Super Macro Brothers: the Weigh-In

I’ve been reading up on Macro photography quite a bit lately. Well, that’s not quite true… I’ve been thinking of buying a proper macro lens for several days—the Tokina 100mm f/2.8, specifically—and reading review after review and spec sheet after spec sheet, and in the process I decided to see how the macro rig (the 75-150mm E Series, reversed and extended) and the Super Macro brothers stack up against the real Macros…

So I took a bunch of pictures of a ruler.

*yawn*

And I got some pretty interesting results:

The D7000’s sensor measures 23.6mm by 15.6mm. (For Sanity, we’ll say 24×16. Also, from now on all measurements will be in millimeters unless otherwise noted.)

The macro lens I’m considering produces a 1:1 reproduction at 11″ (~4.5″ from the end of the lens).

Well, the 75-150mm f/3.5 gets close-ish:

    • Simply reversed, the 75-150 reproduces roughly 36.5 x 24.5 @ 14″ (6.75″), or 1:1.5.
    • Reversed and Extended, it reproduces 17 x 11 @ 13.75″ (3.75″), or ~1.5:1!

The 36-72mm, by contrast, does simultaneously better and worse:

    • Reversed, it reaches 13 x 9 @ 8″ (3″). ~1.75:1
    • Reversed and Extended, 7 x 4.5 @ 11″ (2″). 3.5:1!

This focusing distance is ludicrously small, and very difficult to work with. I had to move the entire set up all around to even focus on the ruler, as the depth of field becomes rather small.

Something interesting happens when they come together, though.

  • 75-150 mounted straight, 36-72 reversed, we get 5.5 x 3.75 @ 15″ (2″), or ~4.2:1
  • and both reversed yields 5.25 x 3.5 at the same 15″ from the sensor plane, or (slightly less than) 2″ from the front of the lens.

This is interesting to me. Why is there so little difference between two? It would seem that two reversed lenses would be better than one, yet it seems to matter very little whether the first lens is straight or not.

In fact, some vignetting happens when the 75-150 is on straight.

I’m sure there’s a mathematical explanation for this, but I’m not much of a mathematician. If you can help, let me know in the comments.

Now I want to get closer! Closer! How close can I get?* I don’t know, but the depth of field is going to be tiny when I get there! I can only hope the bokeh is pleasing…

*I’ll maybe get a bit closer in the next week or 10 days: I just ebayed a Nikkor 24mm f/2.8 ai and an EL-Nikkor 50mm f/2.8 photographic enlarging lens, and another set of extension tubes and some more reversing rings, and I’ll have another report when I get all that stuff played with. And I decided to hold off on the Tokina for awhile since I’m already getting to 4+:1 with the Super Macro Bros.

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