Scene widths for achromats on Panasonic 45-175

Discussion in 'Native Lenses' started by gardenersassistant, Jul 13, 2012.

  1. This graph shows the width of scenes covered by four achromats on the Panasonic 45-175 on a G3.

    The achromats are:
    Canon 500D (2 diopters)
    Raynox 150 (4.8 diopters)
    Raynox 250 (8 diopters)
    ADDED: Raynox 150 and 250 stacked
    Raynox MSN-202 (25 diopters)
    With the camera on a tripod and focus rail, I focused on a 1mm scale on a ruler to get the numbers for this graph. I moved the camera as near to the subject as I could while reliably being able to get the autofocus to lock on. The exact numbers measured can I think vary depending on the precise approach used.

    Approximate scene widths for achromats on Panasonic 45-175mm by gardenersassistant, on Flickr

    The kink in the line at 45mm for the 150 and 250 appears to be genuine. I double checked the 45mm and 50mm measurements and came up with the same answers.

    I took measurements at maximum and minimum zoom for the 45-200mm.

    At 45mm, within the limits and variability of my measurements, the results appeared to be the same as those for the 45-175 at 45mm.

    At 200mm, the scene widths were only very slightly smaller than for the 45-175 at 175mm, except for the Canon 500D, where the measured scene width was the same. The fractions of a mm are very rough approximations, but the sizes are something like:

    MSN-202 at 175mm, scene width 4 1/2 mm
    MSN-202 at 200mm, scene width 4 1/4 mm

    Raynox 250 at 175mm, scene width 12 1/4 mm
    Raynox 250 at 200mm, scene width 12 mm

    Raynox 150 at 175mm, scene width 19 mm
    Raynox 150 at 200mm, scene width 18 1/2 mm

    The reason I did these measurements is so that, with some on-screen measurements for a suitably aligned subject and a little simple arithmetic, I can get some idea of the size of some of the subjects I have captured.

    For example, this springtail, captured with the MSN-202, turns out to be about 2mm in length (excluding the antennae).

    0436 43 2012_07_12 P1490563 PS1b CrLet Df7x30CuSL9 Sa-Cu900hSS140x0.3 Cr by gardenersassistant, on Flickr

    In contrast, this one turns out to be about 0.4 mm. Poor quality, but it illustrates the point. (I have only recently started using the MSN-202. I have set myself a little challenge to try to get some better pictures of these little fellows - even with the MSN-202 operating with full zoom you still have to use a rather large crop for something this size).

    0434 02 2012_07_08 P1470212 Cr Df7x30CuSL9900h SS100x0.3 by gardenersassistant, on Flickr

    To illustrate the extent of the crop, here is the full frame from which it was cropped.

    P1470212 PS1 800w by gardenersassistant, on Flickr

    The calculation was as follows.

    Width of the full frame image as it shows on my computer screen, 400mm.
    Length of the subject as it shows on my computer screen, 35mm.
    So the real-world length of the subject is 35/400ths of the real world scene width of the image.

    The image was taken at 175mm with the MSN-202, so the real-world scene width was about 4.25mm.

    Therefore, the real-world subject length was 35/400*4.25 mm = 0.4 mm.
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  2. I have updated the graph to include a line for using the Raynox 150 and 250 stacked together.