Lens Aperture Not Round

[kimd]

Just noticed that the aperture in my new (used) Planar 85 f1.4 doesn't form an even "circle" when it is stopped down. In other words, it is more of an oval because two opposite aperture blades are exposed more than the other six.

It would make sense that this issue could potentially affect exposure (ie. ovals and circles let different amounts of light pass through) as well as blurred highlights. Does anyone know if it really makes a difference? It seems to be a relatively common occurrence with lenses.

Bottom line: Is this is problem worth fussing about? I want my lens to operate properly, but am not sure it's worth going through the whole rigamarole to exchange it...

Thanks, Kim

 

[crocus63]

Kim,

I happen to have a 50/1.7 with the condition you describe. It appears to happen only with the middle apertures and not at the extremes. The aperture blades could be getting worn. But In usage, the images appear to be fine as well as the exposures. Though I don't recall if I shot any images at 1.7-2.8 to see if the bokeh was oval. I didn't bother to fix this lens as the price of repair was more than what I had paid for the lens. In your case, you may want to consider it if it bothers you. Otherwise I would shoot some chromes with the lens wide open to see if the ovalness affects your images.

Regards, Gary >

 

[kimd]

Hi Gary,

When the lens is close to wide open (f2), it's hard to tell if the aperture is round or not. At f2.8, it's slightly out of round. From f4-16, it gets progressively worse - with f16 being quite noticeable. The aperture blades don't look worn at all and the rest of the lens body and glass is spotless.

Since I have the time, I think it's a good idea to test the lens at all apertures before making a decision whether or not to send it back.

Cheers, Kim