Thread: Compound magnification

Originally Posted by rlmnshvstr8

I received my loupes in the mail. And after a day of playing around and doing a little bit more research on focal length, I can say it works. Adding two jeweler's loupes in series once placed in correct distances will produce a decent magnified image that is more than either loupe by itself. Issues that I noticed is getting the lighting at the right angle to the blade to see the scratch pattern clearly, ambient light can make the image brighter and harder to see and some light distortion as the reflected light from the blade goes through the lenses. The hardest thing was getting the lenses at the correct distances. If those are overcome this can work.

Note: it is obviously better to have a loupe or microscope with better mag if they are on hand for better optics and control. This was only for me to see if I was just wanting a little closer look and I only had two loupes to use can it be done not must it be done. And as a final note because of quality and that this is not an actual microscope you will not get to the exact multiplied value of the two loupes but at least when done right at leat 50+%

You're discovering by trial and error why good quality microscopes are expensive.

You have several problems, the first is that with a single lens you can not create perfect image of anything more than a single point - everything beyond that single point focuses into a small blot rather than a point. So you have to optimize the two lens surfaces to minimize those blots across a whole area.
The second is the chromatic aberration of a glass - minimizing that is hard and expensive materials science and you can never have a perfectly flat spectral dispersion.
Then you add a second lens and you have the exact same issues amplified by the compound magnification, as well as from the additional blurring from the image of the first lens not being exactly where the second lens expects it to be (that's why the housing of the lenses in a microscope needs to be very precisely machined and the cheap plastic stuff is not too good).
And then you have external light because your two lenses are not housed in a dark tube adding noise and decreasing the contrast.

You certainly can make it work more or less, but you will never be able to get anywhere the qualify of image that even a school-level bausch-lomb produces.

Magnification is useless without resolution (no matter how you zoom in on a blob it's still a blob), that's why the factors above that deal with resolution are what matters.

And even with very high quality microscope like carl-zeiss or leica precise focus and specific lighting is critical for utilizing the high resolution across a wide field that they offer.


On the plus side you can learn plenty with a single lens of high quality and modest magnification. Just use fixed high power directional light and move the blade (and the loupe) a bit until you find the good contrast configuration.

Strong light means your pupil contracts and reduces the blurring from the spherical and chromatic aberrations (just like camera obscura creates a clear image, while a big window doesn't). The brighter the light and the smaller piece of the bevel you want to be on focus the less the quality of the loupe matters.

P.S. The extreme brightness of LED allows for an extremely cheap microscope in origami housing made of paper http://arxiv.org/abs/1403.1211

Thank you Gugi,
From the link and the many page PDF, such a "simple" optical device requires a huge amount of study and work to become useful.
~Richard