AF Calibration charts

I really should get round to checking the calibration of my collection of lenses - they all seem fine but I wonder if some might just benefit from a small micro-adjustment.

There are plenty of charts around - but which one do you all prefer?

None. I did try some of them but it's quite simple just to aim at an angle on the back of a corn flakes pack or something with text on at max aperture and adjust until focus is correct.

is this wide open or shut down? Sorry but I'm still learning to lingo.

Will

The more you stop down, the more of the subject will be in focus. the object is to find the centre of the focus plane so minimum DOF is required.

Wide open is best.

Yup by max aperture I mean wide open.

Thanks for the clarification

Will

Thought I didn't have a problem but have just tried that and ascertained my DFA 100mm macro was back focussing by quite a bit. Have adjusted it to +5.
Then tried my 50mm FA f2.8 Macro and it is spot on without needing any adjustment!
What I cannot understand is that if the focus looks correct in the viewfinder, why isn't it what you get? Also how can different lenses vary in their fine AF adjustment requirements? This seems to be at odds with the whole SLR concept. I don't recall any talk of this issue back in the film camera days.

John K

The problem could have still been there though.

I'll have to try it with the old lenses I was using then and see how they fare. Obviously no facility to correct them if they do need it!

John K

I found this AF chart the best as there's no ambiguity about what is being focused on. Print out the single pages near the end of the pdf.

These are the charts I've used for a couple of years.

All good information, but he makes no mention of how to setup a zoom lens for checking. Should it be set to the short end, long end, or somewhere in between? Who knows?

When using these test charts do you focus from the minimum focus distance of the lens you're testing or is there a set distance for the chart being used?

Or does it not matter?

Thanks for that link. I'm sure there is some good info there but the rough and ready cornflake packet serves the same function - the one I have has a word search on the back and that's just great!

What I am failing to grasp is how some lenses can focus OK on the viewing screen yet be out of focus on the sensor and hence need adjustment, but not others. I always use the centre point or focussing and check it visually as I would a manual lens so that is consistent.

I've just rechecked the adjusted 100mm DFA macro with the camera in manual focus mode and the adjustment I made holds good.

An explanation would be interesting and useful. If it was a camera issue and all the autofocus adjustments were consistent I'd understand, but that is not the case.

John K

Anyone come across/use Focus Tune software?

yes there is - just use the overall adjustment. You've just got to remember to reset it when changing back to other lenses.