A small comparison between medium format and 35mm image quality.


When I took these two pictures I did not intend to use them for a comparison between medium format and 35mm. However, since I had scanned both of them and I had a few hours to kill, I thought it would be an interesting exercise to compare 35mm vs 6x6.

The original 35mm was taken with Canon EOS 650 using 28-105 USM lens, on a tripod, using self timer for shutter release. The 6x6 was taken with a Mamiya C220 TLR using a 135mm lens on a tripod with cable release. In both cases, fuji velvia was used. Other image data, such as fstop and shutter speed were not recorded. The 35mm image was scanned using a Minolta Dimage Dual and the 6x6 image was scanned using Custom Process Photo Lab's Kodak Pro Photo CD service.

As is often debated, there is no simple way to campare the images based on some magnification ratio, because the formats are not the same or even similar. I chose to use the common method of figuring the magnification based on an 8x10 enlargement.

35mm format is aprox 3.6x2.4cm or 1.4inx.95in
so the aproximate magnification ratio to enlarge a 35mm to 8x10 is 8/.95=8.42.

6x6 format is aprox 5.6cm x 5.6cm, or 2.2in x 2.2in
so the aproximate magnification ratio to enlarge a 6x6 to 8x10 is 10/2.2=4.54

So the enlargement ratio between 35mm and 6x6 is 4.54/8.42=.54

The 35mm image was scanned at aproximately 2400ppi, so for comparison I wanted a medium format image at 2400*.54=1296ppi. The medium format image came from a Kodak Pro Photo cd where it was scanned at aproximately 1862ppi. I then used photoshop to resample it at 1296ppi.

Next I clipped a 600x400 section out of both images of aproximately the same region of the subject. Finally, I used autolevels, saturation and contrast, in photo shop to reduce the difference in color balances between the two images.

Below are the two resulting images:

35mm
6x6

There are not many hard conclusions that you can draw from this comparison because not all of the variables were tightly controlled, but I think it is a good indication of the difference you will see between 35mm and 6x6 images. Of course you could make the 35mm image a little sharper by using a sharper lense, a better scanner, and some photoshop magic, but the same is true of the medium format image.

The other major point about this comparison is that it is done at aproximately the scale of an 8x10 enlargment. This conclusion is based on the fact that you need aproximately 300ppi for a fine 8x10 enlargment and the 35mm images was scanned at 2400ppi (2400ppi/8 = 300ppi.) However, if you are looking at the pictures on a 90ppi monitor, a better analogy is an 8x10 print under a 3X magnifying glass.

While you are here you might want to check out some of my more interesting photographs.

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