AF Fine Adjustment on E-M1 Mk II

[c12402]

After some BIF pictures using 75-300mk2 with a difficulty getting pin sharp results, I decided to calibrate the lens in the em1.2.

Two conclussions:
- the calibration System is quite good and easy to use.
- the lens had not any issue that can be corrected with calibration, when testing similar BIF cases using 40-150 Pro, my results were much better so the cheaper lens did not focus the same way a pro model did with this camera.

[Ross the fiddler]

Originally Posted by bassman

I calibrated my
12-40mm 2.8 / 45mm 1.8 / 40-150mm 2.8 and 40-150mm + mc-14
The 40-150mm + mc-14 registers in the data set, as a 56-210 F4.0

With the 12-40mm I settled at -2 Tele/ -1 Wide
40-150mm -2 Tele/ no adjustment at Wide
45mm +4
56-210mm -7 ( I probably hadn't worked out how to adjust and save both ends of zoom when I did this calibration, will check again soon )

Was working at approx distance, 25x of each focal length tested.


Mark

I still have my doubts with M4/3's lenses as it doesn't save them with actual lens ID (lens model & ser no.) as it does with 4/3's lenses where it identifies the lens & TC combination etc.
With the 40-150 Pro lens & the MC14, the MC14 is a 'dumb' device & only identified in the lens with that extra connection pin (two on the lens, for possible other TCs), which then is in the lens data reported to the camera from the lens. The MC14 has a serial number but I haven't found any serial number for it in the EXIF data though (like I can for the lens). BTW, KUSO Exif Viewer V3.0 identifies the 40-150 Pro lens as Olympus Zuiko Digital 35mm F3.5 Macro Unknown Release (16) (unlike Oly Viewer 3 which IDs it correctly + MC14) but does give the lens serial number & firmware version.

[bassman]

Think I understand Ross, must admit I'd not looked for it in EXIF data. The lens + adjustment values are in order, as I have them in my data list, on the camera.

Was confident it registered the 40-150 + mc-14 ok, because it shows as 56-210mm.
When proceed into the 'check' screen for 56-210mm, it shows the focal length + serial number of the 40-150mm but has added an 0A on the end ! ( S/N ABV****330A) presume this is recognition of the MC-14.


Mark

[super_claret]

I wonder if someone could explain step by step how to adjust for back focus. Just got the 40-150 f2.8 PRO and was photographing pheasants yesterday and focusing on the eye/head but they all came out soft. The breast of the pheasant was pin sharp though!

Is it worth sending the lens back and asking for a replacement, as I hired the same lens a few months ago and had no issues with focusing accuracy?

Thanks in advance.

[DanC.Licks]

It is important to realize that that could have nothing to do with front/back focusing. The AF sensors are out for contrast edges, and they are more abundant in feathers than around the eye. The only way to find out whether the lens/camera is really front or back focusing, which I seriously doubt given the nature of the system, is with a dedicated AF fine tuning chart. Can also make one yourself. No need to buy anything.
Important to know also which AF points were selected. Single point is the only way to really select the focus point. Give the camera more choices and it will go for whatever it thinks is best. I have the 300/4 Pro, and there are times when I want the eye and get feathers instead, but it is always with 5 or 9 points selected. Single point is the way to go on static subjects. On the focus fine tune chart it is bang on.
Here is an example from the other day:

Took care to get the focus point right on the eye. The feathers on the shoulder are much more attractive for the AF system, and at that distance, even a single AF point can be problematic.

[super_claret]

Thanks for the reply Dan. It's weird because I don't have these issues with the 300mm f4. When positioning the focus point on the birds eye/head, there was plenty of contrast in that region.

I'll obviously have to do some more tests.

[DanC.Licks]

Naturally with 300mm you will be able to be more selective.
That all said, it is strange that you had no issues with the hired lens. However, lighting conditions and subject mater play a HUGE role in AF, so it is hard to compare unless you have both side by side.

Here is one with the 300 without the MC-14, stopped down to 5.6. It is an ideal situation because the eye and the shoulder are on the same plane.

Even so, we are talking millimeters here, and the feathers just a tad closer are no longer sharp.
Full sized here:
https://c1.staticflickr.com/5/4493/3...a25a3f11_o.jpg

[GyRob]

I agree, Dan has it spot on imho .
For my checking I use a cereal box at about the distance I use with that lens i.e 300mm around 70 ft this gives a clear indication I am at leased at the longer side of how I use it and this will also cover far longer shots too .
If I only shot birds in a tree then I would set the test target at about 30ft .


Rob.

[DanC.Licks]

On top of that, we have to keep in mind that with distance comes air, and air is EVIL! AF systems hate it, and the more there is between us and our subjects, the more they complain.

[Tordan58]

Hi,

I know this is a fairly old thread. Anyway I wanted to share a useful and understandable post from DP Review which I came across in search of other information. That post touches on the pros and cons of PDAF vs. CDAF and then the necessity of tuning (or at least checking) the focus adjustment for 4/3 lenses and how to do so when using the EM-1.1. I think the method should be the same for the EM1.2 as the user interface has not changed.



The post is found here:
https://www.dpreview.com/forums/post/60174208