An obviously silly question on AF fine tuning ...

[billtils]

... unless you believe that "things that are obvious often aren't" and that "the only silly questions are the ones that don't get asked".

I have just finished going through the AF fine tuning procedure because my Tamron 90mm macro lens didn't focus properly on the D810. However, when I began to get serious about macro I went on a couple of workshops with different instructors. Both advised to focus by homing in on the subject using AF then move gently and slightly back and forward to get the sharpest image in the viewfinder.

"Obviously" when it's sharp in the viewfinder it must be spot on for focus, and "silly me" for going to all the trouble of fine tuning when all that is needed is to use manual focus.

What an I missing here?

[Hanginon]

One question - are you using a tripod?

[Manfred M]

The fine tuning process is used to tweak your autofocus system so that it correctly focuses your lens(es).

The "best" way of ensuring 100% accurate focus is to set your focus manually on an enlarged view of the subject where you want sharpest focus, either magnifying and using LiveView on the back of your camera or shooting tethered and using a larger monitor screen to do your focusing. The latter is the standard way that professional video and film shooter focus their cameras. If you ever visit a production site, they generally have a large hooded screen where this is all done.

[billtils]

The fine tuning process is used to tweak your autofocus system so that it correctly focuses your lens(es).

The "best" way of ensuring 100% accurate focus is to set your focus manually on an enlarged view of the subject where you want sharpest focus, either magnifying and using LiveView on the back of your camera or shooting tethered and using a larger monitor screen to do your focusing. The latter is the standard way that professional video and film shooter focus their cameras. If you ever visit a production site, they generally have a large hooded screen where this is all done.

Makes sense Manfred, but your excellent advice doesn't apply when shooting macros of live moving bugs.

[DanK]

I move the camera to achieve focus when shooting bugs. Most macro photographers I know do so. AF just isn’t reliable with such a narrow DOF and moving subjects.

I find a monopod makes this much easier, as you can rock back and forth without moving the camera vertically. A tilt head makes it easier to position the camera correctly


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[Hanginon]

I guess my "silly question" won't be answered, so I'll assume you're not using a tripod.

I'd always wanted a Canon 5D - the original. Four 5D models later, plus people bailing out for Sony, I was able to get two 5D "classics", and some f/2.8 glass for a song. Great, except now I'm getting all these out of focus shots at f2.8 and f4. What?
I try BBF, not focusing & recompose, etc., nothing helps. Do the tripod thing, everything is sharp.

That left me as the variable. I figured out I'm moving - I'm leaning in as I depress the shutter. I've probably always been doing it, but by going to FF & 2.8 lenses, with much less depth of field, it became very noticeable.

Two Nikon FE split-image focus screens and two eyepiece magnifiers later, and using exactly the same focusing technique your workshop instructors recommended, everything is once again sharp.

[billtils]

I move the camera to achieve focus when shooting bugs. Most macro photographers I know do so. AF just isn’t reliable with such a narrow DOF and moving subjects.

I find a monopod makes this much easier, as you can rock back and forth without moving the camera vertically. A tilt head makes it easier to position the camera correctly


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Dan

I find a reliable AF gets you where you need to be for any subsequent manipulations much more quickly. A monopod? I bought one of those a few years back - must dig it out and try! Thanks for the suggestion.

[billtils]

I guess my "silly question" won't be answered, so I'll assume you're not using a tripod.
.

I'll answer it . Correct, I'm not using a tripod, but see the answer to Dan K's post above - I'm going to dig out the mono and give it a go.

[billtils]

Ha - didn't take long to remind me why the monopod was confined to a cupboard .

It is good - very good - for beasties that bask at between waist and head height. Sadly the ones around here are not inclined to bask and prefer to flit around at between knee and ground level .