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

    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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