DIY 4x5 Graflok to DSLR adapter (and drawbacks)

[reddesert]

4x5 to DSLR adapters came up in another thread. This is how I made one with only limited tools / materials. I made this to try it out rather than expecting it to really be practical, so my budget was roughly $0, some time, and lens adapters that I already had.

The application of the adapter is limited by the mismatch between format size and by the back focus (how far the sensor sits behind the original film plane). Commercial adapters exist that allow you to slide the camera around to do stitching, but the drawbacks of a long back focus and vignetting still apply.



The flat sheet is made from 1/16" thick FR4 - a epoxy/fiberglass material often used for printed circuit boards. FR4 is strong and stiff, so it stays flat, but is also easier to cut and drill than metal. The parts where the Graflok sliders clamp need to be 7/32" thick so they are built up with wood superglued to the FR4. I originally made the sheet a little too small, so I had to build it up with a 1/16" shim on one side. If it's a bit undersized, the Graflok sliders won't clamp firmly and you risk the whole mess falling out of the camera.

I don't have a hole saw, so the central hole was made by drilling out little holes and rough cutting the big hole. It's uneven but will be hidden in use.

There are a couple of ways to get the camera mounted to the FR4 sheet. If you have a junk lens flange and some tiny machine screws and nuts, you could bolt the flange to the sheet. I opted to use two pieces that thread together - a normal T-mount adapter, and a piece with a male T-thread. These have enough thread depth that I can screw them together and clamp the sheet between them.

From left, the adapter parts are: a 5mm Nikon extension tube, a Nikon T-mount, and the piece with male T-threads (happens to be a reverse T-adapter: Nikon lens to male T). The last is the only part that is uncommon.

Painted and screwed together:

[reddesert]

This is what it looks like on the DSLR. I measured the overhang of the SLR prism/flash housing, and the depth of the T-adapter; the 5mm extension tube was the minimum to allow this SLR body to physically clear the adapter. It will vary a bit for different SLRs. If you use a longer extension tube, there's more room, but you get a longer back focus, meaning harder to use short lenses, more vignetting, etc.



Why this is sort of impractical: The key fact about these adapters that limits their usefulness is that they have a very long back focus: the sensor is very far behind the usual 4x5 film position, and is sitting at the back of a long "tunnel" formed by the extension tube of the adapter and the mount of the DSLR. This means that:
- you'll have a hard time bringing a wide angle to focus,
- if you shift/rise the back or front a lot, the sensor can be vignetted by the DSLR mount,
- if you use a lot of back tilt or swing, there may be vignetting,
- using back tilt or swing gives a lot of image motion since the tilt axis is far ahead of the sensor.
So it probably works best with fairly long focal lengths used roughly on-axis.

I made this thing mostly to allow fooling around with different lenses with immediate feedback, and tabletop photography with movements.

[reddesert]

Here is a tabletop example of images from the thingy.





The first image is on-axis, no movements, and the second image has some rear backward tilt and front forward tilt. The tilts aren't large so there isn't a huge effect on perspective, but the effect on the plane of focus is very noticeable, I think (compare the components at the rear of the circuit board). This is the camera setup for the second picture (the lens is a 150mm enlarging lens):



Nothing revolutionary, but a useful device for learning how to do macro shots, use movements, etc.

The whole adapter concept would be somewhat more practical with a mirrorless camera as it could have a shorter back focus, but it would still be large and you'd still have to be careful about vignetting, etc.