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02-02-2014, 07:06 PM   #1
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Reflex T Mount Mirror lens - best use?

Hi all,
I am relatively new to photography and I am wondering what the pros and cons of a reflex- mirror lens are? I am interested in a Sakar 500mm F8 Reflex T Mount lens with a K mount adapter. What is the best use for a lens like this? Would this lens be good for astrophotography or macro shots ?

Thanks.

02-02-2014, 07:15 PM   #2
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It is a 500mm telephoto so usually used to bring far things close. Never heard of anyone using it for macro but with extension tubes you could I suppose.

That said those lenses are not that good, better to save for something better IMHO.
02-02-2014, 07:38 PM   #3
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Thanks Jatrax for your help. In the listing it mentions it has a built in macro close up. I believe I can get the lens for $50 or less and it is the k mount adapter included. It seems that at that price it is a steal.
02-02-2014, 07:54 PM   #4
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Don't know about the Sakar, but most mirror lenses don't focus all that close. Some are labeled as macro, and focus closer than other mirror lenses but you're not going to get 1:1 macro with a mirror lens.

The advantage of a mirror lens over a conventional lens of the same length is usually cost, size, weight and usually lack of CA or purple finging, so if you like to shoot pictures of the moon, this is great. The quality of the image from a mirror lens is usually going to be less than a conventional lens due to the bends that the light has to make when travelling through the lens. A mirror lens is usually going to have less contrast and sharpness than a conventional lens, only one F-stop (with the exception of the Ohnar) and usually a very narrow depth of field. But the one real downside is the out of focus highlights. Depending on the background of your image, the highlights in the out of focus area will look like a bunch of doughnuts.

Years ago alot of people found the doughnuts very attractive, and in some cases even today they can add a neat effect to some images, but while they can be avoided with carefull selection on backgrounds, they have a tendancy to become more of a distraction than anything. Again, I can't speak for the Sakar specifically, but if you are looking for a cheap entry into telephoto photography, and a lens that won't break your back carrying it all day long, then a mirror lens can be very enjoyable to use, for $50 I'd say it's worth a try.

Steve

02-02-2014, 07:58 PM   #5
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Thanks for your help Odinz. I enjoy taking pictures of the moon so I think this lens would be good for that.
02-02-2014, 08:33 PM   #6
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Yeah, moon shots are probably one of the strongest uses for a mirror lens.
02-02-2014, 08:42 PM   #7
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The cheaper mirror lenses are not generally very good as far as I have heard. The Tamron adaptall-2 500 mm f/8 lens is supposed to be good. I have their 350mm f/5.6 mirror lens and it is very fine. But that means an adapatll-2 pentax K mount adapter and the 500mm lens (likely $200. from KEH). There are two versions of the 500 mm lens--older one has a tripod mount on the lens--newer one not. If you plan to use a TC and/or extension tubes, then I suggest you need the older one with a tripod mount on the lens. (On the other hand I have heard the newer one is better--read the reviews here--also there is an adaptall-2 discussion group here on the pentaxforums--I believe there may be a mirror lens group as well.)

Yes mirror lens can be excellent for macro, likely to m=0.5 anyway [ which likely means addition of about 125 mm extension, or a 2x Teleconverter (TC)]. I actually bought it partly/largely for this use--the odd doughnut shaped out of focus highlights are generally not as big a problem w/ macro--and the long focal length means a large focusing distance--so skittish insects, etc. may not be so skittish.

But using a mirror lens is very hard to do--it means your camera technique must be good, high iso, usually tripod w/ SR off, not shooting over hot surfaces which cause atmospheric turbulence, etc. Many people give up and say they are NG--but it is often they don't take the care needed.

Last edited by dms; 02-02-2014 at 08:58 PM.
02-02-2014, 08:54 PM   #8
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And yes for astronomy! Newton made the mirror lens because regular lenses had distortion/could not be used. And through the present day many telescopes (and all the big optical ones) use mirror lens.

02-02-2014, 11:02 PM   #9
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QuoteOriginally posted by VisualDarkness Quote
Yeah, moon shots are probably one of the strongest uses for a mirror lens.
Thanks Visual Darkness.
02-02-2014, 11:27 PM   #10
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Thanks a lot for your advice dms. With my budget I will have to go with the Sakar but it will be a good learning curve so I understand how to use a mirror lens. Maybe down the road I will purchase a more expensive mirror lens. I plan on using the lens for macro shots in addition to taking pictures of the moon. Is there much difference taking pictures of the moon with a mirror lens as opposed to a "regular" lens? I understand the technique fairly well, at least enough to take decent pictures of the moon with my Pentax A 1:4 70- 210 lens.
02-03-2014, 01:04 AM   #11
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Taking moon w/ 210 mm versus 500 mm f/8 lens. Some of the following you may already have done.
-- Need to carefully focus the mirror lens--cannot simply set on infinity.
-- the f/8 is for depth of field--actual for exposure is likely f/11 to f/16, but the camera will meter the moon.
-- If you did it already you know to spot meter moon and set exposure at +2 to +3 e.v. about.
-- Hang weight on the tripod
-- Use 2 sec. mirror up and anyway it may take longer for vibrations to die down--so use cable release/remote/do gingerly.
02-03-2014, 11:43 AM   #12
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Thanks dms.
02-03-2014, 04:06 PM   #13
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QuoteOriginally posted by t.manning Quote
Hi all,
I am relatively new to photography and I am wondering what the pros and cons of a reflex- mirror lens are? I am interested in a Sakar 500mm F8 Reflex T Mount lens with a K mount adapter. What is the best use for a lens like this? Would this lens be good for astrophotography or macro shots ?

Thanks.
From a practical point of view a 500mm is going to be hard to use handheld.

If you want to use it as a general tele lens then you might be better off getting one of the less common 300/350mm ones (Ohnar, Super Paragon, Tamron etc.).

Manual focusing is not going to be easy (catch-in-focus often does not work and depth of field is quite shallow) and unless you swap your focusing screen for a better one than the stock Pentax you might have to rely on LiveView focusing. A good deep hood is just about essential and even so you might have to tweak the contrast a bit in post-processing. Check out the Mirror Lens Club thread for many useful hints and pics.

And there are those hated or loved out of focus doughnut highlights...




... which can be avoided if you are careful.




Hours of fun and frustration await you !
02-03-2014, 06:28 PM   #14
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It has this peculiar bokeh ...
02-03-2014, 08:23 PM   #15
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QuoteOriginally posted by t.manning Quote
Thanks a lot for your advice dms. With my budget I will have to go with the Sakar but it will be a good learning curve so I understand how to use a mirror lens. Maybe down the road I will purchase a more expensive mirror lens. I plan on using the lens for macro shots in addition to taking pictures of the moon. Is there much difference taking pictures of the moon with a mirror lens as opposed to a "regular" lens? I understand the technique fairly well, at least enough to take decent pictures of the moon with my Pentax A 1:4 70- 210 lens.
Besides the other post of advice, the moon's motion is a big factor at 500mm. You need a reasonably fast shutter speed to avoid motion blur.
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