Back focus problems and solution, Sony SLT-a55

Back Focus?  Sony Does Not Agree

My Sony SLT-a55V has had focus issues that I was having a hard time quantifying, as they were inconsistent. Some photos would be sharp but many others would show significant (and frequently severe) back focus, focusing on a point well behind the depth of field.  My usual focusing method is to use “Local” mode, i.e. I select a specific focus point, most often the center point but sometimes one of the points on the sides. I don’t often trust multi-point focus or automatic subject recognition. If the camera focuses on the wrong subject, I want that to have been my fault, not the camera’s algorithm which I can’t predict (it usually focuses on objects closer than the main subject).

After renting a Sony 70-400mm lens and taking it on an African safari trip (photo gallery) and finding far too many photos sadly out of focus, I took most photos with this lens with manual focus and wondered why autofocus wasn’t working right.  The longer the focal length I used, the fuzzier the image; only with very small lens openings were most photos even vaguely acceptably sharp.  On the other hand, a few photos were absolutely tack sharp, but I couldn’t find a common reason.  I initially blamed the lens and convinced the rental company to send it to Sony for service.

But after a few photos with my trusty and known-to-be sharp Minolta 135/2.8 lens showed the same problems, I experimented a little more and found pretty (IMHO) indisputable evidence of back focus under more controlled conditions.

So finally I sent the camera in to Sony for warranty repair. They inspected it, said it was “within spec” (in fact had slight front focus!), and sent it back unmodified (and missing the rubber eye cup, another story). This diagnosis was so far from correct I dug into the issues more deeply. Step one is find a way to test focus myself.

Focus Testing

Jeffrey Friedl has some outstanding photo resources, primarily Lightroom plugins but also an excellent focus test chart with clear explanations of what a good focus test chart needs to have and how to use one. Print the chart on an inkjet printer on photo paper (matte preferably) for high contrast and sharpness.

In the end, I discovered that my camera’s problem was a large variation in focus accuracy depending on which focus point I chose (and an explanation of why Sony didn’t find this). First, more detail on the testing procedure.

Focus Testing Procedure

I tested with three lenses: Minolta 50/1.7 and 135/2.8 primes, and Sony/Zeiss 16-80mm zoom. I found consistent and large back focus when using the center AF point. On a hunch, I tried testing with other AF focus points. The results were very different over different AF focus points. Using the 50mm lens, f/1.7, focus distance 80 cm to Friedl’s chart, I got roughly the following initial results:

  • Right cross sensor: imperceptible focus error
  • Center cross sensor: 1.5cm back focus (1/2 DoF is 0.8 cm, so this is 1x outside the DoF range)
  • Left cross sensor: 3cm back focus (3x outside 1/2 DoF)

I decided to do this more carefully now as I think I understood what the underlying problem was: a tilted AF sensor unit. Testing conditions:

  • Manual exposure
  • Tripod
  • Remote shutter release
  • AF-S mode
  • AF Area set to Local Area, picking from among the three cross focus points (left, center, right) where the vertical and horizontal arrays intersect in the viewfinder
  • Shot at 32° angle from horizontal

Focus Testing Results

The camera was focused on the dark bar in the center of chart according to Friedl’s instructions, and I confirmed that it was unable to lock focus a bit above or below the bar.  The following table gives my best estimates of where the camera actually focused by finding the sharpest digit and converting that to cm (the digits on Friedl’s chart are 0.55 cm apart; including foreshortening due to the 32° angle of the shot, convert Friedl’s digits to cm by multiplying them by 0.47). Negative numbers are back focus results, positive (if I had any) would indicate front focus results.

Lens Distance f AF Point Result 1/2 DoF Error Photo
50mm 80 cm 1.7 Right 0 cm 0.8 cm 0x focustest-2814
50mm 80 cm 1.7 Center -1.5 cm 0.8 cm 1.9x focustest-2809
50mm 80 cm 1.7 Left -3.5 cm 0.8 cm 4.4x focustest-2813
50mm 120 cm 1.7 Center -3 cm 1.8 cm 1.6x focustest-2808
16-80mm @50mm 80 cm 4.5 Right 0 cm 2.1 cm 0x focustest-2811
16-80mm @50mm 80 cm 4.5 Center -2.5 cm 2.1 cm 1.2x focustest-2810
16-80mm @50mm 80 cm 4.5 Left -5 cm 2.1 cm 2.4x focustest-2812

 

The Error column tells how many multiples of 1/2 DoF the focus point is from the ideal focus point. An error greater than 1.0 means it focused outside the DoF region (due to the complex math of DoF, this is not exactly correct, but for small DoF it is good enough). If the camera focuses outside 1/2 DoF, then the subject will not be in focus (“in focus” being defined as the blurring being less than the circle of confusion of 0.02 mm, a standard setting for the 1.5x crop factor APS-C sensor in the a55.)

I also did a quick test of every focus point with the 50/1.7. The table below attempts to show the focus results for each of the AF points in the a55’s viewfinder. Values are the number of digits on Friedl’s chart that focus is off; negative numbers are back focus, positive are front focus. This time the focus chart was shot at 45° angle, so to get actual distance in cm multiply each value by 0.55 * 0.71 = 0.39. Presumed cross focus points have values in red. The values are not as bad as the test above, but they agree in trend. Since this was a quick test, values could easily be off by 1-2 digits in either direction.

-1
-5 -2 +1
-3 -4 -2 -1 -5 0 0
-3 -2 +1
0

This pattern confirms the conclusion that the AF sensor unit is correctly adjusted on one side but far off on the other side. The center sensor is halfway between. Some research led to a post on DPReview.comof someone who had figured out where the AF unit adjustment screws are. This turned out to be straightforward to do, if you take a lot of care and go at it patiently with some time to spend on it.

Adjusting the Autofocus Unit

How the AF Unit is Constructed

As with most or all DSLR cameras these days, the a55’s AF sensors are mounted inside a unit that can be adjusted as a whole. It is likely that the AF unit looks something like the figure in this post, which takes a bit of time to understand but it is crucial to knowing how to adjust the unit. The camera in that figure is a Sony A700, which is a traditional DSLR. The Sony SLT’s AF system is simpler, since it does not have an AF secondary mirror; the translucent pellicle mirror bounces the light up (not down) into the AF unit at the top of the camera. However, the AF unit itself is probably about the same, although it is at the top of the camera pointing down, not at the bottom pointing up. In any case, the light for the AF unit comes straight up from the a55’s translucent mirror, and is bounced forward by a 45° mirror inside the AF unit. The AF sensors themselves are at the front of the AF unit, facing backwards. So now we can see that the three adjustment screws have the following effects:

  • The left/right pair of screws each raise or lower one corner of the AF unit where the light enters it. This serves to lengthen or shorten the path the light takes from the translucent mirror to the mirror at the light entrance to the AF unit. This is what adjusts front and back focus. If the left screw is loosened, that corner of the AF unit is pushed downward towards the translucent mirror, and the light coming in to that side of the AF unit takes a slightly shorter path to its AF sensor.  This tells the camera’s AF computer that the subject is further away, and would increase back focus (or decrease front focus) for that side of the AF system.  In other words: move screw in, move focus in (forward).  Move screw out, move focus out (back).
  • The front screw raises or lowers the front of the AF unit where the AF sensors are, without affecting the length of the light path to them. This adjustment would be used if, for example, your AF points are focusing on something above or below them (as seen in the viewfinder).

Making the AF Unit Adjustments

After prying up and removing the two small plastic covers under the pop-up flash, the three screws are exposed. They are all 1.5mm hex screws (technically 1.5mm Allen bolts), and easily accessible with a 1.5mm hex key.  See below (click photo for a larger version).

SLT a55 autofocus adjustment screws

SLT a55 autofocus adjustment screws

Note: “Right” and “Left” here, as is standard, refer to right and left as seen when looking at the rear of the camera.  Be sure you understand that the screw on one side affects the focus of the sensor on the other side!

Turning the screws in (clockwise) moves the focus point forward (toward the camera).  Loosening the screws (counter clockwise) moves the focus point back.

We have two choices here.  One is to make small adjustments to the current screw settings (which is what I did initially).  The other is to essentially reset the settings entirely.  It is entirely your choice how to proceed.  The Sony Service Manual says when installing a new AF Module to screw all three screws all the way in, then turn them out 1/2 turn each and use that as the starting point.  Either way, this adjustment method will work fine.  I revisited this adjustment almost 2 years later and decided to go back to the start by turning the screws all in, backing them out 1/2 turn, and starting from there.  It actually was easier to converge, I think.

After a couple of iterations of this method, I like the following best.  I now have the camera pulling pretty close to perfect autofocus on all focus sensors.

Setup

  1. Place the test chart on a flat surface at a steep angle (i.e. lying down about 30-40 degrees from horizontal).  As described above, flat and perfectly aligned is absolutely critical since the differences in focus you will be measuring are just a couple of millimeters, or a tenth of an inch.  Every little inaccuracy in the setup will affect the adjustment.  Take your time on this step!
  2. Put the camera on a tripod at exactly the same height as the center of the chart, perfectly level (use the SLT’s level indicator).  Select Local AF Mode and select the center sensor.  Situate the tripod so the width of the test chart covers the entire frame.
  3. Screw all three adjustment screws all the way in (but not too tight!), then back them all out 1/2  turn.
  4. Put the camera in Local Focus mode and select the center sensor.
  5. Flip out the LCD screen to use for all measurements.
  6. Check that camera is level (using level indicator on EVF)

Measure and Adjust Center Sensor: Adjust Both Screws Same Amount, Same Direction

  1. Look at the LCD and get the camera’s active focus sensor on center focus point on the chart
  2. Press the shutter release halfway down to activate AF.  This may require moving the camera a little to be sure it sees the focus pattern.
  3. Using the focus magnification feature (click the trash can button twice and use the navigation controls to move the magnifier window), look at the side scales of the chart to see where the focus actually happened.  If best focus is behind the zero point (back focus), turn the two sensor adjustment screws (refer to photo above) in an equal amount.  If best focus is in front of the zero point (front focus), turn both screws out an equal amount.  It’s impossible to give a good guideline of how much to turn because it all depends on the specifics of your setup and the lens, f/ratio, focus distance, etc.
  4. Keep doing steps 2 and 3 until the best focus is right at the zero point of the chart.

We now have the center sensor perfectly focus-adjusted.  The sensor may still be crooked, so we will fix that next.

Measure and Adjust Left and Right Sensors: Adjust Both Screws Same Amount, Opposite Directions

  1. In Local AF Mode, select the far right focus sensor
  2. Move the camera physically to the left so the right focus sensor indicator on the LCD is right at the chart’s center focus point. Be sure that camera is still perfectly aligned with the chart, just that the center point of the focus chart is now directly under the right focus sensor.
  3. Press the shutter release halfway down to activate AF and, using the focus magnifier, see where the best focus is.  Do this a few times and look for an average result because the AF does not settle on the exact same location every time.
  4. Because we already made sure the middle of the sensor is correctly focusing in the previous step, we know that if we find that the right sensor is not right, we will need to move both adjustment screws equal amounts but now in opposite directions.  So if the focus is behind the zero point, we will need to turn the right sensor adjustment screw (the left screw!!) in a little bit, and turn the other adjustment screw out exactly the same amount.  Opposite for focus in front of the zero point.
  5. Keep doing steps 3 and 4 until focus is right at the zero point.
  6. Now in Local AF Mode again, select the far left focus sensor, move the camera to the right, readjust camera and tripod so everything is all straight again.
  7. Press the shutter release halfway down to activate AF and assess focus as above.  Press a few times to see where the AF settles on average.
  8. If we have done a good  job so far, there should be minimal adjustment to do, but nothing is ever perfect.  There may be a small adjustment required… or not.  If so, remember that the screws have now reversed sense from the previous step 4 because we are using the focus sensor on the opposite end.  If the focus is behind the zero point, the left screw needs to be screwed in, and the right screw needs to be screwed out by exactly the same amount.
  9. The adjustment in step 8 should have been quite small (less than 1/10 a turn of the screws).  If not, then you may have not aligned the setup with enough precision, or the camera

At this point I would highly recommend repeating all the above steps one time (without going all the way back and screwing the screws all the way in!).  The second time through the adjustments should be very small.

This sounds complicated but after a couple of times through the procedure, it takes about 10-15 minutes for a full run through.

Repeat With Other Lenses

I did the initial run through the procedure using a 135 mm f/2.8 fixed prime lens and it was easy to get a quick, accurate, and consistent focus.  Then I tried with my favorite CZ 16-80 f/3.5-4.5 lens at 80mm, and it is more difficult because of the increased depth of field, close focus to fill the frame, and lower contrast.  It is possible that doing the test with a stronger light source would have helped, and I will have to try that next time.

A Few Points of Advice

A couple of points learned from experience:

  • Always keep to Friedl’s instructions and make very sure the camera is squared against the test chart, the test chart is flat, and everything is level. I used the LCD display with grid and camera level guide turned on. The center horizontal grid line in the LCD should pass right through the chart’s focus bar and the 0 digits on both sides of the chart. The a55’s level guide on the display may be helpful to ensure the camera is level (if you know the chart is level). These are all very critical as you are adjusting focus to within a few millimeters (given that 1/2 DOF can be as small as 5 mm!), and it is easy to have the focus chart crooked by enough to make the adjustments worthless unless you are very careful about keeping everything absolutely straight.
  • Use the a55’s “Local” AF area and alternate between the left and right sides of the AF array. You will constantly be going back and forth between these. You will have to either physically move the camera sideways when switching AF sides, or slide the test chart. In either case it is crucial to keep everything perfectly square, straight, and lined up over and over again — you cannot just pan the camera left and right.
  • Keep very careful track of how much you are turning the screws. Always, always, always know exactly how much you have turned each screw so you can get back to where you started in case this just does not work out due to whatever reasons (lens focus or other problems).
  • For initial adjustments, especially with fast lenses (f/2.8 or below), the black/white alternating patterns along the edges of the focus chart will clearly show you the DOF region on the LCD, and it is sufficient to just center the DOF region around the center horizontal grid line.
  • As adjustments get finer, or your lens’ f/ratio is higher, use the a55’s focus magnification feature after AF locks, and zoom in to the chart’s edges to assess focus accuracy.
  • The left/right focus adjustments are quite sensitive. The up/down adjustment (front screw) is not very sensitive.

Note on the third (front) screw adjustment, although I did not find any issue: if your left/right screw adjustments result in an overall raising or lowering of the AF unit, then the front screw should be adjusted to match the average adjustment between the left and right screws. In my case I ended up adjusting the left/right screws almost exactly in opposite directions, so did not modify the front adjustment. But if I had, for example, turned the left screw in 1/2 turn and the right screw in 1/4 turn, I would suggest adjusting the front screw in by the average adjustment, 3/8 turn, to raise the front of the AF unit by the same average amount as the rear was raised.

Results

After following this procedure, I was able to get focus on right, left and center AF points to be within 1 unit of perfect focus on Friedl’s chart for all three lenses–all within 1/2 DOF. Once left and right are accurate, the center is also. I’m sure a professional shop could do better, but part of the issue is that each lens has a slightly different focus signature and the a55 does not have the capability to customize focus for each lens as some high-end DSLRs do, so no one adjustment is ideal for all cases.

My results on real subjects were dramatically better. There is no obvious evidence of front or back focus anymore. I now have, literally, a completely different camera.  Now, if only we could go on our Africa trip again…

Why Sony Didn’t Find a Problem

This explanation became clear to me while working on the adjustments.  In a followup call with a Sony SLT support specialist, it was confirmed in detail.

The first thing a technician will do when diagnosing a camera is reset it to factory defaults. Among other things, this sets AF Area to Wide Area, i.e. using all focus points. The focus test consists of shooting a flat (planar) test pattern. The specialist I talked to confirmed that the one AF sensor finding the closest object to the camera will register as the subject and the camera will use that sensor’s focus determination and ignore the others.

With the tilted AF sensor I had, the left side AF sensors were telling the camera they the objects on that side were further from the camera even if physical distances were all the same, as they would be if shooting a planar focus test pattern. Therefore the camera ignored the left and center sensors in Sony’s focus test, and used the focus determination only from the right sensors, which happened to produce correct focus, and possibly even slight front focus.  So my measurements detailed above match the diagnosis initially given to me by Sony from their (flawed) focus test procedure, and explains why they returned the camera unmodified.

I requested that the specialist I talked to try to change the focus test, because it lets severe focus problems pass.  The test needs to test at least a few sensors individually instead of relying only on Wide Area focus to choose the sensors used.  He said he’d escalate it but couldn’t guarantee anything.

Clearly Sony has a problem assessing focus accuracy in both production and support, and I would encourage other Sony DSLR owners to voice their opinions on this to Sony Customer Support if they have focus accuracy problems (and, preferably, have test data to back it up).

(And shipping the camera back with a missing piece (eye cup) is kind of unprofessional, especially since it took three weeks and three phone calls to get one sent back. Sony needs to improve here.)

Leave a comment

34 Comments

  1. Anna

     /  May 28, 2016

    Hi. I need help with my Sony Alfa 100. Where to find micro adjustments?

    Reply
  2. Alexandre Campos

     /  Apr 5, 2015

    Hi

    I have a Sony A700 and I had to calibrate the sensor recently because of a back focus problem. After I’ve done this, the focus is very sharp but I now have a new problem. I can’t focus on infinity using wide angle lenses. Even on manual focus. I’ve tried different lenses with the same result. It seems that the lens stops in a break before it can reach focus. Can you help me on this?

    Reply
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  4. Hi, thanks for the guide! I have been here before, but didn’t have much luck with adjusting the AF module (it did work perfectly only with the lens I was using to fix it and very bad with the others).

    I came back here recently, modified your protocol and added few more control steps here and there and now all my lenses work perfectly!

    Thanks for sharing your version, it’s been a very good starting point and to know what the screws do in the first place! 🙂

    Reply
  5. Jeremy

     /  Dec 13, 2013

    I followed the instruction here to adjust the AF module of my Sony A55 and it was a great success. Now my Minolta 50/2.8 Macro focusses very precisely.

    An alternative method to that described is to just adjust left and right until both are in focus. You will then find that the center is in focus too.

    Reply
  6. Joonas

     /  Oct 27, 2013

    BIG thank you for this! You should be awarded a medal!

    I was prepared to toss my a580 with serious backfocusing issues but with these instructions I managed to get the camera tack sharp, irrespective of lens. Sony service could not do anything about it.

    A580 has screws in the bottom under the sticker in the middle, but otherwise the same procedure. Found the latter procedure much better, i.e. screw all 3 fully in, and then 1/2 turn open and then start adjusting. Mine was an additional 3/8 turns on every screw.

    Same problem with my old alpha 100, will adjust it next.

    Reply
  7. Sergii

     /  Sep 6, 2013

    Thanks for the article. I have A55 and recently bought Minolta 50/1.7. Several tests showed that I have a front focus with this lens. Before that I used 18-55 kit and Minolta 35-70/4 lenses. They are not that fast, so I did notice the problem. Anyway, I’ve tuned the AF, thanks to your article, and here are my observations:
    1. After tuning the AF for 50/1.7, I’ve tested other two lenses and there seems to be some back-focus problem on 18-55 at 18 (at 55 it is OK), and there is a huuuuuuuge back-focus on 35-70 at 35. Strange…
    2. I’ve first tried to play with left and right bolts with no success. Then I’ve tried to screw them (all 3 bolts) tight and release half of the turn. This position was used as a reference point and what was really strange – AF did not react on those two bolts (left and right). But I was able to move focus plane front and back using the third bolt (Focus height adjust). I do not know what is wrong with my actions, but I’ve tried several times to adjust it with left and right bolts – no success. When I turned left or right bolt too much, it would stop focusing at all, I had to compensate it with “Focus height adjust” bolt, which also affected the front/back focus, which makes it even more difficult to adjust something with left and right bolts.
    Do you have any ideas why it was like that? I’d expect it to work in a different way: left and right bolts are used to adjust front/back focus, and third bolt is used to move sensors up and down (so that actual sensor position will match rectangle in the viewfinder).

    Reply
  8. Steve M

     /  Sep 1, 2013

    Thank you for this excellent article and explanation of how to adjust the auto focus. Worked well on my SLT-A33. Fairly easy to do and it sure beats sending the camera into Sony with only so-so expectations of a good result.

    Somehow, I had developed what I suspected to be a serious AF problem. Using the autofocus test chart from Jeffrey Friedl’s Blog ( http://regex.info/blog/photo-tech/focus-chart ) I was able to confirm that a pretty large amount of front focus was the problem. I didn’t have time to do a precise correction, but did a rush job before going to an indoor volleyball shoot and had a significantly better time getting usable shots. I’ll go back and fine tune things next, but I just wanted to go ahead and say now how much I appreciate the help provided here.

    Reply
  9. Rick

     /  Feb 24, 2013

    I just got my A 55 back from Sony (Feb 2013) and the dumb asses are still saying no problem found. These people are pathetic at best. You would think after three years of experience with the well documented back focus problem they could hit their ass with both hands, but I guess not.

    Reply
    • Mike

       /  Jun 22, 2013

      No kidding. It’s so blindingly obvious if they would just use the far left and right local focus points in the test, in addition to the wide area which is the factory default setting.

      Reply
  10. Dennis C

     /  Feb 18, 2013

    It’s taken me too long to find you! Thanks for a great post.
    My CZ 16-80 appears to have more backfocus than the original kit lens. Now I’m going to spend some time tweaking

    Reply
  11. Thank you for nice article! I have the same problem with my Sony A380. It’s so irritating! Newer had problem like this with it before, so i just bought a new nikon D3100.

    Reply
  12. Riaan Roux

     /  Dec 27, 2012

    I have another issue. On my A55 when I zoom I have back focus, but when full wide I get front focus. I have tried this with a few lenses. I have calibrated mine for the Sony SAL 28-75 f/2.8 at 50mm as it is the lens I use the most, but I am still unhappy. Zooming to 75mm will give me back focus, but one wide (28mm) I get front focus.
    Any ideas?

    Reply
    • Mike

       /  Jun 22, 2013

      While I can’t answer your questions specifically, I recently went through a little more learning about the AF system theory and construction and found an excellent article on understand autofocus: http://www.clarkvision.com/articles/understanding.autofocus/. This may or may not be the case for the a55 but there are different groups of AF sensors that can be used depending on the f/ number of the lens on the camera. Wider apertures (f/2.8 or lower) are supposed to able to take advantage of AF sensors further apart which therefore have better distance discrimination and are faster and more accurate to focus. I am wondering whether maybe f/2.8 is right on the borderline and at one focal length extreme the f/2.8 sensors are used and at the other they are not.

      Another thing I am noticing with my lenses after revising this post is that not only does AF accuracy differ from lens to lens, but also for different focus distances. I tuned my AF sensors for a Minolta 135/2.8 and it reliably and consistently snaps into essentially perfect focus at a range of distances from about 2 meters on up. I have an old, cheap Minolta 50/1.7 that shows significant front focus when the test chart fills the field, which is at about 0.7 meters distance. The front focus reduces as distance increases, but never quite gets to accurate focus before the focus mark in the center becomes too small and the AF sensor starts picking up the patterns on the sides of the chart to focus on.

      Reply
    • Peter

       /  Jul 24, 2015

      Dear Riaan, did you ever manage to sort out what was wrong here? I have exactly the same problem, except I get back focus when fully wide and no problems when fully long.

      Reply
  13. Mikey

     /  Sep 28, 2012

    Awesome article – I was able to fix the backfocus on my a33 a few months ago.

    Just got an a57 and I’m going through the backfocus issue again! Any ideas on how to adjust the focus sensor? There doesn’t seem to be any access panels near the flash anymore and I’ve tried removing some of the top screws but I still can’t find those adjustment screws.

    I’m reluctant to bring it back to Sony. They kept my a33 for 2 months just to tell me there were no backfocusing issues.

    Reply
  14. Aaron

     /  Aug 8, 2012

    I just stumbled upon your EXCEPTIONAL post concerning the Sony SLT-a55 focus issue. This was after having visited my local camera shop Sony expert today for the same problem; and leaving with the feeling that I should consider sending my a55 to Sony for repair. After reading your post and others’ comments, I think that would be a waste of my time and money! So, I think I want to try performing your adjustment myself — as I apparently have the same problem you experienced with your camera.

    I looked at my camera and tried to determine where the two covers are under the pop-up flash and where to pry to pop them off so I can access the three adjustment screws. It’s not obvious to me. Could I impose on you to describe in detail how to do this — so I hopefully won’t damage my a55 while trying to fix a problem I should never have had?!!

    Thanks in advance for any additional guidance you can provide — AND, for the EXCELLENT description of the problem, solution, etc.!!!

    Reply
    • Aaron

       /  Aug 9, 2012

      Oops! I must have stayed up too late last night. Re-reading your original post this morning revealed that I had somehow missed your link to the DPReview.com post that showed pictures of the cover removal process. As a result, feel free to remove both of my comments to eliminate the clutter.

      Many thanks again!! I feel you have done ALL Sony a33/a55 users a HUGE favor in making this information available!

      Reply
  15. Mike

     /  Jul 10, 2012

    I *REALLY* wish someone actually finally went ahead and peel the darn shell of the body of an A57 or A65 and show the world where in the bloody hell those darn adjustment screws are. It’s *REALLY* getting annoying at this point !

    Reply
  16. Histrionic

     /  Jun 19, 2012

    I’m also interested in more details or pictures of the covers that were removed to access the adjustment screws.

    Reply
  17. Eric Stoiber

     /  Jun 10, 2012

    I bought a A65 in november of 2011 and by december it didn’t turn on then the thing was sent in and with in a month the batteries were draining all the while talking with sony tech’s and having focusing problems which they said was me then finally in late march did some testing and sent the tech tewst pictures they told me to send it in with the new lens i had bought 70-400G and i got it back 5 weeks later and it was just as bad and contacted them again and sent in test .Now they have it again and we will see . But 6 months of provlems with a brand new sony A65 and a brand new 70-400G and talking on my cell cost tons of money you would think they would get it right and compensate people some how for their mistakes. I think i will run the tests when i get it back right away again and if it has problems i think i will sell all my sony stuff off and go to nikon what a shame . For right now i’m using my A330 and get better pictures then with the a65 and my 70-400g lens wow that says something and they don’t sell DSLR’s any more only SLT”S , Bad move.

    Reply
  18. Mike

     /  May 14, 2012

    A65… problem worse I’ve yet seen. Makes the 24mp sensor entirely pointless. Yes, it’s *that* bad. Every single photo spoiled by back focus !

    Reply
  19. Cindy

     /  Apr 24, 2012

    I have had this same issue with my A55 since I got it. I have an A200 and never had this problem.
    Now the camera is out of warranty. Can you suggest where to take it for repair since I am not very savvy when it comes to doing my own adjustment?

    Reply
  20. Nancy

     /  Apr 13, 2012

    I have an a33 with multiple focus issues.

    First, there are times the image is very sharp, and other times, it is less than satisfactory. I have tried different focus modes (tend to prefer single auto focus so that I can frame the image after selecting a focal point).

    Second, when focusing on faraway objects, many are out of focus.

    Third, when using manual focus for distant images, I have to back up a smidge from the infinity setting.

    Are these issues common to the focus problem you are describing here? And where would you recommend a novice take a camera to to make the kinds of adjustments addressed here. Thanks.

    Reply
    • Mike

       /  Apr 13, 2012

      It is hard to say whether you are seeing the same issues I’ve described without some testing along the lines of what I did. The default (wide area) auto focus mode takes focus readings from a number of sensors and selects one that it thinks is the subject. From the Sony rep I talked to, the most likely selection mechanism is to use the one corresponding to the sensor that sees the closest part of the subject. But it adds uncertainty into the process. One hint is whether the default focus consistently chooses a sensor that is off-center and does not seem like the right selection.

      From a big picture point of view there are two possible significant focus issues. One is that the focus sensor block is mounted straight in the camera but the whole sensor is not correctly adjusted, so no auto-focused images will be sharp. The other is that if one of the sensors is correctly located but the block is crooked (that was my problem, and this kind of misadjusted sensor passes Sony’s focus test). To figure this out you will probably need to use local area focus and try focusing using the leftmost sensor, center sensor, and rightmost sensor and see if there is a consistent pattern at each sensor. In my case I finally figured out that using the rightmost sensor always produced sharply focused images, but using center or left sensors produced poorly focused images, and the further left the further out of focus.

      I don’t know if this has anything to do with needing to back up a smidge from infinity using manual focus, since the auto focus is not used at all and it may have to do with the lens. My guess is that most lenses are designed to allow focus to go slightly past infinity so that normal manufacturing tolerances and wear over time will still let the lens focus at infinity without running out of focus range before infinity is reached.

      Reply
  21. Thanks for the info.

    I had my A55 in to Sony for something else asked them to take a look at the focus. They fixed the other problem but didn’t even respond to my comcerns about focus. Now I’ll send my camera to someone else to get it fixed and try to get Sony to reimburse.

    Reply
  22. Jack

     /  Mar 1, 2012

    Can you provide guidance or pictures of the covers that you removed to access the adjustment screws?
    Thanks, Jack

    Reply
  23. Kashan

     /  Feb 21, 2012

    Outstanding and in depth analysis, I am facing the same issue with my A55, I did give my camera to Sony repair center, they updated the software but it has still not solved the issue, As I am not as technical as you, I have now your email to back my concerns.
    Thank you

    Reply
  24. Nice atricle was going to write one just like it as I experienced the same situation with the alpha 580, such a great camera (when you sort this little problem out) but Sony really letting themselves down by not paying enough attention to the autofocus allignment.

    On the non SLT models like the a580 the screws are at the base of the camer under the L shaped sticker.

    Reply
  25. Janez

     /  Dec 13, 2011

    I have same problem on Sony a65. Does anyone know where AF focus unit adjustment screws are on sony a65?

    Reply
  26. Mike

     /  Nov 28, 2011

    Same experience. Sony, give us micro-adjustment in all cameras so we don’t have to deal with support centers unwilling to spend the time it takes to properly adjust the AF.

    Reply
  27. erix

     /  Oct 25, 2011

    Thanks for the article. I have A33 and exactly the same situation. Camera has been sent to service center and today received it back with “we could not repeat the problem”. Back focus is pronounced with wide angle – 18mm with kit lens or 28/2.8, but at the same time focus is perfect with 50/1.7 lens.

    Reply

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