[tduell]

Hello All,
Sorry if this should have been raised on an old/existing thread.
I have a genuine 'Pentax Mount Adaptor K' and have been trying to see how I can use my old Meyer Optik Gorlitz f/1.8, 50mm lens from my Practica days.
I set 'Using Aperature Ring' to 'Enable' and set the focal length to 50mm, however it still shows F-- on the LCD.
I have made couple of test shots using M mode which look OK, but it is a real pain to do this.
Firstly, the lens has manual stop down button, which was positioned on the RHS when the lens was mounted on the Practica. When mounted via the adaptor to the K3II this stop down button is adjacent to the lens release button, hence really difficult to actuate with a finger whilst actuating the shutter...well it is with my hands.
It is as if the thread on the mount has been started in the wrong position. Anyone seen this issue before?
Secondly, when in M mode with a normal K mount lens, the camera displays the exposure setting. With the manual lens I get no indication of exposure so have no idea how to adjust the shutter speed.
I have read the guides on the forum as to how to use a manual lens, but have not seen any of these issues addressed.
Clearly things are not right, as I can't imagine anyone ever being able to reasonably use a manual lens under these conditions, so I assume I don't have things set up correctly.
Can someone please give me a few clues on the above issues?

Cheers,
Terry

[farhaddad]

That's how manual lenses are supposed to work. The lens has no electronic contacts to communicate with the camera and that's why you can't see the aperture number on the screen. I'm not sure I understand what you're trying to say about exposure. You simply press the green button for metering but that's only a reference ( a start point) for you. You should change your shutter speed according to the scene. Think about it like using an old film camera with the ability to see the images you take and a built-in light metering. I use spot metering instead of centered weighted but as I've said before, metering in manual mode is just a start point for you and you should change your shutter speed according to the scene.

[tduell]

That's how manual lenses are supposed to work. The lens has no electronic contacts to communicate with the camera and that's why you can't see the aperture number on the screen.

I think I understand that, but the camera shouldn't need to know the aperture No. to measure the exposure in manual mode, it measures the incoming light, and hence should be able to show me if it is under or over exposed.

You simply press the green button for metering but that's only a reference ( a start point) for you.

OK, that sets a shutter speed.

You should change your shutter speed according to the scene. Think about it like using an old film camera with the ability to see the images you take and a built-in light metering. I use spot metering instead of centered weighted but as I've said before, metering in manual mode is just a start point for you and you should change your shutter speed according to the scene.

OK, I now understand what the camera is doing, but blowed if I know what sort of hand one is expected to have to be able to press the lens stop down button at the same time as pressing the green button or the shutter. On this lens the setting of the aperture ring is only a pre-set and to stop down one has to press the button on the side of the lens. I would have expected the lens to mount in the same angular position relative to camera as it did on the Practica but is something like 60 degrees further clockwise looking from behind the camera.
I really would like to know where the stop down button on this lens is positioned on others who have a similar set up, so I can confirm if my mount adapator is correctly manufactured.

Thanks for your help.
Cheers,
Terry

[Not a Number]

You have to take into account screwmount lens were designed for bodies with no tabs, buttons or levers for releasing the lens. So lens designs did not take into consideration such obstructions. Pentax k-mount bodies perhaps took into consideration the possibility that lenses had tabs or switches in this area as up until DSLRs the lens release was a tab/lever on the side or a button that lay flush to the mount pedestal.. With a gap of 3 to 6 decades or more between designs some incompatibilities are sure to be found.

I have 3 OEM adapters. 2 made in the Philippines and one made in Japan. All my Takumar lenses align more or less with the focus pointer at the 11 o'clock position. This tells me that a good degree of precision is used in where the screw entry points are placed. If you have a few Takumar lenses see where the focus pointer lines up - chances are it will around the 11 o'clock position. A number of people report some of their lenses will line up close to 12 o'clock.

[i_trax]

you just set the camera to Av, do the focus and take the picture, camera will do the rest.
you do not need green button
when is darkish, fully open the lens, do the focus, close it back and take the picture
green button is only for K and M lenses

[Adam]

I think I understand that, but the camera shouldn't need to know the aperture No. to measure the exposure in manual mode, it measures the incoming light, and hence should be able to show me if it is under or over exposed.

If the diaphragm is set to manual, the metering should be correct in Av mode. However, your viewfinder will also darken.

[farhaddad]

Sorry for the misleading info. I misread what you've wrote and though that you're using k mount lens. I didn't see the adaptor part! I apologize.

[UncleVanya]

As said above. Set to manual aperture on the lens and use Av mode. The adapter does not provide aperture linkage to operate the m42 lens diaphragm so the green button has no benefit (no way to stop down). In many ways it is like using a preset lens - open, focus, stop down by dialing in the aperture, Av adjusts shutter speed, use exposure comp to shift around things or switch to M mode to manually adjust.

[tduell]

In many ways it is like using a preset lens - open, focus, stop down by dialing in the aperture, Av adjusts shutter speed, use exposure comp to shift around things or switch to M mode to manually adjust.

Is it is pre-set lens...perhaps I don't express my self very clearly.
The fact that it's a pre-set is one of the basic problems I have using the lens.
I find it almost impossible to push the stop-down button on the lens and the shutter button at same time.
As I said...it would be good to be able to disable the pre-set function, so that I can adjust the aperture directly via the aperture ring.

Cheers,
Terry

[stevebrot]

I find it almost impossible to push the stop-down button on the lens and the shutter button at same time.

Perhaps this photo will help our readers understand...




The lens is an auto-aperture M42, but instead of having a M/A switch, it has a button on the base of the lens that must be held in the depressed position to stop down the lens. This would be very difficult with the grip in the way. The best solution might be to do minor surgery and slip a small diameter tube over the aperture actuator pin so that it is always stopped down (converted to fully manual aperture).


Steve

[tduell]

Perhaps this photo will help our readers understand...
The lens is an auto-aperture M42, but instead of having a M/A switch, it has a button on the base of the lens that must be held in the depressed position to stop down the lens. This would be very difficult with the grip in the way. The best solution might be to do minor surgery and slip a small diameter tube over the aperture actuator pin so that it is always stopped down (converted to fully manual aperture).
Steve

Thanks Steve, I probably should have put up an image of the lens in the first place...would have saved a lot of confusion.
I have been looking for ways of effecting the 'surgery'. Not sure if I would be able to get a tube over the actuator pin, it is a very close fit in the body.
I have pondered on whether there is a way of holding the pin in the 'in' position by some internal modification, but don't have much to go on at the moment. I am reluctant to open up the lens without have a good idea that it worth doing so.

Cheers,
Terry

[i_trax]

I did bend the pin a little bit and pushed it in, it does stay in.

[stevebrot]

I have pondered on whether there is a way of holding the pin in the 'in' position by some internal modification

The "tube over the pin" fix requires partial disassembly and is the solution used by owners of the Helios 44M-4 to convert their lenses to full manual aperture.

You Tube

You Tube

Steve

[tduell]

The "tube over the pin" fix requires partial disassembly and is the solution used by owners of the Helios 44M-4 to convert their lenses to full manual aperture.

Bonza...that looks like a reasonable solution, and is readily reversible.

Cheers,
Terry