AF Fine Adjust

Found this chart and printed it out on photo paper. Set it at a 45 degree angle. Set the camera to AF-S, single point, and wide open. Focused on the 6, and here's what I got.



Looks like it actually focused on the 1. Is that what's called back focusing? Now I go into the settings and adjust that, correct?

Actually, I think I saw Jake say to use the most used focal length to take the test shot, which means I should probably do this again after I check lightroom to see where I shoot at most. Probably 70mm. This is a 17-70mm lens.

Though I'm still a little confused on how far the camera should be from the ruler.

Make sure you are not too close as to effect the shot by exceeding the minimum focus distance of the lens

Also used a tripod?

Yup, it's on a tripod, and the minimum focus distance is 8.something inches across all focal lengths. So, I'm good there. Thanks!

LR says I have shot 659 photos at 17mm, and 761 photos at 70mm, and various amounts in between. That's kinda close. But looks like over the long run 70mm will win, so I'll go try it again at 70mm.

Rick's exactly right. Here's a link on Lens Calibration that explains the how to fairly well, and can be followed even if you don't use the tool named in the blog.

Within that article they have a link to the LensAlign tool, and while you can spend money for something like that, the cool part about the link is the Distance Tool tab that will give you an idea of what the depth of field is for a particular camera sensor, focal length and aperture. Set the sensor type (Full Frame or 1.5 Crop for Nikons), your focal length and aperture and look in the righthand panel to see how deep your depth of field is. Change the value in the "Camera to LensAlign Distance" box until you get a DoF that you think will allow you to accurately calibrate your lens (the narrower the better). The smaller the DoF the more accurate you can be. But as Rick mentioned, make sure you're far enough away to allow for the minimum focus distance to be on your target - use single point and make sure it's on that 6 (or whatever number you choose - you're better off with something in the middle of the ruler).

Kias said:

Yup, it's on a tripod, and the minimum focus distance is 8.something inches across all focal lengths. So, I'm good there. Thanks!

LR says I have shot 659 photos at 17mm, and 761 photos at 70mm, and various amounts in between. That's kinda close. But looks like over the long run 70mm will win, so I'll go try it again at 70mm.

Click to expand...

Wider frames are more forgiving of backfocus, at least in wider vistas, so that's why I usually go for the max zoom. If your lens has the tendency to go soft at extremes back the max zoom off a bit (I did my 150-500 at around 400mm since it loses a bit of sharpness at 500).

Took some more pics and realized something was amuck as every photo looked different even though I didn't change anything. Then I realized I never turned off the stabilization. I read somewhere that it tries to compensate for shakes that aren't there when it's on a tripod, and always turn that off when it is on a tripod. So I shut it off, and the photos are now the same each time.

At 70mm wide open, here's what I got.



Again, I focused on the 6, but now I'm thinking the 7 is more in focus. Can't really tell. It might be my eyes.

You do have your aperture at maximum (wide open), right?

(edit) Ooops - you said that. Tough to tell, but it looks like it could be front focused a bit. Maybe try and bring it a little closer to narrow the DoF.

It degrades pretty fast before 5 and in front of 7. I'd say it's spot on. There are other factors involved (and these tests won't help) in the curvature of the lens, angle to the sensor outside of the focus box, ect.

I do. f/4 at 70mm is as wide as it'll go.

Are you getting unsharp pics using this lens?

Here's more of that same shot.

Rick M said:

Are you getting unsharp pics using this lens?

Click to expand...

Sometimes. Never knew if it was me or the lens. Plus I knocked over the whole camera/lens/tripod onto pavement once (Tripod was at it's lowest), and I've been freaking out ever since, and probably seeing things in my photos that aren't really there.

Now I think I know it's just me. layful:

Took a whole bunch of pics with the adjustment at various values, I think +5 seems to be the best.

Thanks for all the help, and all the links! I have something else to obsess over now.

hold on here your target is too small ..A4 ..you need to be 10 to 20 times the focal length away ..so use an expanding rule pulled out to about 4 ft set at 45 deg horisontal and focus on the 24 in ....you will see it in a trice if you zoom in on your computer screen

pistnbroke said:

hold on here your target is too small ..A4 ..you need to be 10 to 20 times the focal length away ..so use an expanding rule pulled out to about 4 ft set at 45 deg horisontal and focus on the 24 in ....you will see it in a trice if you zoom in on your computer screen

Click to expand...

Ack!

Ok, I'm on it.

wait, 10-20 times 70mm is only 2.75 - 5.5 inches away. Am I doing the math wrong?

Don't forget to try a normal view photo (someone or something you would photograph at a normal distance) to check the validity of your adjustments.

If I do it this way, this photo is at -5, and it looks like the 23 is more in focus. I'm going to wind up at 0, huh. LOL

My mistake, that was at -12. I'm at -8 now and it looks good. Think I'm gonna stick with it. Off to take some pictures!

Thanks!

may the lord help us ..70mm x10 is 700 mm a bit over 2 ft so you need to be about 3-4 ft away .

but having said that is looks good with 21 and 27 being equally blurd