directly reportable experience of the results with such a lens on a small sensor dSLR?

Thanks
Nigel

[FlyingPete]

There is no reason why a mirror lens cannot be of excellent quality - indeed as the optical surfaces are reflecting rather than refracting there will be less risk of chromatic aberration, and less loss of resolution due to wavefront diffraction at each air/glass interface. This is the case for reflecting astronomical telescopes - it is easier to make an excellent Newtonian reflector than an equivalent refractor. However the central obstruction (due to the secondary mirror, in this case the silvered spot on the inside of the corrector plate) causes a problem at the eyepiece of such a telescope - if the exit pupil of the eyepiece is small, you get a floating dark spot in the centre which affects your view. I was thinking the the smaller sensor size of the 300/350/10/20 Canons would have the same effect - in other words, compared to full frame the central obstruction could reduce image brightness, and possibly resolving power as all the image circle of the lens is not being used.

So the real question again is - has anyone got any directly reportable experience of the results with such a lens on a small sensor dSLR?

Thanks
Nigel

I am wondering if one of the main reasons people don't like these lenses is expectations. Telescopes typically are used to view an object that for all itents and purposes is a flat field, such as the sky.

I have been tempted to try one for sky watching, as it has a simular focal length to my refracting telescope.

As for if they work on a small sensor, Gday3, has used one on his 20D, non of his complaints about the lens relate to issues with a dark spot caused by thecorrector plate.

[KevC]

Hm. MC Rubinar 1000 f/10 reflector for ~$250. That's quite interesting. Maybe to shoot moons or somethin....

[ron chappel]

There is no reason why a mirror lens cannot be of excellent quality .........


So the real question again is - has anyone got any directly reportable experience of the results with such a lens on a small sensor dSLR?

Thanks
Nigel

Mirror lenses can be quite good *if* you buy a high quality brand.
That means using something like a Zeiss mirotar,Leica or the current nikkor,etc via an adapter.
But even then a mirror lens will allways have less contrast than a normal lens because of the way the central obstruction effects the resolution output of the lens .
No i don't fully understand it either :)-Bob Atkins gives an explanation of it here .(as well as a good comparison with a canon L lens on a DSLR )
http://photo.net/learn/optics/mirrors/


From my own experience i haven't noticed any real problems/benefits when using these lenses on a reduced frame DSLR
(except the obvious benefit of being able to take shiploads of images and improve them in photoshop-which makes the cheapo mirror's *allmost* bearable to live with)

[rdenney]

Mirror lenses can be quite good *if* you buy a high quality brand.

Bob's article is excellent. I particularly liked is demonstration that MTF will be lower at 40-60 lines/mm than at 30 lines/mm, meaning that the lens will still be sharp but with somewhat reduced contrast. Constrast we can always add, of course.

But there are excellent mirror lenses that are not expensive. The Soviets in particular were really into mirror optics, offering both Schmidt and Maksutov designs. One of these days, I'm going to get the MTO 500/8, though I might go instead with the Hartblei upgrade of the Rubinar 500/8 for medium format and adapt it down to the EF mount. Both are much cheaper than the Tamron Bob tested, and reputedly far better than the 500/8 cheapies like the Samyang.

There is even a 500/5.6 Rubinar, but the 8 has better resolution.

They are mighty tempting.

Bokeh sucks, as expected with mirror lenses. Thus, don't use them when bokeh is important.

For hand-holding, we should remember (because here it's really important) that we have to use the equivalent full-frame 35mm focal length when using the 1/focal length rule of thumb for sharpness. Even if that rule works for a given person, the minimum shutter speed with a 500/8 for hand-holding is 1/1000. At f/8, that means on a sunny day, we can expect to have to use an ISO of 400 at a minimum, and 800 if the subject isn't lit by the sun. Monopod=good. But they are so light that it's tempting to forget the monopod.

Rick "noting also that an f/8 aperture on a mirror lens is more like f/9 or f/10 when it comes to exposure, because of the centreal obstruction" Denney

[puttick]

Thanks to Ron Chappell for the link to Bob Atkins' excellent article that really has all the answers. Of course it is possible to find a good used Tamron for relatively little, whereas a Canon 500/4.5 is a fabulous beast.

From astronomy I know about the reduction in contrast due to central obstruction, but I don't believe that applies to terrestrial subjects which are "extended objects" - stars are point sources surrounded by diffraction rings that are visible even in very good unobstructed optics - with a central obstruction light is lost from the point (star) and diffracted into the rings which reduces the contrast and somewhat reduces resolving power too for close binary stars.

In fact I have an excellent apochromatic refrating telescope - a TeleVue Genesis 100mm f5 (i.e 500mm FL) which uses flourite elements and has a field flatening group, is very close in size and aperture to the Canon, but has no diaphragm, and is somewhat heavier. I already have a T2 mount in EOS fit for it and have used it to photograph the transit of Venus. However, I would NOT want to shoot handheld with it!

[dale65bama]

I have a Vivitar 500mm mirror lens to use with my Canon Digital EOS (300D). Since effective focal length is 800mm, it needs a rock-steady tripod and remote shutter release. I worked with it today and all the images were about the same fuzz and blue fringes. The picture looks OK at a small size, but just won't work for more than a 4x6 inch print.

No problem with a central dark spot, but the donuts from background highlights are a little distracting.

I think I will get a eyepiece and use it for a spotting scope.

[jwceach]

I have a new Rebel and want to know how far a canon 100-400mm lens will go out and give a good picture?

[CyberDyneSystems]

All the way to 400mm...

If I understand your question correctly?

[Perfect_10]

1.6 x 400 = 640mm

[Sloany]

I have 3 Russian MTO mirrors. 1000mm, 550mm, and a 500mm that i use on my 20d with very good results on nature shots and moon photos. I also have a celestron C-90, a Meade C-97 1000mm, and a Meade EXT 90. The MTO`s out perform them as far as photo`s go. The others are great to look through but for some reason they do not shoot the sharp image the eye see`s ?? As far as the Bokeh goes, you just have to pay attention the the back ground i guess. At some point i would like to try a Sigma mirror, they seem to get good reviews. I have goofed aroung using the MTO 1000mm with
2, M42 vivitar , 2x matched multipliers for super close up work from 10ft. and moon shots, LOL. The Vivitar 70 - 150 2x Matched Multipliers are excellent (m42 ). I use them with many types of M42 mount lenses. You can`t beat the old glass. I also use some Nikor lenses on my 20d with outstanding results. I shoot almost always in manual mode. To date i have nearly 1100 shots of Dragon flies alone. If you don`t mind shooting in manual mode, you can find some great stuff at real good prices. I have 33 Vivitar M42 mount lenses, a handfull of Zeis, Sigma, Nikon, Nikor glass also. I found it cheaper to experiment with the M42 mount lenses to see what works for me.

[Wilt]

I have a cheap 500mm f8 for the 20D, made some test shots:

1) Focusing is not easy because of the viewfinder not haveing a split field


Even if your camera did have a split field rangefinder area, you would still not be able to use it with an f/8 lens because half of the split goes dark!

[jajurek]

I have Russian mirror 500/8. Use it on my Rebel XTi and results are not bad, and much better then on Rebel XT (contrast especially), maybe sensor is better too. Times should be shorter than 1/500, aperture seems darker then 8, near 11. I am used to FM and the sharpness isn't big problem. Setting is AP. CA isn't problem too.