7.14.2012

Auto Focus Micro Adjustment and the Sony a77

I couldn't really adjust for this lens but that's okay, 
I know from recent experience that it's "wicked sharp."

As I work more and more with the Sony a77 I find lots of things to like about the camera and very few disappointments. One of the reasons I chose to go with the a77's as my primary shooting cameras ( in addition to the brilliant EVF and really nicely implemented video) was the Auto Focus Micro Adjustment control.  I've been pre-occupied with other camera controls in my quest to really master the camera and I left lens adjustments to last.

But recently I've been working nearly wide open with the 50mm 1.4 lens and I noticed that it would routinely back focus. This led me to jump into the menu and get busy.  I also noticed that my 70-200mm G lens (a whopping $2000) wasn't as sharp as my previous Canon and Nikon zooms so I thought I'd take a crack at that one as well.  In the end I tried every Sony lens I owned on both bodies and now, after hours of being really compulsive and fastidious, I am even happier with my little Sony system than before.

When I first accessed the control the ability to adjust was greyed out on the menu. I finally decided to push the "clear" button and a message came up telling me that 30 lenses had already been registered and that I would lose all those settings if I continued.  Since I'd been using the camera with this control deactivated anyway I decided that it would be "no skin off my nose" to go forward.  I pushed clear.  Now I could make adjustments to any of the Sony branded lenses I put on the camera and it would save up to thirty lenses of my choice.  Do I think the camera was used before me? Decidedly not. I think the camera comes that way by default.

I actually kept notes as I worked.  The 50mm needed a "minus 8" correction.  The 70-200 needed a "minus 6" correction and the 50mm 1.8 DT lens needed a -3 correction.  Most of the lenses were right on.  The little 85mm 2.8 shocked me.  I've always used it to shoot portraits and nothing with sharp lines or edges. When I blew up my test file with the LensAlign it was so sharp wide open that I was temporarily giddy.

I tested all my lenses at 2.8.  I figured most gaussian lens designs will have a bit of focus shift from wide open to 2.8 and that trying to get them just right at 1.4 was perhaps a futile endeavor.  Happily, once I adjusted the 50mm 1.4 at 2.8 I went back and checked it wide open and was happy to find the same correction needed.  At least the lens is consistent.

I tested eight lenses and I did this on two bodies and there were mild differences between bodies.  I almost messed up the test entirely as I had inadvertantly set the focus mode to local which allows the camera to choose between a little cross of squares.  When I aimed at the target I would get different readings each time and when I tested at different distances I needed different numerical values as well.  Once I realized my mistake and set the  camera to center spot AF everything fell right into place.

The 70-200mm is now very sharp wide open and wickedly sharp one stop down.  I took the time to re-test at every marked focal length and found that, once you've set the right value, it tends to be the same for all.

In addition to the stellar performance of the 85mm 2.8 I was also amazed at just how sharp the 16-50mm 2.8 lens is.  It's the sharpest wide to short tele high speed zoom I've ever played with. I can go out shooting now with a sense of assurance that I'm getting the ultimate performance for myself and my clients.  And it was a bonding experience for me and my camera.


15 comments:

MichaelT said...

Hi Kirk, SInce this is a somewhat technical post I will ask a somewhat technical question: did you deviate from LensAlign recommended procedure? I have an A900 with lens from 20 to 300 mm (fixed and zooms) and have always had a nagging suspicion that one or more may need a focus micro-adjust but never have gotten to it. Your post reminded me of that fact. Thanks for post!

kirk tuck said...

I did it just as the LensAlign people recommend. But I did try the same tests at various distances, out of curiosity.

Ron Nabity said...
This comment has been removed by the author.
kirk tuck said...

Absolutely right. My only concern with adjusting at full aperture is the very real nature of focus shift as one stops down. I prefer to adjust to the lowest regularly used aperture but I'm sure someone will prove me wrong.

Ron Nabity said...

(reposted from earlier - originally placed in wrong reply location - sorry)

I have always tried to adjust at the widest aperture, didn't think about giving it a stop or two to make it easier. These adjustments can be tedious, but it is important to do, if your camera offers the ability. I have found that the same lens will need similar adjustments across several bodies.

Without setting the micro-adjustment, it would be like never changing the diopter adjustment to match your eye. It's amazing how many people are startled to learn that their viewfinder can be focused (and needs to be.) Makes me wonder what the heck they were quietly thinking when it was fuzzy.

This focus variance is absent with the mirror-less design, one more thing to like about them.

Low Budget Dave said...

Generally, only the high-end cameras offer this feature. These days, though, even the low-end cameras offer such good resolution that a "fine-tune" feature would save lenses that would otherwise need to be returned.

I guess if they offered this on too many cameras, though, people like me would never upgrade.

Unknown said...

I once spent a full day on this, 8 lenses, two bodies. Then I spent the next week doubting my technique and the sharpness of every image. I wonder if there's a professional you can hire to do it for you?

Robert Roaldi said...

I think it's kind of neat when you can buy something, a camera, use it for a while and then one day, presto, you discover/rediscover some feature that really improves it. It's like getting a new camera without spending the cash. Product manufacturers should embed stuff like this in more products.

JJ Semple said...

KIrk,

Was looking for this feature on the a57. Don't think it has it. Would you know for sure?

kirk tuck said...

No micro adjust on the a57 or the a65. But then my experience has been that only a few of my lenses REALLY needed the adjustment. Mostly only the expensive ones...

JJ Semple said...

Thanks,

So far I have the Sony 35mm, the Vivitar 13mm, the Sony 55-200mm, a rather el-cheapo array. I like the 35mm, got some nice architectural images with it and some portraits with the 55-200mm.

I want to get the 17-70mm Sigma, but they're back ordered. Too bad Sigma sttopped including OS for their lower focal range lenses.

kirk tuck said...

JJ, the 55-200 is a shocker. It's a really, really good lens. If i had tried it first I might have never gotten around to picking up a 70-200 2.8. Really, it's that good.

Mark Hespenheide said...

MichaelT,

If I can be allowed to chip in here, I own a Sony 850 and just went through the hassle of testing and adjusting most of my lenses. It's well worth it. Some of the "better" lenses, a ZA 24-70/2.8 and a Minolta 80-200/2.8 were quite close and didn't need much adjustment. A Tamron 28-75/2.8, Sony 70-300G, and Minolta 50/1.4 all needed bigger adjustments and now perform significantly better than they did before, particularly at wider apertures.

I'll only add one change to the protocol from LensAlign: Since the a900 and a850 lack live view, it's tedious (but necessary) to make sure that the target is completely aligned such that the front and back "plates" are perpendicular to the lens. It's a process of shoot, pop the card out, look at 100%, see if the circles are lined up, move the target slightly, and repeat. Instead, I put the lens cap back on the lens and shone a laser pointer through the target. When the laser dot hit the middle of the lens, I knew I was good. Much faster. Worth borrowing or buying a laser pointer for, in fact...

Mark Hespenheide said...

I feel like it *should* be offered on any camera 12MP and higher in resolution. Really, it's only software/firmware, so there's no reason not to include it except that [1] people might mess up an adjustment and make it worse and [2] the companies might get more complaints that lenses are not up to spec or [3] consumers might realize how imprecise those specs are...

JJ Semple said...

When I get the focus right as for the portrait cited above, the 55-200mm is great. I want to try out the magnification feature with this lens.

My son plays college BB. I want to try to get some action shots with the a57 and the Sigma 70-200mm this season. Fortunately, Sigma kept the OS for this lens, which is supposed to be a great additional two-stop feature. Any tips on focusing under such difficult conditions? The light in the CCAA gyms is abysmal. Probably set ISO to 1600 or 3200 to begin with. Do you think a monopod might help? What about zone focus? Do sports photogs use it?