Aperture stuck while previewing DOF

[nelson cotrim]

I just bought a mint 28 1.8 USM. It arrived today. When I was testing

it, checking the diafragm, I pressed the DOF preview button (Elan 7e)

and varied the apperture (in Av mode). The apperture on the lens

didn't change, following the apperture set on the camera. I had to

release the button and when I pressed it again, the apperture would

close correctly. When I did the opposite, pressing the button and then

opening the apperture, everythinhg was normal, the apperture would

open with each click. The apperture also worked correctly at all

settings when shooting (I tested it in bulb, so I had time to see the

diafragm).

 

The contacts are clean, the AF works properly... What should I do?

[derek_linney]

Nelson,

<p>

Don't worry about it. Never even thought to try such a thing. Just did it with my 1V and 10D with 50mm f1.4 and it opened and closed as I changed aperture. Did it with 50mm f2.5 on 10D and it opens up but doesn't close down while keep DoF button pressed [lens works perfectly in normal use]. Obviously lenses vary in how they respond to changing aperture signals while DoF is also signalling.

[nelson cotrim]

Thanks Derek. All my other lenses close gradualy... this is the only one that doesn't. I do it so my eyes can acomodate to the loss of light more easily when I'm stopping down too much. But it won't be an issue... It's just a quick way to check the diafragm of a new lens.