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06-30-2013, 12:32 PM   #1
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Join Date: Jun 2013
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Mirror mirror on the wall

Hi all. This is my first post on the forum.
Recently bought a Pentax Q. I wanted a camera to use some of my old cine camera lenses on , and as the Q sensor seems about the same size as 8mm film, it seemed the obvious choice.
My question is about using a 500mm mirror lens on the Q. I know it will be far "bigger" than 500mm, but just how big?
I have read the various postings about crop factors and there seem to be as many theories as there are grains of sand on a beach, and I am very confused!.
Help please!

06-30-2013, 12:52 PM   #2
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
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Hey, welcome!
Which Q do you have? Original Q, Q10, the brand new Q7? If its one of the former two, the crop factor is 5.62. So 500*5,62=2810mm. But the quality will be pretty bad, the lens will be very dark (high f-stop), and any vibration will show up in the photo and reduce sharpness (so you need high shutter speed). Because of the high f stop and shutter speed, you will have to bump the ISO sensitivity, which will add a lot of noise to the photo.
If you really want to try it, get a big lens hood and a strong tripod, then use timer release or remote.
Or you can get the K adapter and mount a regular manual 135mm lens. It won't be as extreme as 500mm, but it will still bring things much closer. And it has a much higher chance of actually being useable
Here is a relevant thread:
Here is an example of 300mm mirror lens on Q:

Last edited by Na Horuk; 06-30-2013 at 01:42 PM.
06-30-2013, 12:52 PM   #3
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The Q has a 5.6x crop factor, so it'll be the equivalent of a 2800mm lens on a FF or film camera. That's a looooooong tele!

Unless you have a very good mirror lens (like a Tamron or Tair) the image quality is probably gonna be poor. And you'll need to use a sturdy tripod. I've tried a Tair on it with reasonable results, but any lesser quality lens will be dicey.
06-30-2013, 03:56 PM   #4

Join Date: Oct 2006
Location: Chicago suburb, IL, USA
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Hi biggles,

First of all, welcome to one of the best Q fora on the web! I calculated the crop factor of the original Q by reverse calculating the FL Equivalents given Q system lenses from Pentax and got 5.58x, but who really cares. . .

I like long teles adapted to the Q, but have yet to have much success with my Tamron SP 500 f8 Adaptall 2 Mirror. Admittedly, I haven't done much shooting with it. My impression is that i need much more stable support and need to use much better technique to get the results I would want from this combo. Personally, I'd rather concentrate on shorter lenses that I can get better results from and would be more practical for me in the field.

I have had pretty good success with a DA 55-300 at 300mm (1678mm EQ) -- handheld even, and this has been very satisfactory for me as I originally wanted the Q for Super Tele shooting with adapted lenses when it was first introduced.

I think that although many people are impressed by the crazy long FL EQs that can be achieved with the Q, but I think that most Q-with-adapted-lens users are finding that it's best to start off smaller and work your way up.

Show us some of your work once you get settled in with your Q.


07-01-2013, 12:27 AM   #5
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Join Date: Jun 2013
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Original Poster
Mirror mirror on the wall

My thanks to all those who have taken the trouble to reply to my query. I have the original Q , and I already had a Samyang 500 mm mirror lens I use on my Canon 5D11. I bought D and C mount adapters to use my old Bolex cine lenses, and I will have a go with a T2 adapter with the mirror lens - but from your remarks I won't expect anything spectacular!.
I'll post pictures - when I have some, and when I have figured out how to do it!.

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