I'm making an effort to find out if other copies of the smc P-FA 50mm F1.4 lens exhibit the same feature or if mine is problematic.
I've been using my copy of this lens for more than a year and I'm noticing a problem that appears to have been around since I got the lens. I found the problem because I've been trying to get those nice, round out of focus highlights that are so popular with holiday shots and portraits.
It seems that one or two aperture blades on my copy are a fraction slower to close than other blades. Or that there's a blade or two that closes too quickly. Not sure which...
Here's what the lens looks at f22:
Notice how the blades form an uneven shape in the center.
at f2:
You can see that there is not a smooth transition from one blade to another on one side of the lens, giving little "spikes." These shapes form distortion on the images, readily apparent below.
and f1.7:
This shows more easily how one side of the lens seems to be moving more than another side.
Of course, at f1.4, all is good, since the lens is wide open.
Here's what an image looks like at f2:
I checked against an old f2 50mm lens I had kicking around and while it has only 6 blades, there were still some issues with "spikes" showing around the edges at the first two stops. My 135 and the SDM lenses I have don't seem to have the same issue.
I'm curious now... do other copies of this lens seem to show the same behavior?