Need advice for photographing artwork with a SLR camera (filter, Fuji, 50mm)

[Visvaldis]

I am an artist and paint with acrylics. Most art galleries accept only slides as submissions. Because professional photographers charge about $80 per artwork, I have been photographing my own paintings (both prints and slides).
I have a Minolta X-300 SLR Camera and do the shoots outdoors on a sunny day, but not in the direct sunlight to avoid glare spots.
My paintings (most are 2 feet by 3 feet) are often detailed, with clearly defined edges. Lately, I have been using a tripod, shooting from a distance of about 8 feet, with an aperture between 11 and 16, f-stop at 30. The colors and details have come out very well on the prints, but, when viewing the prints with a magnifying glass, the lines are somewhat blurry.
I have used a gray card, which seems to help. The film I use is ASA100, preferably Fuji. I wonder that maybe the lense is not the quality required for catching close-up detail. The lens is a Minolta MD 50mm 1:1.7, manufactured in Japan. On the lens I also use a Skylight 1A filter.
Does anyone have any ideas on how I could improve? I'm thankful for all tips and suggestions.

[dynimagelv]

A heavier tripod, a cable release and a higher shutter speed....you don't necessarily need the small aperature since depth of field is not a concern on a 2d object.

Make sure the film place is parallel to the surface of the artwork.

And practice.

and focus focus focus........

did I mention focus?