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D7000 AF fine tuning fun facts

Vlad_IT

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Vlad_IT Silver Member Nikonian since 21st Sep 2011
Sat 02-Mar-13 03:21 AM | edited Sat 02-Mar-13 03:25 AM by Vlad_IT

Hello all,

It’s late now, but i wanted to post some results from half a day of fine tuning AF system on my D7000 to the various lenses i have. I must to say that no big surprises here, just the facts:

1. My D7000 just has been serviced by Nikon and they adjusted the mirror angle as well as fine tuned AF and upgraded FW. So I will consider the AF system is well aligned.

2. The tests were done in a well-lit room, allowing 1/500 speed at ISO 100, using wide opened aperture and a good tripod. The target was a flat lens align target 8”x8” in size. AF-S with focus lock priority and center point were used.

3. Lenses manually put to infinity before each test and then to zero before the next test to make sure the focus acquired correctly while lens is rotating in either of the sides.

4. After AF acquired using in viewfinder mode, using AF-ON button, I switched to LV mode, digitally zoomed on the target and use 10x lope to read LCD display image. While still staying in LV mode I moved the focus ring left and right a bit to see if imaged will become sharper (or more blur). On the lenses that have distance window I just marked position of the distance scale. Tests for each lens were repeated at least 4-5 times. This is preliminary step to find out if the image was as sharp using AF in viewfinder mode as it would be in LV mode.

5. The Second part of the test for the same lens was to focus using LV mode (2 times – manual focus as well as AF – they always were on the same mark anyway. In this mode the distance mark (from the LV mode focusing) considered to be a “golden”/correct distance to get the sharpest image. After that the camera was switched off LV mode and focused as per #4 above (before each focusing the focus ring was moved eigher to infinity or to zero.

7. If the mark on the distance scale window matched in both cases (LV focusing and viewfinder focusing) – the lens did not require any AF Fine tuning. If the mark on the distance scale was on higher side than ‘golden” distance – than positive value had to be added for the lens AF fine tuning and vise-versa.

8. Any of my primes did not required any AF fine tuning – 35mm f1.8, 50mm f1.8, 85mm f1.8, 60G micro f2.8 and 105G VR micro f2.8 - all were good. I’m very happy to let everybody know that the primes very well made and aligned.

9. The 70-200 VRII lens required only +5 adjustments on 70mm Focal Length and did not require any adjustment on 200mm FL. So I left it at 0 as 200mm side is more important for me.

10. Sigma 50-500 OS – did not require any adjustment at all. Tested on 50mm, 70mm, 200mm, 300mm and 400mm. I did not have enough room to test on 500mm FL

11. Tamron 11-16 f2.8 – it required +20 adjustments and even then it was not perfect. I would think couple more digits would be even better (like +22/+24). But camera allows only +/-20 range. But the images were clearly much sharper when +20 adjustment was used. Tested at 11mm and 16mm

12. 17-55 f2.8 – required +19 adjustments. Tested on 17mm, 35mm and 55mm

13. A Big surprise was my old 18-135 f3.5/5.6. It did not required any adjustment. Tested at 18mm, 35mm, 70mm and 135mm. It is definitely one of the sharpest Nikon consumer zooms ever made.

Best regards,
Vlad

Here is a test from Tokina 11-16 at 14mm handheld @ 1/25 sec, F/2.8, ISO 800 100% crop (571x378 pix) out of D7000 AFTER +20 adjustment. PP'ed in LR4. looks like a quite sharp image to me for wide open. So i think Tokina is still performs well, beside the fact that it's 2-5 points under adjusted.



Click on image to view larger version


Attachment#1 (jpg file)

elec164

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#1. "RE: D7000 AF fine tuning fun facts" | In response to Reply # 0

elec164 Silver Member Nikonian since 15th Jan 2009
Fri 01-Mar-13 02:39 PM

Your experience sort of mimics mine with regard to various lenses.

Unlike you though, I find my 17-55 f/2.8 pretty much dead on. Perhaps you might consider sending it to Nikon for recalibration for -19 seems somewhat extreme.

Then again my 18-105 was always less than impressive to me, contrary to comments by many others whom post about their experiences with that lens being fairly sharp.

To sum up for me out of the six lenses I have, I only feel the need to Fine Tune two of them. The Sigma 50-150 f/2.8 with a -10 setting, and the Nikkor 18-105 f/3.5-5.6 with a -13.

Pete

Pete

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Vlad_IT

US
1354 posts

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#2. "RE: D7000 AF fine tuning fun facts" | In response to Reply # 1

Vlad_IT Silver Member Nikonian since 21st Sep 2011
Fri 01-Mar-13 04:21 PM | edited Sun 03-Mar-13 01:44 AM by Vlad_IT

>Your experience sort of mimics mine with regard to various
>lenses.
>
>Unlike you though, I find my 17-55 f/2.8 pretty much dead on.
>Perhaps you might consider sending it to Nikon for
>recalibration for -19 seems somewhat extreme.
>
>Then again my 18-105 was always less than impressive to me,
>contrary to comments by many others whom post about their
>experiences with that lens being fairly sharp.
>
>To sum up for me out of the six lenses I have, I only feel the
>need to Fine Tune two of them. The Sigma 50-150 f/2.8 with a
>-10 setting, and the Nikkor 18-105 f/3.5-5.6 with a -
>

I retested the lens at day light. 17-55 is a keeper with correct adjustment

Omaha

Omaha, US
566 posts

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#3. "RE: D7000 AF fine tuning fun facts" | In response to Reply # 0

Omaha Registered since 07th Jan 2012
Sun 03-Mar-13 03:43 AM | edited Sun 03-Mar-13 03:46 AM by Omaha

I have a question about how autofocus can vary from lens to lens.

I really don't know anything about how this stuff works, which I'm sure is why I have this question!

BUT...From what I understand, there is something inside the camera, a separate (from the main sensor) auto-focus sensor that looks at the image and decides if its in focus or not. And if is not, it orders an adjustment, either through the AF motor in the camera or through the internal AF motor in the lens, until it decides that the image is in fact in focus.

And this second, AF sensor is still optical in nature. It is "looking" at the image produced by the lens, and then using some form of electronic magic to ascertain focus and trigger the adjustments.

So then, how can the lens ever be responsible for bad auto-focus?

I can see how the body could be. If the AF sensor and the image sensor are not "synchronized", then its logical that the body would deliver consistent AF error.

But if the AF sensor (and related circuitry) are satisfied that a particular image is in focus, how can it be that the image sensor ends up seeing an image that is not?

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Vlad_IT

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#4. "RE: D7000 AF fine tuning fun facts" | In response to Reply # 3

Vlad_IT Silver Member Nikonian since 21st Sep 2011
Sun 03-Mar-13 07:15 AM | edited Sun 03-Mar-13 04:42 PM by Vlad_IT

>I have a question about how autofocus can vary from lens to
>lens.
>
>I really don't know anything about how this stuff works, which
>I'm sure is why I have this question!
>
>BUT...From what I understand, there is something inside the
>camera, a separate (from the main sensor) auto-focus sensor
>that looks at the image and decides if its in focus or not.
>And if is not, it orders an adjustment, either through the AF
>motor in the camera or through the internal AF motor in the
>lens, until it decides that the image is in fact in focus.
>
>And this second, AF sensor is still optical in nature. It is
>"looking" at the image produced by the lens, and
>then using some form of electronic magic to ascertain focus
>and trigger the adjustments.
>
>So then, how can the lens ever be responsible for bad
>auto-focus?
>
>I can see how the body could be. If the AF sensor and the
>image sensor are not "synchronized", then its
>logical that the body would deliver consistent AF error.
>
>But if the AF sensor (and related circuitry) are satisfied
>that a particular image is in focus, how can it be that the
>image sensor ends up seeing an image that is not?

Jeff, it’s an excellent question. For my 1.5 years with Nikonians I remember reading about how the phase detection AF works, but I do not remember anyone ask/answered a question like yours.

Here is a link to how AF system using viewfinder works in general:
http://photographylife.com/how-phase-detection-autofocus-works.

Best regards,
Vlad

jbloom

Wethersfield, US
7735 posts

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#5. "RE: D7000 AF fine tuning fun facts" | In response to Reply # 3

jbloom Gold Member Awarded for the continuous and generous sharing of his high level expertise and his always encouraging comments in several forums. Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014 Nikonian since 15th Jul 2004
Sun 03-Mar-13 04:11 PM

>So then, how can the lens ever be responsible for bad
>auto-focus?

The short answer is that lenses are imperfect and that AF sensors are not quite the same thing as the image sensor, so they respond to a lens' imperfections differently.

Here is a more detailed description. Although it is about the Canon AF system, the Nikon system uses the same technology:
http://www.openphotographyforums.com/forums/showthread.php?p=109296#post109296

I got that link from a long article about AF systems here:
http://www.dpreview.com/articles/5402438893/busted-the-myth-of-open-loop-phase-detection-autofocus

That's probably more information than you want, but there it is.

The important takeaway is that a lens that needs an AF Fine Tune value isn't necessarily "bad."

-- Jon
Wethersfield, CT, USA
Connecticut High School Sports Photos

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G