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08-07-2013, 09:51 PM   #1
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Using canon lenses on pentax k

Hey everyone,

I really want to get a pentax k5ii at christmas and i do bird photography. Ive been looking at the 7d but im not impressed with the IQ and noise performance. I have 2 questions... 1) does sigma have enough long good quality lenses for me to use if one day i want to invest lots in a good lens? And 2) if they dont, can i use some canon lenses with a good lens adapter ( af confirmation and infinity focus ) to get the extra reach? Also tell me if you think otherwise about the IQ and noise on the 7d vs the k5
Thanks for your help

08-07-2013, 10:06 PM   #2
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To by honest I'm not too sure about how many good long lenses is Sigma currently doing for K mount. Hope somebody else will answer that for you.
As for the Canon lenses on K mount, I believe you can't use them. EF mount has shorter flange distance and I believe larger mount diameter. Even if there was an adapter it would just add to the flange distance so you would be loosing more and more from infinity, or it would have to have an glass element which would almost certainly degrade the IQ (at least to some extent). Anyway, I believe there isn't an EF>K adapter.

As for 7D vs K5ii. Tough one. As you can see from my sig, I jumped. I was upgrading from K-7 and the choice was 7D or K-5. Went for the 7D. Since you are asking about IQ only, I think K-5 has an edge. Both of these cameras use (for my taste) strong AA filter, but 7D has stronger, which means you'll need more sharpening. In an ideal scenario of properly exposed shot on lower ISO, with no shadows lifting, I think the 7D equals K-5 for IQ. But in any other conditions the K-5 wins. It simply has a better sensor, that allows you to work the files more than that of 7D. Having said that, 7D is not all that bad and I've seen many sunning bird shots with that camera.

In your place though I'd get 1D Mark III, it's 2 years older than 7D and has "only" 10 mpx but the IQ is better than 7D and is better camera overall IMO. As you can see, switched 7D exactly for that and never regretted it.
my 2p
08-07-2013, 10:07 PM   #3
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No experience with Canon but most reviews show k-5 as best in class for it's price range.

Sigma has some very good glass, 500mm f/4.5 is generally consider excellent and most test shots I've seen bear that out. If 300mm is long enough Pentax has excellent DA*300mm. They also have DA 560mm but that is very expensive.

You cannot use Canon lenses on Pentax as the registration distance is shorter. There might be optical adapters that make it possible but the loss in IQ would IMHO make it less than useful. And it would be all manual, no AF, no aperture control. But I'm not aware that such a thing even exists.

Lots of people use Pentax glass on Canon but it doesn't work the other way.
08-07-2013, 10:09 PM   #4
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If your interest is in birding go here: All you ever wanted to know about Pentax, birds and long glass.

08-07-2013, 10:19 PM   #5
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Good Evening,

Each brand of camera has a dimension associated with its design referred to as the registration distance. This is the distance between the front, where the lens mounts, back to the sensor (or film). Canon has one of the shortest distances, while Nikon has one of the longest. Pentax is somewhat in the middle. What this means to you, is that Canon can use other brands of lenses - primary because there is sufficient distance for an adapter - since each manufacturer has a different mechanical mount for their respective lenses.So in a way, you can mount Pentax lenses on Canon, by way of an adapter - however, not the other way around. Also, when you mount a Pentax lens on a Canon body, the Canon AF does not match or work with the Pentax lens' AF - either the mechanical screwdrive linkage or the electronic AF SMD interface. So, in essence you wind up with a fully manual lens.

Mounting a Canon lens on the Pentax body -
  1. Physically does not work - as the mechanical mount interface as indicated above is different.
  2. Because the registration distance is different - longer for the Pentax K mount, the shorter Canon EOS mount distance will not work, since the lens will need to essential sit inside the mirror box in order to be able to focus as Canon intended.
  3. The Pentax K mount screwdriver and SMD AF will not work because of the differences in both the mechanical and electrical interfaces.
  4. Yes, you can adapt some other lenses (but certainly not every lens vendor) to Canon's AF interface like the Contax N lenses (the only one that comes to mind), but its very expensive.
  5. Yes, you can adapt - via a lens mount change, use other lenses on the Pentax K mount - like the older Contax C/Y mount. When mounted they act like a fully manual lens. Pentax's AF confirmation still works, but you the photographer still need to turn the lens' manual focus ring in order to focus. This does not work for all longer registration distant lenses - like Nikon lenses mounting on Pentax with an adapter really does not work that well and there needs to be additional optics, so its on a case by case basis.
  6. Yes, you can use third party lenses like Sigma, Tamron, Zeiss, etc. on Pentax bodies since these lens manufacturers design and build their lenses to specifically use the Pentax K mount, and the Pentax AF interface.
So, in this case - if you really want to use Canon lenses, the best route would be with a Canon body.

hope that helps....

08-07-2013, 10:46 PM   #6
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Canon FD lens on K mount Pentax cameras

I can confirm the futility of mounting FD Canon lens on K-mount Pentax cameras. I have a wonderful Canon 50 mm f 1:1.2 lens, and wanted to use it on my Pentax film and DSLR cameras. I purchased an adapter, incorporating optics, to make this possible. It is possible, but the necessary optical feature of the adapter degrades the quality of the FD lens so much that the exercise is not really worthwhile. For me the best way to use that great old lens is simply to keep an old Canon F-1 or A-1 camera around for the job. My advice to anyone else wanting to try the adapter is don't, Save your time and money for something else!
08-07-2013, 11:00 PM   #7
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Forum members have contributed six reviews of the Sigma 500/4.5 here, seven of the Sigma 50-500/4.5-6.3 here, and eleven reviews of the Sigma 150-500/5-6.3 here if you haven't seen them before.
08-07-2013, 11:46 PM   #8
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Thanks guys i will check out the reviews Rob and also the over 300 club. I think ill stick with getting the pentax after talking to my friend that has an ist d and a 200mm lens and he only does birding and his photos are impressive.


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