R5 When setting up focus modes, does using eye detection slow focus, compared to subject tracking?

[LaneW]

I'm setting up back button focus on my R5, specifically for birds in flight.  I have been told that using eye detection with full frame auto focus slows focusing down, as compared to, say, subject detection or face detection without eye detection activated.  Is that true?  What I am trying to do is set a back button for full frame and another for full frame plus eye - but i dont know if I need to do that. The logic being that, since the R5 is not likely to pick up the eye of a flying bird at some distance, but will easily grab the body, NOT using eye detection might be faster or more accurate?

I'd appreciate any other info you may have on set up for BIF in the R5.

[shadowsports]

Hi LaneW,

Eye detection can slow AF in comparison to subject tracking alone, but not in every situation.  A cameras focusing system does have to work a little harder to identify and prioritize eye tracking, but factors like contrast between subject and background, as well as movement can influence the overall impact to AF speed.  So in some situations, it will be slower and in others you might not notice a perceptible difference.  

[LaneW]

Thanks for this reply. Very helpful.  So what I"m struggling with and the reason for my question is this. I am finding that, when tracking a bird in flight, my r5 is not finding the bird as quickly as it once did and does not stay on the bird as I follow it.  I'm talking about a more distant bird here, with background distractions, not one that is close enough that I would expect eye focus to grab.

So in that instance, I was wondering if I should set up a BBF for one mode with eye af and another with tracking only, not eye. I have to admit, I don't know yet how to set that up, but......Does this make any sense?

Also, I am using AF Case 2 with both sliders set to -1, if that helps.