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Microscopy -- achieved
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PostPosted: Sat Mar 30, 2013 1:28 am    Post subject: Microscopy -- achieved Reply with quote
A few weeks ago I posted about reversing lenses on my K-7 for extreme macros -- up to 5.85X magnification with my 18mm zoom. I set a goal for achieving microscopy -- 10X magnification. To that end I bought a 55mm to 49mm male-male reverse ring. I put a 42-to-49mm step-up ring on the male-male ring and screwed the assembly into my macro bellows. With my Canon FD 24mm 2.8 mounted on the back, I managed to enlarge an area of about 1.25mm to fit the K-7's 25.6mm-wide sensor. That's a 20.48X magnification factor.

Here's what that looks like on a millimeter ruler:


I had to make a small compromise and move the lens slightly back to focus on the ruler's surface.

Here's what it looks like in the real world on tree bark and lichens:



THe DoF at this magnification looks like it's only a few microns. The small lichen spot in the second image was smaller than a pin POINT. The DoF on the images changed if I rested my hand on the tripod, and may have changed if I leaned on the tree (which is about an 24-inch caliper.) So this is pretty tricky, and fairly useless, in outside-world applications. I tried to get a flower petal, but the DoF was thinner than the petal's texture and even with no perceptible wind the flower kept moving in and out of focus. At ISO 500, f2.8, the exposure in full sun required 1/30th of a second. That's equivalent to approximately a FOUR SECOND exposure at f16 on ISO 100.

Those bark shots were 1/8th of a second at f2.8 with the camera set at ISO 400. So there's a lot of light loss.

Anyway, microscopy achieved, I now have to figure out a practical use for it and how to do it repeatedly. I think I need a heavy-duty copy stand, like an old repronar, retrofitted to hold any camera.


PostPosted: Sat Mar 30, 2013 6:56 pm    Post subject: Reply with quote
nice!!


PostPosted: Sat Mar 30, 2013 9:58 pm    Post subject: Reply with quote
Angenieux 6,5mm F1.8 Retrofocus @ F2.8, about 25:1

(A pic I made while reproducing this experiment http://www.youtube.com/watch?v=fnyBldC4Ra4)
Small format lenses are working pretty nice when reversed Smile They have a higher resolution than most normal lenses and fast apertures!


PostPosted: Sun Mar 31, 2013 9:26 am    Post subject: Re: Microscopy -- achieved Reply with quote
David wrote:
A few weeks ago I posted about reversing lenses on my K-7 for extreme macros -- up to 5.85X magnification with my 18mm zoom. I set a goal for achieving microscopy -- 10X magnification. To that end I bought a 55mm to 49mm male-male reverse ring. I put a 42-to-49mm step-up ring on the male-male ring and screwed the assembly into my macro bellows. With my Canon FD 24mm 2.8 mounted on the back, I managed to enlarge an area of about 1.25mm to fit the K-7's 25.6mm-wide sensor. That's a 20.48X magnification factor.

Here's what that looks like on a millimeter ruler:


I had to make a small compromise and move the lens slightly back to focus on the ruler's surface.

Here's what it looks like in the real world on tree bark and lichens:



THe DoF at this magnification looks like it's only a few microns. The small lichen spot in the second image was smaller than a pin POINT. The DoF on the images changed if I rested my hand on the tripod, and may have changed if I leaned on the tree (which is about an 24-inch caliper.) So this is pretty tricky, and fairly useless, in outside-world applications. I tried to get a flower petal, but the DoF was thinner than the petal's texture and even with no perceptible wind the flower kept moving in and out of focus. At ISO 500, f2.8, the exposure in full sun required 1/30th of a second. That's equivalent to approximately a FOUR SECOND exposure at f16 on ISO 100.

Those bark shots were 1/8th of a second at f2.8 with the camera set at ISO 400. So there's a lot of light loss.

Anyway, microscopy achieved, I now have to figure out a practical use for it and how to do it repeatedly. I think I need a heavy-duty copy stand, like an old repronar, retrofitted to hold any camera.


Besides a copy stand, You will also need a stage micrometer and stacking software...


PostPosted: Sun Mar 31, 2013 10:09 am    Post subject: Reply with quote
Microscopy by definition starts at 50x and requires two-stage magnification. All smaller than 50x is macro.


PostPosted: Sun Mar 31, 2013 12:59 pm    Post subject: Reply with quote
David, at that high/huge magnification you have to work with a slide stage ( velmex, newport, thorlabs,etc) and a stacking software.
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