1DX burst - help needed

[Besisika]

Hi all,
I am wonderring if anyone may have a theory, or have encoutered my little issue.
I am using a 1DX, YN-622c and Einstein 640.
Issue is with burst mode.
When using lenses with widest aperture less than 2.0 (I tested it with 1.2, 1.4 and 2.0) the max burst I have is around 4 fps at any aperture. Einstein at any power level, but I tested it mainly at 1/16th to be able to shoot more than 4 times.
I can reach the standard 11 fps if the widest aperture is bigger or equal to 2.8 (tested it with 2.8 and 4.0)
The focal length seems not to affect it.
All work perfectly when I put a 3-stop ND filter.

I am wonderring if it is related to the 1DX , the Yongnuo or the Einstein.
Any theory is much appreciated.

Thanks,
Besisika

 

[neuroanatomist]

Are you shooting at Xsync (1/250 s)? You need to be at 1/1000 s or faster for max burst.

 

[brad goda]

hahahahaha free advice…..