When the Urge strikes
When the Urge Strikes to play
OK all you fellow “wanna be” DIY camera hackers . . . let’s figure out where we are going to start hacking some cameras / lenses to get some use from that spiffy digital camera that has an inter changeable lens . . . so we’ve kinda pointed in a direction, but, before we head down the lane with a camera / lens and wad of gaffers tape let’s side track ourselves with some “data”, “knowledge” thought applied to our endeavor to maybe . . . just maybe . . . give ourselves some chance this conflagration will work . . . enter F/FD
What’s that? F/FD . . . well now this is the distance from the mounting flange (the metal ring on the camera and the rear of the lens) to the film or sensor plane.
Not wanting to re-write all that glorious information, as one, it would be a tedious read . . and another, is it’s already been written about Ad nauseam . . . So just Google it or wait till the end of this read for some links to more data then your lil’ol heart can stand!!! “Flange focal distance or F/FD” and read through the Wiki for all “da facts Jack or Jill” . . suffice to say this about it . . . Most camera manufactures have different F/FD’s that are proprietary to their brand . . . that is why we can adapt certain lenses to one camera, but theirs may not be adaptable to ours.
Lets take the following example, I can adapt a Nikon lens to a Canon body, but I cannot adapt a Canon lens to a Nikon body ! Why? . . The F/FD’s are different, the current Canon’s EF mount F/FD is 44.00 mm where as the Nikon’s is 46.50 mm (meaning the Canon’s lenses have a shorter F/FD distance and would have to be reaccessed into the body of a Nikon in order to be able to focus at infinity. . . NOT good for mirrors). The longer F/FD systems can be easily adapted to shorter flange-to-sensor/film distances(F/FD’s). Like adapting a Nikon lens to a Canon or a Canon lens to one of the new breed of mirror-less bodies. (example: Ricoh or Sony NEX, Fuji-X series or any of the the 4/3rd series cameras).
Oh boy . . . here comes the math portion of this little Urge!
Let’s take the following example of adapting a (Nikon 50mm lens to a Sony NEX-7 E-mount)
- F/FD of the Nikon is 46.50 mm
- F/FD of the NEX-7 is 18 mm
If we subtract the NEX’s 18 mm from the Nikon’s 46.5 we have a distance of 28.5 mm that needs to be added to the mount of the NEX body so the lens will focus properly.
Now we can use one of my favorite DIY items to play and mock up a working item, enter “Foam board” personally I like black with the black core, means I do not have to paint it later. Up next is plain old 5×7 index cards which make great shims.
Above you see one of my setups for playing with lenses. A: cheap Bellows, B: cardboard Lens-board, C: nikon-M42 adapter, D: M42f-M42m Helical focus tube, E: Vest pocket camera lens/shutter mounted on a cardboard lens-board, F: a Doublet from a broken donor lens, G: old 1900 circa lens/shutter waiting tests . . . I brainstorm this junk at the kitchen table, my drawings are made as I work to keep track of ideas (like the bulldog clips and Cokin adapter! sheer genius I tell ya!) anyway always loads of fun making soft-focus lenses.
All you need to make this a bit more permanent is a lens mount and you can add that into you F/FD adapter length and you can use it with out taping it to your camera body. Let’s say you have several lenses you want to adapt from the same manufacturer, the easiest way is to get a broken body and remove the lens mount and attach it to your adapter (making the appropriate adjustment to your lengths of course). Wow that lens you found in the box in the attic from 1801 doesn’t have a focusing unit (helical) how am I going to focus it, well, now we have more fun. You can make the box within box focusing unit or you can use more modern things like Black PVC tubes that nest into each other. For ease I would suggest a foam-core box within box for any fixed focal length lens that does not have a focusing unit. One idea I use often with small Medium format or Large format lenses is an old generic close up bellows with M42 screw mount lens mounts, because we are using (seeing) only a very small portion of the image circle of the lens we do not worry about vignetting caused by the DIY mount we have made.
What to expect, this is where the fun begins and also this is where a lot of confusion ensues about lenses and camera format, A lens designed for Large format camera has an image circle much larger then one designed for a 35mm format camera. Digital camera’s (DSLR’s) are either full frame FX (35mm Film 24×36 mm) or less DX or even less such as 4/3rd sensors. This smaller size of the image sensor compared to 35 mm film format results in cropping of the image. This latter effect is known as field of view crop or Crop Factor. It does not change the focal length of the lens which is a common misconception. The lens remains whatever focal length it originally was but using smaller sensors means you have the same view if you where to use a lens of whatever the crop factor would calculate to using that sensor size. Confusing I know but it is more marketing ploy then factual . . . just realize you are seeing less of the image circle then what the lens was designed for. Example: a normal 35mm camera lens of 50mm mounted on a NEX-7 may have the same field of view as a n NEX lens of 150mm, meaning your Field of View is equal to a 150mm lens.
As sensor size diminishes it is harder to make wide angle lenses, another factor that comes along with smaller sensors is DOF or depth of field. DOF increases as sensor size shrinks, so that wonderful control you had over DOF with a Full frame camera is gone.
Well we sure went farther afield then I expected . . . lets rein this in a bit and get back to our original ideas of adapting lenses to those mirror-less camera bodies. Yes it can be done, what to expect can be just as fun. As you can make some pretty cool things such as tilt shift, macro, soft-focus . . ect . . . you can make a pano where you use that bigger image circle and move the camera body across it and later stitch them in PS or some other program. All it takes is some thinking, a few hand tools, x-acto knife, gaffers tape and a cheap micrometer (readout in mm) and the kitchen table.
I have added a few links below to get you started, the games afoot so to speak . . add a pinch of imagination, perhaps an old flea-market camera or lens, the lens from a one dollar magnifier, an old bellows or as seen in the picture below . .
. . or just some black foam-board, tape and a mirror-less camera with interchangeable lens mount . . don’t despair, you could use that PAS (point and shoot) just by making a chimney of the proper length to fit over the viewing screen of grandpa’s old waist level twin-lens camera that you cant get film for . . be creative, make old new again . . play.
Like I said . . . The games afoot . . . if you have an urge to play . . . play
So brave photog . . . if you like this post please share it with friends, I am neither an expert or do I claim to know it all . . one last disclaimer, if you screw up your gear I’m not at fault. Like everything you take full responsibility for your own actions. I am a just crazy photographer! whats your excuse? Now get off your duff and go play if the urge strikes!
Links for further information, Wiki info
– Flange Focal Distance F/FD
– Image Circle or Image Area
– Film Format Sizes
– Digital Format Sensor sizes