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04-08-2015, 05:50 AM   #1
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Micro adjusting focus - How have you got on with it?

I've never bothered with micro adjusting my lenses and never really felt the need to, but today I received my 300mm F4 FA - and it's lovely.

But as with any lens I test out the shots and see how well it renders things, the sharpness wide open and so forth.

When manually focused in live view it's spot on. The lens is very sharp indeed and as sharp as my 300mm F4 A.

But when using the camera's auto focus it's a little bit out. I've tried to correct this by fine tuning the auto focus but it doesn't seem to make any difference. Be that +10 or -10. I've ruled out it being the lens as I tried my 150mm and 120 macro. Same all over with an (expected) difference in sharpness between manual and autofocus shots.

Ordinarily I'm not over critical like this. Take the lens down half a stop and it's fine so it could be a combination of things. (Camera is on a tripod too, high shutter speed).

I'm rambling I guess. But what has everyone else's experience of the AF fine tuning been?

Edit: It seems manual focus and live view focus is fine. In camera focus is off considerably. Other lenses are fine and don't behave this way.


Last edited by Chris Giles; 04-08-2015 at 06:36 AM.
04-08-2015, 06:39 AM   #2
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What camera are you using with the DA* 300mm lens? What method(s) are you testing the accuracy of the lens focus?
04-08-2015, 07:06 AM   #3
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I'm using the 645z.

Setup was the camera and lens on a sturdy tripod, pointing at a test chart as well as a book with clear text on.

I used centre point AF, then used micro adjust to see if anything changed. I noted that the difference between the lens markings and worked out that if I was going to correct it with fine tuning the AF it would be about 40-50 points out and the Z only allows 10 points either way.

With live view on and half pressing the shutter to auto focus it was pretty much spot on. But through the viewfinder af it was way out. It was only on this lens. None of my other primes showed this difference. It's already left to go for servicing at Johnsons.
04-08-2015, 07:15 AM   #4
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QuoteOriginally posted by Chris Giles Quote
I'm using the 645z.

Setup was the camera and lens on a sturdy tripod, pointing at a test chart as well as a book with clear text on.

I used centre point AF, then used micro adjust to see if anything changed. I noted that the difference between the lens markings and worked out that if I was going to correct it with fine tuning the AF it would be about 40-50 points out and the Z only allows 10 points either way.

With live view on and half pressing the shutter to auto focus it was pretty much spot on. But through the viewfinder af it was way out. It was only on this lens. None of my other primes showed this difference. It's already left to go for servicing at Johnsons.
I had an FA28 and F50 that suffered from the same fate. I just could not get them anywhere close to on plane with my K3. I read somewhere, I think, that that is a potential issue with film era lenses because where film sat in the focal plane is different than a sensor. I still own several film era lenses and luckily I have been able to calibrate them, but they range anywhere from -8 to +7 in micro adjustments. I am certain of this though, I would never purchase a high end camera that did NOT allow micro AF at this point, now that I realize how important and useful it is.

04-08-2015, 08:36 AM   #5
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LensAlign with FocusTune (assuming that software can handle 645z files) might help. But it's important to understand how to do the tests to make sure they're accurate. Lots of info on that here: https://mtd.zendesk.com/hc/en-us and here: LensAlign/FocusTune? Information Center and Discussion Forum - MTD Product Info Center (the old forum for the product - I don't think the data from there is all copied over to their newer site)

You have to make sure that everything is solidly controlled - lighting, placement of the camera and the target where they won't move, and making sure they're lined up properly, etc -- when the only factor that changes is the result of autofocus. And when you defocus the lens, you only do it a little bit, in the same direction each time (once you get the adjustment set, you can test it out from other directions and larger amounts of defocusing to verify that it doesn't need further adjustment).

If you can't do it within the adjustment the camera offers, yeah, you need to send the lens and body in so it can be adjusted (unless it's a sigma global whatever lens, then you can use their nifty lens dock).

Also, I think the camera allows a global adjustment that stacks with the local adjustment -- so if all your lenses are at least -5, you can set the global to -5 and then adjust the locals by 5 to compensate. That might help in a borderline situation. But I've never tried that, so research it first
04-08-2015, 09:32 AM   #6
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Disclaimer .. I'm not a MF shooter but I saw this thread on the homepage.

I shoot with a K-3 and I had to adjust the AF for all but one lens. My setup for checking was pretty simple. I mounted the camera on a tripod and pointed it down toward the ground at a 45 degree angle. My photo target is a piece of paper filled with text. I photograph the sheet with the lens set to the widest aperture. The sheet is rotated so the text runs vertically in the picture. With a very shallow depth of field, only the dead center of the image should be in focus. If not then the AF value should be adjusted. I perform this test at minimum focus and then double check with real world shots for longer distances. All of this is done in a somewhat controlled environment. Everything must decently well aligned and I do this during the day. Natural sunlight coming in from the window evenly illuminates the paper.

Each of my lenses required a different AF adjustment value.

The before / after difference is amazing!
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