Been playing around with the motion blur and DOF in 2.4 but using 2.37 directions ( a bit different )
I noticed the DOF render iterations is eight passes. I thought first this was a combination of pathlength IPO and whatever, but it seems to be the default setting.
Motion blur uses the same samplecount option as OSA - the 5/8/11/16 buttons under the big OSA button. increase that and you’ll increase the blur sample count.