Image Sharpness Test
I did the following test to find out what sharpness I could get out of
my 35mm Camera.
The following photo was taken at Mt Ainslie, Canberra, on a misty day.
I used a Pentax "Program A" with a Pentax 50mm 1:1.7 lens, on a tripod.
Aperture was 8, can't remember exposure, something around 1/30 sec. The
film used was a Fuji Velvia ISO 50 slide film, known for it's sharpness
and fine grain.
After development, I scanned the picture directly from the slide at
2700dpi, on my Nikon Coolscan III. The scan has approximately 3600x2500
pixels, which equals a 9 Megapixel resolution.
This is the whole picture in low resolution, without image manipulation:
Here is a detail (large box), displayed pixel by pixel. Assuming your
monitor has around 80 dpi, the whole print at this resolution would be
about 120 cm by 80 cm large. Click on the picture to see a lossless PNG image file (large, 450 kbyte!)
This is the same detail, after applying an Unsharp Mask filter, with
radius 0.9 and 160%.
Here is a further detail (small box), approximately 100x100 pixels.
This corresponds to one squaremillimeter on the original slide.
(left image is unmanipulated, right image is with sharpening)
The same image, upscaled by 300 percent. Now, at the size you see it on
your monitor, the whole print would be 3.6 meters by 2.4 meters large.
On the left is the original upscaled image. In the middle, the image
was sharpened first, and then scaled, on the right it was scaled first
and then sharpened (radius 2.7, 200 %).
I think the resolution of the whole chain is quite satisfactory. With
some sharpening (maybe not as extreme as shown here), even a print of
one meter size would not look too blurry, even though it would lack
some detail. Prints in A4 size (20x30 cm) look absolutely fantastic.
Projections of the slides look even better, and very spectacular, also
because of the nice colour range of the Velvia film.