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Canon 6D MFA with 85 f/1.8 vs f/4.0

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Geronimo73

Geronimo73

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While using my 85 1.8 on my 6D, is it possible that I come with differents MFA settings for f/1.8 and f/4 (+8 and -15) ?

I thought that changing the aperture would only give me a bigger DOF but would not change the MFA...
 
When I had my 5d mk II and 85L, 135L, I also discovered that the Micro Adjustement could vary a little bit depending on the aperture. Btu from what I remember, it was a few points in worse case.

the difference you mention seems significant. On what do you make this setting ? I guess comparing the result with Live View on a clear plane with a contrasty shape ?

Could you give a little bit more detail on your methodology to adjust it ?
 
Geronimo73 said:
While using my 85 1.8 on my 6D, is it possible that I come with differents MFA settings for f/1.8 and f/4 (+8 and -15) ?

I thought that changing the aperture would only give me a bigger DOF but would not change the MFA...
Click to expand...
Were these determined at the same focus distance? At the risk of stating the obvious, the amount of MFA required can vary depending on the focus distance. 6D can set different correction values for close and far focus.

Or, some wide aperture lenses, specifically the EF 85 f/1.2L and 50 f/1.2L, exhibit focus shift as the aperture is stopped down, especially at shorter focus distance. I've not heard of that phenomenon with the EF 85 f/1.8 USM, but maybe.
 
Lemming51 said:
Geronimo73 said:
While using my 85 1.8 on my 6D, is it possible that I come with differents MFA settings for f/1.8 and f/4 (+8 and -15) ?

I thought that changing the aperture would only give me a bigger DOF but would not change the MFA...
Click to expand...
Were these determined at the same focus distance? At the risk of stating the obvious, the amount of MFA required can vary depending on the focus distance. 6D can set different correction values for close and far focus.

Or, some wide aperture lenses, specifically the EF 85 f/1.2L and 50 f/1.2L, exhibit focus shift as the aperture is stopped down, especially at shorter focus distance. I've not heard of that phenomenon with the EF 85 f/1.8 USM, but maybe.
Click to expand...
 
Last edited:
jhendrix said:
jhendrix said:
Geronimo73 said:
While using my 85 1.8 on my 6D, is it possible that I come with differents MFA settings for f/1.8 and f/4 (+8 and -15) ?

I thought that changing the aperture would only give me a bigger DOF but would not change the MFA...
Click to expand...
Were these determined at the same focus distance? At the risk of stating the obvious, the amount of MFA required can vary depending on the focus distance. 6D can set different correction values for close and far focus.

Or, some wide aperture lenses, specifically the EF 85 f/1.2L and 50 f/1.2L, exhibit focus shift as the aperture is stopped down, especially at shorter focus distance. I've not heard of that phenomenon with the EF 85 f/1.8 USM, but maybe.
Click to expand...
Click to expand...
 
Lemming51 said:
jhendrix said:
Lemming51 said:
Geronimo73 said:
While using my 85 1.8 on my 6D, is it possible that I come with differents MFA settings for f/1.8 and f/4 (+8 and -15) ?

I thought that changing the aperture would only give me a bigger DOF but would not change the MFA...
Click to expand...
Were these determined at the same focus distance? At the risk of stating the obvious, the amount of MFA required can vary depending on the focus distance. 6D can set different correction values for close and far focus.

Or, some wide aperture lenses, specifically the EF 85 f/1.2L and 50 f/1.2L, exhibit focus shift as the aperture is stopped down, especially at shorter focus distance. I've not heard of that phenomenon with the EF 85 f/1.8 USM, but maybe.
Click to expand...
Click to expand...
Click to expand...
 
Geronimo73 said:
While using my 85 1.8 on my 6D, is it possible that I come with differents MFA settings for f/1.8 and f/4 (+8 and -15) ?

I thought that changing the aperture would only give me a bigger DOF but would not change the MFA...
Click to expand...
You MA at your widest aperture only.
 
You're right I did MFA at widest aperture but wanted to check with other aperture to double check...

Dot-tune method give +5 and with the incline ruler was -3.

Try couple shot and +5 was better than -3... I'm puzzled...
 
''don't take test shots of a ruler on your desk''

Exactly what I did in the beginning. My mistake...

I redid it with my tripod and with miror lock up...
 
Geronimo73 said:
You're right I did MFA at widest aperture but wanted to check with other aperture to double check...

Dot-tune method give +5 and with the incline ruler was -3.

Try couple shot and +5 was better than -3... I'm puzzled...
Click to expand...
You might want to explain in detail your entire setup.
 
I recently completed adjustments of all my lenses using the Focus Tune software and Lens Align. With a 6D and the 85mm f1.8, I was able to easily get the required adjustment factor, however when I tried to repeat the process with my new 7DII and the same lens, I could not get consistent results, until I tried f2.0, at which time I got the consistent clean line and points I was expecting. I'm not an expert by any means, simply relaying what I experienced. When it first occurred, I checked and rechecked my settings, alignment, the whole list, only to get results that were all over the place. Finally thought that perhaps f1.8 may not have been the sharpest, and low and behold, as soon as I pushed it to f2.0, everything clicked into place. So, I now know not to push the 85mm fully open if I want sharp pics, stop down to 2.0 and leave it there. I only had this problem with this specific camera and lens combination so I don't think either piece alone is defective ????? Is this a incorrect assumption?
 
Focus can shift with apertures, focal length, and distances.

Aperture: As mentioned above, this is focus shift, where focus changes when lens is stepped down near its largest aperture size. This is known issue affecting select lenses, particular larger aperture lenses. This is part of the lens design and cannot be corrected. Have not heard 85mm 1.8 having this issue.

Focal length: Can be calibrated. Obviously not an issue with fix focal length 85mm lens.

Distance: Definitely can be a problem. Can be calibrated. I suspect OP's issue is possibly this problem. So make sure you do your test with various aperture without changing distance. I.e. use a tripod.

If your lens is truly exhibit different focus at different distances, you have to contact Canon. They should be able to calibrate the lens for you. But you really don't need to do this, unless you are sure you have a problem and that it is significant enough to affect your photos.

To proof that focus can change with focal length and distance, just look at Sigma. Some Sigma lenses are notorious for having focus shifting with focal length and distance. I should say they are notorious for not being calibrated straight from the factory. Newer Sigma lenses can be calibrated by user using a software (Sigma Optimization Pro Software and USB dock).

Here is the link to Sigma Optimization Pro Software: DP Review Link

Here is the screengrab showing the MA calibration for focal length and distance: Screen Grab

I personally have not had any issue with 2 Canon lenses I own. I had problem with Sigma 50mm 1.4 (older version EX DG HSM, not the new ART version); brand new straight from factory. This was the MA results at varying distances, all using same f/1.4 aperture:
  • 6 ft: +16
  • 10 ft: +1
  • 15 ft: -4
  • 30 ft: -6
Very significant shift. Sent it into Sigma and they calibrated the lens. It was perfect after that.
 
Trout479 said:
I recently completed adjustments of all my lenses using the Focus Tune software and Lens Align. With a 6D and the 85mm f1.8, I was able to easily get the required adjustment factor, however when I tried to repeat the process with my new 7DII and the same lens, I could not get consistent results, until I tried f2.0, at which time I got the consistent clean line and points I was expecting. I'm not an expert by any means, simply relaying what I experienced. When it first occurred, I checked and rechecked my settings, alignment, the whole list, only to get results that were all over the place. Finally thought that perhaps f1.8 may not have been the sharpest, and low and behold, as soon as I pushed it to f2.0, everything clicked into place. So, I now know not to push the 85mm fully open if I want sharp pics, stop down to 2.0 and leave it there. I only had this problem with this specific camera and lens combination so I don't think either piece alone is defective ????? Is this a incorrect assumption?
Click to expand...
If you are saying you can't get sharp shots wide open with the 7DMKII with the 85mm 1.8 it most likely is just the tighter pixel pitch and greater magnification of having 20MPs in a 1.6x crop vs 20MP in FF shot. The 85mm 1.8 is a 2 decade old lens in design and the 20-24MP APS-C sensors are asking for a bit more in optics (at least wide open). The pixel pitch of 20-24MP APS-C is like a 50MP FF sensor...quite a bit more than the Sony/Nikon 36MP FF sensors.
 
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