K-3 III How-to: Using M and K Lenses

How to use M and K series lenses with the K-3 III

By PF Staff in Articles and Tips on May 27, 2021

The process of using manual focus lenses with no A-setting on the aperture ring has been vastly improved with the new Pentax K-3 Mark III DSLR. It is now as easy to shoot in Av mode with The K-3 III as it was with the beloved film cameras like the ME, K2, Super Program, Super A, etc.

Add to this the improved viewfinder with its 1.05x magnification, which makes manual focusing easier and more accurate.

For users of legacy lenses these two improvements alone may be sufficient to justify upgrading to the K-3 Mark III!

Step 1: Prepare the Camera

Bring up the Custom Menu page 6 and:
a) Set Length Input on Startup to On
b) Set Using Aperture Ring to On
c) Set Aperture Info Record to On

By setting Length Input on Startup to On the focal length will be saved in the EXIF information block, and, more importantly, by entering the focal length when you mount a lens you enable Shake Reduction to work properly. This setting is highly recommended, but optional. If you don't set it, you should disable Shake Reduction.

By setting Aperture Info Record to On you can save the aperture used in the EXIF information block. This is optional.

You need to make these settings only once and can leave them set to On forever. They won't interfere with your use of modern lenses.

Step 2: Set the Focusing Mode to MF (manual focus)

Step 3: Set the Exposure Mode to Av

One can also use TAv mode (the camera will only adjust the ISO in this mode) and M mode (fully manual with green button stop down metering). P and Sv mode will default to Av mode and Tv will default to M mode.

Step 4: Set the ISO, or Set it to "ISO Auto"

Step 5: Mount the Lens

Step 6 (Optional): Enter the Focal Length on the Rear Monitor

In case you did not set the focal length when prompted, you can do it in the custom menu page 6, item MF Lens Focal Length.

Step 7: Set the Aperture on the Lens

Step 8 (Optional): Set the Aperture Value on the Camera

Only if you have enabled Aperture Info Record in step 1: enter the aperture value into the camera by using the rear e-dial. The "F" will be flashing on the LCD and the info panel to remind you about it.

Step 9: Shoot and Enjoy

Compose the image, focus by turning the focusing ring on the lens, and press the shutter button!

The lens will stop down to the set aperture, the camera will meter the scene and set shutter speed and ISO to match. There is but an insignificant delay in this process.

Unless you want to change aperture (or ISO), you can just go on shooting by repeating step 9. It is that easy!

Below is a sample photo (jpg out of camera, no post) shot with an SMC Pentax 28mm F3.5 lens at F11, ISO 200, center-weighted metering (multi-segment metering is not available with these lenses). The scene was shot at several F-stops from F3.5 to F22. Exposure was quite consistent across that range.