Would it be viable to use my camera as a low power microscope?

Question

I sometimes do pcb soldering and it is useful to have a microscope on hand with zoom of anywhere between 7x-12x to view the tiny components. I don't really want to spend several hundred dollars on a dedicated microscope though.

Would it be viable if I bought a set of cheap macro filters for my Canon t5i so I can set it up as a "microscope"? I think 5x zoom would be enough for me, and I can find a way to vertically mount my camera body. I have checked and my camera model can indeed stream video to an external computer monitor. My concern is the usable working distance and DOF.

I have no idea how my lens's focus range will change and how the DOF will change. If I need to get three inches away from my subject for a good image, it would be useless to me. I need at least 6-8 inches of clearance between my lens and subject. Is there some way I can calculate how my focus will change? Would I still be able to focus out to infinity (or "far away") if I wanted to raise my camera up an additional 12+ inches? How can I calculate that as well?

Camera body - Canon t5i

Available lenses:

• 18-135 f/3.5-5.6 kit lens
• 50mm f/1.8 STM

Answer 1

"Infinity" focus will be mapped to a finite distance. That distance is the inverse in meters of the lens strength in dioptres. If you aim for a maximum distance of 8" (roughly 0.2m) for infinity distance setting, that gives you a maximum strength for a closeup lens of 5 diopters.

A "set of cheap macro filters" will essentially be garbage with dubious sharpness and chromatic aberrations as you move from the center. Due to the limited zoom factor, you'll be able to move farther away and get better depth of field and magnification with a small-sensor superzoom (pitching for 600mm-800mm) and a moderate closeup lens (very preferably achromatic) of 3 dioptres or so.

Note that you'll also want continuous lighting sufficient for stopping down aperture as far as possible.

There is a non-zero probability that you'll be better off just taking that lighting and the intended closeup lens and mounting the closeup lens at a suitable distance between object and eye. Not going through the photographic plane will actually be a big boon with regard to things like depth of field and the impact of aberrations.

Answer 2

Consider getting a reverse ring to try to reverse the 50mm or the kit lens. There are really cheap options, without aperture control (you have to remove the lens while holding the aperture preview button...) Or more costly options, with full aperture control.

Here is the result I got when reversing my 28mm 1.8 (on full frame... about 2-3x). If you do this + extension tubes + APS-C sensor, I bet that you could achieve 5x ! Do consider using a off camera flash...

Answer 3

No, you cannot get 6 inches of working distance with your lenses and close-up adapters. For a test, I put a 10 diopter close-up on my 50mm lens. The working distance is about 3 inches, too small for your use. Also note that magnification calculation is different for a camera compared to an eye magnifier. For a camera it is the ratio of image to sensor size.

I like to define it as the size of an object that will fill the frame. This is less ambiguous.

The depth of field is poor here, but can be improved if you have a LOT of light and can stop down (this is f6.3)

Answer 4

Here is an example shot using a $20 Mini Endoscope, sometimes called a Borescope. It's not super quality but it produces real-time video so you can see what you are doing.

It has a builtin ring of LED lights that you can control the intensity of, but this shot is just ambient room light. These are sold as smart phone plugins requiring a custom app to use them, all of which are rife with terrible reviews. However this one is just a USB-C connector I plugged into my Linux machine and used "guvcview" to interface to it.