Filter selection normally has one chosing type, eg. maximaly flat, linear phase, equi-
ripple, pulse response, cheby, bessel, ......but in this case it seems main purpose of
filter to reject body movement and high ambient light levels.
One suggestion to the image posted by Bob. Try reducing the filter gain from 0dB to some -ve value. If the filter gain is set to 0dB, you can see that there are ringing above 1. So this could saturate your filter if you do not handle your input & outputs properly. In order to avoid this, you can reduce the filter gain to a value so that step function peak is well within '1'.