5DSr and Otus 85mm - NOT SHARP!

[charleshansen]

Anyone else with this combination please chime in...

I get razor sharp results before the picture is taken looking in either the viewfinder or Live View. Then, when the picture is actually taken wide open, at 1.4, the image is completely blurred. There is NO vibration - using a Really Right Stuff pod with BH-55 head, and cable release. I am NOT locking up the mirror, as I should not have to with this setup.

The exposures are 1/4000 at f1.4.

If I start stopping down, then 4-5 full stops later, sharpness starts to return in the final snapped exposure. But I consider this not only unusual, but quite ridiculous. The 5DSr performs perfectly with other lenses. I bought this lens to use wide-open at 1.4!!!

A tech rep at Zeiss has asked me if I have locked-up the mirror - my reaction is why would I have to do this at 1/4000 second?

How would I lockup the mirror if I were to hand-hold and shoot a head-shot at 1.4? I don't get it.

[kvbarkley]

Obviously this does not make sense. If it is in focus in live view, the image should be in focus.

Why don't you experiment with mirror lock-up, that will at least give you some ammo with the manufacturer.

It sounds like the lens is going slightly out of focus during the shot, which is solved at f4.5 because of the increased depth of field.

Are you in manual focus? Is the image in focus after the shot?

And quick shutter speeds might not help when you have mirror slap. the camera is moving quickly, so 1/4000 might not be quick enough to freeze it, After all, the mirror is moving *fast*.

[charleshansen]

Thank you for your thoughts. But consider this..this Otus lens is only manual focus!! No auto-focus mechanism.
So, how would the focus shift? It's the same razor sharp image on live-view and viewfinder after the exposure (blurry) is made!
But I do intend to use mirror lockup, even though I don't want to, to complete the trouble-shooting.
This is now making me think there's a fault in the 5DSr.
Hoping another 5DSr owner can chip-in also...
Thank you for responding

[kvbarkley]

I am thinking there is play in the OTUS focus mechanism and the mirror slap moves it slightly, the image is taken, and then it moves back.

I suspect an OTUS issue, what could the 5Dsr be doing to cause it?

[kvbarkley]

Another wacky thing to try is to focus from one direction (near to far) take a sample image, then focus far to near and try the same thing.

That might help to isolate any backlash issues.

[charleshansen]

IDK...a mystery
All I know is I can't live with this after spending all this money

[kvbarkley]

I don't have this problem wiht my Rebel and kit 18-55. 8^).

[charleshansen]

But there's zero lash...it is a fantastic, precise mechanism, heli-coil. And the sharpness is astounding.
Literally, the problem is only in the electronic snapped exposure.
A real brain tease. 40 years of photography, and I don't get it

[charleshansen]

...you only get stuff like this after trying to chase perfection

[RobertTheFat]

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@charleshansen wrote:
...you only get stuff like this after trying to chase perfection

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Is there possibly a lesson to be learned from that?