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12-14-2007, 08:01 AM   #1
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Modify Canon 400mm 5.6 to fit k10d?

Hello everyone,

I used this lens a few times, both on a Canon 40D and a 400D Rebel XTi, and its image quality is pretty amazing. I looked in the back of the lens, and if I recall correctly, there's no glass element at the site of its mount. So, this got me wondering: how cool would it be if this lens could somehow be modified to K mount with electrical contacts which could be controlled by the k10d's SDM? This lens is light, and would be super for sports, birding, etc. and would probably benefit from the k10d's shake reduction. Also, it costs about $1100. Any electronics gurus out there? (I'd rather just have a DA* 400mm 5.6, but good luck with that one.)


Last edited by button; 12-14-2007 at 08:12 AM.
12-14-2007, 09:16 AM   #2
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The EF 400 f/5.6 is an amazing lens and if it could be modified to work on the K10D, that would be very tempting.

However, I do believe that Pentax will put out something in the 400mm flavour in the next couple of years because there's a lot of talented people using Pentax who do shoot wildlife/birds/sports that would love (and who would also need) a 400 with SDM. Whether it's an f/4 or f/5.6 would be the first question and the second would be 'when?'. I'll even go as far as to say they'd be very foolish not to do a lens like this.

The Canon 400 f/5.6 beats out the FA* 400mm f/5.6 in sharpness so when Pentax does re-do the 400mm lens (whether a zoom or prime), I hope they make it (1) just as sharp as the Canon, (2) SDM & weather-sealed, and (3) sooner, rather than later would be much better.
12-14-2007, 10:07 AM   #3
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Let's also keep in mind that couple factors likely make the 'adaption' impossible.

1) Registration distance, you would likely have to use optics to get the lens to be able to focus back onto infinity. But by doing so you may be defeating the purpose of the adaption.
2) The Canon EF lens is completely electronic in terms of communication with the body, the AF, aperture and so forth, one would have to have a CPU translating information from the pentax and into canon's language and vice versa (and what if one doesn't have an equivalent to a command), and such may add the extra bulk to the lens extension. Likely would need to be manual focus only, and even then figuring out how to accurately stop down the lens from the body or shoot wide open.
3) Power requirement for the lens might not be provided from the pentax mount, or least not in the correct voltage or amperage, thats assuming of course you found a way to make the pentax communicate with the lens in order to autofocus, IS, or stop down the aperture. The aperture could likely be rigged mechanically but accuracy would be another issue.
4) Unless you could make the adapter easily switchable to a variety of lens, and work accuracy and quickly, there will never be enough of a market for anyone to bother investing in.

So if you adapted it, you'd probably 1) have to take it appart to give it a new mount at the correct registration distance, 2) rely primarily on manual focusing 3) and shoot wide open.

But lets consider the DA40 was pretty much the same as a pentax-m 40, however the new DA is hell of a lot sharper, we can perhaps be hopeful that a DA variation of a long telephoto prime lens will also be designed in this aspect. If that happens you wouldn't have to worry bout the mess and loss of functions you'd get from trying to adapt a lens. If it were a mechanical lens in some way, then it would be easier.
12-14-2007, 12:30 PM   #4
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QuoteOriginally posted by kb244 Quote
take it appart to give it a new mount at the correct registration distance
That's what I had in mind. Obviously, a pretty risky thing to do. I'm assuming that the lens has a microchip in it for control purposes.

John

12-14-2007, 01:19 PM   #5
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What we need is some sort of rear mount that could adapt all the different mounts, or maybe some sort of universal mount which screws onto all the cameras.

They could call it "adaptall" or "universal screw mount" or something clever...
12-14-2007, 01:39 PM   #6
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QuoteOriginally posted by d.bradley Quote
What we need is some sort of rear mount that could adapt all the different mounts, or maybe some sort of universal mount which screws onto all the cameras.

They could call it "adaptall" or "universal screw mount" or something clever...

:P except with the electronics now days, no one would come to an agreement on sharing the same 'communication' :P Course lets be thankful adaptall lens work fine on a pentax, but have worse limitations on say a Canon and most current Nikons.
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