On 18/12/04, Shel Belinkoff, discombobulated, unleashed: >I was watching the PBS show "Frontline" a couple of nights back, and during >the intro a video collage is played, in which a 9.8mm f/1.2 lens is shown. >Clearly it's a lens for a video camera or 16mm camera, or some such. That >got me thinking about the possibility of adapting such a focal length to a >DSLR that uses the small sensors. First question, of course, is how does >the size of the istD sensor compare to the frame of a video, 16mm, or 35mm >movie camera . I think a 35mm movie frame is about 1/2 the size of a 35mm >still camera frame. Anyway, what might the possibility be of adapting such >a lens to a digi SLR? Any thoughts on that? Looking at the Sony digicam, >it's 7.5mm or so at the wide end ... shouldn't some of these movie camera >lenses work pretty well for digi slr use? Cotty?
Well now, there's a can of worms opened ;-) In theory I would have said yes it should be possible. Sort of. Depends on the lens. I have found that when wanting to adapt a lens to a body, several things are crucial : the register distance for the lens, the register distance for the body, the type of mount on the lens, and the type of mount on the body. The register distance is the measurement between the mating surface of the body /l ens and the film plane / sensor, and expressed in mm or fractions of an inch. A pretty good table of of registers can be found here: <http://www.a1.nl/phomepag/markerink/mounts.htm> Past this, the next crucial stage is, what is the video lens mount type (if wanting to try a video or motion picture camera lens onto a still camera body) ? There are loads. Your old Bolex 16mm camera was C mount IIRC which is a basic screw on system, sort of the Pentax M42 equivalent of the movie old movie world. But different manufacturers have different systems (well there's a surprise) like Aaton, Arriflex, CP etc etc - So, let's take (say) a C mount lens which has a register distance of 17.52mm, and (say) a Pentax K mount camera with a register of 45.46mm. That's a big difference, and going 'the wrong way'. Basically, if the register distance on the stills body is less than the register distance on the lens, then all that is needed is a spacer to move the lens further away from the body the requisite distance. Lets say you have a camera with a register of 50mm and a lens with a register of 70mm and they will mate up okay, but the lens will try and focus to a point a further 20mm behind where the film is in the body. To counteract this, you move the lens further away from the body by 20mm and hey presto, the lens focusses onto the right point. The trouble starts when the body has a register of (say) 70mm and the lens has a register of 50mm - this needs the lens to move 20mm further towards the film plane, and that's a bummer - there's chunks of camera in the way, and you might even get rear elements contacting mirrors and all sorts. So instead, you keep the register distances as is, and bend the light by incorporating a lens into and adapter - expensive and heavy going! But there are several such adapters available - try www.srbfilm.co.uk for more info. Popular makes only ;-) The EOS register is 44mm dead, which meant that all I had to do to was take a Pentax lens and move it 1.46mm further away from the EOS body when mounted. That gets the back focus into the right place and the thing will focus properly onto the film plane / sensor. To put a C mount lens onto a Pentax K would need an optical adapter, natch. However, look at Aaton - lenses made for the Aaton bayonet fitting have a register distance of 48mm - and good old Pentax K is only 45.46 - so bingo - you have room to build an adapter with an extra 2.54mm of metal in it to move the lens that crucial distance further away. BUT !! The Aaton lens is designed to fill a picture area quite small - a 16mm frame is tiny - the thing probably wouldn't get anywhere near to filling a 35mm frame of (say) an MX. And not enough for an *ist D. So as well as register distances, you have to take into account the actual area the light falls onto at that said register distance. Follow this? I'm no engineer 0 just bumbling my way through on a 'need to know' basis. I was lucky - I was adapting similar lenses and even luckier - onto a camera with a smaller sensor. Which is interesting - I haven't tried the Pentax lenses on an EOS film body - I might get vignetting! Sorry for the length, but it's a complicated subject, well to me at least. I haven't mentioned actual fitting - suffice it to say that any good precision metal worker can perform miracles. Again, I was lucky - the EOS / M42 adapter is as common as muck (as we Brits say) and the nice thing about M42 and PK is that the register distances are the same (at 45.46mm) so I instantly had my correct register distances. But obviously the M42 won't accept a PK lens, so why not remove the PK lens mount and simply bolt the EOS / M42 adapter straight onto the back of the PK lens? In essence this is exactly what I did. So to sum up, it *should* be possible but depends entirely on the lens and the registers..... This email will self-destruct in 5 seconds. Good luck ;-) HTH Cheers, Cotty ___/\__ || (O) | People, Places, Pastiche ||=====| http://www.cottysnaps.com _____________________________
