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12-30-2012, 02:22 PM   #1
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QTII 500mm F8 Mirror Lens

I just purchased the subject lens and wonder if anyone else in this forum has experience with this or similar mirror lenses. I got it on a whim and thus far I am pretty unhappy with the quality of the images I get. I was forewarned that images would be flat with narrow depth of field, but I what I am getting seems to suffer from much more.

What I see in the view finder appears very crisp when in focus, which is, admittedly, quite sensitive, However the images I get are always out of focus, or out of something,

Anyone have any actual experience with this sort of lens?

Thanks,

Bill

12-30-2012, 02:50 PM   #2
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Not familiar with that particular brand but I did (briefly) have a 500mm f/8 mirror. I never did get a decent picture from it. However, I was just starting out and I've learned a lot since then. But even so I'm not tempted to try again.

I'm going to guess and say you paid maybe $150usd for it? Note that a really good 500mm, the Sigma 500mm f/4.5 goes for about $4,500. The new Pentax 560mm will be around $7,000.

There are a few things you can do to help but you just are not ever going to get great images from that lens. Anyway, a tripod and really bright light will help. Check a DOF chart or calculator, the DOF on that lens is really small. Try focusing with liveview zoomed in. 500mm lenses are an art form to use properly, just because the mirror lens is so small people think it is easy to use but it is still 500mm. You need a solid tripod, possibly weighted with sand bags, no wind, remote release, mirror lock up and anything else you can do to eliminate vibration.
12-30-2012, 05:17 PM   #3
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Hm, mirror lenses tend to be quite.. special. Can you maybe post a sample photo?

At 500mm and f8 you really should use it on a tripod.
I also heard that a lens hood will significantly improve the quality of a mirror lens (and the hood can be quite big. Lots of people make one themselves).
You can try calculating the DoF online, so you can see how narrow the DoF actually is.
Oh, and mirror lenses have a special kind of bokeh - donut shaped. It can work great in some photos, but can ruin others, so you have to work with it.
12-31-2012, 06:02 AM   #4
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Hi there.

I've owned several mirror lenses, and only one that I've owned has been a good one. The Russian Tair 3M-5CA. Even on a tripod, the others ranged from disappointing to awful. That said, unless you're using a tripod and a lens hood, you don't really know how well yours performs. I would take some test shots in good light of something with some detail, on a tripod with a lens hood attached and see what kind of results you get. If it's still disappointing, ditch the lens and look for a Tair 3M-5CA, 3M-5A, 3M-6A, Tamron 55B, or 55BB. These are about the only good mirror lenses for Pentax that I'm aware of. The Tair 3M-5CA is a teeny bit sharper than the Tamron, but the Tamron is a little more elegantly designed. You won't go wrong with either, though.

My wife has a Tokina 500mm mirror lens, and it's certainly much better than the off-brand lenses, but softer than the Tair or Tamron. Those are the big Kahunas.

Just keep in mind you really need a hood to get the best out of any mirror lens, and either a shutter speed of 1/750 or higher, or a tripod is a must.

Cheers & good luck!
Bobbo :-)

01-01-2013, 01:26 PM   #5
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When your subject is miles away, atmosphere has a big impact on image quality. I can see the Rockies from my deck but they're 30-50 miles away and lots of city or suburbs in between, so the air is usually disturbed. Even a great mirror lens has trouble with atmosphere.

Mirror lenses often have rear-mounted filters, and a filter issue (wromg one, dirty, missing) might cause problems.

You need some light to handhold a mirror lens, like Ev 15 (full sunlight). When you have enough light, it can be the worst time of day for a good-looking shot.
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