Planar 80 mm C T*

Hi all.
My question is to those who have/know Planar 80 mm C T*. I noticed a strange behavior of diaphragm. I removed the back from 500 c/m, set f-stop to 22 and push mirror lock up button. The diaphragm leafs closed to ~f8 stop. After pushing exposure button diaphragm leafs have closed down to f22 position followed by the shutter execution. Is this abnormal functionality?

Cheers.

You have accidentally engaged the preview button and left it in the preview mode. That makes the lens stop down. See the attached information.

Sirius Glass said:

You have accidentally engaged the preview button and left it in the preview mode. That makes the lens stop down. See the attached information.
View attachment 155827

Click to expand...

Thank you Sirius for quick response. I did not touch preview button. F-stop was set to 22 and after the MLU was pushed the leafs had closed not to f22 position but to ~F8 and than was closed to F22 only after pushing exposure button.
Your pic is about CF.

Cheers

Hi phass,

same behaviour wich my 500C/M and 80C T*. Double checked it with the 40 Distagon and the 150 Sonnar - they behave similar (f11 instead of f8, but these two lenses can be stopped down to f32).

Regards Matti

Using my 500C/M, I have just performed this test with my older C lenses (80/2.8 and 250/5.6) as well as newer CF lenses.

In all test cases, the pre-release caused the shutter to close, mirror to rise, the rear baffles to open, and the aperture blades to close to f/22. Pressing the shutter release caused the shutter to operate and the aperture blades remained at f/22.

I tried various speeds from 1 second to 1/500 and several other apertures, including f/45. In all cases, the pre-release operation caused the aperture to close down to the selected aperture immediately.

In no case did I see the aperture be wider than the selected aperture and then close down further upon pressing the release.

It seems that your blades are sticking until the actual release. Not ideal, but it works for now. Your lens likely needs a CLA.

I'm still quite sure that it's a feature of a certain generation of T* lenses and not an issue. When you unlock speed/aperture with MLU and stop the lens down, aperture blades close in the way one would expect it down to f8 (f11) and stops there. It does not look like a malfunction, I can reproduce this behaviour again and again on three lenses.

MattiS said:

I'm still quite sure that it's a feature of a certain generation of T* lenses and not an issue. When you unlock speed/aperture with MLU and stop the lens down, aperture blades close in the way one would expect it down to f8 (f11) and stops there. It does not look like a malfunction, I can reproduce this behaviour again and again on three lenses.

Click to expand...

Based on those results, I agree with you. The Synchro-Compur shutter is used in many cameras, but I would love to know the details of any modifications Zeiss had performed for its line of Hasselblad lenses.

Perhaps one day I'll find and buy a defective CZ Hasselblad lens for the purpose of disassembling and studying it.

Thank you all for comforting feedback. I have never used f-stops above f8, though i would like to have enough confidence that i won't overexpose a shot because at 1/500 the leafs won't move fast enough to chosen high f number.
Cheers.