An AF Fine Adjustment setting question

Joyce Keay · 08-14-2017, 06:20 PM

Hi, I have been having focus issues with my K-70 (purchased last August) and wonder if I should play around with the AF Fine Adjustment setting. Is this something that happens often with cameras - that they are not really fine tuned when manufactured? I've been using back button focusing and have been making sure that the focus spot is dead on the subject, and have been using a cable release on my tripod. Any thoughts? Just curious. Thanks.

Adam · 08-14-2017, 06:29 PM

Originally posted by Joyce Keay

Hi, I have been having focus issues with my K-70 (purchased last August) and wonder if I should play around with the AF Fine Adjustment setting. Is this something that happens often with cameras - that they are not really fine tuned when manufactured? I've been using back button focusing and have been making sure that the focus spot is dead on the subject, and have been using a cable release on my tripod. Any thoughts? Just curious. Thanks.

If your photos are coming out sharp, then no, I wouldn't worry about applying adjustments. An easy way to test this is to compare viewfinder AF with live view AF, or you can use the full testing procedure outlined here.

But to answer your question, yes, it is considered normal for a lens-camera combo to require fine tuning within the range that you can select in-camera.

JohnX · 08-15-2017, 08:04 AM

The camera comes out of the factory set so focussing etc is within the manufacturing tolerances. The same happens with the lenses. When you combine a body with a lens you have two sets of tolerances that might not play nicely together straight off, so you use AF Fine Tuning to adjust the camera focussing to work with the lens. You need to do this for every lens.

When it comes to zoom lens, you can either fine tune for your preferred focal length, or average the adjustment between the long and short ends of the zoom.

Joyce Keay · 08-15-2017, 06:21 PM

Originally posted by JohnX

The camera comes out of the factory set so focussing etc is within the manufacturing tolerances. The same happens with the lenses. When you combine a body with a lens you have two sets of tolerances that might not play nicely together straight off, so you use AF Fine Tuning to adjust the camera focussing to work with the lens. You need to do this for every lens.

When it comes to zoom lens, you can either fine tune for your preferred focal length, or average the adjustment between the long and short ends of the zoom.

Thank you for the very easy-to-understand explanation. I did a little test today at three different focal lengths and f-stops using the viewfinder and did another set of exposures using live view. This was with a measuring tape, my camera and my tripod using my 18-135mm lens but didn't see any appreciable focus problems. I did notice, though, that f/5.6 resulted in a clearer, bolder image than f4.5 or f4.0 at various focal lengths. Does that make sense? I've ordered a focus test kit from Amazon to test more scientifically. I also have the Pentax 55-300mm lens so will do the test with both lenses

mee · 08-15-2017, 09:44 PM

Originally posted by Joyce Keay

Thank you for the very easy-to-understand explanation. I did a little test today at three different focal lengths and f-stops using the viewfinder and did another set of exposures using live view. This was with a measuring tape, my camera and my tripod using my 18-135mm lens but didn't see any appreciable focus problems. I did notice, though, that f/5.6 resulted in a clearer, bolder image than f4.5 or f4.0 at various focal lengths. Does that make sense? I've ordered a focus test kit from Amazon to test more scientifically. I also have the Pentax 55-300mm lens so will do the test with both lenses

Yes. The larger the aperture number (and thus smaller the actual aperture or 'hole' the lens makes for light to pass through) the sharper the image.. well to a degree. Once you get beyond f/11 it tends to soften again.

If you're testing AF adjustments, you'll want to test with the fastest aperture (smallest number) you have available for your lens. This will make the Depth of Field smaller (less of the scene will be in focus, just a sliver) which will aid in determining if your lens and camera combination are set properly.

In some cases 0 AF setting might be the correct setting, but it doesn't hurt to test and see (actually I'd recommend the test!).

Joyce Keay · 08-17-2017, 01:44 PM

Originally posted by JohnX

The camera comes out of the factory set so focussing etc is within the manufacturing tolerances. The same happens with the lenses. When you combine a body with a lens you have two sets of tolerances that might not play nicely together straight off, so you use AF Fine Tuning to adjust the camera focussing to work with the lens. You need to do this for every lens.

When it comes to zoom lens, you can either fine tune for your preferred focal length, or average the adjustment between the long and short ends of the zoom.

Hi, I bought a DSLRKIT focus test kit and just did a few shots to test my camera (a K-70). With the setting at 0, sharpest focus is in front (I used the scale on the right side of the kit). I'm using one dot for focusing. The scale way over on the left side of the kit shows sharpest focus is a little to the back. Now when I change the setting to -1, sharpest focus is in the back so probably the correct setting for my lens would be .5. So would it be better to leave it at 0.0 or make the change to -.1 and have the sharpest focus slightly in back of the subject? Thank you.

pschlute · 08-17-2017, 03:03 PM

Originally posted by Joyce Keay

Hi, I bought a DSLRKIT focus test kit and just did a few shots to test my camera (a K-70). With the setting at 0, sharpest focus is in front (I used the scale on the right side of the kit). I'm using one dot for focusing. The scale way over on the left side of the kit shows sharpest focus is a little to the back. Now when I change the setting to -1, sharpest focus is in the back so probably the correct setting for my lens would be .5. So would it be better to leave it at 0.0 or make the change to -.1 and have the sharpest focus slightly in back of the subject? Thank you.

Whoa hold on there. If your first test shows that the right side of the test chart is sharpest in front, and the left side shows sharpest in back....you don't have the chart aligned correctly. Either that or you have dropped your lens from a first floor window. The AF/FA setting can only correct front/back focussing. There should not be any difference left to right hand sides.

If in doubt post the pictures of your tests on here.

Joyce Keay · 08-17-2017, 06:25 PM

Originally posted by pschlute

Whoa hold on there. If your first test shows that the right side of the test chart is sharpest in front, and the left side shows sharpest in back....you don't have the chart aligned correctly. Either that or you have dropped your lens from a first floor window. The AF/FA setting can only correct front/back focussing. There should not be any difference left to right hand sides.

If in doubt post the pictures of your tests on here.

Hi, Well it looks that way to me. Perhaps my vision is off. Here's a pic of the test I ran with the fine adjustment set at 0. The yearn at the side was to help me line up the focus point with the zero. What does it look like to you? I haven't had a chance to use that lens yet. I did the same test on the 55-300 lens and used it tonight. I believe there was an improvement. Thanks. Joyce

pschlute · 08-17-2017, 07:08 PM

Check the instructions that came with the chart, you should be focussing on the target point in the middle of the chart, not the side. The chart needs to perfectly aligned with the camera.

Having sad that if your "ruler" on the extreme right of the chart is aligned with the camera, and it appears that it is, then your test is probably valid....but only for using that side of the chart....dont even look at the rest.

Joyce Keay · 08-17-2017, 07:19 PM

Originally posted by pschlute

Check the instructions that came with the chart, you should be focussing on the target point in the middle of the chart, not the side. The chart needs to perfectly aligned with the camera.

Having sad that if your "ruler" on the extreme right of the chart is aligned with the camera, and it appears that it is, then your test is probably valid....but only for using that side of the chart....dont even look at the rest.

Thanks. There were six identical charts in the package and, would you believe, not one word of instruction. I learned through a youtube video about placing the camera 50x the focal length of the lens.

pschlute · 08-17-2017, 07:51 PM

Dont rely on one single test to determine the best setting for any adjustment. Do ten tests, each time making the camera AF from the long/short ends on the focus setting. Do the same after you make any AF adjustment. That way you can be sure you got the adjustment right.

08-14-2017, 06:20 PM	#1
Joyce Keay Senior Member Join Date: Oct 2016 Posts: 123	An AF Fine Adjustment setting question Hi, I have been having focus issues with my K-70 (purchased last August) and wonder if I should play around with the AF Fine Adjustment setting. Is this something that happens often with cameras - that they are not really fine tuned when manufactured? I've been using back button focusing and have been making sure that the focus spot is dead on the subject, and have been using a cable release on my tripod. Any thoughts? Just curious. Thanks.

08-14-2017, 06:29 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	Originally posted by Joyce Keay Hi, I have been having focus issues with my K-70 (purchased last August) and wonder if I should play around with the AF Fine Adjustment setting. Is this something that happens often with cameras - that they are not really fine tuned when manufactured? I've been using back button focusing and have been making sure that the focus spot is dead on the subject, and have been using a cable release on my tripod. Any thoughts? Just curious. Thanks. If your photos are coming out sharp, then no, I wouldn't worry about applying adjustments. An easy way to test this is to compare viewfinder AF with live view AF, or you can use the full testing procedure outlined here. But to answer your question, yes, it is considered normal for a lens-camera combo to require fine tuning within the range that you can select in-camera. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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08-15-2017, 08:04 AM	#3
JohnX Pentaxian Join Date: Jul 2009 Location: London Posts: 1,116	The camera comes out of the factory set so focussing etc is within the manufacturing tolerances. The same happens with the lenses. When you combine a body with a lens you have two sets of tolerances that might not play nicely together straight off, so you use AF Fine Tuning to adjust the camera focussing to work with the lens. You need to do this for every lens. When it comes to zoom lens, you can either fine tune for your preferred focal length, or average the adjustment between the long and short ends of the zoom.

08-15-2017, 06:21 PM	#4
Joyce Keay Senior Member Join Date: Oct 2016 Posts: 123 Original Poster	Originally posted by JohnX The camera comes out of the factory set so focussing etc is within the manufacturing tolerances. The same happens with the lenses. When you combine a body with a lens you have two sets of tolerances that might not play nicely together straight off, so you use AF Fine Tuning to adjust the camera focussing to work with the lens. You need to do this for every lens. When it comes to zoom lens, you can either fine tune for your preferred focal length, or average the adjustment between the long and short ends of the zoom. Thank you for the very easy-to-understand explanation. I did a little test today at three different focal lengths and f-stops using the viewfinder and did another set of exposures using live view. This was with a measuring tape, my camera and my tripod using my 18-135mm lens but didn't see any appreciable focus problems. I did notice, though, that f/5.6 resulted in a clearer, bolder image than f4.5 or f4.0 at various focal lengths. Does that make sense? I've ordered a focus test kit from Amazon to test more scientifically. I also have the Pentax 55-300mm lens so will do the test with both lenses

08-15-2017, 09:44 PM	#5
mee Veteran Member Join Date: May 2010 Posts: 7,403	Originally posted by Joyce Keay Thank you for the very easy-to-understand explanation. I did a little test today at three different focal lengths and f-stops using the viewfinder and did another set of exposures using live view. This was with a measuring tape, my camera and my tripod using my 18-135mm lens but didn't see any appreciable focus problems. I did notice, though, that f/5.6 resulted in a clearer, bolder image than f4.5 or f4.0 at various focal lengths. Does that make sense? I've ordered a focus test kit from Amazon to test more scientifically. I also have the Pentax 55-300mm lens so will do the test with both lenses Yes. The larger the aperture number (and thus smaller the actual aperture or 'hole' the lens makes for light to pass through) the sharper the image.. well to a degree. Once you get beyond f/11 it tends to soften again. If you're testing AF adjustments, you'll want to test with the fastest aperture (smallest number) you have available for your lens. This will make the Depth of Field smaller (less of the scene will be in focus, just a sliver) which will aid in determining if your lens and camera combination are set properly. In some cases 0 AF setting might be the correct setting, but it doesn't hurt to test and see (actually I'd recommend the test!).

08-17-2017, 01:44 PM	#6
Joyce Keay Senior Member Join Date: Oct 2016 Posts: 123 Original Poster	Originally posted by JohnX The camera comes out of the factory set so focussing etc is within the manufacturing tolerances. The same happens with the lenses. When you combine a body with a lens you have two sets of tolerances that might not play nicely together straight off, so you use AF Fine Tuning to adjust the camera focussing to work with the lens. You need to do this for every lens. When it comes to zoom lens, you can either fine tune for your preferred focal length, or average the adjustment between the long and short ends of the zoom. Hi, I bought a DSLRKIT focus test kit and just did a few shots to test my camera (a K-70). With the setting at 0, sharpest focus is in front (I used the scale on the right side of the kit). I'm using one dot for focusing. The scale way over on the left side of the kit shows sharpest focus is a little to the back. Now when I change the setting to -1, sharpest focus is in the back so probably the correct setting for my lens would be .5. So would it be better to leave it at 0.0 or make the change to -.1 and have the sharpest focus slightly in back of the subject? Thank you.

08-17-2017, 03:03 PM	#7
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,202	Originally posted by Joyce Keay Hi, I bought a DSLRKIT focus test kit and just did a few shots to test my camera (a K-70). With the setting at 0, sharpest focus is in front (I used the scale on the right side of the kit). I'm using one dot for focusing. The scale way over on the left side of the kit shows sharpest focus is a little to the back. Now when I change the setting to -1, sharpest focus is in the back so probably the correct setting for my lens would be .5. So would it be better to leave it at 0.0 or make the change to -.1 and have the sharpest focus slightly in back of the subject? Thank you. Whoa hold on there. If your first test shows that the right side of the test chart is sharpest in front, and the left side shows sharpest in back....you don't have the chart aligned correctly. Either that or you have dropped your lens from a first floor window. The AF/FA setting can only correct front/back focussing. There should not be any difference left to right hand sides. If in doubt post the pictures of your tests on here.

08-17-2017, 07:08 PM	#9
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,202	Check the instructions that came with the chart, you should be focussing on the target point in the middle of the chart, not the side. The chart needs to perfectly aligned with the camera. Having sad that if your "ruler" on the extreme right of the chart is aligned with the camera, and it appears that it is, then your test is probably valid....but only for using that side of the chart....dont even look at the rest.

08-17-2017, 07:19 PM	#10
Joyce Keay Senior Member Join Date: Oct 2016 Posts: 123 Original Poster	Originally posted by pschlute Check the instructions that came with the chart, you should be focussing on the target point in the middle of the chart, not the side. The chart needs to perfectly aligned with the camera. Having sad that if your "ruler" on the extreme right of the chart is aligned with the camera, and it appears that it is, then your test is probably valid....but only for using that side of the chart....dont even look at the rest. Thanks. There were six identical charts in the package and, would you believe, not one word of instruction. I learned through a youtube video about placing the camera 50x the focal length of the lens.

08-17-2017, 07:51 PM	#11
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,202	Dont rely on one single test to determine the best setting for any adjustment. Do ten tests, each time making the camera AF from the long/short ends on the focus setting. Do the same after you make any AF adjustment. That way you can be sure you got the adjustment right.