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:

 Whole image

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!)

original size

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.

detail  detail sharpened

(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.

detail2 detail sharpened 1 detail sharpened2

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.