Setting backfocus with beamer (16x5.5 lens)
 

Hi all,
We recently used a 720p beamer via component to set the backfocus, as no monitor was at hand. We didn't manage a sharp image at both focal ends !!
Is that because the image on the beamer is too large ( but same resolution as the Panasonic monitor we usually have) or because our stock lens is actually deficient ?
We used the Siemens chart from the lens manual.
Thanks !