+15 AFMA on a New 24mm f/1.4L II - Keep or Return

[HDNitehawk]

Focal recommends 25x to 50x for target distance.

For some quick conversions that is 23.6" and 47.2"
The DOF for a 24mm on a 1D X at f/2.8 is listed on the DOF calculator at 47" as 16.7" Deep
Here is my theory, at 47.2" the 24mm will have a DOF is 35% of the distance.
It is a big target to pinpoint an exact point that is the optimal setting for accuracy.
Longer lenses would have a similar DOF but a smaller target by percentage.

I would get as close as you can.
Change the settings and at stops wider than F/2.8 as well.

I had trouble getting consistent results. A few of the things I did and maybe these will help if you are not doing them already. Set the camera and the target at the exact same height as the target. Set your camera as close as you can to square with the target both horizontal and vertical. Lighting on the 24mm is tough because you are so close. You get shadows if your lighting is only from one direction. It helps to get lights from both sides and no shadows, diffusion helps. Use the lens hood, you get stray light coming from the sides. Cover the view finder, this is very important, I have seen tests several points off because I forgot to cover the view finder before the test started.

I did quite a bit of testing on my 24mm in manual mode. I would get results from +4 to -2 that were very consistent and would have good IQ.
I have 32 files saved from the individual tests I ran with focal. I probably deleted that many when I was testing. I finally arrived at an average of +1 to +2 as the optimum setting to use.

As a comparison as primes go, I have 1 test I saved and only ran a few with my 500mm to confirm it is +0.
I ran just a few test and have 3 I saved for my 300mm f/2.8 to confirm it at +5
I have 24 files saved from my 35mm.
The wider it gets the harder the test to confirm.

Good luck with the test.
I still wouldn't hesitate sending it back if you are not sure.

[conropl]

Focal recommends 25x to 50x for target distance.

For some quick conversions that is 23.6" and 47.2"
The DOF for a 24mm on a 1D X at f/2.8 is listed on the DOF calculator at 47" as 16.7" Deep
Here is my theory, at 47.2" the 24mm will have a DOF is 35% of the distance.
It is a big target to pinpoint an exact point that is the optimal setting for accuracy.
Longer lenses would have a similar DOF but a smaller target by percentage.

I would get as close as you can.

I am pretty confident in my set up other than the distance. I was a distance quit a bit further than the distance you calculated. FoCal does publish Canon's recomendation of 50X focal distance, but suggested a distance closer to the intend use. So I moved back as far as I could and still get a lock on target and pass the "Target Test". In reading your logic, I think I agree with your approach more, and will retest at a closer distance to see how it goes. Yesterday, at high speed bursts and focussed at short distances, I was seeing a lot of variation (but that was a quick test and not as ridgedly mounted as I would like.... back to the tripod and test set up).

Below is the latest from FoCal on target distance (the last paragragh is what I focused on):

"The distance to the target will usually affect the AF microadjustment value by a small amount. As you approach minimum focus distance (MFD), the values can sometimes become quite different to the rest of the range.

What does this mean? Well, in reality, it means that you can either calibrate your lens to work as well as possible very close and not very good far away, or go for the opposite way round.

In one of their MA calibration documents, Canon recommends calibrating at 50x the focal length of the lens. This generally keeps well away from MFD and is not such a bad "standard" for all lenses.

FoCal won’t stop you calibrating at any distance, but if you are using the FoCal target and Target Validation, it will inform you if you are testing away from Canon’s recommended distance.

In practice, the distance you calibrate at is the distance that the selected AF microadjustment value will be correct for. So you should try to pick a distance that is around the "most used" distance for your particular shooting style."

Change the settings and at stops wider than F/2.8 as well.

Can you chose the apeture limits, or is this set by the software?