AF Micro Adjustment

[malcy]

Hello all. I have read in the a900 manual that lenses can be 'fine tuned' and in the a900 brochure it also says 'AF Micro adjustment' is also possible. The lenses I now have are 24-70 cz, 135 cz, 70-400G and the 500mm mirror and 105mm sigma. Should I be concerned that these lenses need to be 'altered' in any way or should I leave well alone. As far as I know they are all ok and the results are exceptional. What conditions, if any, would alter this?

[David Kilpatrick]

I have not needed any microp AF adjustments for my A900. Maybe I am just being over tolerant, but as I use them, all my lenses work perfectly without.

David

[malcy]

Thanks, David. I will leave well alone. As they say , if it ain't broke, don't fix it.

[01af]

On the A900, my SAL-70400G will focus better overall with a -1 correction. With telephoto lenses, one step of micro-adjustment will make more of a difference than with wide-angle lenses.

Shoot one lens at different apertures, lighting conditions, and ranges, carefully scan the results for obvious front-focus or back-focus, then decide if a micro-adjustment is required. Do not base your decision on just one or two mis-focused samples. Most lenses can get away without any adjustments, some do need a correction ... and if so, then in the minus direction more often than plus (negative adjustment values will compensate back-focus; positive adjustment values will compensate front-focus).

-- Olaf

[lightdreamer]

Sorry David,

but your statement concerning AF microadjust does completly differ from my
experience with my A900. I only own one single lens that does not need any
correction, its the CZ24-70. Especially old Minolta primes and zooms (I own
some dozends myself) perform definitly visibly better if they are correct adjusted.

I can only recommend to try out and use this feature. For most lenses out there
it makes a real difference.

The lack of this feature for me leads to the decission to sell the A700.
Its just as simple:
For myself never a camera again that does not allow micro adjust.

BG lightdreamer

[rogprov]

My experience has been the same as David's - no adjustmet needed. The only Minolta lenses I have now are the 35-200mm xi and the Konica-Minolta 17-35mm D and they are both okay. My Sony lenses are fine also.

[David Kilpatrick]

Obviously the function is there because it may be needed. I do intend to set it up better for my 500mm f/8 RF Minolta as I don't think that has ever focused accurately on any body. And in the first months of using the camera, I microadjusted for the 12-24mm Sigma, but I found the lens has such a curved focus plane that f/11 is the only solution. You can get a perfectly microadjusted centre focus spot at f/4.5 and 12mm, it doesn't mean the edges will be sharp!

I also know that my 70-300mm SSM G has BF errors on the A700, but attempts to microadjust on the A900 were very focal length and focus distance dependent. The optimum microadjustment for small animals at 300mm near minimum focus distance was spoiling landscape shots at 70mm. What's really needed, of course, is microadjustment which can store three focal lengths for each zoom lens and for Sony to issue a recommended focus distance for setting the adjustment, at every focal length.

David

[cidrmakr]

I purchased the excellent ebook by Gary L Friedman which included a description of and instructions for using the microadjust. Printed the target and checked it out. all my lenses were right on requiring no adjustment so I left it turned off. However, one never knows until you do the test.....

[UrsaMajor]

Sorry David,

but your statement concerning AF microadjust does completly differ from my experience with my A900. I only own one single lens that does not need any correction, its the CZ24-70. Especially old Minolta primes and zooms (I own some dozends myself) perform definitly visibly better if they are correct adjusted.

I can only recommend to try out and use this feature. For most lenses out there it makes a real difference.

The lack of this feature for me leads to the decission to sell the A700. Its just as simple: For myself never a camera again that does not allow micro adjust.

My experience with my A700 and my KM 7D is identical with what David found with his A900. I tested the lenses that I frequently use on my A700 and KM 7D and found that all of them focus correctly - at least when shooting wide open at a minimum distance of 25 times the focal length.

With the exception of my KM 28-75 f:2.8 lens, all of the lenses I tested were old Minolta primes and zooms. I tested my 50mm f:1.7, 135mm f:2.8, 70-210mm f:4.0, and 28-135mm lenses. All of these lenses focused correctly, which was a relief since the rumored v.5 firmware that was supposed to provide micro-adjustment for the A700 never appeared.

I have some additional lenses that I did not test, so it is possible that these might have some focus issues. However, these were lenses that I seldom use, such as my 28mm f:2.8. Since I had already spent several hours testing my frequently used lenses on two cameras, I did not bother to verify the performance of lenses that are seldom used on my cameras.

I also did not bother testing at any aperture other than wide open, as I made the assumption that the increased depth of field at smaller openings would compensate for any shift in focus with changing f-stop.

With best wishes,
- Tom -