Lens Fetish Club

[8540tomg]

That's an amazing collection of rare Pentax glass Jim. Bye-the-way what is a colormonger?

Tom G

[frank]

Originally Posted by Syb

Yikes, Frank! You were careful weren't you? No doubt you were fearing an earthquake...

Yeah, I was more than careful when taking the photo. That's why I could only do this after midnight when the kids were all asleep

Luckily here in Singapore we haven't got any major earthquake for a very long time

Originally Posted by lbam

My! that's a long one

Yeah, I know. Actually I had an FA*24 w/ me at that time, but failed to add that one on due to the stability problem w/ such a 'long' lens. Probably would be easier if they had something like IS/VR/OS built in

[frank]

Originally Posted by Douglas_of_Sweden

"NASA just announced that the Apollo 2.8 mission has been successfully launched from Cape Pentaxedy. The two first stages burned up over the Pacific Ocean and the third stage entered the outer space with an escape velocity of 1/2000 second!"

Haha, I won't let that happen

[jamesk8752]

Originally Posted by 8540tomg

That's an amazing collection of rare Pentax glass Jim. Bye-the-way what is a colormonger?

Tom G

I coined it by analogy to ironmonger, one who sells good made of iron. Back when I was still a wage slave, I developed and marketed (sold) new color concepts for automotive exteriors.

Regards, Jim

[jamesk8752]

Originally Posted by Douglas_of_Sweden

Mmmh, I was just guessing that from that the aperture ring was up front. But then the aperture setting must just be transferred to the iris in the center. Maybe this is the case also with the older lenses with the aperture ring in the front? Have forgot most of what I learned on optics long ago: maybe the iris has to be at the focal point to work? I think so. So I made a stupid assumption, should go to bed instead.
It looks on the lens diagram as thought there is one lens behind the shift mechanism, doesn't it?

Upon re-reading your question, I believe that I initially misunderstood what you were asking. The aperture rings *are* at the front of the lens, but I suspect that this is because it is a preset design, not because of interference with the shift mechanism (my other preset lenses all have the aperture rings at the front also). The shift only involves a flat plate at the very rear of the lens and would probably not interfere with focusing or aperture setting even if the aperture control were in its usual position near the rear of the lens barrel. And no, there are no lens elements behind the shift plate - the plate is slotted so the rear element group, which protrudes into the camera body slightly at infinity focus, can move freely at full shift.

Regards, Jim

[anomaly]

You people are creepy.

[Douglas_of_Sweden]

Originally Posted by jamesk8752

Upon re-reading your question, I believe that I initially misunderstood what you were asking. The aperture rings *are* at the front of the lens, but I suspect that this is because it is a preset design, not because of interference with the shift mechanism (my other preset lenses all have the aperture rings at the front also). The shift only involves a flat plate at the very rear of the lens and would probably not interfere with focusing or aperture setting even if the aperture control were in its usual position near the rear of the lens barrel. And no, there are no lens elements behind the shift plate - the plate is slotted so the rear element group, which protrudes into the camera body slightly at infinity focus, can move freely at full shift.

Regards, Jim

Thanks Jim for taking your time to answer my questions.
Why is this lens a preset lens when no other (?) K generation lenses are? Isn't preset aperture a feature found among older Takumar lenses? Where there a previous m42 version of this lens which they just put a K bayonet on?

My reason for asking about the positions of shift mechanism in relation to iris and lens is a crazy idea that I might try converting an ordinary lens into a shift lens, just because these Pentax shift lenses are so awfully rare. The shift mechanism itself is not so complicated a construction. But it is just a wild idea.

[Miserere]

Originally Posted by Douglas_of_Sweden

My reason for asking about the positions of shift mechanism in relation to iris and lens is a crazy idea that I might try converting an ordinary lens into a shift lens, just because these Pentax shift lenses are so awfully rare. The shift mechanism itself is not so complicated a construction. But it is just a wild idea.

In order to do that you need to have a lens that projects a much larger image than the film size. If you take a 35mm film lens and convert it to shift to use on an APS-C DSLR, then it might work to some extent.

[Douglas_of_Sweden]

Originally Posted by Miserere

In order to do that you need to have a lens that [projects a much larger image than the film size. If you take a 35mm film lens and convert it to shift to use on an APS-C DSLR, then it might work to some extent.

Exactly my thought. A real shift lens like Jim's here must be optically like a large format wide angle, which one can imagine from the look of the front lens. But an old and cheap 28mm lens for 35mm film with some distance between the last lens and the mount could maybe do on APS-C. Could take an m42 lens. Would need some metal work though. Just a wild idea.

[axl]

here are two of my most valued primes, giving me 40-400 f2.8 - f5.6 combo...
shame it's not constant aperture

[Nesster]

Damn, there's some seriously wicked glass around here
The long and the short of it

Here's a Tele-Takumar 200/5.6

[jamesk8752]

Originally Posted by Douglas_of_Sweden

Thanks Jim for taking your time to answer my questions.
Why is this lens a preset lens when no other (?) K generation lenses are? Isn't preset aperture a feature found among older Takumar lenses? Where there a previous m42 version of this lens which they just put a K bayonet on?

I think that it has to be a preset design because the shift mechanism would interfere with the aperture readout lever, which is very sensitive to position for accuracy, and the aperture stopdown lever. If the lens were shifted I don't think mechanical linkages would function properly. Of course, in a modern electronic mount design such as Canon uses this would not be a problem.

In any event, I think that stopdown metering would be necessary anyway because of the light falloff at the edges of the large image circle. Even so, I found that images metered at full shift required extra exposure from what the center-weighted TTL metering of my *ist-D suggested.

As far as I know, Pentax did not offer this lens (or any other shift lens design) in M42 mount - it is an original design. Since it was a preset design, there was no need to update it as the later versions of the K-mount lenses were developed. Boz's site indicates that it was still being made as late as 2004.

My reason for asking about the positions of shift mechanism in relation to iris and lens is a crazy idea that I might try converting an ordinary lens into a shift lens, just because these Pentax shift lenses are so awfully rare. The shift mechanism itself is not so complicated a construction. But it is just a wild idea.

Sounds possible, but as others have said, I think that you would need to use a MF lens to get a sufficiently large image circle to accommodate a significant amount of shift.

Regards, Jim

[Douglas_of_Sweden]

Originally Posted by jamesk8752

I think that it has to be a preset design because the shift mechanism would interfere with the aperture readout lever, which is very sensitive to position for accuracy, and the aperture stopdown lever. If the lens were shifted I don't think mechanical linkages would function properly.

That makes sense, should have thought of that.

Originally Posted by jamesk8752

Sounds possible, but as others have said, I think that you would need to use a MF lens to get a sufficiently large image circle to accommodate a significant amount of shift.

Regards, Jim

Yes, that's what I've seen others do. I suppose one could get a limited effect with a full frame lens. But besides enough image circle, one would need enough space behind the last lens (without an aperture ring in the way) to be able to cut off enough of the lens to keep the same distance to the sensor and keep infinity focus. The most simple conversions I've seen did not keep infinity focus, since they basically just put some sliding mechanism between the lens and the body allowing the distance between optics and sensor to increase.

Realizing I've hijacked this thread. Sorry.

[Mechan1k]

I need to get myself a light tent and have a real go at this though.
My shot of my Super Tak 28mm is avergage compared to some of these great images.

Click on the image to view it in a larger size

[Reuben0]

Here's the M*300/4 and M200/4 - not much difference in size



R