Big disapointed about AF - Miss target a700 :(

[Barry Fitzgerald]

I am not happy with the may of my shots. I use the center auto focus
and if my subject is moving slowly it's hit or miss, like walking.
That should not be a problem.

Many of my shots require to get the focus then re compose the picture
so that the subject is to the bottom or the side. I do know the focus
point is not very forgiving. You really need dead on with this
camera. It seems my 7d would do better in this regard.

If I use continuous focus then recompose the shot it will focus for
the the center.
I guess you have to move the focus points away from the center..
y problem is I need to do this fast to catcht the shot.

I do need to get this figured out.

Just curious, are you guys using "release priority" or "AF priority" ala it wont fire till focus confirmation in continuous shooting.

I ask because in the KM manuals it always suggested setting it to "release priority" ala it will fire without confirmation, it said to do this for action shots.

Now not sure if if says something silmilar in the A700 manual, but I found results were better for me on the KM5D anyway when I changed the setting.

--



Clint is on holiday! Soon to return! ;-)

 

[Dan179]

target is that what I make with red line.Is not coretly AF is out of target back of subject

 

[Dan179]

distanse from horse was 4,5 5 meters AF-s central point AF aimet eariel.Ewrything is ok

 

[travelshots]

When I got my A700, first thing I did was checking the AF precision because I had read that some A700s had backfocus problems. I did those tests on close distance and the A700 performed perfectly which all lenses I checked (Minolta 2,0/28; Minolta 1,7/50; Minolta 4,5-5,6/100-300 APO and Konica-Minolta 3,5-5,6/18-70). It also works fine with the telezoom at 300mm plus 1,5x Teleconverter even in low light situations.

When I read your post I checked the long distance performance as well. I used the 100-300 APO at 300mm open at f5,6. Focus point was the bole of a birch tree. Distance was about 15-20m. The bole was sharp while objects before and behind were not sharp. Hence, my A700 AF works well on long distance too.

If you operated your camera properly and had those focus problems, there must be something wrong with your A700. Before returning it for exchange, do the following:

• Make sure you were not operating in a mode that re-focusses alt release
• Switch AF to AF-S and see if the problem still appears
• Put the AF-lock function on the C button and use this for locking the desired AF spot

If the problems can't be solved, exchange your A700 for a new copy. Nomally, the A700 AF works very well and is definetly a big enhancement compared to D5D / D7D.

Edit: Your problems remind me on situations with my D5D when I was shooting birds and the AF (A or C) sometimes did not follow properly and sometimes did not lock on the bird but on the background. That's why I proposed to try the AF-S mode if you are operating with a fixed focus point (and of course use the center AF).

 

[Corkcampbell]

but am thinking about buying an A700 so will follow your suggestions if I do make the purchase.

 

[Dan179]

I use for that shoots AF-S mode ,AF-C give worse results on long distanse. For 1-5 meters AF in my a700 work wery good

 

[Craig]

I am trying to figure out why release priority would do the trick.
It will not refocus, is that the problem with af priority?
Or it will take the shot no matter if the subject is in focus or not?

 

[travelshots]

If your lens worked well (without backfocus) on your previous camera body, return your A700 for a new one.

 

[Barry Fitzgerald]

I am trying to figure out why release priority would do the trick.
It will not refocus, is that the problem with af priority?

Well in C/AF, its constantly doing AF...

Or it will take the shot no matter if the subject is in focus or not?

It will take the shot even if no AF lock is confirmed. however, if you think about it, the idea of predictive AF, is it works out where the subject should be, and thus the AF should be a bit ahead of itself, if you get what I mean.

Well it worked well enough for me..worth a try at least..see how you get on with it.

--



Clint is on holiday! Soon to return! ;-)

 

[Craig]

I normally use the spot focus with the mode on A. auto priority.

However since I shoot weddings I find that for example when people are walking down the isle for some reason I am not getting sharp focus.
They are a bit back focused.
I thought the A mode would give you some continuous focus too.
So you are saying for moving subjects I should use C and release priority..?

 

[Craig]

I have to admit that all these focusing modes, are hard for me to figure out..

you have 3 modes on the a700. wide, spot and local..Plus A,C, S .... The manual does not give enough information on how to use these.

Since many of my subjects on not in the center I can't trust the camera to select the right focus spot, so I always use spot focus.

I also have noticed that even then, the focus spot sometimes misses my subject and I miss a shot..
If I used manual focus I think I would do better a lot of times.

 

[MarkyM]

Hi,

I just verified the same problem in a "quick & dirty" test using my A700 with Tamron 90mm Macro lens at f/2.8. (the longest f/2.8 lens I have)

The "system" is clearly backfocusing at these distances and under these scene conditions which, obviously, are far less than ideal.

Like the OP, closer subjects focus perfectly with this same camera and lens.

Do you think contrastier subjects and better lighting would improve the situation or is this a flaw in the cameras AF at distances greater than about 15 feet?

I am thinking that this is not a "sample variation", (where just my A700 and the OP's A700 are "bad") but should be repeatable with any A700.

Can a few of you please try a similar test?

I will be focusing manually from now on in these situations but wonder if this is something that could be fixed in firmware, an adjustment being made improperly at the factory or something that we will just have to live with?

Here are the test crops:

The first blue & white box is 18 feet away, the AMD box is 2 feet beyond that (20 feet) and the Panasonic box is another 2 feet away (22 feet).

These are crops, Spot Center AF, Matrix Metering, Tungsten WB, ISO 3200.
(Obviously poor quality but good enough to see the focus point the AF selected)

AF on the rearmost Panasonic box. OK so far:



AF on the center AMD box. Backfocused on the Panasonic box:



AF on the frontmost blue & white Key Digital box. Backfocused on the AMD box:



--Mark--

 

[Mark VB]

I use for that shoots AF-S mode ,AF-C give worse results on long
distanse. For 1-5 meters AF in my a700 work wery good

One possible problem, other than back focusing, is that when you re-compose your shot after focusing, you are not actually getting locked focus and the camera is readjusting the focus after you have re-composed the picture. At that point, the center sensor is no longer over the point where you focused but something else. Using the shutter release to lock focus in AF-S mode can sometimes not work as well as one might like because it has such a light feel. When I want to lock focus, I use the AF-MF button on the back of the camera, which completely disengages the AF mechanism (my camera is set to that button engages manual focus). Alternately, use the focus lock button on the 70-200/2.8 lens (assuming your camera is set so that is the button's function, rather than depth of field preview).

Thus, the problem you are experiencing might be the result of an accidental user error rather than back focusing. But, it also could be missed focus. You are shooting in somewhat lower light levels (indoor arena), in which case it is best to try to focus on an area that has lots of contrast (in the first of your sample images it looks like you tried focusing on a blue sign that was lacking in contrast; I don't recall the second sample) (I also wonder why you did not focus on the cross-bar where the horse would be jumping rather than the sign on the side of the jump). No AF system is foolproof, and these systems sometimes make mistakes. You also need to pay attention in the viewfinder, as the degree of back focusing that appears in your images should have been easily visible in the viewfinder, in which case you could have readjusted the focus.

Having said all of that, it certainly is possible that your camera has a back focus issue, although the degree of back focus in your samples seems excessive, particularly given that you say other shots at some shorter distances are fine. I would suggest doing some careful testing of the camera and lens, and also try to pay particularly close attention to what is happening when you shoot horse shows or competitions such as the one in your sample images. When the problem could be either the camera or human error, it is best to try to eliminate as best you can the potential for human error.

Finally, I would ignore the comments of those people who say they have no focus problems, or who say they do have focus problems. What other people experience is irrelevant to your specific situation, and whether the problems you are experiencing are human or camera error.

Good luck in resolving the issue.

Also, out of curiosity, where are you located? From the signs in the arena I'm wondering if you are in Poland. (My brother lives in Warsaw.)

--
Mark Van Bergh

 

[Dan179]

last weekend was World championship of horse jumping central europe. In Poznan

No shuter relase button was corect pressed I have 100 % now that Something wroong is with my AF .I wait for sony reaply

 

[HUM469]

The A (automatic AF, a hybrid single/continuous "between" setting) will give you continuous focus, and that is exactly the problem I think in your case. Specifically, in A mode, the camera is supposed to hold focus when you are holding the shutter halfway unless it detects motion in the scene, then it automatically switches to continuous. If I understood your technique right, you are aiming the center spot at the subject (people walking the aisle correct?), holding the shutter release halfway, then swinging the camera over a bit to re-compose, then clicking the shot. If I am correct in this, I think what happens is the camera detects the motion of both the whole scene, as well as the people walking, but since it is locked in spot (and therefor out of using all it's points to follow the motion) it is having to attempt to guess which way the subject went since it cannot "see" them with the other points.

I see your solution as very simple therefor. I see a couple possibilities for you to try. First, try allowing wide area with continuous and just compose as you want so that the camera is fully able to track the people as they walk, I think you will be surprised that it is usually able to keep with them. The second option, if you don't want to trust the camera, would be to compose as you wish, and manually select the point that they are currently crossing. For this you would need to have a fairly fast thumb, but then most people at a wedding don't seem to move too quickly. The final option might be to use single and the center point, focus with them centered, then hit the quick AF/MF button and track them manually while you are recomposing. Personally, I have had plenty of success with the first option (wide area/continuous) tracking my children who are much more difficult to follow than your subjects. Unfortunately I still need to buy my own and had to give the loaner back the other day, otherwise I would give all settings a try again on people walking by me today and let you know what I found easiest.

As for the OP, since the images are cropped, there is a bit of a language barrier, and we don't have the full story, I am not sure what is going on. It could be something similar since he has said that he uses spot. But then we don't know what his origional framing was or whether he pans. If someone speaks his language, please translate this for him and maybe it will be some help. I don't know though, YMMV.

 

[JusLookN]

Barry, your analysis is the main reason I asked the first few questions. Because release priority could be the cause of this. I was just trying to eliminate some of the possibilities! Dan, as I stated earlier, I'm not doubting your problems with the A-700. It's just that there are more variables to consider, before making a definite conclusion. As someone stated earlier, it could be a problem with the lens. But Barry's analysis could well be the cause, which is why he asked about release priority. Someone mentioned the autofocus modes in a statement that wasn't exactly interpreted right. There are autofocus, modes, and there are autofocus areas, and both have to be matched according to the priority(release or not). As stated by Barry, if you have the camera set on release priority, it will fire the shot whether you are focused on your subject or not. In continuous autofocus mode, the camera is "continuously adjusting the focus area, according to the area you select. Depending on your settings this could be a large area or a small area that makes it almost impossible to do the task that you are attempting,especially with moving subjects that are moving at a really fast pace. Maybe I missed the point again, in which case I am not explaining the point that is being viewed by some of us where it is being understood by the OP. I shall resign myself back to the sidelines to see what the outcome will be. (I'm just trying to understand the problem) I'm not arguing that there isn't one. Just trying to figure out exactly what is causing it.

On another note, Dan I'm not blaming your technique. Just trying to be helpful in finding the solution.
--
Glenn

I'm kinda partial to video, but I'm hangin!

 

[JusLookN]

Thanks, Mark, your explanation sounds better than the points I was trying to make! I like the way you put it out there.

--
Glenn

I'm kinda partial to video, but I'm hangin!

 

[JusLookN]

Mark, I have no doubt that I have experienced the same with mine. However, try the test again with Spot & Spot, then with Spot & Local area and see how it comes out! You should see an improvement, if the lighting and contrast is enough. Thanks for your time.
--
Glenn

I'm kinda partial to video, but I'm hangin!

 

[Syed W haider]

I purchased Sony A-700 and had trouble with camera corrupting images on sandisk ultra II CF card. I exchanged it for another one which gave me soft images. When I posted the problem on this forum that I will be reurning my camera, I was chewed by people here, called names etc.. Anyway, I exchanged it again and it failed during taking shots at my daughters birthday at lazer extreme. The feel for half preesed shutter to focus was gone and I lost image playback.
I switched brands and luckily have not had a problem yet.

I loved the feel of the A700 body and the idea of having in camera based image stabilization but feel the Sony needs to get a mature product on the market and have better quality control then this.

--
Nikonn D300
Nikon AF-S 17-55 f2.8
Nikon AF-S 70-200 f2.8 VR
Nikon AF-S 18-200mm VR
Nikon SB 800

 

[Syed W haider]

--
Nikonn D300
Nikon AF-S 17-55 f2.8
Nikon AF-S 70-200 f2.8 VR
Nikon AF-S 18-200mm VR
Nikon SB 800