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Old Jun 19, 2007, 12:17 PM   #11
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baltochef920 wrote:
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Hayward wrote:
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Well again the two I have are exactly like a K mount lens.... clicks into the cam mount springs, the release button just releases..... why would a mount need a spring...lenses don't.... and still physically mount flush no less? The mount is just a plain pice of machined aluminium.... no mechanics at all.....


Again why would there be a reason for a spring on the mount???? There aren't on K lenses?
Good questions Hayward!!

I was wondering the same things as to why the mount has a spring & the lenses do not..

Hopefully someone with more knowledge will provide us with the answers..

Bruce
Thats because the K lenses have a notch for the pin on the camera body. This keeps the lens from rotating on the body. Pressing the lens release button depresses the pin out of the notch allowing the lens to rotate.

A flangeless adapter (like the genuine Pentax, Kalt etc.), due to their physical characterisitics, have no such "limiter". So, they have a spring that catches onto the body cavity and keeps it from rotating and falling off the body.

/\/\ax


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Old Jun 19, 2007, 1:45 PM   #12
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Well, it depends on which adapter you have.

If you have one with a flange that covers the contacts on the camera mount, then there is indeed no spring, and the adapter just works like a K-mount lens, like Hayward said.

One of these: http://www.fotodiox.com/shop/images/..._K_adapter.jpg


But, if you have the Pentax-made (or a copy of it), that looks like this: https://www.foto-walser.de/artikel/510x510/10987.gif

it goes inside the mount completely, doesn't have a flange covering the contacts, and thus providing M42 lenses with the exact same register distance as the K mount lenses. (this means the end of the lens is at the same distance from the sensor as a K-mount lens would be, or as that lens would be on an old Spotmatic camera. With K-mount and M42 the register distance is 45,5mm)

This one obviously can't be 'clicked' in and out like a normal lens, as there is nothing covering the contacts, and nothing covering the little pin that's used to hold a lens on the camera. (push the lens release button without a lens ont he camera, you'll see what I mean)
you can see it in the picture on the upper left.

So, what they did is use a little metal plate and a spring, to make the adapter click into place (and preventing it from turning back and falling off)

But, since the lens release button doesn't have any effect on that little ring, you need an alternative way to release it from the camera.
For this, a special "key" is used to push back that little spring, allowing the adapter to turn back and come off.

However, if you glue this kind of adapter to a lens, you have no way of using the "key" to unlock it...so you have to remove the little spring first.

Tom


P.S.: more on regsiter distance: http://www.mflenses.com/content/view/50/29/
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Old Jun 19, 2007, 2:33 PM   #13
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Ok ... I just placed an order for the Kalt adapter from B&H. I realize that the Kalt does not have a spring to stop it from rotating out of the slot. This is good for two reasons:

1. I can take the lens out along with the adapter instead of using a key to remove the adapter. This will help switch between AF and MF lenses.

2. I plan to drill a small notch on all my lenses at the precise location where the pin from the camera body tries to mate with a notch on the lens. This will take care of problem #1.

Eureka !

/\/\ax

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Old Jun 19, 2007, 7:06 PM   #14
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Thats the way to go //ax, a flush type adapter to preserve the register distance and a little hole or notch drilled to stop the lens falling into the pond!
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Old Jun 20, 2007, 2:30 PM   #15
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umenon wrote:
Quote:
Ok ... I just placed an order for the Kalt adapter from B&H. I realize that the Kalt does not have a spring to stop it from rotating out of the slot. This is good for two reasons:

1. I can take the lens out along with the adapter instead of using a key to remove the adapter. This will help switch between AF and MF lenses.

2. I plan to drill a small notch on all my lenses at the precise location where the pin from the camera body tries to mate with a notch on the lens. This will take care of problem #1.

Eureka !

//ax
Hey /\/\ax

When you finish the notch conversion to a M42 adapter would you be able to post some images & dialog to explain to others how to do it??..

I'm real interested in something like that..

Thanks, Bruce
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Old Jun 22, 2007, 4:41 AM   #16
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I should mention that some lenses do not have a shape that allows the locking notch to be made.
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Old Jun 25, 2007, 7:56 PM   #17
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Sorry just got back from vacation. The Kalt has a spring and I removed mine...Yes I loc-tite them on and have yet to lose one. Drilling a small hole or notch for the spring catch is a good idea that I'll have to try myself.



Dawg
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