I have some questions, but first the background.
Yesterday I succumbed by my NAS and bought a silver 45mm f/2.8 AiP. The pricing was 200 EUR, and as seller hadn't use the lens for the past few months, he checked it and found out the aperture was sluggish, in his words, beyond f/8. With that known issue, I got him to sell it to me at 150 EUR. Prices equivalent from Singapore dollars.
Sure enough I tested it there was some sluggishness in the aperture, and initial shooting at f/16 yielded about 1.3 stops of overexposure. Brought it home, exercised the diaphragm, and this morning I tested the aperture to close down "correctly" at f/11, and at f/16 the value was about between 2/3 and 1 stop out (closing to 1 stop). Unscientific test, using the lens on a Df and shooting a scene outside my window, cycling through the apertures from f/2.8 through f/16. Significant vignette at f/2.8, improving by f/4, gone by f/5.6. Consistent histogram from f/5.6 through f/11, and at f/16 to shifted to the right, determined to be between 2/3 and 1 stop by shooting at f/8 and using exposure compensation and watching the histogram. Weather condition remained relatively constant - overcast, which is good, as there would be little change of lighting.
My question:
- could this issue be due to storage of lens at its widest aperture, hence putting the spring at tension in storage?
- subjectively, if I now store the lens at the minimum aperture, and exercise the lens (use the lens) regularly, would I be able to get the aperture back to (or close to its original performance specification?
I have tested and am satisfied that up to f/11 there is no problem. And should be able to work around the f/16 issue if needed (like shoot manual exposure with lens stopped down).
Thanks.