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01-24-2011, 03:28 PM - 2 Likes   #1
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Pentax Full Frame DSLR (Well, sort of...)

No, I do not know from a very reliable source that there is a FF Pentax coming this year. Different story here.



To start from the beginning: I have always been a sucker for subject separation and shallow depth of field which is why I have piled up a bunch of pretty fast glass.
Also, I was one of those fools hoping for a sign of a FF Pentax at the last Photokina for being able to put this onto a whole new level, but there was "just" the K5.
So I recently pushed myself to what I had been thinking about for quite a while already: Hunt down a cheap Canon FF DSLR to use my beloved Pentax lenses with. I managed to catch an old, well used 1Ds.



So far, that is no big news as it has been done before. I remember one thread regarding FA ltds on a 5DII. However, as the aperture lever and protection shield of Pentax lenses protude too far into the mirror box, this requires the infamous leverectomy.
I did not want to do this to my precious lenses - and besides, I wanted to be able to still use them on my K7 - so I decided to do it the other way around: Modify the mirror box. (This is what it usually looks like)


Clearly visible here, I grinded off a considerable amount of metal and plastic from the left and the bottom of the mirror box. The only tools I used were a Dremel and a black marker which is why it does not look perfectly clean, but it works like a charm. One day I might replace the marker paint with some less reflective matte paint, but for now I am happy with it.
I did not compromise the camera's contacts. Should I ever end up with a Canon EF mount lens, I can still use it on my camera without any restrictions.

Using a PK-EOS adapter that mounts the lens top up instead of at 2 o'clock like most adapters do, the mirror is able to pass the lever and shield and I can use any of my Pentax lenses that have an aperture ring with it. Without any modification to them, just the way they are.


I have barely touched my K7 since then. The 1Ds is a freakin' huge and heavy monster and it makes my K7 look like a high ISO wonder above ISO 400, but in terms of subject isolation it obviously smashes the K7 against the wall. Oh, and the big viewfinder is nice, too.
I am still - or rather even more now - looking forward to a "real" Pentax FF DSLR (at about the size of a K7, pleeease). But until this happens, my enhanced 1Ds will do the job.


Some of the first results:

SMC-A* 85mm/1.4 wide open


SMC-A 50mm/1.2 wide open


Vivitar 28mm/2.0 Close Focus @ 2.4



Last edited by 721; 02-01-2011 at 05:55 PM.
01-24-2011, 03:58 PM   #2
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Cool. Do you think this would work with a Canon 5D? I've been kicking this same idea around for awhile.
01-24-2011, 04:09 PM   #3
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You might have slightly tighter tolerances between the lever/shield and the mirror, but that should not be a big deal. In the worst case you might have to mount the lenses a few more degress counterclockwise by modifying the adapter or something like this.
I do not know how thick the material of the 5D mirrorbox is. When doing a test run on an old film EF-M (R.I.P.) I broke through the bottom of the mirror box. That does not make it unusable, but may need some extra effort to avoid internal reflections.

Other than that, I see no reason why it should not work.
01-24-2011, 04:50 PM   #4
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Impressive (and daring) work, taking a Dremel to the inside of a camera!

01-24-2011, 05:14 PM   #5
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Very clever. I like it.

1DS original, yes?

Something I've considered getting myself. Maybe you've inspired me....
01-24-2011, 05:42 PM   #6
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Great shots. Good that you managed to pull off the modification. Any issues with infinity focus?
01-24-2011, 05:43 PM   #7
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@ DeadJohn
I used an excessive amount of tape and plastic foil to seal the mirror box as good as possible except for the concerned parts. I got some individual dust specks between the prism and the focusing screen that I still have to clean out, but all in all it worked quite well.
My first idea was to completely disassemble the camera and mirror box, but I decided that this would have been too much of a hassle. Long live my laziness!

@bkpix
Yes, 1Ds Mk I. But basically it should work with any Canon FF camera. Choosing a 1Ds Mk I was just a matter of money for me. Also, in case that for some reason it did not work or I did screw it up, its loss would have been easier to swallow than that of a 5D II or even 1Ds III or something.
Now that I know that and how it works, I may replace it with a more recent model at some point in the future. Unless Pentax finally manages to come up with one themselves, that is.
01-24-2011, 06:23 PM   #8
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can u tell us more about the PP you used? I love the b&w & blue effect

01-24-2011, 07:28 PM   #9
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@ creampuff
None that I have noticed. Canon's register distance is shorter than Pentax's, so there is no problem in achieving infinity. Regarding focusing past infinity, this is an adapter issue - mine seem to work well here, although I have not formally tested them yet.

@dankoBanada
Sure, B&W conversion and split toning in Lightroom. The rest is basically global and local contrast adjustment as well as some local sharpening.
01-25-2011, 03:11 PM   #10
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Almost pocketable...



By the way, in case somebody else makes his Canon FF undergo that little surgery, I would be curious to read and see of it here.
01-26-2011, 02:52 PM   #11
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Great out of the box thinking (well kind of in the box if you know what I mean ;-) )

I'm dreaming of the day Pentax will really go full frame
01-26-2011, 03:48 PM   #12
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I have no idea why you are doing any of this but that shot of the Aprilla is STUNNING. I love how it is in focus and nothing else is. I am going to have to try that.
01-27-2011, 10:51 AM   #13
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That is exactly what I did it for, in order to achieve shallow depth of field. Larger sensor means wider angle of view means I can get closer to the subject or use a longer focal lenght for the same framing means less depth of field.

To pull off a comparable shot (perspective, framing and depth of field) to the Aprilia one with a Pentax crop DSLR, one would need something like a 55mm/0.95 lens - preferably one that has the wide open performance of the A*85. For the second shot one would need something around 35mm/0.8. I imagine one might have some difficulties finding such lenses...
01-27-2011, 12:28 PM   #14
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Looking forward to seeing more shots from you 721. I know a way I can get a pretty cheap Canon 5D to experiment on, if you keep posting great images it may push me over the edge into action
01-27-2011, 03:50 PM   #15
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QuoteOriginally posted by 721 Quote
Almost pocketable...



By the way, in case somebody else makes his Canon FF undergo that little surgery, I would be curious to read and see of it here.
wow looks great, but you need big pockets

Great pictures!
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