This decayed thread might need a little resuscitation and MORE about USB digital cameras - can anyone add to it.
I aim to include references in my not very popular series of ‘Community Guides’ here https://www.ispotnature.org/communities/uk-and-ireland/view/project/844368/a-series-of-community-guides
Not sure what I can add apart from maybe a couple more examples of when I’ve used it. One thing that’s annoying about my inexpensive device by Plugable is that the default resolution is 640 x 480. The highest is 1600 x 1200 and I always have to try and remember to set it to this; otherwise the result is always poor.
That sounds annoying, however the basic optics of microscopes means that the resolution is always going to be relatively poor from these ‘cheap’ devices - resolution of the sensor is not really the issue, it is diffraction caused by the optical system.
There is a trade off between size of aperture and depth of field - bigger hole giving shallower depth of field and so less in focus (fraction of a mm depth of field). So you are tempted to use smaller hole and these usb devices have a smaller hole than the very expensive microscope lenses but at these magnifications this results in a lot of image degredation by diffraction.
The way the expensive research microscopes get round this is to have high quality wide aperture objective lenses but then automatically stack lots of images above and below the focal plane to get good depth of field.
Thx, Mike, that’s very useful information. I daresay in due course I’ll opt for something of better quality, particularly if I can get more worktop space.
Oh for a focus-stacking option with these devices. Considering the Digital process it should not be too difficult.
I would stack in the old fashioned way IF the focus was a bit more stable. The whole device (all that I tested) is very lumpy when the focus lever is touched.
Yes, depth of field is the true limiting factor for these cheap USB cameras. Nonetheless, they can reveal interesting details. For a recent example, see https://www.ispotnature.org/communities/uk-and-ireland/view/observation/873890/a-bit-late-for-ifocus-seeds1
With the USB, you can see the little stalk nodule where presumably the seed was originally attached to the husk.