Autofocus adjustment testing target

Started Mar 4, 2013 | Discussions
coronawithlime
Senior MemberPosts: 2,214Gear list
Like?
Autofocus adjustment testing target
Mar 4, 2013

Presented entirely without comment.  I'm only relating what I THINK I observed.    If somebody wants to point out an error in this I would be grateful, because there is almost certainly some pilot error in here somewhere.

I decided to do some lens AF adjustment retesting today.  Bright sun.  No Wind.  Tripod.  Mirror up.  AF-S.  Wide open and 1/6000.  Regular stuff.  Used a Nikon 60mm f2.8 macro and a Nikon 28-70 f2.8 @ 70mm, both on a D800.  On a whim I decided to use the FoCal target outside.  Printed three of them and lined them up on a wall.  Noticed that my lenses would not focus on the target.  Live View focused ok, but using the viewfinder was a no-go.

Tried the Lens Align device and got better results, but still seemed to be a bit sluggish.  I guess that's too relative to quantify, but that seems to be the best way to describe my subjective impression.

On a whim, I downloaded and printed out one of the targets that are said to be similar to what Nikon shows in their service manual and uses in their shop.  Looked a lot like the one Thom Hogan has in his article on FA testing.

I trimmed the target and glued it on the Lens Align device in place of the oem target.

The focus operation seemed MUCH crisper and I got more consistent results.  I also got results closer to 0 AF fine tune than I had previously gotten.

I'm interpreting this to mean that my previous testing was faulty due to inconsistent focusing on a more difficult target.  Which is kinda distressing, because I had convinced myself that I did a pretty good job the first time around, but I believe I was mistaken.  

-- hide signature --

One day long ago, a sorcerer and a warrior did battle, as such things were commonplace in that age. Sometimes the sorcerer won, and the sum value of human abilities was improved some trifling amount. Sometimes the warrior won, and again the human race improved by some insignificant amount, for a sorcerer who can't defeat one miserable warrior is a poor sorcerer indeed.

Nikon D800
If you believe there are incorrect tags, please send us this post using our feedback form.
Julian Vrieslander
Contributing MemberPosts: 952
Like?
Re: Autofocus adjustment testing target
In reply to coronawithlime, Mar 4, 2013

coronawithlime wrote:

I decided to do some lens AF adjustment retesting today. Bright sun. No Wind. Tripod. Mirror up. AF-S. Wide open and 1/6000. Regular stuff. Used a Nikon 60mm f2.8 macro and a Nikon 28-70 f2.8 @ 70mm, both on a D800. On a whim I decided to use the FoCal target outside. Printed three of them and lined them up on a wall. Noticed that my lenses would not focus on the target. Live View focused ok, but using the viewfinder was a no-go.

Very odd.  I have never had problems with the FoCal target - when I use it with my D800E, I get a rapid focus lock.  I can only guess at the possible causes for what you are seeing, most of which are probably obvious for you.  Camera to target distance inappropriate for the target size?  Camara optical axis perpendicular to target?  Reflections or flare?  Are you using matte paper?  AF sensor positioned over the right area of the target?  Don't trust the bracket markings in the view finder - you may need to do a bit of testing to see the real position and extent of the sensors.

And, of course, double-check all camera settings.  I can't even guess at the number of times I have made silly mistakes in setting up shots and tests.

On a whim, I downloaded and printed out one of the targets that are said to be similar to what Nikon shows in their service manual and uses in their shop. Looked a lot like the one Thom Hogan has in his article on FA testing.

Is this the type of target with a non-periodic black and white bar pattern, similar to the one I made and uploaded here?

http://julian.marmotandweasel.com/photos/AF_target.pdf

This particular target was designed to be printed on an 8.5x11" page and placed at a distance 50x focal length of the lens you are using.  For testing the outer (line shaped) AF sensors, the bars should be oriented horizontally.  For the center (cross shaped) sensors, the orientation can be vertical or horizontal.

I get good AF lock with this target, but I can't say that it works noticeably better than the FoCal target.

I'm interpreting this to mean that my previous testing was faulty due to inconsistent focusing on a more difficult target. Which is kinda distressing, because I had convinced myself that I did a pretty good job the first time around, but I believe I was mistaken.

It might be worthwhile to do at least one run with the bar target to see if you get the same AF Fine Tune results as you got with the FoCal target.  Perhaps you won't need to run all your tests again. Let us know what you find.

Reply   Reply with quote   Complain
samjstern
Veteran MemberPosts: 6,497Gear list
Like?
Re: Autofocus adjustment testing target
In reply to coronawithlime, Mar 4, 2013

just because you got a different AF number the 2nd time does not mean it is correct.

Like going to a doctor to get a 2nd opinion.

Just beacuse it if different does not mean it is correct.

Set the AF tune to each result, take some real life pictures and compare thew results.

-- hide signature --

Sam
www.samjsternphotography.com
www.abingtonheadshots.com

 samjstern's gear list:samjstern's gear list
Nikon D70s Nikon D600 Nikon D610 Nikon D750 Nikon AF-S Nikkor 24-70mm f/2.8G ED +8 more
Reply   Reply with quote   Complain
Robin Casady
Forum ProPosts: 12,089
Like?
Re: Autofocus adjustment testing target
In reply to coronawithlime, Mar 5, 2013

coronawithlime wrote:

On a whim I decided to use the FoCal target outside. Printed three of them and lined them up on a wall. Noticed that my lenses would not focus on the target. Live View focused ok, but using the viewfinder was a no-go.

Probably not it, but what about the reflectivity of the paper? Distance to target?

-- hide signature --

Robin Casady
http://www.robincasady.com/Photo/index.html
"The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts."
— Bertrand Russell

Reply   Reply with quote   Complain
coronawithlime
Senior MemberPosts: 2,214Gear list
Like?
Re: Autofocus adjustment testing target
In reply to Julian Vrieslander, Mar 5, 2013

Julian Vrieslander wrote:

Is this the type of target with a non-periodic black and white bar pattern, similar to the one I made and uploaded here?

http://julian.marmotandweasel.com/photos/AF_target.pdf

It was your target I used    Worked much better in this instance.  Thanx for sharing.

-- hide signature --

One day long ago, a sorcerer and a warrior did battle, as such things were commonplace in that age. Sometimes the sorcerer won, and the sum value of human abilities was improved some trifling amount. Sometimes the warrior won, and again the human race improved by some insignificant amount, for a sorcerer who can't defeat one miserable warrior is a poor sorcerer indeed.

Reply   Reply with quote   Complain
coronawithlime
Senior MemberPosts: 2,214Gear list
Like?
Re: Autofocus adjustment testing target
In reply to Robin Casady, Mar 5, 2013

Robin Casady wrote:

Probably not it, but what about the reflectivity of the paper? Distance to target?

Matt paper at about 7 feet, which is close to half way between what Lens Align says is minimum and maximum.

-- hide signature --

One day long ago, a sorcerer and a warrior did battle, as such things were commonplace in that age. Sometimes the sorcerer won, and the sum value of human abilities was improved some trifling amount. Sometimes the warrior won, and again the human race improved by some insignificant amount, for a sorcerer who can't defeat one miserable warrior is a poor sorcerer indeed.

Reply   Reply with quote   Complain
coronawithlime
Senior MemberPosts: 2,214Gear list
Like?
Re: Autofocus adjustment testing target
In reply to samjstern, Mar 5, 2013

samjstern wrote:

just because you got a different AF number the 2nd time does not mean it is correct.

Like going to a doctor to get a 2nd opinion.

Just beacuse it if different does not mean it is correct.

Set the AF tune to each result, take some real life pictures and compare thew results.

Thanx Sam.  I have a weather wood landscape structure in the back yard with a bunch of big rusted nail heads in it.  The wood is real rough and grainy and seems to work well for an autofocus target when shot at an angle.  (I know, I know, but it seems to york good).  Looks like it front focuses just a tad in the real life photos.  I added a bit more positive correction and I'll see what happens over the rest of the week.

-- hide signature --

One day long ago, a sorcerer and a warrior did battle, as such things were commonplace in that age. Sometimes the sorcerer won, and the sum value of human abilities was improved some trifling amount. Sometimes the warrior won, and again the human race improved by some insignificant amount, for a sorcerer who can't defeat one miserable warrior is a poor sorcerer indeed.

Reply   Reply with quote   Complain
Testing123
Regular MemberPosts: 459Gear list
Like?
Re: Autofocus adjustment testing target
In reply to coronawithlime, Mar 5, 2013

coronawithlime wrote:

Presented entirely without comment. I'm only relating what I THINK I observed. If somebody wants to point out an error in this I would be grateful, because there is almost certainly some pilot error in here somewhere.

I decided to do some lens AF adjustment retesting today. Bright sun. No Wind. Tripod. Mirror up. AF-S. Wide open and 1/6000. Regular stuff. Used a Nikon 60mm f2.8 macro and a Nikon 28-70 f2.8 @ 70mm, both on a D800. On a whim I decided to use the FoCal target outside. Printed three of them and lined them up on a wall. Noticed that my lenses would not focus on the target. Live View focused ok, but using the viewfinder was a no-go.

Tried the Lens Align device and got better results, but still seemed to be a bit sluggish. I guess that's too relative to quantify, but that seems to be the best way to describe my subjective impression.

On a whim, I downloaded and printed out one of the targets that are said to be similar to what Nikon shows in their service manual and uses in their shop. Looked a lot like the one Thom Hogan has in his article on FA testing.

I trimmed the target and glued it on the Lens Align device in place of the oem target.

The focus operation seemed MUCH crisper and I got more consistent results. I also got results closer to 0 AF fine tune than I had previously gotten.

I'm interpreting this to mean that my previous testing was faulty due to inconsistent focusing on a more difficult target. Which is kinda distressing, because I had convinced myself that I did a pretty good job the first time around, but I believe I was mistaken.

I read that you sent your D800 to the LA facility and it came back with the center focus better, but the left and right side focus worse than when you sent it (http://forums.dpreview.com/forums/thread/3391505#forum-post-50949461).

Have you sent the camera back in the mean time or are you talking above about the same (after that service) situation?

Thanks,

Allen

 Testing123's gear list:Testing123's gear list
Nikon D810 Nikon AF-S Nikkor 24-70mm f/2.8G ED Nikon AF-S Nikkor 70-200mm f/2.8G ED VR II +1 more
Reply   Reply with quote   Complain
TOF guy
TOF guy MOD
Forum ProPosts: 11,185Gear list
Like?
Re: Autofocus adjustment testing target
In reply to coronawithlime, Mar 5, 2013

coronawithlime wrote:

some lens AF adjustment retesting today. (snip) Bright sun. (snip) got results closer to 0 AF fine tune than I had previously gotten.

Where the previous results also obtained in day light ? I'm asking because it seems that some cameras require different fine focus adjustement values for bright light and incandescent light.

-- hide signature --

Thierry - posted as regular forum member

 TOF guy's gear list:TOF guy's gear list
Nikon D810 Nikon AF-S Nikkor 70-200mm f/2.8G ED VR Nikon AF-S DX Nikkor 12-24mm f/4G ED-IF Nikon AF-S Nikkor 24-70mm f/2.8G ED Sigma 150mm F2.8 EX DG OS Macro HSM +3 more
Reply   Reply with quote   Complain
coronawithlime
Senior MemberPosts: 2,214Gear list
Like?
Re: Autofocus adjustment testing target
In reply to TOF guy, Mar 5, 2013

Well, you may have hit it.  

I had previously done all my testing inside with photo floods because of the weather.  This time I did them in bright sun.  Since probably 95% of my photos are in bright sun I started testing that way when possible.

If physical focus requirements are different depending on lighting conditions that would pose a significant challenge for me.

-- hide signature --

One day long ago, a sorcerer and a warrior did battle, as such things were commonplace in that age. Sometimes the sorcerer won, and the sum value of human abilities was improved some trifling amount. Sometimes the warrior won, and again the human race improved by some insignificant amount, for a sorcerer who can't defeat one miserable warrior is a poor sorcerer indeed.

Reply   Reply with quote   Complain
coronawithlime
Senior MemberPosts: 2,214Gear list
Like?
Re: Autofocus adjustment testing target
In reply to Testing123, Mar 5, 2013

Allen, this is the same service instance.  I decided to reevaluate my test results after the service with the idea of being able to send it in again with more information for the service tech.

I thought it might be helpful if I could say something like "the center spot focuses dead on at +6 but the left requires a -8 and the right requires a -4", and include prints along with the digital files to support the findings.

It occurs to me that the tech must have some kind of output measurement system where he gets evaluated on the quantity of work he turns around.  The less investigation he has to do himself the more likely he is to actually address the complaint. (or at least that's my optimistic fantasy for today   )

-- hide signature --

One day long ago, a sorcerer and a warrior did battle, as such things were commonplace in that age. Sometimes the sorcerer won, and the sum value of human abilities was improved some trifling amount. Sometimes the warrior won, and again the human race improved by some insignificant amount, for a sorcerer who can't defeat one miserable warrior is a poor sorcerer indeed.

Reply   Reply with quote   Complain
Testing123
Regular MemberPosts: 459Gear list
Like?
Re: Autofocus adjustment testing target
In reply to coronawithlime, Mar 6, 2013

Well, I'm taking my D800, 24-70 & 70-200 to the LA facility on Thursday. Hoping to have the camera and lenses fine-tuned together as well as have them clean the mirror box and sensor.

I'm very much hoping to be able to offer a positive report in a week or two.

Allen

 Testing123's gear list:Testing123's gear list
Nikon D810 Nikon AF-S Nikkor 24-70mm f/2.8G ED Nikon AF-S Nikkor 70-200mm f/2.8G ED VR II +1 more
Reply   Reply with quote   Complain
Keyboard shortcuts:
FForum MMy threads