doom9 capture guide (the first version) suggests that filtering is not needed for lo-res capturing; i suggest you take a look at this screenshot from a work i did a while ago with "in'n'out" screenshot (input video and output divx are visible)

few notes (as in-printed comment is in croatian);
"izvor" means "source"
"oko" means "round" here (otherwise "oko" means "eye")
"note" reads;"blown for better visibility"
"kodirano" means "coded"
"filter:seinfeld_t4_ss3_35_80_" refers to the .vcf file that was packaged with this screenshot (as a filter recommendation for noisy lores capturing solution) this means "temporal smoother at 4th tick,and smartsmoother with 3-35-80 setting" (newer versions of smartsmoother have one more parameter,but these three are the main ones..."diameter,treshold,amount" respectively)

352x288 image was blown(upsized) a bit so you can see the effects of filtering better
in'n'out_.jpg [this image was created 19.02.2002 in glorious days of VDub and lo-res capturing]

you decide if filtering was needed or not.........