Lens Tests. November 2008

November 2008 lens tests

This is not an exhaustive, or general discussion of lens testing. It is just a couple of simple examples from my current lenses, held online mostly for my own reference. There is little here to interest anyone else.

Test method is very simple. A sheet of newspaper was imaged at a repropuction ratio of 1:10 with each lens at both its widest and its mid-range aperture. Exposure was determined by the AE prism. Shown at the top is the full 6x6 frame and then for each test frame I show just a cropped section form the centre and the far top-left corner. No exposure compensation has been applied between the two cropped sections, so vignetting in the field corner may be assessed. All images were scanned and processed the same way and no software sharpening has been applied. Film was Ilford FP4 Plus.

Possible future refinements to the test

The paper was salvaged from the recycling bin and not very flat. This was exacerbated by hard side lighting.

Using black and white film is hiding any chromatic aberration or fringing.

I could perhaps have chosen a more cheerful page of the newspaper.


80mm PS f/2.8 Full frame, 1/30 @ f/8, 3.4 feet

110mm PS f/4.5 Macro 1:1 1/125 @ f/4.5, 4 feet	110mm PS f/4.5 Macro 1:1 1/15 @ f/11, 4 feet

80mm PS f/2.8 1/250 @ f/2.8, 3.4 feet	80mm PS f/2.8 1/30 @ f/8, 3.4 feet

40mm S f/4 1/60 @ f/4, 1.75 feet	40mm S f/4 1/8 @ f/11, 1.75 feet

Some thoughts

The 80mm and 110mm are both PS (final generation) lenses whereas the 40mm is from the older S series.
80mm f/2.8 is unsurprisingly the sharpest
Both 80mm and 40mm show some vignetting when wide open.
80mm and 110mm are impressively consistent across the field with very little significant softening in the corners even when wide open.
40mm is impressively sharp on axis. It is predictably soft in the corners though not much worse wide open than stopped down.

My overall impression is that all the lenses give pretty consistent performance both across the field and as a function of aperture. I am sure my 35mm would show more variation than this though sadly I did not think ahead enough to simultaneously test them with the same setup.

Following image is from the 110mm at a reproduction ratio of 1:25 as a test of its 'near infinity' performance. I am sure I could enhance the legibility of this text with software processing, but for this test I have simply applied the same defaults as for all the above images.

Lens: 110mm PS f/4.5 Macro 1:1
Exposure: 1/15 @ f/11, 10 feet, scale 1:25

Of course the macro lens is really intended for higher reproduction ratios, so to be fair, here's a small crop from a frame taken at scale of 1:2.

Lens: 110mm PS f/4.5 Macro 1:1
Exposure: 1/8 @ f/11, 1.5 feet, scale 1:2

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