AF micro adjust

[jabbermack]

Hi,
I have just been having a crack at micro adjusting my 50D with a sigma 18-200mm.
On my initial attempt a week ago I adjusted the camera to +20, which I thought couldn't be right.
So I have just had another ago in the garden with good light, and my results now are completely different.
They came out at -7.
Does this sound about right to any of you that have had experience in micro adjusting or is that way off the mark.

 

[hollis_f]

What are you using for an AF target? I've read loads of posts from people who report inconsistent results and a vast majority of them are using unsuitable targets. You need something that's large enough to cover the AF point totally (remembering that the actual points are at least twice as large as the rectangles in the viewfinder). The target should be parallel to the sensor plane and it should be 20 - 50 times the focal length away.

Here's a new take on MFA that I'm planning to try as soon as we get a wind-free day.

 

[Tugster]

http://www.luminous-landscape.com/forum/index.php?topic=29881

There are some targets here and an example of the Moire effect. You may wish to read the other bits on the same site about micro adjustment.

Zooms are totally different in the way that the micro adjustment works as the micro adjustment only works at a specific distance and at a specific zoom position.

I tried with my 120-300 Sigma F/2.8
I calibrated it at the 300mm setting at approximately 30m @F/2.8

Have a read and I hope all will become clear.

Simon

http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/down_sample_files/Rings1.gif

http://www.xs4all.nl/~bvdwolf/temp/OPF/AF_Microadjust_Moire.jpg

http://www.xs4all.nl/~bvdwolf/temp/OPF/MicroFocusAdjust1.gif

 

[jabbermack]

There are quite a few ways of carrying out this procedure, that it can get quite confusing as to which is the easiest or the best.
I shall give a few of them a try and make a note of the different results.
At the moment I only have the 1 lens to set up, but I'm going to Africa next spring and hoping to buy the canon 200mm 2.8 L series to take with me.
So I would like to have everything fine tuned before I go.

Thank you for all the advice and the links, I look forward to giving them a try.

 

[Tugster]

Mick, I tried out using the targets and found it the easiest way as I had total control over everything.

Another way I tried was to place pegs in the floor at the distance I wanted to shoot...3 pegs in total in a line away form the lens with approx 2ft between each peg. So one infront of the target distance and one behind.

Then put the lens on a tripod and opened the aperture up to the max.

I had the mirror locked up and then commeced taking a few shots with AF selected. I then focussed on the middle peg and took the shots 3-4 to allevita any camera shake or movement.

Next was to examine the images to see where the focus was....either infront or behind the indicated focus point by the camera. Then I adjusted the micro adjustment then started again until the actual focus point was the same as indicated by the camera.

Time consuming but worth it. Especially when you have more than one body which you use the same lens on...

Its important to remember the max aperture to give you the smallest DOF.

Any slight knock to the lens or body now has my mind wondering if the AF needs calibrating again. Just me being a bit over pedantic !!!

Good luck

 

[hollis_f]

Any slight knock to the lens or body now has my mind wondering if the AF needs calibrating again. Just me being a bit over pedantic !!

It's been almost a year since I first did MFA on my 300 f2.8. Because I've got new TCs I thought I'd better re-do it for those. I also checked out the bare lens and there was no change, so it must be fairly stable.

I used the tethered method I linked to above. Really quick and easy - about 20 minutes for all three calibrations.