Field test of the Pinhole Lab Camera with revised shutter

 I made some minor adjustments, corrected some mistakes on the template and built another copy of the new Pinhole Lab Camera.

The shutter on the earlier copy was just kluged together from a couple older shutters. It turned out the openings were too small and the shutter extended out too far from the front of the camera. When using the widest angle setting with the negative 30mm from the pinhole, it got in the way and blocked a significant bit of the sides leaving just a nearly square image.

I made the openings as large as possible, made beveled cuts on the sides of those openings and the sliding shutter itself and eliminated a layer of cardboard to reduce it’s depth on the front of the camera. I also got rid of any dividers between the holes on the front of the camera.

The shutter was only a problem at the 30mm distance. One issue I encountered in testing it was that the vignetting is so pronounced from the center to the edge at this angle that the image faded to black before it got to the sides. The edges of the frame are twice as far from the pinhole as the center. That translates to four stops. A bit of a challenge for contrasty paper negatives.

I looked for scenes that had lighter backgrounds and with some burning in of the center and dodging the sides, I could tell that it does seem to be wide enough.

The sky gave me a bright enough background to get a significant exposure across the frame and now I can see that the edge of the shutter still impinged the side where the third pinhole, which gives the rising front capability in the vertical orientation, is. The pinholes are 10mm apart. The rising pinhole on James Guerin’s RSS 6x6 camera is 15mm above the axis. I could probably move that pinhole a little farther and get rid of that little bit of blockage.

One time I tried to slide the shutter on that pinhole over a tiny bit to see if I could get it out of the way. The shutter itself is two layers of card stock above the pinhole. The angle of view is so wide that the second pinhole could see through that narrow gap and formed a double image on that side of the frame.

 I really can’t get the shutter any nearer the pinhole and still have the removable pinhole mount, but if I had a little more room between those pinholes and made some internal changes to the shutter, I could put a little baffle on the back of the edge of the shutter and block that gap.

With a curved image plane with a 60mm radius the edges of the negative go all the way to the front of the camera. Quite a bit of the image is blocked although you still have an almost 150 degree angle of view with what’s left. The image area is just slightly wider than with the flat film plane. Of course in this configuration you also have the more uniform exposure since the distance to the pinhole remains the same across the image and, of course, the characteristic distortion of a curved image plane.

With a strip of paper the entire width of the 8x10 sheet of paper curved and attached to the center of the back at the 120mm distance, the edges of the negative don’t quite reach the front of the camera. There is still a bit of blockage. The angle of view is still about 150 degrees but now it’s spread over twice as wide a negative. Another difference is that the angle of view vertically is 28 degrees at the center where it’s 120mm from the pinhole and spreads to 53 degrees at the outside edges where it’s only 60mm away. Pinhole fun, eh?

One thing that’s hard to illustrate in a blog where there’s a limit to the width of the image is how much bigger that 10 inch negative is.

The shutter is no problem at the other lengths. Here it is with the back at 60mm with the camera sitting level on a table using the on-axis pinhole.

Still at 60mm, the camera is mounted on a tripod for this one but I used the on-axis pinhole and just tilted it up to get the whole magnolia in the frame. You can really see the converging verticals in the houses at the sides of the frame.

The utility of the rising front is of course to keep those verticals parallel when photographing a tall structure where otherwise you’d have to tilt the camera to get it in the picture. Again at 60mm with a tripod but this time with the camera carefully leveled and using the rising pinhole. 

One thing I’m pleased about is how reliably the negative can be placed nice and square in the camera. That one was done in a changing bag where I couldn’t see what I was doing. It’s the whole negative with no post-processing rotation. I also switched the pinholes a couple times in the bag and had no trouble.

One of my pet peeves on Pinhole Day is how many images are submitted with the camera sitting level on the ground in the town square. Most of them are intended to be of the city hall or local cathedral, but the surface of the pavement fills the bottom half of the image. This one is at 90mm with the rising pinhole. The camera isn’t quite sitting on the ground - it’s about 7 inches up on an upside down plastic gardening pot leveled with a few twigs under the camera.

Again the camera sitting on the gardening pot, but using the rising pinhole to get the frame a little higher, this time at the 120mm distance to the pinhole.

And again at 120mm with the rising pinhole to keep the walls looking plumb.

All these were done with the .3mm pinholes except for the three done at 120mm for which I used .55mm pinholes. The negatives are Arista.edu grade number 2 glossy paper developed in Ilford paper developer.