Bronica SQ-Ai / PS lens - Unsharp Negatives due to Shutter (Not Mirror) Vibrations.

[Andre Noble]

I am having problems with critical optical performance of my Bronica SQ-Ai/PS lens system and finally narrowed the problem down to the vibrations caused by shutter. [COLOR=Blue]I do NOT mean 'mirror flap' [/COLOR] - What I am reffering to is a critically unsharp image problem even with mirror locked up, and time allowed for those vibrations to subside - due to the heavy mechnism in camera and lenses that trip the actual leafs in the lens. It seems the problem is most pronounced with focal lengths 150mm and longer, and starts at shutter speeds of 1/60th second, but in my limited tests was more likely to be very prononced at 1/30th second.

I did testing with a heavy 1300 series Gitzo w/ center column weighted down and Arca Swiss B1 head, and RRS arca style quick plate.

Anyone who is familiar with the shutter mechanism knows that it causes vibrations itself even though the actual blades are leaf, very subtle, and not a problem in themselves. The mechanism that trigger these leafs, are pretty heavy duty high tension springs, rapidly rotating levers and a rapid stop there of. When you trip shutter carefully via cable release you can feel the camera vibrate even with the mirror locked up.

My question is for any Bronica users who are already aware of this and have addressed it: Other than fastening camera on a steady tripod, using cable release and mirror lock up - [COLOR=blue]what have you done - if anything - to get critically sharp shots at shutter speeds 1/30th and slower?[/COLOR]

Second question: I only tetsted three speeds 1/125, 1/60/ 1/30 so far - problem was most often at 1/30th and w/ longer lenses 150mm, 180mm, 250mm - especially the 250mm at 1/30th.

[COLOR=blue]At what longer shutter speed can one expect the problem of uncrtically sharp iamges due to camera vibrations to be minimized again?[/COLOR]

Thanks in advance for any knowledgeable or general input on shuutere vibrations on this particular system.

[David Henderson]

I don't have problems getting critically sharp negs and transparencies at any speed with my Bronicas. I use 150mm and 250mm lenses (amongst others) and I think 1/30 would be about the speed I use most frequently. I use a decent tripod- but only Manfrotto 055/190 models. Mostly I don't use a cable release, but the shutter release on a Speedgrip. Fortunately it does seem like yours is the exception not the rule and the steps you are taking have provided sharp images for me on my current and previous cameras. Maybe it needs technical help?

[Andre Noble]

Hello David, we corresponded a few weeks ago on Zeiss vs. Zenzanon via email.

I am getting much better performance from my PS lenses with Mirror lock up, cable release, and tripod but noticed that my frequent speeds of 1-60th and especially 1-30th of a second, images show blur due to shutter vibrations hence this post.

Particular camera does not need servicing. This problem occurs with all my SQ'Ai bodies. Its shutter vibration. If you look with a high quality loupe at 12x there is a distinct effect at 1-30th and sometimes 1'60th. I will test slower speeds later.

[David A. Goldfarb]

In general, mirror/shutter vibration issues are most problematic between 1/30-1/4 sec, but of course it will depend on your system, and it would be easy enough to test for yourself.

Have you tried another tripod system? Even if you have an heavy tripod and head, it may be tuned to a resonant frequency that is produced by the camera, and there is no convenient way to predict it without testing. You might also experiment with putting a beanbag on the camera to dampen vibrations with long lenses.