Seed Pod

A test with a 10x microscope objective

This is a test of a cheap microscope objective that I borrowed to test for focus stacking. It’s a very sharp 10x objective, and this image is about 10x larger than life on the camera sensor (the sensor is 36mm wide, and the objective ‘sees’ about 3.5mm across its width.

The depth of the focus range is 1.2mm, front to back (the camera was moved that far in order to focus during a series of 77 images. I made the smallest move I could by hand on the threaded shaft, and the amount of each move was 1.2/77 or approximately 15 microns per move. That’s about as small as I can do it manually; sometimes, I’m not even sure I moved it at all, but looking at the images, even the imperceptible moves were real moves. I think it’s far to say that 10X is about the highest power I could use with my manual set up.

(More advanced setups use industrial rails that can make moves as small as 2-5µm, some even smaller than that. Maybe in my future sometime?)

There were some rather serious issues with this objective. It has considerable curvature of the field over the outer third of the image; you can see blurring and various artifacts around the bright bits. But the center is really sharp, so it would be most useful for small subjects that only fill the middle third or so.

Another interesting artifact is the ‘fogginess’ around some of the details. Individual images are about 99% out of focus, and that ‘leaves a mark’ on the brighter areas when they focus stack gets stacked. I think it’s a typical result when you do deeper focus stacks (longer depth covered). There’s no way to avoid the remnants of the out of focus images with the software I have, though some (Affinity Photo, used here; and HeliconFocus) do better than others (Photoshop).

Even with the defects and artifacts, I still enjoy this image quite a bit. Perfection is out there, and perhaps even attainable—but for now, just having a blast doing macro. I plan to test as many different microscope objectives in as many different ways as I can. High magnification is cool, but wide views are also quite interesting and challenging.