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DPChallenge Forums >> Photography Discussion >> Focus help - Is my lens acting up?
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09/09/2011 11:27:42 PM · #1
This is an unedited Jpeg from my D700. I'm using my 80-200 f2.8 in my profile.

I seem to be getting bad focus. I took many "real world" test shots today and yesterday. One of them is below. I was zoomed at 200. 1/200, f6.3, flash with diffuser.

The black mark is my focus point. As you can see, the focus is missing.

I do have a slightly damaged manual/auto ring but it just requires a little force to get it into position. The lens has never been dropped or bumped around.

What do you think?



EDIT: Here is another - 1/640 f2.8 - In my opinion, it looks like it is focusing behind my focus point of the knot in the wood.



EDIT: My other f2.8 lens seems much better. But it only zooms to 70mm so I'm not sure if it is fair to compare.

Message edited by author 2011-09-09 23:38:02.
09/10/2011 12:45:05 AM · #2
The top photo looks to be front focused. There are several test charts available to check for front/back focus, but first, be SURE that the viewfinder eye piece diopter is adjusted to give the best, clearest image of the marks in the view finder. After adjusting the diopter, take some photos and see if that fixed the problem. When you are sure that the viewfinder eyepiece is adjusted correctly, look on line for "focus chart". There are several available, but you are looking for one with a high contrast center mark, such as the one at //focustestchart.com/chart.html. If you are checking manual focus only, just use a 12" scale and focus on the 6" mark. Take a photo with the long axis of the scale at 45 degrees to the axis of the lens, and look for the measurement with the sharpest focus to determine if front or back focus.
09/10/2011 08:33:44 AM · #3
I tested by lens with a ruler this morning. On every shot...handheld, tripod, mirror up, etc... the auto focus and manual focus is focusing about one inch behind my focus point. I tested on another lens and it seems to be ok. So I guess this means it is the lens.

Is it time to send the lens in for repair? Can something like that be repaired?

I'll post a few pics in a bit.

Thanks,
09/10/2011 10:56:32 AM · #4
If manual focus is not spot on, then maybe it's the diopter setting like thompp1 said.
If it's a VR lens, then the VR could be having a problem, esp if you are shooting your test shots using a tripod plus VR. VR has a problem with tripod mounted shots, and should be turned off for that.
To accurately set the diopter adjustment, put the camera on a tripod, and using a known good lens, auto focus on something with a good contrast line, so that you can see exactly where it's focusing, then turn the camera off, and set the diopter so that you can see that focus point best. Using the heads-up display to set diopter works, but only gets you pretty close to right. This is best done while not drinking.
Once you get that right, put on the suspect lens, and see if you get the same results.
I don't know about the D700, but with the D7000, there is an option in the tools menu to fine tune AF. I would imagine that would affect focus with any lens you are using.
One other thing could be dirt or a smudge. Check your sensor and the lens for any nasties on glass surfaces.
ETA, Since it's only one lens giving you trouble, it's not likely to be a dirty sensor. When you check for lens smudge, hold the aperture open by moving the little lever at the mount so you can look through the lens wide open both directions. Also, hold the lens so that light reflects off the front and rear elements to look for smudge. Sometimes oily smudge can be there and you can see right through it.
If you breathe on the elements and watch as it clears up, you can also see if there are any anomolies there.
We used to read the numbers on music amp tubes that way, even if the numbers were completely gone they would show up with that technique.


Message edited by author 2011-09-10 11:04:15.
09/10/2011 01:09:05 PM · #5
I sent my 18-135 to Precision Camera for repair recently. Took about 3 weeks to get it back. They fixed it for about half of what a good used one would cost. Their pricing appears to be fixed fee based on the lens model. Need to send my wife's Sigma 70-300 now as well.
09/10/2011 05:58:37 PM · #6
I will check them out. My lens is focusing as the "brick" photo represents. I even tried it on a D90 and it does the exact same thing.

I tried the "fine tune" thing in the D700 but it did not do ANYTHING. I'm not sure if I'm even using it correctly. There is little info about it out there.

Originally posted by Yo_Spiff:

I sent my 18-135 to Precision Camera for repair recently. Took about 3 weeks to get it back. They fixed it for about half of what a good used one would cost. Their pricing appears to be fixed fee based on the lens model. Need to send my wife's Sigma 70-300 now as well.

09/10/2011 10:03:46 PM · #7
Yo....I checked it out....says $250 to fix but didn't ask any questions about problems. Is it one price fix all?

Originally posted by Yo_Spiff:

I sent my 18-135 to Precision Camera for repair recently. Took about 3 weeks to get it back. They fixed it for about half of what a good used one would cost. Their pricing appears to be fixed fee based on the lens model. Need to send my wife's Sigma 70-300 now as well.
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