As if my exposure times were just not long enough, I’m going to start trying filters on my 120 pinhole camera. I did an initial test of the filter holder and a took a few photos to figure out the exposures. Good news is that the filter holder isn’t causing a vignette on the image but the bad news is that my exposure times are going to be REAL long. Even more so when I take in the reciprocity failure factor. With a number 003 Cokin
filter the exposure compensation factor turned out to be an 8. That’s a loss of three stops. My pinhole camera has an aperture of 220 so with the filter I drop to a metered stop of f/600! If only my DoF would change too…
Here is the camera with the holder and filter in place. The lumps on the sides of the Cokin filter holder are super magnets with a healthy dose of gaffers tape. These are grabbing on to two pan washers that are held on to the camera body with, what else, gaffers. I had to carve away some of the holder to get the cable release to fit right. It should still work on a regular camera, if I ever buy a mounting ring. The project works pretty well for being held together with tape and magnets. I think I’ll incorporate metal in to the front of the cameras so I can use magnets as mounting devices in the future.
Magnetic filter for pinhole camera