I got this old zoom lens knowing that it is a auto-only M42 lens. I had the previous experience in altering an auto-only diaphragm into manual diaphragm m42 lens. It is equivalent to switching to M in most of the M42 lens with A/M switch. For manual stop-down, one has to use M setting as most of the current digital bodies don't have the mechanics to depress the aperture pin for the proper stop-down.
Every lens is different and this one does not come as a surprise in terms of difficulty. I first found the aperture pin not working even upon full depress into the lens. I later found a stuck linkage between the pin the aperture diaphragm. Once I get the pin to work properly, I added a little hollow insert using a fragment of a pen refill tube to make the pin pressing on the aperture diaphragm control at all time.
But once I get the stop-down mechanics working with manual diaphragm opening with the aperture ring, I found another issue and it is something that I have not dealt with before. The old M42 lens leaks oil likely from the helical housing in the focus and zoom compartments.
The lens has potential and I start liking its strong build and unique character that little is known about it.
It works quite well when stop downed properly. And here are some test shots done with Pentax K20D
Shot wide open in f/3.5
soft but nice bokeh
soft but nice bokeh
stopped down properly after fixing the aperture pin
Impressions & Notes
- It is a bummer to be able to fix a lens with aperture issues and stop short in fixing it completely due to the oil leaking from the lens helical to aperture blades
- The oil and wet blades don't affect the lens performance immediately as I find no issues in the test pictures but it is something to be less desirable
- The zoom lens has internal moving part for the zooming. Upon changing from 80mm to 200mm or vice versa, the lens does't extend or retract to a different length.
- Bokeh and sharpness are found decent. The lens perform quite evenly across the range though I prefer to shoot in 180mm instead of 200mm as I think sharpness is better in 180mm.
- This M42 zoom can work straight in Av mode in my Pentax K20D from f/4.0 to f/11. In wide open shot in f/3.5, I usually dial in +0.3 to +0.7 Ev.
- Contrast is sometimes low when I shoot into objects with harsh lighting. It seems lacking on coating like the SMC in Pentax. The contrast is usually a easy fix in post processing.
- I have decided to move on and sell it for cheap to others with full disclosure on the wet blade with oil issues