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Archive 2015 · Spent some time listening to guys talk about lens calibration

  
 
runakid
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p.1 #1 · p.1 #1 · Spent some time listening to guys talk about lens calibration


Do all cameras and /or lenses have to be calibrated? I have a D7000 and feel that the lenses that I have work ok but am I missing something? I never thought until Saturday at L/D #14 that I might be missing something. How would I decide if calibration is needed? How would I or someone else calibrate my combination? Please let me know if this should be posted else where on FM? Be glad to move it, if necessary.


Jan 14, 2015 at 11:34 PM
chuhsi1
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p.1 #2 · p.1 #2 · Spent some time listening to guys talk about lens calibration


i always calibrate my bodies and lenses because i tend to shoot wide open.

shoot a picture at your maximum aperture. if it's sharp, you're set. if it's not, try fine tuning. search for the dot tune method here. it's easy and free.



Jan 15, 2015 at 12:22 AM
lorac
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p.1 #3 · p.1 #3 · Spent some time listening to guys talk about lens calibration


runakid wrote:
Do all cameras and /or lenses have to be calibrated? I have a D7000 and feel that the lenses that I have work ok but am I missing something? I never thought until Saturday at L/D #14 that I might be missing something. How would I decide if calibration is needed? How would I or someone else calibrate my combination? Please let me know if this should be posted else where on FM? Be glad to move it, if necessary.


How you decide is if you are not satisfied with sharpness with a particular lens in general or at specific aperture or focal length. Or if you wonder if you could do better say wide open or at the long end of a zoom. I didn't use AF fine tune for a long time, then decided to go through my lenses. I was surprised at the extra level of crispness I was able to obtain with some lenses. I agree the Dot Tune Method is the best I've tried. Here's the link not sure if for Canon or Nikon, doesn't matter since link for other brand will be included.

https://www.fredmiranda.com/forum/topic/1187247





Jan 15, 2015 at 01:50 AM
Steve Perry
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p.1 #4 · p.1 #4 · Spent some time listening to guys talk about lens calibration


I actually check all my lenses. If I see any potential issues, I calibrate the lens - and verify in the field. I feel like if you don't check / calibrate, you're not getting the most from your glass. This is especially critical for long glass or fast glass you're shooting wide open.


Jan 15, 2015 at 08:07 AM
Gunzorro
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p.1 #5 · p.1 #5 · Spent some time listening to guys talk about lens calibration


I also check all my lenses -- on all my appropriate bodies. It's time consuming, but well worth the final results.

A good way to check is to mount camera on tripod and take a photo in AF using camera's "choice" with wide open aperture (or nearly so). Without moving the tripod, switch to manual focus and live view to get precise focus at 10X or whatever is the camera's highest magnification. Compare the two. Do this for various distances from close-up to infinity. Correct the lens if needed.

Over many years using manual focus, I know there are times the image looks sharp and good-to-go in the viewfinder or LCD, only to have it pop into even sharper focus with a very minor tweak of the focus ring! Many times "good enough" is not! Precise observation and evaluation of results is your best technical skill.




Jan 15, 2015 at 10:07 AM
Jim Holtz
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p.1 #6 · p.1 #6 · Spent some time listening to guys talk about lens calibration


It's easy to test. Shoot an image with live view and one with PDAF (normal) focus and compare the two images. Live view is the gold standard to compare to since it's off the sensor.

Here are recommended settings and the fine tune process;


Set AF mode to AF-C

a1 - AF-C priority set to focus during testing. Release preferred for general photography.
a3 - Set to OFF.
a6 - Number of viewfinder focus points = 11 (optional)
f5 - Assign AEL/AFL button to AF lock only.
I choose the number of auto area focus points based on the requirements of my subject.
• 1 point for static or slow moving objects. (preferred)
• 9 points for predictable direction moving subjects without background clutter.
• 21 points for erratic moving subjects (like hummingbirds), that only fill a small portion of the scene.
With this AF set-up, keep your shutter button half pressed so the lens continuously adjusts focus until you actually fully depress the shutter. Focus and re-compose is accomplished by pushing and holding down the AFL button after subject focus is achieved.

To fine focus the camera/lens, try Dot-Tune 1st;


If Dot-Tune doesn’t satisfy you, the complete fine focus process is listed below;

What is the best way to use the Micro Focus Adjustment?

The question is simple enough, but the answer really depends on the lenses you're using and the way you use them. The point of focus can be adjusted up to +/- 20 steps in 1-step increments. Also in both cases, any adjustments you make apply only to the specific camera body in question; lenses themselves are never modified by the camera's AF micro-adjustment settings. The amount of focus adjustment per step is proportional to the maximum aperture of the lens, with the goal being to increase the precision of the adjustment with large aperture lenses since they have a smaller depth of focus. With all that as a preamble, here the procedure for selecting and using an AF micro-adjustment setting:

1. Mount the camera to a sturdy tripod.
2. Position a reference target for the camera to focus on. The reference target should have sufficient contrast for the AF system to read, should be flat and parallel to the camera's focal plane, and should be centered with respect to the picture area.
3. Print out either this Siemens Star Focus Chart or this Focus Test Chart on regular letter size paper. You can print it on a laser printer or inkjet (doesn’t really matter). Make sure to print on regular paper, not anything glossy like photo paper.
4. Scotch tape or some other adhesive material to keep the focus chart on the wall.
5. Lighting should be bright and even.
6. Camera-to-subject distance should be no less than 50 times the focal length of the lens. For a 50mm lens, that would be at least 2.5 meters, or approximately 8.2 feet.
7. Set the lens for AF and the camera for One-Shot AF, and manually select the center focusing point.
8. Shoot at the maximum aperture of the lens via manual mode or aperture-priority AE, and adjust the exposure level if necessary to achieve an accurate exposure of the reference target. Use a low ISO setting to reduce noise.
9. If the lens has an image stabilizer, shut it off.
10. Use a remote switch and/or the camera's self-timer to release the shutter. Use mirror lock as well.
11. Take three sets of images at micro-adjustment settings of -5, 0 and +5, i.e, three consecutive images at -5, three consecutive images at 0, and three consecutive images at +5. Then take a live view image for comparison.
12. Examine the resulting images on your computer monitor at 100% pixel magnification and compare each image to the live view image.
13. Take additional sets of test images at different micro-adjustment settings if necessary until the sharpest image is achieved and most closely matches the live view image.
14. Save the corresponding micro-adjustment settings in the camera.

Here are a few additional precautions to observe:

• Do not attempt to autofocus on an angled chart, because doing so will degrade the consistency of the camera's focusing measurement. Keep in mind that the camera's AF sensor is comprised of multiple pairs of linear pixel arrays. If you attempt to autofocus on a single line in an angled focusing chart, only a few pixels from each active pixel array will "see" the target. Ideally, the contrast in the reference target should cover the entire area of the camera's center focusing point, and the reference target should be perfectly parallel to the camera's focal plane.
• For best results, manually set the focus on the lens to infinity for every exposure before allowing the camera to autofocus the reference target.
• Expect some minor variations in focusing accuracy within each set of three test images, even though they were all taken at the same micro-adjustment setting. This is completely normal, and is due to the tolerances of the camera's AF system.
• Expect smaller micro-adjustment settings to have a greater effect with telephoto lenses, and vice versa for wide-angle lenses.
• If you are attempting to set micro-adjustments for a zoom lens, it is important to realize that the camera's setting may only be accurate for the focal length setting you test. The instruction book suggests testing at the longest focal length of the lens, but you may find it more efficient to choose the focal length you use most often.
• Some cameras and some zoom lenses may require more sophisticated calibration than the in-camera AF micro-adjustment settings can provide. In such cases, it may be necessary to have calibrations performed at a Factory Service Center.



Jan 15, 2015 at 10:12 AM
ckcarr
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p.1 #7 · p.1 #7 · Spent some time listening to guys talk about lens calibration


This was quite the hot topic here a year or so ago. There are lots of threads related to lens calibration.


Jan 15, 2015 at 11:00 AM
MitchSC
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p.1 #8 · p.1 #8 · Spent some time listening to guys talk about lens calibration


It may just be me being anal and thinking like an engineer, but is the OP referring to calibration (factory mechanical adjustment) or fine tuning (field adjustment).


Jan 15, 2015 at 11:31 AM
CanadaMark
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p.1 #9 · p.1 #9 · Spent some time listening to guys talk about lens calibration


I too cannot tell whether the OP is talking about factory calibration or user calibration...I will assume he's talking about user calibration.

Since my D300 in 2007 (I believe my first body with lens calibration capability), I have yet to have to calibrate a lens. I always check them, and +/- 0 has always been the best for performance. Even my cheap-o 50mm/1.8 G is bang on, CDAF and PDAF matching perfectly at F1.8 and every tested distance.

Nikon cautions against AF fine tuning, because it only works at the specific subject distance AND focal length that you fine tune it at, *possibly* making it worse at all other focal lengths and/or subject distances. It is especially tricky with zooms. Unless you have a lens that responds perfectly to a global adjustment at all subject distances and all focal lengths (some people seem to have luck with this), I would be returning the lens for a sample requiring zero AF fine tune. In ~8 years I have yet to do that, but I would personally not accept a lens that required any AF fine tuning when there are so many out there not requiring any.

In addition to this, I would not feel comfortable selling a used lens to someone knowing that it required any AF fine tune on my camera bodies, because it would likely need adjustment on theirs as well, which may or may not be possible to correct.

YMMV of course, this has just been my experience with AF fine tune.



Jan 15, 2015 at 11:52 AM
Mark_L
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p.1 #10 · p.1 #10 · Spent some time listening to guys talk about lens calibration


In day-to-day use the non-repeatablity of the phase detect af system will sometimes mask problems so it is best to check every lens against your body, with the dot-tune method is really does not take long. If you spend a lot of money on bodies and lenses it really is worth it to get the most out of them and if everything comes up bang on (unlikely) then you have good confidence in your gear. Nikon's manufacturing tolerences mean that every lens and every body don't all work well togther. If you never shoot with long lenses or wide apatures you may never notice it of course.


Jan 15, 2015 at 01:12 PM
lorac
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p.1 #11 · p.1 #11 · Spent some time listening to guys talk about lens calibration


CanadaMark wrote:
I too cannot tell whether the OP is talking about factory calibration or user calibration...I will assume he's talking about user calibration.

Since my D300 in 2007 (I believe my first body with lens calibration capability), I have yet to have to calibrate a lens. I always check them, and +/- 0 has always been the best for performance. Even my cheap-o 50mm/1.8 G is bang on, CDAF and PDAF matching perfectly at F1.8 and every tested distance.

Nikon cautions against AF fine tuning, because it only works at the specific subject distance AND focal length that you fine tune it
...Show more

I'm not sure if you realize just how very incremental these AF tune adjustments are. It's not really about need, it's about want for those who are desirous of the utmost sharpness. I've never had any lens "need" more than + or - 5, now I would be somewhat concerned about adjusting out to the extremes of AF Fine Tune. That IMO might need actual calibration.

A lens you think is fine with no adjustment, I might prefer with a wee bit of adjustment. So to say you would be returning a lens or not accept for resale one that someone preferred a bit of adjusting is a curious opinion. To each his own.




Jan 15, 2015 at 01:22 PM
CanadaMark
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p.1 #12 · p.1 #12 · Spent some time listening to guys talk about lens calibration


lorac wrote:
I'm not sure if you realize just how very incremental these AF tune adjustments are. It's not really about need, it's about want for those who are desirous of the utmost sharpness. I've never had any lens "need" more than + or - 5, now I would be somewhat concerned about adjusting out to the extremes of AF Fine Tune. That IMO might need actual calibration.

A lens you think is fine with no adjustment, I might prefer with a wee bit of adjustment. So to say you would be returning a lens or not accept for resale one that someone
...Show more

I fully understand how it works, but perhaps I did not explain myself very well. I am extremely picky, probably to a fault. On my quest for maximum sharpness, and getting the most out of my lenses, +/- zero has always given me the best results with the lenses/bodies I have owned after controlled testing & subsequent confirmation in the field. If I wanted more sharpness, it would not happen by fine tuning a +/- value. Another way to put it would be that if you had my lens/camera combination, and you preferred it with some adjustment, it would mean you preferred it to either front or back focus to some degree off of it's best setting.

Will I eventually buy a lens that requires some AF fine tune? Have I just been lucky so far? Quite possibly. I have had so many lenses requiring no AF adjustment that when I do run into one, I won't feel bad exchanging it for one that is like the rest.

PDAF in general isn't the most accurate of AF methods, especially with the distance it has to move some lens elements and various tolerances involved. You get it as close as you can though, and the D810 makes that pretty easy .



Jan 15, 2015 at 01:54 PM
Christian H
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p.1 #13 · p.1 #13 · Spent some time listening to guys talk about lens calibration


If, on the other hand, you're a photographer not an engineer, don't worry about it. This is largely a "problem" made up by pixel peepers and/or the sort of people who enjoy using tripods.



Jan 15, 2015 at 02:01 PM
runakid
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p.1 #14 · p.1 #14 · Spent some time listening to guys talk about lens calibration


Thanks for all the feedback.


Jan 15, 2015 at 02:02 PM
afm901
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p.1 #15 · p.1 #15 · Spent some time listening to guys talk about lens calibration


Christian H wrote:
If, on the other hand, you're a photographer not an engineer, don't worry about it. This is largely a "problem" made up by pixel peepers and/or the sort of people who enjoy using tripods.


Artists still need their tools to be properly calibrated. Think about a musician. Their music would not sound as good as it should if their instrument was out of tune.



Jan 15, 2015 at 02:06 PM
CanadaMark
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p.1 #16 · p.1 #16 · Spent some time listening to guys talk about lens calibration


Christian H wrote:
If, on the other hand, you're a photographer not an engineer, don't worry about it. This is largely a "problem" made up by pixel peepers and/or the sort of people who enjoy using tripods.


It is a legitimate issue that occasionally happens, and definitely not made up, or there would be no reason for camera bodies to include tools for correction.

Why should photographers not care if their equipment is working properly or about sharp images? Try telling a Bride her photos she paid $5-10K for aren't in focus because she hired a photographer and not an engineer.

How is this a problem made up by astro-photographers, landscape photographers, wildlife photorgaphers, and any others who frequently enjoy using tripods?

Obviously this issue occurs in varying degrees, combined with people's varying individual tolerances for what they consider sharp, however it should not be dismissed altogether.



Jan 15, 2015 at 03:18 PM
lorac
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p.1 #17 · p.1 #17 · Spent some time listening to guys talk about lens calibration


CanadaMark wrote:
I fully understand how it works, but perhaps I did not explain myself very well. I am extremely picky, probably to a fault. On my quest for maximum sharpness, and getting the most out of my lenses, +/- zero has always given me the best results with the lenses/bodies I have owned after controlled testing & subsequent confirmation in the field. If I wanted more sharpness, it would not happen by fine tuning a +/- value. Another way to put it would be that if you had my lens/camera combination, and you preferred it with some adjustment, it would mean
...Show more

I'm picky about sharpness too, and I absolutely believe in QC differences in terms of lenses and AF tolerances. You must have been lucky with the perfect marriages between lens and camera body, though I've had a few lenses that couldn't be improved upon with AF Fine Tune.




Jan 15, 2015 at 06:01 PM
rw11
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p.1 #18 · p.1 #18 · Spent some time listening to guys talk about lens calibration


Christian H wrote:
If, on the other hand, you're a photographer not an engineer, don't worry about it. This is largely a "problem" made up by pixel peepers and/or the sort of people who enjoy using tripods.


unfortunately, I found that to be not true when taking photos of my puppy with an 85 AF-D f1.4 lens on my D610 - now, those photos can never be repeated



Jan 15, 2015 at 07:17 PM
ADCOLE
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p.1 #19 · p.1 #19 · Spent some time listening to guys talk about lens calibration


If I'm not mistaken, wasn't there an AF issue with the D7000 series?


Jan 16, 2015 at 11:46 PM
robby521
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p.1 #20 · p.1 #20 · Spent some time listening to guys talk about lens calibration


going to have to try this with my d3s and nikon 24-70 that i just got used.its good and crisp like i want it but sometimes its not even close.if i shot it being flat it does great but when i turn it sideways and use the other buttons its seems to be off.i do move the focus square up if this makes since.


Jan 17, 2015 at 01:59 AM
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