[Just1MoreDave]

I bought a flanged adapter for a couple of reasons. One was curiosity. Do the Takumar lenses have enough adjustment for infinity focus to allow the adapter work properly? They do have an adjustment range, but the threads on the focusing helix stop eventually.

I tested a Super-Multi-Coated Takumar 50mm f1.4 (metal focus ring version). The answer is, almost but not quite. My infinity focus target is a mountain 55 miles away, and I use an MX with a split-prism screen. At f1.4 and 55 miles (88.5 kilometers), a depth of field calculator tells me that everything from 88.3 meters to infinity is in focus, but the split-prisms don't quite line up.

Possibly some other lenses would work, or this is close enough for you. It would be useful for the newer cameras that have metering errors unless the pins are shorted out. When I was buying my adapter, I saw the focus screen supplier "jinfinance" had some adapters with thinner flanges, but I can't find them today. These might be just thin enough to work.

My other reasons for a flanged adapter are for possible mount replacement, and I think it'll make a good drill guide for drilling a locking pin hole for a permanent K-mount conversion with a non-flanged adapter.

[stevebrot]

...My other reasons for a flanged adapter are for possible mount replacement, and I think it'll make a good drill guide for drilling a locking pin hole for a permanent K-mount conversion with a non-flanged adapter.

Interesting idea. Some lenses have a ton of infinity adjustment. Using this approach would allow semi-permanent placement of the adapter on the lens without making any permanent modifications to the lens itself.

Steve

[richard64]

Interesting idea. Some lenses have a ton of infinity adjustment. Using this approach would allow semi-permanent placement of the adapter on the lens without making any permanent modifications to the lens itself.

I don't think the suggestion was to use the flanged adapter as a replacement rear plate. There's no screws on the back of a Takumar and hence no removeable rear plate to replace. It might be possible for *some* other M42 lenses, but not with the ones I have (CZJ, Helios): when you remove the screws at the rear, the A/M switch assembly comes off too. In other words they don't have a flat back plate that you could swap for the flanged adapter. Of course, if you don't want infinity focus and willing to use longer screws (might not be necessary) then you could drill holes in the flanged adapter and screw it to the back of the lens.

From what I can tell, the suggestion was to use the flanged adapter as a guide to where to drill a locking pin hole on the rear of the lens, and then to use a non-flanged adapter. This *may* work. My doubt is whether the screw thread starts in the same place on the two adapters. Unfortunately that is not my experience.

When I drilled the hole in the rear of my battered Flek I screwed the adapter that I was going to use all the time with this lens tightly on the lens, then I used a white oil pastel pencil and rubbed it on the end of the locking pin. Then, holding the pin in, I attached the lens and released the pin so that it came in contact with the lens rear face. Then I pressed the lock release to pull the pin back out and removed the lens. That left a faint white mark on the rear of the lens that I marked gently with a punch. As a sanity check, I had also stuck two pieces of masking tape on the body so that their edges lined up with the edges of the pin (ie the gap between the bits of tape was the width of the pin). When the lens was attached I stuck two more pieces of masking tape on the lens and lined them up with the tapes on the body. With the lens removed I confirmed that the mark from the oil pastel was between the tapes on the lens.

The interesting thing is that this hole is in *exactly* the right place for the Kood adapter that I have semi-permanently screwed on that lens, but it is not quite in the right place for the genuine Pentax adapter that I use with my Taks. (That's not a great issue since, as I've said, the Kood is always on the Flek, but I do have to remove the Pentax adapter from the camera if I want to use the Flek.)

Before Dave uses the flanged adapter as a guide to drill the locking pin hole, maybe it would be an idea for him to do the oil pastel thing using the non-flanged adapter and then screw on the flanged adapter and check that the white mark is aligned with the hole in the adapter. If they are aligned then the good news is that the flanged adapter can be used as a guide.

Richard

[stevebrot]

I don't think the suggestion was to use the flanged adapter as a replacement rear plate. There's no screws on the back of a Takumar and hence no removeable rear plate to replace.

I don't think so either...

My interpretation was that Dave was wanting to:

• Screw the adapter onto the lens and leave it there
• Adjust the infinity focus to compensate for the flange distance.
• Notch or drill the flange to engage the mount release pin
• Ta! Da! K-mount conversion with no permanent modifications to the lens

Steve

(Of course, maybe I was wrong...still a good idea though...)

[feverbeaver]

The flanged adapter works for some of my lenses.

I adjusted the focus ring on a 200mm 4.0 s-m-c Takumar and on two 35mm 3.5 s-m-c Takumars.

The modification was not possible on the 50mm 1.4 Super-Takumar.

I look forward to seeing how the drill guide experiment comes out,,,

But I use the flanged adaptor for use with a M42 bellows unit... if you use the other style with the locking spring with a bellows, it can get stuck on your camera.

[Jewelltrail]

Just1moredave: I bought a flanged adapter for a couple of reasons. One was curiosity. Do the Takumar lenses have enough adjustment for infinity focus to allow the adapter work properly? They do have an adjustment range, but the threads on the focusing helix stop eventually.

I tested a Super-Multi-Coated Takumar 50mm f1.4 (metal focus ring version). The answer is, almost but not quite. My infinity focus target is a mountain 55 miles away, and I use an MX with a split-prism screen. At f1.4 and 55 miles (88.5 kilometers), a depth of field calculator tells me that everything from 88.3 meters to infinity is in focus, but the split-prisms don't quite line up.

Possibly some other lenses would work, or this is close enough for you. It would be useful for the newer cameras that have metering errors unless the pins are shorted out. When I was buying my adapter, I saw the focus screen supplier "jinfinance" had some adapters with thinner flanges, but I can't find them today. These might be just thin enough to work.

My other reasons for a flanged adapter are for possible mount replacement, and I think it'll make a good drill guide for drilling a locking pin hole for a permanent K-mount conversion with a non-flanged adapter.

Great to see this kind of fresh, rethinking. I eagerly await any of your results. Please post here--thanks.