wogears Posted June 21, 2015 Share Posted June 21, 2015 <p>I just picked up one of these to use on my new-old OM-1. I noticed the following diaphragm peculiarity. When I set the aperture to f3.5, the diaphragm stays open all the way as I zoom from 70mm to 35mm. If, however, I set the aperture to 5.6 or smaller, the diaphragm will close slightly when I zoom out of 70mm, then remain slightly closed as I zoom out to 35mm. When I press the DOF preview, the lens will stop down all the way to the set opening (say, f11). I assume this is because the lens is an early variable aperture, and that this is not a Bug, but a Feature (in other words this is normal operation). Am I correct in this? It does make focusing difficult with the microprism if I am not set at wide-open.</p> <p>Thanks to all,<br> Les</p> Link to comment Share on other sites More sharing options...
david_carroll4 Posted June 23, 2015 Share Posted June 23, 2015 <p>I honestly think there's a problem with the lens - variable aperture (usually a smaller aperture at the long end) is a result of the physical "window" (the front element) remaining constant as the focal length increases, necessitating a smaller max aperture. I have never heard of a lens diaphragm adjusting to reduce the aperture. That sounds a bit self-defeating. I had two Zuiko 35-70's, the 3.5-4.5 and the 3.6, and I never noticed this behavior with the 3.5-4.5. </p> Link to comment Share on other sites More sharing options...
wogears Posted June 24, 2015 Author Share Posted June 24, 2015 <p>Have contacted the eBay seller. Very reputable one, so I expect it will just be a return. Still, I'd like to know for sure what's going on.</p> Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now