Home-made Lenses

David · Expire: 2013-01-25

I've tried a few home-made lens experiments recently because I'm curious about pictorialism and seeing what I can do with a single-element lens. I picked up three single-lement lenses from Surplus Shed last year, two meniscus lenses and one double-convex. I took photos with my K-7 for two -- the 97mm meniscus and the 114mm DCX. The other meniscus has an infinity focus shorter than the Pentax flange and auto bellows minimum extension, but I did get some macros in with the Pentax MG. I don't have those developed yet.

With the 114mm lens, I also used an M42 lens diaphragm to test sharpness and Dof.

To mount the lenses, I built housings out of step-up and step-down rings. Each began with a 42mm to larger ring (67mm for the DCX and 62mm for the meniscus.) Then I used other rings to create a housing that will hold them in place.

All three of these SHOULD cover 4X5, although the 97mm may only cover 6X7. The results on APS-C are interesting. The 97mm has VERY deep convex and concave sides, so it understandably is very soft. Even though the 42mm step-up ring cuts the maximum opening to 39mm (making it a 97mm f2.5.) The DCX also has a 39mm maximum opening, but I used it with an M42 aperture that has a 24mm max opening, making it an f4.8.

Here are some samples:

97mm meniscus. This lens' huge radius makes it stupidly susceptible to flare. Seriously, it pokes out from the lens housing further than anything I've seen. The lens itself, outside of the housing, is about 30mm tall (the actual glass thickness is only about 10mm, maybe 15mm, due to the concave side of the meniscus.)

I did not mount the aperture behind the 97mm lens at all, but perhaps I should have. I suspect that cutting out the aberrations would result in a sharp, contrasty, and color-rich image.

Such dreamyness.

The DCX is a significantly different story.

Stopped down about half-way, the lens is surprisingly sharp.

Even wide open, though, the 114mm DCX does a nice job of controlling the aberrations. A lot of this may be due to the iris reducing it to f4.8.

Here it is stopped down to, probably, about f11 or f16. The colors are pretty well saturated and the sharpness is unexpected.

Here's a macro with the lens stopped down to, approximately, f56. (the iris closes down from 24mm to 1mm or less, but much beyond the 2mm mark this lens loses sharpness.

The same macro at f4.8.

One last test. Here is the lens somewhere between f32 and f45.

f4.8. From f4.8 to f8, the lens retains the edge softness. That's exactly the look I wanted with this lens -- that gooey sofntess that comes from old Brownie Hawkeyes and cheap triotar lenses.

The meniscus, I hoped, would create pictorialist-type photos that look as though they were taken in a fog. On both counts, I think the experiment worked. Not shabby for $13 in lenses and $14 in filter rings (for all three lenses.)

Next project, take these out on a 4X5 and see what happens. Also I have a 300mm f2.3 DCX that arrived last week. That should be a lot of fun.

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

Nice attempt, and stopped down is impressive (although maybe in such lenses we do not look for perfection).
I did something similar in the past (http://forum.mflenses.com/meniscus-diy-t57964.html) and never finished, i.e., mount was under standard to be fair. Sooner or later I'll put together again something similar... I have also a compact camera lens to recycle Smile

David · Expire: 2013-01-25

My next goal is to take some nice, experiential-type shots with a single-element lens. I have a 4X5 SLR that I've been fixing up (someone had epoxied plywood to the mount to modify the mount) and I'm going to affix a 300mm f2.3 BCX lens to the front and see how that performs. I'm really looking forward to it, actually. Your results are spectacular. I hope I can come close to matching them.

enzodm · Joined: 11 Sep 2010 Posts: 350 Location: Italy

An excellent source of inspiration is this thread by a forum member: http://forum.mflenses.com/meniscus-lenses-t63197.html, in particular if you are interested in pictorialism. I think there you can see really nice examples of what can be done - I just proved myself a meniscus could be done but then I left all in a drawer Sad

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David · Expire: 2013-01-25

Yeah, I've been following his thread pretty closely. Serkol is doing exceptional work.