I have been trying out different M42 lens on my Pentax K-x. Results in the final images are good but I find that K-x does have some minor glitches with M42 lens when compared to Pentax K20D.
- I can't use Av mode on M42 lens like K20D. I found myself under-expose by a big factor as in 2 to 3 stops. I have not found if the difference is consistent so that a simple +Ev compensation will make K-x work with M42 lens in Av mode.
- For consistent metering, I have to use M mode together with either green button or (+/-) button for metering. I prefer the use of (+/-) button as K-x's green button location is awkward to access in the field. The (+/-) button is more natural for me to use.
- Ev compensation is omitted in K-x. This is unlike K20D which allow Ev compensation even in manual mode. I get spoiled with Ev compensation so that I can set a preset compensation adjustment for consistency with an M42 lens.
- I do miss the red focal point overlay for focus reference
- It is difficult to see bottom of viewfinder especially in bright daylight setting. The green hexagon is not bright enough to view in K-x. I rely mostly on the beep which is unsettling in the shooting.
Results are quite good when I tried my Pentax K-x with Vivitar 70-150mm f/3.8 from Kiron in M42 mount. In some of the close up, I used the Cosina 1:1 matched macro adapter which works like diopter with +3 to +4 magnification.
Impressions & Notes
- The Kiron zoom lens is great in terms of sharpness. It is not too big and works well in K-x.
- The close up works in the 70mm end and I think it is about 1:4 in magnification. With the diopter, it is roughly around 1:3
- The catch-in focus is absent like many M42 lens.
- Metering is center weighted and I have not tried the trick with aluminum foil to see if matrix metering and catch-in focus can be resumed in this m42 zoom on K-x
- As mentioned, I used M mode and green or (+/-) button for metering.