#1. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 0 Tue 12-Feb-13 04:18 PM by km6xz
St Petersburg, RU
Welcome to Nikonians Ganesh Focus is a complex topic so naturally many questions just like yours can be found on the forum. The first you would need define what you are seeing that causes you you to question image focus. Is it a vague feeling or definite blurred image that impacts all parts of the image? Does every every image give you the same impression regardless of lighting, movement of the subject and mode of af? Is any part of the image, on different focal planes sharp to your satisfaction? With both lenses? How are you viewing the images; what distance and magnification? These questions are aimed at narrowing down the source of the problem between camera, lens, settings or technique. Is it possible to upload an image that is typical of what you are seeing? It would be a big help, so we are seeing the same problem you are. Stan St Petersburg Russia
#2. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 0
Brighton and Hove, GB
The first thing I'd suggest is shoot a lot of different images in focus priority mode (shutter won't trip unless the camera has acquired focus) and with your shutter speed around double the focal length you're shooting at (1/500s at least for 300mm, for example). If these don't turn out sharp and you're aiming at nice contrasty focus targets, then you may have a problem.
I spent quite a bit of time blaming the camera for things that turned out to be missed focus or motion blur.
#5. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 4 Thu 14-Feb-13 12:18 PM by Gamecocks
I would believe that both subjects would have been difficult to get precise focus as there is little contrast. Although manual was used in the first picture I would wonder if the focus was really achieved at time of shot because of the pattern. With aperture selected in the second shot and focus being on the sand again there is little contrast and this could cause the focus point to be different (see page 93 in manual). I suggest you try the same procedures on subjects with more contrast and believe you'll see better results, imo. Also, I got better results with my 70-300 using an f stop around 8. Good luck.
Nobody should seek his own good, but the good of others. <><
#6. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 4 Thu 14-Feb-13 02:23 PM by elec164
Ganesh, the actual focus sensor area is larger than the square marker in the viewfinder.
Sometime ago when testing this is approximately what I determined the actual focus area to be in relation to the square marker.
So as stated already by others, if the area under the square is low contrast but there is an area just outside the square that's higher contrast, then the camera AF will select the area outside the marker. That's why real world results are difficult to use for testing.
Self testing possible calibration issues with AF need to be done carefully and meticulously. It's best to use a standerdized resolution chart. I used this ISO12233 Chart ,but there are numerous others that will suffice. Mount it on a wall and your camera on a tripod and aligned the camera to have the sensor parallel to the wall. Make sure there is sufficient illumination for the AF system.
After not being happy with the results of 2 of my 6 lenses and careful testing, I Fine Tuned them and am now satisfied with their results. But I would caution against just AF Fine Tuning as a matter of fact and only do it after careful consideration.
Hope this helps!
Edited to add:
Also being that the DOF is so thin in your examples, hand holding can be problematic. A small shift in your position forward or back (especially using AF-S) will cause the focus plane to shift from where you think it should be. That's why when testing for focus errors it's best to use a tripod.
#7. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 4
Hi Looking at your 2 pics, reminded me when using my old Nikon F2 film camera that the depth of field (sharp zone) on a lens specially when focusing close to the camera was showing on the lens barrel always a farther distance (in focus zone) in the back of the focusing point compared to the front distance. This is what seems to happen on your 2 pics. It is specially more visible on the pic where you have ants. On this pic the pavement (ciment) is perfectly in focus at the focus point and farther away from it that in front of that point where it is out of focus.
#8. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 0
St Petersburg, RU
As others have suggested, the focus target in both these cases are difficult for AF to figure out what you intended. The sand because of lack of contrast or edges and the first one with the highly complex subject with many focal planes in the same focus point. The problem you have may be real or not, these images are not going to demonstrate a problem however. If, for example, you had targeted the flies in the second image, because they present distinct edges and contrast separate from the indistinct low contrast sand, the test would have been a better illustration of focusing accuracy. A focusing chart, at the recommended distances, with strong uniform light would be the best way to see if there is a problem. Since you mention that other subjects or times, focusing is what you intended. Do you have an example you could post so we can see one? If there was a AF miss-calibration, I would guess that all images would be biased to the wrong focal plane. The reason many people assume AF is not working correctly is because AF guessing your intent, it really does not know what is your intended subject and if there is any ambiguity in focal planes falling under the focus point, a guess could deliver a well focused subject, but not your intended subject. AF has become so good in recent years, most of us assume that when an image is off, that there is a problem, when in fact, the surprising thing is how often the system guesses the same focal plane we wish for. Your camera might have a problem or might not, tests that isolate the AF system as much as possible as the variable are needed to find out. The variables needed to remove from the test include: Camera motion so a tripod is needed. Target ambiguity, so a parallel flat focusing target is needed Edge contrast, using a recommended test pattern target Light fluctuation, meaning using continuous strong lighting, not florescent which varies greatly in intensity and color during each cycles of the mains line frequency. Broadspectrum light, so that shift of focus plane is not a problem when testing wide aperture lenses. Different wave lengths of light are diffracted differently by the lens glass Mirror bounce, use mirror up and a relatively fast shutter speed to negate the vibration that the mirror bounce generates and can induce image blur. Camera steadiness, so use the ML-3 wireless remote, timer or wired remote so your button press does not shake the camera. Focus target needs to be a recommended distance from the camera, the distance depends on the chart itself so follow the instructions for any particular chart. Random fluctuation in focusing, by taking a series of shots and place the greatest weight on the focusing plane that the most images in the test represent. Lens hysteresis, between each shot, set the focus to infinity so the AF has to approach and stop at the focal plane. The balance this effect, repeat the tests but where each shot is begun with the focus is set to minimum. Compare the two sets. Reference image, take one shot with Live View which uses an entirely different method of focus target selection, and one where you tell it precisely what focal plane you want. Under these test conditions, Live View should be more consistent and reflect the ultimate capability of the camera, lens and AF system. All the items mentioned above are highly variable in our hand held shots so while some complain of occasional missed focus, some of us marvel at how many of these compromise conditions are overcome to produce as many sharply focused images of our intended targets the AF delivers. When dealing with complex targets and having a specific artistic focus point in mind, many of us who grew up on manual focus, switch to MF and control it ourselves. You always get the focus plane you set in MF, but you might not get the optimum focus plane because we missed ourselves. The owner's manual for the D7000 has an excellent list of good and poor AF target types. Feeding the AF system with good AF target types really increases the number of results where the resulting images match or expectations. Good luck, but mostly, have fun! Stan St Petersburg Russia
#10. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 9
>Thanks a lot for all your interests and help.... I think I >have to do a lot of homework based on the input you all have >given. I will come back after getting my results achieved. > >Thanks again to all..
Hi, any updates/results of your tests. Thanks in advance.
#11. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 10
While trying to 'debug' an issue i was having (D7000 or 70-200 f/2.8 missing focus... a lot) i stumbled across a program called 'FocusTune'...
The idea is to take a set of pictures (changing the focus fine tune adjustment with each set) of a target image... and the program will tell you where to set your 'focus fine tune' to get the sharpest picture.
I'll admit... its kind of addicting... It will diffidently tell you if your camera is back focusing.
#12. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 8 Sat 09-Mar-13 06:20 PM by ardoluc
This is a photo taken at 1/125 sec at f1.8G DX in a chic restaurant in montreal named "Birks café". The AF was in AF-S and the focus was on my son's scarf. The focus was achieved instantly, I was sure it focused perfectly. The next day I went outside and took a serie of pics all at f1.8 with the same lens at different distance from my subject, and they all came out pefectly focused on the focus point for everyone seen at 200% magnification. I tried other pics inside and I found that under fluorescent light in low light particularly the AF gets fool and back focus a great distance from where the focus point was. I know that in those situations I have to switch to manual focus. If anyone of you had this same experience please share with us. imglink:415499
#14. "RE: How to ensure my Nikon D7000 does not having back-focus issue" In response to Reply # 13
Hi Joseph The red square (focus point) on the pic is not created by me, it is a screen shot of the raw file in "View NX2". I took it with "Snagit" and immported to Photoshop CS5 and saved it as a jpeg. Here are the info I get in "edit" mode of "View NX2"