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04/03/2004 07:21:54 PM · #1 |
Last week I received my 58mm macro coupling ring from B+H, so I wanted to see what the magnification would be with my 50mm f/1.4 reversed on the end of my 100mm macro lens. I ran some "measurebation" tests, shooting a steel ruler graduated in 1/100 inch (.254mm) units.
I used the macro alone for reference(should be 1:1, or 1.00 magnification), and then started combining this with extension tubes, a 2.0x II teleconverter, and the reversed 50mm lens. All tested a minimum focus on the 100mm lens.
The following table tells the magnification story:
As you can see, the magnificaton can be very high, in excess of 6 times life size. The horizontal field of view is only 3.6mm, or 0.14 inches at this magnification. A ladybug would more than fill the frame! the DoF will, of course, be pretty darn small.
The magnification with the reversed 50mm lens is very similar to using the 2.0x II extender and 12mm extension tube. The reversed 50mm results in a much brighter viewfinder image, as we would expect, since we're not cropping the image exiting the optics as we are with the 2.0x converter.
The working distance with the reversed 50mm lens is very much shorter, however.
I foresee uses for both combinatons, and I do plan on trying some extreme magnification stuff with the whole setup. I can't wait for Summer and some interesting bugs!
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04/03/2004 07:29:39 PM · #2 |
Cool Kirbic! Do you have some test shots to show us??? :-)
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04/03/2004 07:35:39 PM · #3 |
Originally posted by kosmikkreeper:
Cool Kirbic! Do you have some test shots to show us??? :-) |
Unfortunately I would have needed to set up on-tripod with flash to test with actual images, but did not have the time. I just used the viewfinder image; this is prolly why I am getting 7% more magnification than expected with the 100mm alone; there is a very slight crop on the viewfinder.
Hoping to do some of that tomorrow in conjunction with another set-up shot I have planned.
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04/04/2004 11:14:12 AM · #4 |
Nice on the 6.xx mag! That's more than Canon's MPE 65mm lens. You should add some depth of field measurements there too!! :: wink wink , nudge nudge ::
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04/04/2004 11:54:19 AM · #5 |
You are getting 1.07:1 because the 10D viewfinder only covers (95%?) of the actual frame. Measurbation aside, thanks a lot for sharing. I've been wanting some images at 1.5:1 and I think adding extension tubes will do the trick. How close are your from the subject with the 12mm + 25mm tube?
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04/04/2004 02:09:39 PM · #6 |
Originally posted by Jacko:
You are getting 1.07:1 because the 10D viewfinder only covers (95%?) of the actual frame. Measurbation aside, thanks a lot for sharing. I've been wanting some images at 1.5:1 and I think adding extension tubes will do the trick. How close are your from the subject with the 12mm + 25mm tube? |
Yep, the 95% coverage surely contributed. I'll have to update the numbers after I do some actual imaging. the changes should be very minor, my own measuring error probably is as much a factor.
With the 12mm+25mm tubes, I'm at 4.9 inches (124mm) working distance (measured from the front element).
I was thinking that for 1.5:1 the other option would be the reversed 50mm, but with the 100mm lens set to infinity. I tried that, but it still gives over 1.8:1, so possibly too much for what you are looking to do. The working distance is also only 40mm.
The other missing parts of the equation here are the DoF and exposure compenstion. I know the reversed lens lets in much more light, at the expense of working distance. I need to document just how much difference there is. I'm thinking this combination could be hand-held (braced) with the right flash set-up.
The DoF should remain constant for a given magnification, and I should be able to calculate it w/o a problem; I don't really trust the equations in that matter though. I'll make some measurements to see what I feel is the useful DoF, & compare with the equations.
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