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A700 FF/BF adjustment

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Pete Ganzel View Drop Down
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Post Options Post Options   Quote Pete Ganzel Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2008 at 18:24
Beline:

The adjustments do seem counter intuitive because of the optical path of the AF sensor module below the mirror box.

Here's a little generalized sketch showing the complexity of the focus/viewing geometry in AF SLRS;



Not to discount some folks successes with DIY adjustment, but you need to do this carefully and be able to turn things back where they were if it doesn't work for you. The AF adjustment sequence starts with AF area adjustment which adjusts the viewing and secondary mirror, followed by rough adjustment of the module screws and then final tweaking of individual AF areas in service software.

Pete

 



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goodwrench View Drop Down
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Post Options Post Options   Quote goodwrench Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2008 at 18:39
Thanks Pete. Yes people need to be careful, that is why I stress keeping notes of all your adjustments.

Using the screws is a bit of a crude method BUT it has worked of me. Also you must use the screws to align the sensor in middle if this is your problem then by ajusting all 3 screws you are just making sure the distance between the focusing screen the mirror is the same as the from the mirror to the AF module.

I will add that there are other focus problems that can occur as Pete has sugested. The CCD could be too far forward or back or tilted. The mirror could be misaligned too (some Nikon FF/BF can be fixed by adjusting this).

Good luck!

Garth
My grab bag - A850, KM 17-35, SAL 50 1.4, Min 85 1.4 RS G, 200 2.8 HS APO G - All in a Slingshot 100     
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beline View Drop Down
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Post Options Post Options   Quote beline Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2008 at 19:17
ok, so there are ALOT of variables, when you send the camera in, do they actualy make sure EVERYthing is proper?
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beline View Drop Down
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Post Options Post Options   Quote beline Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2008 at 19:24
Basically, one must first be sure one has a perfectly adjusted lens, then one must adjust the camera.

Which is more sensible? Send in all of one's lenses for adjustment, once they are all spot on, adjust the camera?

Make camera adjustments based on the current state of all of one's lenses?

Or just send the camera in, and then send in the lenses that need help based on how the camera comes back?

Mind you, I am talking about a 5D here, son to upgrade to a A700... So... advice?
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Mick View Drop Down
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Post Options Post Options   Quote Mick Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2008 at 19:32
Originally posted by beline beline wrote:

ok, so there are ALOT of variables, when you send the camera in, do they actualy make sure EVERYthing is proper?


Doubt that VERY much, beline. When you take your ar in for a service do they make sure everything is proper? No. They check the things you're likely to notice...people are the same everywhere and in every industry. My car was under the manufacturer's warranty for the first three years' of servicing. When that expired I had the chance to service it myself;
Air filter element - original to car. I'd paid for 3.
Fuel Filter - original to car. I'd paid for 1.
Pollen filter - ditto.
At one service I'd forgotten to give them the puzzle key for the wheels - so they couldn't remove the roadwheels. Came back with a clean bill of health (I didn't remember about the key for about 2 weeks!) even though they couldn't have checked the car properly without removing the wheels.

After some wrangling, they eventually offered me a free full service!! As if...

Anyhows, sorry for that. I expect camera repair shops to be the same. To check everything means to spend uneconomical amounts of time.
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goodwrench View Drop Down
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Post Options Post Options   Quote goodwrench Quote  Post ReplyReply Direct Link To This Post Posted: 03 February 2008 at 20:14
On the camera you need to check all your lenses to see if there is a problem with one or just a problem with the camera.

I sent in all my lenses with my 7D 2 years ago, they lost everything for 2 months - they found my stuff, adjusted my camera and it was the same -THIS is why I adjust myself.

I sent in my 7D for FFB repair and they said it needs 4 new curcuit boards- so my 7D is now DEAD. (It suffered from FFB for months while I waited for the A700 to come out, it didn't make it that long, I had to buy a A100-THEN I bought the A700-GREAT service for a good customer eh?)

On the Car note, I am a auto Mechanic and own a repair shop, I have 4 mechanics working for me and 1 service advisor.

For the most part DON'T go to the dealer, find a good indipendant repair shop. At the dealership unless YOU complain about a problem while your car is under warranty-they won't mention it-UNLESS it's saftey related. So when your warranty is up there is all this work to do. Dealers get paid less $$/hour from the manufacurer and less hours per job from the manufacurer (say 1.5 hours for that gasket instead of 2 hours on the reatil end). Manufacurers are also clamping down on warranty repairs (they needed to cus the dealers were robbing them blind).

I could talk ann day on this but if you have any questions PM me.

Garth
My grab bag - A850, KM 17-35, SAL 50 1.4, Min 85 1.4 RS G, 200 2.8 HS APO G - All in a Slingshot 100     
 



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Post Options Post Options   Quote imacxum Quote  Post ReplyReply Direct Link To This Post Posted: 04 February 2008 at 07:30
Originally posted by goodwrench goodwrench wrote:

On the camera you need to check all your lenses to see if there is a problem with one or just a problem with the camera.

Definitely agree. I checked all my 12 lenses on 3 bodies. A700 back focuses on all but one lens; A100 & 7D front focuses on that one lens. Discovered a clear pattern. Printed out the results and sent it in to Sony repair. I hope they don't lose my stuff for 2 months!
A700/VG A350/VG 9xi 800si 7 M35-200xi M24-50/4 M70-210/4 M50/1.7 M28/2.8 M24/2.8 T17-50/2.8 T90/2.8 S50/1.4 S18-250
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beline View Drop Down
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Post Options Post Options   Quote beline Quote  Post ReplyReply Direct Link To This Post Posted: 04 February 2008 at 17:40
Originally posted by Shaocaholica Shaocaholica wrote:

Well I have a split image screen and I can tell right away if the AF is off and it is for some lenses but its not big enough that its totally useless. Its ~2mm off subject with my 90mm Tamron Di Macro. In most cases, this isn't a problem.

So if the main screw is the main adjustment, what are the other screws for?


So, would I be correct in assuming that if the focus screen is in focus (split) then the resualting image should be in focus. But that's not the case with AF. Meaning a split screen is always accurate, regardless of the lens used or whatever.

They have split screens for the 5D?
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pegelli View Drop Down
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Post Options Post Options   Quote pegelli Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2008 at 15:46
There was so much talk about FF/BF, especially with 2.8 lenses that I decided to do a test as well, and first indications are that my A700 with my new 200/2.8 backfocusses about .75 inch at 4 m. With the beercan at the same distance it's still noticable but dof at f4 is starting to mask it. The big beercan at f5.6 hardly shows the problem.

Allready tested the AF area and that's spot on, so I only have a BF issue it seems.

I'll do a lot more testing before taking the "goodwrench" way (i.e test all my other lenses) but if I dare to do it I'll post the results here. First obvious test is the KM 100/2.8 Macro and the 50/1.7 that I have.

If others have good/bad experiences with this maybe they can collect it in this thread as well.
Mind the bandwidth of others, don't link pictures larger then 1024 wide or 960 pix high, see here
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Post Options Post Options   Quote willybol Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2008 at 13:29
Hi Pegelli,

Better be carefull and think twice (ore even more) before ajusting anything on the a700 yourself! I took of the self adhesive to get to the three screws, but all the srews have this dot of glue telling Sony someone has been in the camera before and you will loose your warranty!

I do have major backfocus and never realized it until I bought a 35mm F1.4 and a 85mm F1.4. The rest of my lenses are all F2.8 lenses and backfocus does not showed up there to much, so I never bothered. Now shooting with my F1.4 lenses on the a700 I have to use DMF to adjust focussing after the camera believes it's spot on to correct it.

Went to Sony repair three weeks ago. At first they did not even know the backfocus problem and it took them two weeks to figure out what I meant, after telling me to upgrade to another firmware, check if my camera was on autofocus and not manual e.d e.d. I got angry with them and ensured them it was backfocus which is a know problem. Oke they said, bring it in and it will go for repair...at least THREE weeks they need to service the camera!!! When I asked them if they had a camera to borrow me, they told me they only had one and that it was out. ONE a700 for the whole Netherlands... Well I think you get my point, Sony service in the Netherlands does not have any expertise and service is bad!!!

Still I never adjusted the backfocussing myself although I had a wedding yesterday. Monday I will still bring it to the Sony service center. If you do adjust it yourself I would really like to hear the details from you!

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pegelli View Drop Down
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Post Options Post Options   Quote pegelli Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2008 at 13:42
@willbol,

I'll think twice and even three times. I'm just thinking about it.
I just have 1 year US warranty, so wouldn't risk that much though.

Problem is my backfocus starts showing with f 2.8 already (about 4 cm at 2 meter distance at 100 mm f/l, so outside the dof zone of +/- 1.9 cm at f2.8 at that magnification)

I'm interested in you're DMF procedure. How do you know how much to adjust after the camera thinks the AF is spot on ?

Mind the bandwidth of others, don't link pictures larger then 1024 wide or 960 pix high, see here
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Post Options Post Options   Quote willybol Quote  Post ReplyReply Direct Link To This Post Posted: 17 May 2008 at 18:38
"I'm interested in you're DMF procedure. How do you know how much to adjust after the camera thinks the AF is spot on ?"

Well, Pegelli, I don't. It's a matter of experience. Not easy I can say, because with every focussing distance another amount of ajustment is needed, but just practise! At least it can help you out when you really need the camera for a shoot.

My backfocus is comparable. With my 85mm at a minimum focussing distance I have a backfocus of about 1.5cm, which is increased to about 6-10 cm at a distance of 2-3m.
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Post Options Post Options   Quote carusoswi Quote  Post ReplyReply Direct Link To This Post Posted: 18 May 2008 at 10:06
I have both the A100 (feel guilty . . . took some classic shots with it, but haven't tripped the shutter since purchasing the A700) and A700. Downloaded a chart and checked the A100, but couldn't really be certain of my results. I guessed at the 45-degree angle suggested by the supplier of the chart, and my results seem to indicate sharpest focus point slightly forward of the zero point on the target.

Haven't tested the A700, and, in situations where focus in my images is less than desirable, I can always point to other conditions that are less than optimum (poor lighting, slow shutter speeds, shallow DOF, etc.) My other concern is that no lens stops exactly where AF tells it to stop. That's why Sony offers us (what do they call it) the option to adjust manually after using AF.

I'm guessing that most of my lenses would vary in accuracy depending upon whether the camera was pointed up down or horizontally and how tight their focus travel mechanics.

When I hear talk of how one lens shows the problem more than another, I think to myself that this might be due to a combination of optical/mechanical influences not related to the integrity of the in-camera AF.

That said, it would not surprise me to learn that Sony tech has some preset or company issued test that explains why BF exists in the first place and why some of you get cameras back after sending them to Sony that are no better off (or should I say better on?).

I feel that AF gets me close, and, when there is no time to fine tune, then, I should select exposure settings that mitigate any focus issues (including those two orbs that infect my face with annually decreasing focus accuracy!!). Fussing with the camera adjustments strikes me as akin to adjusting the alignment on an analog reel to reel tape recorder using only your ears. What sounds better to you may be better, worse, or no different, but, if it makes you happy, then, record away.

The result will be heard (or in the case of cameras, viewed) by eyes that have no clue or concern whether the instrument of capture suffered from or was free from AF accuracy issues. The result is either good or not.

I don't mean to denigrate those of you who have taken solution of this "problem" on yourselves. OTOH, I think I'll spend some more time shooting pictures before I worry about whether my AF is accurate or not.

Almost every shot I take gets a dose of sharpening in post. Is that an AF problem or a sensor problem or a digitial photography issue. I don't know, but the adjustment in post seems to work fine.

Caruso
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pegelli View Drop Down
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Post Options Post Options   Quote pegelli Quote  Post ReplyReply Direct Link To This Post Posted: 19 May 2008 at 07:44
OK, I've gone as far as purchasing a 1.5 mm allan hex tool and have taken the sticker off to take a look. I need some more encouragement to take the next step (moving the 3 screws)
Couple of questions:
- for BF should I start turning clockwise or counter clockwise (with the camera upside down.
- the 3 screws seem to be "glued in place" with a clear glue. After final adjustment do you need to glue them back again to avoid creeping towards BF/FF or are they tight enough by themselves to stay in place and is the glue only there to tip sony off they can void the warrenty.

@ carusoswi: I wish you were right, but I have now scientifically proven my BF is such that I cannot use my 2.8 lenses wide open. This was done with a high contrast set-up, from tripod and 2 sec MLU/self timer and repeated many times. Inbetween I manually set the lens either to infinity and/or closest focus distance and it doesn't matter from which side the AF approaches the target. It's always ~ 2.5 +/- 0.5 cm backfocus with a 200 mm at 4 meter distance so outside the dof zone. I think I could live with anything inside the dof zone, but this is too much. I still enjoy taking pictures, but only at f4 and smaller apertures and that's not why I bought my 200/2.8 G. I've also done the test with a beercan at f4 and f5.6 and it shows the same BF result, but then the BF is within the dof zone, so for me acceptable.
Mind the bandwidth of others, don't link pictures larger then 1024 wide or 960 pix high, see here
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