Took about 50 shots tonight doing some further work with my D800 and 70-200 II lens, 2nd night out with them trying to see how they perform. Had a series of shots with these pair of white tail deer where I focused right on the head/eye area of the animal, but I feel like the setup is backfocusing. However, I have several others in the series, with same focus on eye of another animal, or other targets (tree stump, bird house, etc) where everything is fine and pics are great. Worked all the time on a monopod, leaning against a tree to try and maximize my stability.

I've attached a sample photo, would appreciate thoughts or suggestions. Is this due to my (poor) technique, is this an example of a setup that is backfocusing, as the grass seems in great focus, but the head of the further deer does not - and that was the target. ViewNX2 confirms the focus point directly on the head of the deer. Some of the other photos that came out well and gave me crisp results were in much poorer light. With my shutter speed, I expected the first deer (ear scratcher) to be OOF, figuring I was slow, but the gal behind was standing stock still, which is why I focused on her.

70-200mm lens @ 200mm; f/2.8; 1/500; ISO200 on monopod using RRS BH-40 ballhead. This is a crop of the original RAW with nothing applied other than downsizing and conversion to jpeg in CaptureNX2.


Any thoughts?
Tom

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Attachment #1, (jpg file)

Definitely looks back focused. However, it's hard to tell you why with just the sample photo posted online. For example, the camera/lens combination could be the reason. Or perhaps you've accidentally changed focus manually while shooting by touching/twisting the focus ring while adjusting zoom. That was a problem I've had while shooting with a Bigma since the zoom ring was further away than the focus ring (part of my palm would rest on the focus ring and it would turn while I zoomed).

I'd suggest you try some more formal/controlled testing to see if it's reproducible. If it keeps happening with no good explanation, the combo should be sent to Nikon.

-Alex Rosen
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I had the same problem with my 200-400mm f4. I found that I had to do two things to correct the back focusing. First, I turned off VR. For some reason, it trashes my 200-400mm shots although it seems to work most of the time with my 70-200mm f8. Second, I executed the AF Fine Tuning procedure described in the following links:

http://support.nikonusa.com/app/answers/detail/a_id/15869/~/how-do-i-use-the-%22af-fine-tune%22-feature-on-my-d-slr-camera%3F

http://www.youtube.com/watch?v=soPFToTnx9M

http://www.tunerphotography.com/uploads/Instructions_for_using_the_AF_Fine_Tuning_Focus_Chart.pdf

I ended up placing a yard stick at about 50 feet to get the best AF fine tuning because it more closely matched my shooting distance.

I found that I had to dial in -5 for the lens. That moved the center of my DOF back about 6 inches closer to the camera.

I tested the new settings with sandhill cranes yesterday and the focus point is now dead on.

Larry Jordan

D800E, 14-24, 50, 24-70, 70-180 Micro, 70-200, 80-400mm AF-S

Website:
http://larryjordan.smugmug.com/

I would use the feature in ViewNX2 or CaptureNX2 to see where the focus point was during the shot and verify it wasn't on the grass or spanning the deer and the grass.

Rick Walker

My photos:
GeoVista Photography

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This is how I set up my AF Fine Tuning target. My focus point was the vice grip wrench. I would zoom in to 100% to see where my DOF centered on the measuring stick relative to the vice grip. I had to shoot several images, because it was not always easy to read the numbers to see what was in focus even though the contrast between the numbers and stick was good.

I put it in the back of the SUV so I could move the target to different distances without moving my tripod/camera.

Larry Jordan

D800E, 14-24, 50, 24-70, 70-180 Micro, 70-200, 80-400mm AF-S

Website:
http://larryjordan.smugmug.com/

Attachment #1, (jpg file)

<Had a series of shots with these pair of white tail deer where I focused right on the head/eye area of the animal, but I feel like the setup is backfocusing. However, I have several others in the series, with same focus on eye of another animal, or other targets (tree stump, bird house, etc) where everything is fine and pics are great. >

Intermittent focus errors are not a backfocus problem - they are more likely technique issues or missed focus. If you have a focus problem, you should still get a tight distribution where every image is out of focus the same amount in the same direction. Even then you need to confirm the problem with controlled testing.

The D800 is so sharp that it is very unforgiving of focus areas. As in the image you posted, you can clearly see what is in focus and what is not.

I'd try some testing with a clean, easy focus target and see if you are getting errors. Then expand your testing to a field test like this which is more a test of technique than your camera or lens.


Eric Bowles
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Be sure you set the focus area to single. one thing I've found is that the D800 is far more aggressive even in stationary objects of moving the dynamic focus area around. Whether too aggressive or not is a matter of opinion but it absolutely will mislead you if you don't either use single, or check the focus point after the fact before using the results to judge.

That said I did find the D800 required far more significant adjustment with most lenses than my D300. Same lenses.

But the one above is far enough off my first guess would be the focus point.

I haven't foudn any lenses that I couldnt' fine tune.

Comments welcomed on pictures: Http://captivephotons.com

Many thanks all. Will do some more formal testing this week. ViewNX2 shows the focus right on the head of the further deer in this shot....but within the red ox defining the focus point you can also see it catches some of the far grass. I was using center weighted focus not single for this shot. Hopefully it is just a 'miss' due to that and ,y technique. N I took a dozen other shots same night of a new 9/11 memorial inour area and the US flag flying and they were all fine with same setup.

Given I had some in and some out perhaps it is technique related issue. How do you judge the accuracy of the focus point then in nx2 when it completely covers the head, along with whatever else in the background that fits to determine where the true point was? Does that make sense?

Many thanks all. More testing to do.
Tom

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Bundle of Paws Photography.

If the focus point spanned more than just the deer, you can have problems, especially if the area you don't want in focus is bright and contrasty compared with the intended subject. My guess is that with increased awareness of the issue, you'll be fine.

Rick Walker

My photos:
GeoVista Photography

Download from our library of Image Doctor podcasts here

Thanks Rick. That makes a lot of sense as the grass was far brighter than the deer. Many thanks again to nikonians all for your thoughts and suggestions. Will test some more and report what I find...

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Note also that the area of each focal point's sensitivity is large than the box displayed in the VF. It appears that the grass is better focused which would not be expected if there was a true back focus situation. In back focusing, a rarer phenomena than is assumed, the area in focus is related to the target, but offset some amount so nothing is likely to be in focus unless there is something accidentally on the same plane as the offset.
This image looks like a classic case of a more attractive(to the AF system) target captured its attention than the duller, less contrasty intended subject fitting into the same focus point sensitivity area.
The camera does not know what you intended but picked a target it is most sensitive to as the intended target since they both are covered by the same sensor.
If there is any ambiguity in targets the camera will be biased to picking the one that is the higher quality target which is the correct one the photographer intended in many cases. Just not in this case.
Stan
St Petersburg Russia

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