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Old Feb 19, 2012, 9:01 PM   #11
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Default test at 35mm

The first is the Tamron 17-50mm 2.8 at 35mm. Second is the same lens at 50mm again. Third is again the same lens at 50mm but focused through the Live View screen. Big difference eh? the Last is Tamrons 28-75mm 2.8 at 35mm focused again through the View Finder. Agian these were shot from a tripod aimed at 45 degrees from a distance of 4 feet.
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Old Feb 19, 2012, 9:49 PM   #12
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I don't like shooting focus charts at all and use them as an indication (or to verify what I've already seen in real world shooting). The one big thing is before you take what you see as a definite front or back focus, verify that the camera CAN'T lock focus on the lighter printed lines. I ended up printing the lightest grey chart, and still can't use it in strong light or else my camera may focus on one of the lighter lines (the AF spot is larger than the focus indicator on the camera) and I get inconsistent/inaccurate results. I have some lenses that required adjustments with my camera, just happy I have that option because one of my lenses is really horrible without adjustment.
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Old Feb 19, 2012, 10:16 PM   #13
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LOL, I dont like shooting them either anymore....I repeated the whole ball of wax again with my D-90 and it was virtually the same. The D-700 was diffferent, in that every lens seemed to fall within the scope of acceptibility. I even tried a Tamron 70-200mm 2.8 with the 7000 and it was deadnuts on at every focal length. So where do I stand now....right where I did a couple of hours ago.
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Old Feb 19, 2012, 11:27 PM   #14
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Focusing with Live View should be right on. The focus is determined by the image sensor. Front Focus/Back Focus happens when the image sensor and the Phase Detect sensors don't agree.

So you did the same thing with each of a D7000, a D700 and a D90. The D7000 and the D90 produced similar unstatisfactory results, while the D700 was good with all lenses (using Live View or the OVF?), as was the Tamron 70-200/2.8 on the D7000 (using Live View or the OVF?)

Are there any corrections in the D7000 now?
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Old Feb 20, 2012, 2:05 AM   #15
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You are using very poor light in those shots. This really doesn't help when tuning your AF system.

Make sure you use good light. Focus charts aren't a bad idea, but they aren't necessary either. At 100% magnification you can see fairly well which of a series of shots is the sharpest.

Just take a series with each lens at various correction levels in good light from a fixed position - use the self timer and a tripod or beanbag. You could write the adjustment on a piece of paper or computer screen/ipad for each shot so you can view them at 100% on your computer later to choose the best adjustment.

This is the sort of thing the camera techs will do if you send your camera and lenses in for calibration.
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Old Feb 20, 2012, 5:16 AM   #16
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Focusing with live view was spot on with all lens involved. I understand the issue with proper lighting here and though Ive not been able to point a finger at a focusing issue in the past while shooting different subjects out of doors it may very well be the lack of good lighting in this case. Yet one would have to assume that this camera should be able to acquire a target and focus in on it, in this type of lighting esspecially at this distance. Afterall people do use this one with the proper lenses at weddings and simular indoor events. I have not made any adjustments in the cameras Fine Tune as yet, and will hold off until I do some more shooting under better lighting conditions to see how she does.
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Old Feb 20, 2012, 6:16 AM   #17
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Quote:
Originally Posted by emptyquiver View Post
Focusing with live view was spot on with all lens involved.
Of course. It ALWAYS will be. What you are trying to do is to calibrate your camera's phase detect AF system with your lenses.

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Originally Posted by emptyquiver View Post
I understand the issue with proper lighting here and though Ive not been able to point a finger at a focusing issue in the past while shooting different subjects out of doors it may very well be the lack of good lighting in this case.
The point is that poor lighting will result in dodgy AF. What you are trying to do here is CALIBRATE your system. You cannot do that if you do not give the system all the information it needs to get the best lock it can.

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Yet one would have to assume that this camera should be able to acquire a target and focus in on it, in this type of lighting esspecially at this distance. Afterall people do use this one with the proper lenses at weddings and simular indoor events.
You're missing the point somewhat. It will manage, but as the light levels drop off the AF system's speed and accuracy will decrease. This is normal. But you need to calibrate the system first. Think of it like tuning your car's suspension for example. You want it correctly calibrated so that when you go racing it works as best it can, but the time to try to tune it is not while you are racing it. You do the tuning under optimum conditions in the garage, THEN you go race.

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I have not made any adjustments in the cameras Fine Tune as yet, and will hold off until I do some more shooting under better lighting conditions to see how she does.
Look, don't get all freaked out over this stuff. Before these features were introduced to modern DSLRs a few years ago, it was common practice when you got a new camera or lens that you would send in ALL your cameras and ALL your lenses to be calibrated together.

Now you can do it yourself. If you get it wrong for a particular lens, there's no harm done, just remove the adjustment in the menu and try again.

It's just a menu setting that tells your camera that when a particular lens is attached - when the AF thinks it has a lock adjust focus forward or backward by x%.
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Old Feb 20, 2012, 6:24 AM   #18
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Focusing with 'LiveView' will always be spot on. It uses the image sensor to focus with. When testing for Front Focus/Back Focus, you should only be using the optical viewfinder, so you're using the Phase Detect Autofocus system. It's faster and more accurate, if it's properly calibrated so that the phase detect AF sensors are the same distance away from the lens as the image sensor is, but apparently yours isn't. (See Phase detection and Contrast measurement.)

Clearly, the Tamron 17-50/2.8 has a backfocus problem, and from the shots you took with the 28-75/2.8, I think it has a different kind of problem.
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Old Feb 20, 2012, 11:21 AM   #19
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Thank you Peripatetic and TCav for your valued input. I find this all very interesting and will continue to play at this certainly under better lighting conditions before coming to a determination as to how much of a calibration I will make. After thirty years of operating and delegating a work force in a 800MW generation facility nothing gets under my skin anylonger, believe me, and with the lose of my wife of 38 years in December....I welcome something to dwell on an work at during this time. If in the event that I should come across any new data when I make the adjustment, I will post it if you like. Thanks again.
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Old Feb 21, 2012, 3:12 PM   #20
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I moved this shot outside under the porch where the lighting was indirect. Shot all lenses once again and they appear to of focused much closer to the center. All focused nearly identical to one another, regardless of which body they were mounted to. periatetic was correct in noting the poor lighting conditions in the first group. I appreciate both of your help here. No doubt most photographers that are worth their salt go through a simular ritual with each lens they acquire to become familar with its particular nuances in relationship to availible lighting conditions before critical shoots, because quite frankly I know of a few who have never tested this and just slap a lens on and take a trial shot or two and proceed to shoot a wedding. I suppose I can understand why some of their shots weren't nailed to begin with now.
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