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12-25-2008, 11:13 PM   #1
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Mirror Lenses...

I would like to know if anyone has used mirror lenses (Matsukov-Cassegrain or Schmidt-Cassegrain kind-of type) on their cameras. The idea has come to me since i rarely need something that has a long reach (over my 250mm that my 18-250 offers) but once in a while i would like to have some extra reach for various reasons. If you used some, do you like them? Is that usefull? Did it turned out to be a good landfill item?

Quality wise, anyone has some example pictures? I know that it will not come close to a FA* 500mm F4 lens, but for something that will be used 2 or 3 times a year , and the fact that they are generaly cheap to buy...

Thanks!

12-26-2008, 12:31 AM   #2
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You might want to read this prior post. I like the mirror lenses i have despite their quirks.
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/27457-tokina-f8-mirror-lens.html

I shot a bunch of birds in the back yard to test the lenses. go here to see the pics: Art by Michael Wolf - RedBubble
12-26-2008, 12:38 AM   #3
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This was taken with my K100D Super and a 600mm f/8 Sigma mirror lens. The lens is amazingly light and compact for it's focal length, but it's not very sharp, has a fixed aperture and out-of-focus highlights look light donuts. It's fun to play with, but it's limitations can be frustrating.

12-26-2008, 06:48 AM   #4
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Yes... this thread has a lot of info

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/39219-rokinon-...dx-mirror.html

12-26-2008, 08:54 AM   #5
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Thanks for the comments!
12-26-2008, 10:27 AM   #6
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I have a Sigma 400mm f/5.6 mirror lens and am quite happy with it. CAT lenses do have their limitations, but every lens does. The truth is, on a digital camera, the inherent limitations of mirror lenses (low contrast and lack of sharpness being the main two) can be circumvented easily with postprocessing if you shoot RAW, or in-camera settings if you shoot JPEG.

You can find some of my photos with my mirror lens in this thread.
12-26-2008, 11:29 AM   #7
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Hi all,
some very informative threads on here about mirror lenses!

Here are two more links on tests.

Maybe Ben is just right about his Tamron 500,
Mirror Lenses - how good? Tamron 500/8 SP vs Canon 500/4.5L
The result is against the grain of the other tests (or it means that the Tamron is just really good)

Other tests I've seen always put the mirror lenses way down below refractive ('normal') designs, like here,
Lens Comparison Photo Gallery by Token at pbase.com



Tokina mirror lens 500/8 on K100D + tripod


Ivoire,
many thanks for pioneering a little in the Tokina thread and also not missing out on the obvious downside of a mirror lens design.

That same Tokina 500/8 fell in my hands, so I gave it a try. I have found it very hard to shoot without a tripod, but possible if you support the cam/lens by a lamp post or similar - OTOH before too long this will ruin your lens paint (it was mint when I got it, oh oh ;-). The genuine skylight filter was included and stays on the back.

I am basically looking for an inconspicuous walkaround lens, and that is why I wanted to try the Tokina. So far it turns out that 500mm is too long. The K100D shake reduction does a good job, but here it's over the limit. Also, at close distances the SR starts a low frequency buzz / flurring sound which does not sound healthy (pics are blurred when this happens).

Resolution / Contrast / Sharpness / IQ: However you call it, this lens (and FWIW all mirror lenses?) has noticibly less of it than those 'normal' lenses. Allright, no cropping, lots of light needed, take anything to improve this. But: If you can crop a 240mm image to the same quality as from the Tokina, what's the point? For me that would be still an argument, as that 240mm 'normal' lens is still 2 or 3 times physically longer than the mirror lens.

Conclusion: Looking for a small 300ish mirror lens.
- Rubinar 300/4.5 is too big and heavy, although it looks like on top IQ-wise. Diameter is definitely beyond the 'digital flash beak'. Wonder if you'd get infinity.
- Minolta Rokkor 250/5.6 mirror: Saw one go on the bay recently, around 200 euros, mmmh. (would be my ideal solution, tiny lens, reportedly good IQ)
- Ohnar 300mm: Seems too exotic to bother looking for it (IQ?)

Happy holidays,
Georg (the other)

Last edited by georgweb; 12-26-2008 at 03:18 PM.
12-26-2008, 02:40 PM   #8
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I've got the Maksutov 1000 mm F10. Works well, and I got it for a great price. However, I do find focusing a bit tricky with this lens, and thus, you need to use both a sturdy tripod, and possibly a cable release. I shot the moon with this lens. On a wobbly tripod. And using 2 sec mirror prefire. Needless to say it was tricky, but worth it.

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12-26-2008, 02:56 PM   #9
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I have a celestron C90, (1000mm F11) and have had to do some re-work to stabalize it.

my copy has rubber armor and the lens mount is (was) screwed to the lens through the rubber, leaving it less than stable.

I have since reqorked this, by cutting the armor around the mount, and epoxying the mount directly to the body.

I have yet to really give it a work out.

I think peter zack has a meade, and had similar issues with stability and vibration
12-26-2008, 02:58 PM   #10
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I have the Schmidt-Cassegrain 1000mm f10 version. Not very expensive and a fun lens for some subjects. I posted a lengthy thread on this back in July. It's a pretty good performer even if a bit tricky to focus.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/32864-first-te...mm-k10d-2.html

Here's a few pictures taken with the lens since that post.





Last edited by Peter Zack; 12-26-2008 at 03:04 PM.
12-26-2008, 03:20 PM   #11
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Based on your last post, you might want to try the tamron or sigma 70-300mm lenses. they also have their limitations but offer decent performance for the price (usually around $100-150 used or new). they have been discussed extensively in this forum.
12-26-2008, 05:15 PM   #12
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QuoteOriginally posted by ivoire Quote
Based on your last post, you might want to try the tamron or sigma 70-300mm lenses. they also have their limitations but offer decent performance for the price (usually around $100-150 used or new). they have been discussed extensively in this forum.
I would agree. I didn't read those comments fully before posting and think that there are a couple of decent choices. The Sig/Tam lenses would work very well at a reasonable cost. Also the Pentax DA55-300 is reported to be very good and maybe the DA50-200mm is quite compact although the 55-300 would be the better lens in terms of IQ.
12-28-2008, 03:54 AM   #13
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QuoteOriginally posted by georgweb Quote
Conclusion: Looking for a small 300ish mirror lens.
- Rubinar 300/4.5 is too big and heavy, although it looks like on top IQ-wise. Diameter is definitely beyond the 'digital flash beak'. Wonder if you'd get infinity.
- Minolta Rokkor 250/5.6 mirror: Saw one go on the bay recently, around 200 euros, mmmh. (would be my ideal solution, tiny lens, reportedly good IQ)
- Ohnar 300mm: Seems too exotic to bother looking for it (IQ?)
Hi Georg,

I think the lens you're after is the superb Tamron Adaptall II 350/5.6. It's sharp, it's small and 350mm is a focal length much much more manageable handheld than 500mm. The only downside is that the Tamron 350mm is pretty rare.

Here are some pictures taken with mine (sorry to those who have already seen them):








Cheers!

Abbazz
12-28-2008, 04:55 AM   #14
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A good mirror lens can be sharp and have enough contrast for photography. I used a Tokina 500/8 way back in film days with my LX or PZ-1p and always got good results - if you like the donut-shaped oof-circles.

I think many people ignore the simple fact, that mirrors/catadioptrics always are very prone to loss of contrast through flaring. So one always needs to use a lens hood. At 500mm focal length, the lens hood will be at least as long as the whole lens, to be effective. You can make a simple scale drawing to see, whether a hood is long enough to shield the front lens from stray light.

Also, the tiny size of many mirrors fools one to believe it could be used handheld all the time. At 500mm fl it can't.

Certainly there is a "built-in" lack of contrast, compared to standard lens-based lenses and ofcourse the better the internal baffling against stray light, the severer the vignetting gets in a mirror/catadioptric. But if used carefully, they can provide decent results. Just don't use a 89.99 USD lens as a base for comparisson. A mirror lens cannot be produced with decent quality at that price! The mirror's surface needs to be at least two times more accurately figured and polished than a glass lens and that simply costs money.

In my opinion a large part of the bad reputation of mirror/catadioptric lenses comes from people using el cheapo products.

Ben
12-28-2008, 06:11 AM   #15
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A couple of shots taken with a K10D + Sigma CAT 400mm f/5.6, handheld with no lens hood:



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