A closer look at the magnifying glass lens
After sharing a couple of images from the DIY magnifying glass lens for my Calumet 4×5 online, I got some requests for a closer look at the lens itself.
I wanted a flat front to make it easier to use Waterhouse stops to control the aperture of the lens, so I taped the lens on the inside of the lensboard. If it ever comes lose it might fall and damage the ground glass focusing screen. It seems pretty solid, but you never know. If I make another lens I’ll put the glass in a thin box on the outside of the lens board, just to be safe.
The lensboard is made out of two sheets of cardboard, with the ridges orthogonal for increased stability in more dimensions. The lens itself is supported by four L-shaped brackets that are taped to the lens board and then a tight loop around all brackets and the lens. The rest of the tape is mostly there as a light seal.
By itself this magnifying glass gives about f4 at it’s focal length of 170mm. I have made a slot on the front of the lensboard where Waterhouse stops can be slid in place to stop down. This is needed since the lens doesn’t have a shutter and I am dependent on a small aperture to get the exposures in lengths that I can easily count manually.
I found a hole punch that gave me a couple of different size holes from f34 to f56. Then I cut one at f8 by hand. The punched holes are much cleaner, the frayed edges of my f8 stop should have a negative impact on the image quality. I have inked the rims of all the holes black, hoping that it would reduce flares.