I have been browsing elements of the 812 page manual that covers my Canon EOS R50 camera. It has 2 lenses: a wide angle jobbie at 18-45mm; and a mild telephoto at 55-210mm.
On the usual learning process of "press the button and pray" I have found that in many situations the camera gives a much better result than my previous Lumix despite having much less zoom. However I have found a function that offers a digital zoom of 2x or 4x in P mode. The manual warns that the quality of images will reduce if using these settings so I thought I would explore the results. (Note that in all cases I have resized the images to 1000 x 666 pixcels to save downloads and storage.)
The first subject was a Common Bronzewing sitting on our back fence, about 20m from our deck. The first image is the full scene as taken at 210mm.
Here is a cropped image of the bird.Full image using 4X digital zoom.
Cropped digital zoom image.
Now move to Captain Stevenson's Point where a few Bar-tailed Godwits were hanging around on a sandbar, about 300m from where I was standing (thanks Google Earth). Trust me, they are in the centre of this image.
Here is a crop from the previous image. Enlarging this makes it obvious what they are!
This is the full 4X digital zoom. At least the birds can be seen!
A crop of the previous image. Shows the birds more clearly than the previous crop.
On getting home a female Australian King Parrot was grazing on the lawn across the road. Again about 20m away. Again a simple shot at 210mm.
4x digital zoom on a 210mm lens.
Crop from above.
I need to think a little about this, but my working answer is that if the birds are fairly close I get the best result by cropping from an image with no digital zoom. However from more distant birds the 4x digital zoom does a better job.