Fine tuning for 85mm f1.4G

Started Feb 7, 2013 | Discussions thread
boarman
Regular MemberPosts: 110
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Re: Fine tuning for 85mm f1.4G
In reply to mdg137, Feb 8, 2013

mdg137 wrote:

Just wondering if anyone else has run into this issue, to this degree--

I am in the process of fine tuning my lenses using Reikan FoCal. After tests run on different days in different lighting conditions, etc, I have found the following with my 85mm f1.4G:

At 40x focal length (about 11ft.), the lens requires about +17/18 (there is no discernible visible difference between the two at 100%)-- both produce equally sharp results.

At 8 foot, the lens requires +17-- again, sharp.

However, at 5ft down to closest focus distance, the lens appears to require about +7-- at closest focus distance, +17 appears to focus about 1.5 inches behind the target and 0 seems to be about 1 inch in front of the target.

Splitting the difference seems to result in non-optimal sharpness at all focal lengths...

I fully understand that fine tuning is truly only fine tuned to that specific distance-- but has anyone run into such a large discrepancy?

-- hide signature --

I've not done it, but I'm going to sympathize with you cause I think this is crazy.. If this is truly the case then the autofocus must be completely broken. I don't understand how it just can't work, regardless of the focal length. Doesn't the camera evaluate what's coming through the lens and adjust the focus accordingly? I don`t get how it can hit at certain distances or focal lengths but not others on the same camera on the same lens.

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