Stroboscopic effect makes sense ... maybe the camera is actually transmitting a series of views to the viewfinder, say at 24 frames per second (like a movie) -- whereas (just looked it up) a hummingbird's wings beat at around 50 beats per second. So in that case, the camera is only showing half of the views of the hummingbird at any given time, in effect slowing the hummingbird's wings down by half. That would make sense, if that is what is actually happening.
I want to clarify that the wings in the pictures are still more or less blurry (unlike some photos I see where you see the wings crystal clear) but just the fact that I could see and photograph the wings of a hummingbird at all was amazing to me. So could we say that a digital camera viewfinder is actually showing you a series of "preshots," maybe so fast (like 24 frames per second) that you don't know you are actually watching a series of stills, just like in a movie? And then, by pressing the shutter, you are selecting one of those preshots and making it a photograph?
Is this saying the same thing as the above? And that a higher sensitivity sensor and/or larger aperture could do that?
The camera is a Nikon Coolpix (don't have the model number handy). The old camera I don't think has any significance to the question. But what kind of details would help, and how would I find them out?
On reflection, the strobing idea makes even more sense, because of what I have figured out about how autofocus works on these digital cameras. The camera sends out a tiny laser beam and uses its reflection to judge the distance of an object. I figured this out because under some conditions the tiny laser beam can be seen, especially if shooting through glass windows that have some reflectivity. This means that every time you move the camera, and the autofocus is trying to adjust by sending out tiny laser beams, each time the information from the laser beam changes there is a new potential picture in the camera. So it makes sense (to me) that what you are seeing through the viewfinder is actually a rapid series of stills, and that this creates a strobe effect that is not noticeable unless you are filming something like a hummingbird's wings in flight.