The K-01, with it's LV 6x zoom and focus peaking, is proving a popular camera for MF lens. This article looks at using a Super Takumar lens on this camera.

First off, to use a M42-mount lens on a K-01, you'll need a M42-to-K-mount adapter:

https://www.pentaxforums.com/forums/accessory-memory-articles/87287-right-typ...t-adaptor.html

If not already enabled, set Menu C3 item 18, "Using aperture Ring", to Enabled ("2").

Super Takumar lenses have an Auto/Manual switch on the barrel. This is a mechanical switch that activates the aperture override pin in the base of the lens.

Photo of Super Takumar lens showing Auto/Man switch, in Man position, and the aperture override pin:



Later lenses with a "A" position on the aperture ring, or with DA aperture-ring-less, use the mechanical aperture coupler lever protruding from the lens base, both to set the aperture position to the f-number setting the camera specifies, and to hold the aperture fully open before the shutter release button is pressed.

A-series lens showing the aperture ring set to the "A" (aperture controlled by the camera body) position. Aperture coupling lever and guard are also visible:



Operating this way ensures that the OVF is brighter. For example, you are going to shoot a f/1.4 lens at a f-number setting of f/5.6 (4 stops down). If you have to focus while the lens is stopped down, the OVF would be 4 stops darker. Instead, it is held open, and only stopped down to f/5.6 after you press the shutter release button.

Using a old non-"A" lens (i.e. K or M series) with these settings would result in a darker OVF, as would operating an A or later (F, FA) lens off the A position on the aperture ring.

Now with the Super Takumar, the pin in the base, when depressed, is designed to stop down the aperture to the current setting of the aperture ring. The camera body was designed to keep this pin open until the shutter release button was pressed. Again, so the OVF was brighter. (The pin is not there to enable setting the aperture from the body, as "A" position lenses do.)

Anyway, with the Super Taks, the Auto/Man switch follows or ignores the depression of the aperture opening pin.

On DSLRs with M42-to-K-mount adapters, there is no special treatment of this pin. It is still fully depressed when you screw on the lens. (DSLR bodies have no mechanism anyway to release this pin.)

Therefore, on a DSLR, the Auto/Man switch on the Super Tak operates this way:

Auto: obeys pin. Lens is always fully open, even after the shutter release button is depressed.

Man: ignores pin. Lens is set to aperture ring setting. OVF may be darker.

You can manually switch the Auto/Man switch, so you have it on Auto when focusing & framing, and then change it to Man when you go to shoot so your intended f-number is used.

Besides VF brightness, there is another reason for using Auto when manually focusing. You are focusing with a fully open aperture, e.g. f/1.4, which has a much narrower in-focus range, and is thus more definite than focusing say at f/5.6.

So the suggested sequence of operation with a Super Tak in M exposure mode is this:

1. While in Auto position, focus roughly.
2. Press OK to zoom in (I use it to toggle between 1x and 6x) and adjust focus finely based on the focus peaking.
3. Switch to Man.
4. Press the Green button to set the correct shutter speed for the set aperture.
5. Take the shot.

Under Camera settings Menu 3, Button Customisation, ensure that for the Green Button, "Action in M/TAv" is set to Tv Shift . (Default is P Shift, but with manual aperture control, Tv Shift is probably a better choice).

You could leave the lens stopped down in the Man position all the time. With fixed ISO, this would change the brightness in the EVF. With Auto-ISO, the brightness will probably remain the same. However, staying stopped down, with a large aperture lens, is going to make it harder to achieve the best focus accuracy.

You could also keep switching between f/1.4 & f/5.6 on the aperture ring, but if you are doing a lot of shots at f/5.6, I think using the Auto/Man switch will be easier and less likely to cause errors.

Just don't press the Green button in the Auto (fully open) position and then switch to Man (stopped down) and shot, or you'll end up underexposing.

Operation is also possible with M42 lenses in Av mode, where the camera sets the shutter speed automatically. (No need to press the Green button.) Again, I suggest composing and focusing in Auto and switching to Man before taking the shot. Of course, you will need to set your required f-number on the aperture ring.

Dan.