Look, my camera's issue is a lot more than just a focus adjustment problem ... which is relatively easy to do, whereas mine requires they split the camera open and start diggin' through it. Not a lot of fun with these devices unless you are patient and have some serious experience playing with them.
Now, SONY directed me to send the A700 to Precision Camera, because they are now the regional repair center for the east coast, where Laredo, TX is a real SONY repair center. Still, even they return a lot of stuff to Japan for advanced work.
Anyway, do not hesitate on getting your equipment up to standards. That's the most crucial aspect of having the equipment. It is aligned and operating without question. Then you can make real improvements in your photography, based on measured and with the ability to duplicate results.
Let Tamron adjust it. It would be pointless to return a lens just because it has a front/back focus tendency. Tell them what camera it is being used on and they can adjust it.
The fact is that TAMRON does it to a standard ... independent of the model of camera, because all the SONY & Minolta cameras have the identical measurement between the sensor and the back of the lens. Only the A900 (currently) can micro-adjust this measurement.
don, i thought the a700 had micro focus adjustments ?
Well if you can't MF and I mean by tweaking the focus ring and not by measurement, I'm not sure.
I would certainly advocate using the Tim Jackson Focus Chart in preference to the "battery" test. This will offer the AF system a single line with sharply defined contrast and no choices.
More often than not F/B focus issues are down to camera alignment. You have to remember that the AF system is not a distance detector but simply a feedback loop that moves the lens element to a position where the sensor detects maximum contrast between adjacent pixels. The border between a black line on white paper is ideal. Out of focus the border is blurred and less contrasty; in focus gives a sharp divide and maximum contrast. A lens has to be seriously out of kilter to be the culprit and I think it would show up in many ways.
If the AF sensors are misaligned, AF will be bad and MF will be good.
If the APS-c sensor is misaligned, both AF and MF be bad.
Yeah, too bad there's no micro adjust for the AF. That would be ideal.
I see what you are saying now. But if the sensor was misaligned, I would also not be getting good results with other lenses.
Originally Posted by Peekayoh
I did try the focustestchart.com chart and it showed slight BF, but the results aren't as clear cut as the battery test since I have no idea how close I was to a 45° angle. Don't have a geared head which gives degree increments, just a ball head.
No ... that was an A900 exclusive. On it, there are 20 stored adjustments you can make to allow for your different lenses. They are not a lot ... but some +/- adjustments can be made.
Originally Posted by Rooz
The DOF may be disguising the results with other lenses.
Originally Posted by dr4gon
It's not crucial to be at 45°. Near enough is good enough.
What's generally not appreciated is that the AF system puts you "somewhere" within the DOF; the system has to lock on quickly rather than looking for the "absolute" point of clarity, otherwise it would be "hunting" interminably. Usually that, "somewhere", in the DOF is good enough, that is until you have a very thin DOF at which point you may be in trouble and need to fall back on MF to fine tune (or stop down).
Another thing that's not appreciated (maybe) is that nothing in the DOF is in focus except at the actual plane of focus, the rest is "acceptably" in focus and whats acceptable is not the same to everyone.
When you do the test I suggest you
use a tripod (I know you are, dr4gon)
get into bright sunlight if possible
choose maximum aperture
If you still can't MF, I'm stumped.
To be entirely accurate, guys, add some more light to your testing. The camera can be fooled into an incorrect center of focus if the contrast is "fuzzy."
My personal recommendation is to use a 200-300 W bulb as your light source and keep it overhead or over your shoulder, behind you, striking your center of focus on the subject.
Soft light is always rather "iffy" and not a true reflection (pardon the pun) of the actual point of focus.
Alright, more light then lol.... but it's still quite unacceptable to me if it can't AF in what I would say is decent lighting.... doesn't make sense right? It's a low-light lens and if I have to have 300W+ of lighting, then it's just not up to par.
But, I will try it again this weekend.