DIY Periscopic Landscape Lens for 8X10

[desertrat]

Several years ago I bought a number of meniscus lenses from Anchor Optical to experiment with making a periscopic lens for my 8X10. One pair seemed promising, marked 1.5 diopter. Two of them would give about 13 inch focal length, or about normal length for 8X10. Found an old Wolly RR in a Regno shutter about 10-1/2 inch focal length for whole plate. The cells were about the right size for the meniscus elements. Removed the achromats and installed the menisci.

On the GG, the central image looked pretty good at medium stops. There was a lot of field curvature, so f64 had to be used to get most of the image in focus. The menisci didn't have much curvature, or bending in optics speak. I suspected elements with more bending might give a flatter field.

No images were made, and the project went on the back burner.

A few months ago I decided to try again. By this time, Anchor Optical had disappeared and been absorbed back into the parent company, Edmund Optical. None of their available experimenter's meniscus lenses had the focal lengths I wanted. Surplus shed didn't have anything close, either. On a whim, I searched Ebay for 1.5 diopter lenses and got some hits. Nikon made a series of closeup lenses for the F cameras, described as #0, #1, #2, etc. The #1 lenses are 1.5 diopters. Even better, they seemed to have more bending than the typical closeup lens sets on the market. This might help give a flatter field.

So I bought two. They use a 52mm thread. Next went searching for some way to mount them, and found something that would work, temporarily, my 8X10 f7 Turner-Reich triple in a Betax #4. I knew someday that cinder block heavy lens would be good for something. Just kidding, I like that old lens very much, just don't use it often. With the lens cells removed but the cell spacers left in the shutter, the closeup lenses could be mounted in the cell spacers. The lenses were a bit too small in diameter, so the game plan was to build up the outside diameter with wraps of 1/2 inch wide black masking tape I bought at Freestyle about 15 years ago.

With the right amount of wraps, there was a light friction fit going into the spacers, and more tape was used to hold them there. Aligned the lenses as carefully by eye as I could. There is probably some misalignment, but the results weren't bad, in fact better than I could have hoped. A 58mm yellow #8 filter was taped in front of the front meniscus. There was a two fold purpose here, to make the paper negatives less contrasty and I already had some rough exposure guides for using the filter. The other purpose was to reduce the focus error between visual focus and chemical focus since the lenses aren't color corrected. The spacing between the two menisci was about 2.75 inches.

Below are the starting materials for the project. Two Nikon F #1 closeup lenses, the Betax shutter with the T-R cells removed, and the trusty roll of tape.



The closeup lenses built up with tape



The shutter with the lenses taped in and the yellow filter taped in front



Paper negative image results in subsequent posts.

[desertrat]

Set up the camera and exposed three paper negatives, wide open at about f8, f22, and f64. The combined focal length of the two lenses at their spacing is about 14 inches, but haven't measured it carefully yet. The somewhat longer focal length is helpful for simple lenses from surplus elements, because the outer parts of the image are generally out of focus and the narrower image angle helps reduce that. It seems by blind luck, the lenses had about the right bending and the spacing was about right for a flat field, because there was only slight field curvature and other aberrations weren't bad at all, for such a simple lens.


The first image is a detail inset from the whole image, which is second.

[desertrat]

Next up are the two images at f22. First is the detail inset, second is the whole image. If you look carefully, you can see the louvers in the evaporative cooler and the roof vent. They're a bit more visible in the original negatives. I forgot to mention previously that the negatives were scanned, laterally reversed, and inverted in GIMP.

Attachment 181972Attachment 181973

Don't know why these two images showed up as links, but not sure how to fix that.

[desertrat]

Finally, the images at f64. Detail near the center is about the same as f22, some out of focus elements near the edges of the negative are in better focus here.




I think these Nikon closeup lenses are sharp enough at small stops for serious landscape photography if contact prints or alt process prints are the end product. Although mounting them in a barrel and adding a diaphragm and stops might become more costly than buying an old, cheap, off brand RR. But it might be fun for someone who wants to build an 8X10 camera from scratch, including the lens.

[Keith Fleming]

I also have made a periskope type lens using Nikon close-up filters, but I took a slightly different route. I began with a set of Zeiss Protar VII cells (29 cm and 35 cm) that came to me in a Alphax shutter. Concerned about dust and dirt getting into the shutter when using only one of the cells, I had S. K. Grimes make a filter-adapter that I could use to put a 52 mm filter on the front of the shutter. Next I realized I could remove both Protar cells and use that adapter and 52 mm close-up filter on the back of the shutter as a soft focus lens. That still left the front of the lens exposed to dust and dirt, so I had Grimes make another filter adapter. The next obvious step was to use the adapters to hold two close-up filters--a periskope type lens. That also opens up all kinds of possibilities of mixing and matching close-up filters (including cheap non-Nikon ones) for different focal lengths and variations in softness. The shutter iris also adds options for sharpness/softness. And all this was a lot cheaper than buying one of the classic soft-focus lenses.

Keith