HCD 35-90: aperture blades visible when shooting wide open

[epines]

For anyone who owns the HCD 35-90 lens, I'm wondering if you have noticed this: I just got a used one, and I'm noticing that, at all focal lengths except approx. 85-90mm, when I shoot wide open, the aperture blades are slightly visible when I look into the lens (i.e., aren't completely retracted and out of sight). For example, at 35mm, at f/4, when I shoot and look into the front element, I can see the aperture blades slightly contracted, as if it's closing down slightly. And at 50mm f/4.5. And so on, through all focal lengths but the long end. At 90mm (f/5.6), you can't see them at all.

It's not the shutter I'm seeing. At an exposure of several seconds, I can clearly see the aperture blades. And it happens with DOF preview as well.

Is this normal? Does it happen with your copy of the lens?

thanks
ethan

[Greg]

Not exactly sure what you're asking, but I set my lens to 35mm @f4 and did not see anything as you describe.  Sorry I can't be of more help.

Greg

[epines]

Thanks for checking, Greg. To see what I'm describing, try this: At 35mm, set the lens to f/4 and shoot, say, a 10-second exposure. Look into the front of the lens. You'll likely see the aperture blades just slightly, as if they're closing down slightly. Rather than a perfectly round circle in the middle (where the light is passing through), you'll see a subtly octagonal shape. Let me know what happens.

I just went to Samy's (here in L.A.), where I compared my 35-90 to their demo 35-90. And their lens does it too. We tried both lenses on two different bodies. All did the same thing. At focal lengths below, say, 80mm, with the aperture wide open, you can see the aperture blades slightly when shooting or when stopped down. They contract slightly. For those who own one, I can pretty much guarantee that yours does it too. The veteran Hasselblad repair guy there confirmed this. Guess it has something to do with the zoom's construction.

I shot a comparison to my 50mm prime, and both produced identical histograms at all apertures. (Notwithstanding a little more vignetting in the 35-90 when wide open.)

best,
ethan

[tino999]

So everything is fi e with the lense obviously. Does it influence bokeh?
I'm glad you compared it with the 50mm. Which version do you have?
I have the first version and find it a bit soft at times when not stoped down.
How do they compare at f4.5?