Hand Tools

Subject:
Re: We will be going 100% sharpening perv...

Patrick Chase
Advanced photography is WAY worse than tools. My camera was $5K new, the 1X-5X macro lens I referenced is $1K, the tripod/head/rails setup for serious macro/micro work adds another $2K, etc etc.

Higher-end metallurgical scopes from Nikkor etc have numerical apertures of about 1. If we define resolution as the highest frequency with at least 10% MTF, then a perfect microscope (purely diffraction-limited, no aberrations) with an NA of 1 can resolve 1400 cycles/mm at the plane of optimal focus, or a bit better than your 1 micron guesstimate.

The catch is that resolution falls off VERY rapidly as you move out of focus. An NA of 1.0 means that the cone of light forms a ~52 degree angle an the object. Moving 1 micron out of ideal focus in either direction creates a blur disc ~1 micron in diameter. At 2 microns on either side of the plane of optimal focus MTF10 has already fallen from 1400 cyc/mm to 550 cyc/mm. Needless to say, the actual resolution that you can achieve when photographing 3D objects is quite a bit lower than these gaudy numbers would suggest.

For that reason "magnification" matters a lot less than people think, and as you say your scope is probably overpowered relative to its underlying resolution. Beyond a certain point all magnification really does is fill your eyepiece with blur. It's probably worth noting that the aforementioned Nikkor's, which have first-rate optics and basically realize the full potential of visible-band microscopy, top out at 200X or so.

SEMs have much more favorable tradeoffs because of the way they operate.

I'll post a couple images from my setup when I have some spare cycles. It does OK for edge examination. Nowhere near SEM territory, but OK.

EDIT: Fixed "100% MTF" typo. I meant 10.

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We will be going 100% sharpening perv...
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what microscope?
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Evaluation
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