XT2 afc focussing with new firmware

[miguel]

I have been trying to shoot gokarts at our local track with the xt2, battery pack and a 50-140 zoom.

Shutter speeds between 1/1000 and 1/3000 to freeze the karts, apertures f2.8 and f4.

The custom focus was set to 3 which shows a gokart in the setup, should be ideal I thought.

Focussing was done using back button afc focus, held in all the time I was tracking the karts, I also tried assigning afc to the shutter button. Just for consistency I left the focus bracket in the centre of the image and used the two smallest squares to track the karts.

 

The results were a disaster, the focus was never where I wanted it, I shot at 11 fps to try that also, when I pressed the shutter on the lead kart coming towards me, it was not sharp but the 4th or 5th kart behind was reasonably sharp,

 

There is no problem with the outfit as the static shots I took are pin sharp as they should be.

 

Any ideas anyone?

[shashinman]

any samples of the disastrous images to illustrate this behaviour?

[miguel]

Afraid not, I deleted them in disgust.

 

In its simplest form, where I had 3 or 4 karts coming towards me, having tracked the first kart, it was the third or fourth kart that was the sharpest, sometimes the focus was too close to me and none of the Karts were sharp.

I deliberately used the centre single point for focus and kept the kart in the centre of the viewfinder to the best of my ability.

 

I was so disappointed because I used the centre focus point in afc mode on some static shots and they were pin sharp.

 

I shall have to go out on the street and test this setup with oncoming cars.

[miguel]

I may have found the partial answer to my problem,

Apparently if you shoot at greater than 5 fps you will have a lag in the viewfinder,

So with me shooting at 11fps what I see in the evf whilst I am tracking a fast gokart is the lastt frame exposed, not the current view.

Therefore I am tracking the subject based on the last exposed view of the sequence, meanwhile the subject has moved quite some distance suffucient to render it soft or out of focus.

 

The only thing I can not apply this solution to, is why the first frame of each sequence is not sharp?