Linda From Maine wrote:
I have been very happy with the shots of flowers, leaves, animals, etc. that fill the frame at 250mm, so I understand now that I was expecting too much as far as clarity of (cropped) distant wildlife. Thanks so much; this was very helpful!
Interesting that you should mention cropping. You lose the megapixels you crop away from an image.
Your Canon is an 18 Megapixel camera. Filling the frame with a subject and not cropping allows you to keep all 18,000,000 pixels to post process, or print the image.
However, if the subject is actually only occupying 20% of the full view finder and you crop the 80% you don't want to keep, you are only keeping 3,600,000 or 3.6Megapixels of your original capture. That is very severe and a reduction of 80% of your resolution. The new file will now not provide as much resolution as your camera is capable of, nor will the image print up to the same size with the same clarity as the original image.
Cropping is a good tool for small to moderate improvements in aspect ratio and composition, but it's an image killer used in the extreme I offered. I know I will tweak a digital file a bit with cropping, but I prefer to keep it to a minimum.
Sorry to beat on this, but yet another argument for getting closer to the subject, filling the viewfinder, and avoiding large crops or throwing away significant portions of your megapixels.
So, some may say,,,, "why are we paying such huge prices for these telephoto lenses, when we could get by with a $20 pair of Keds?" Unfortunately wildlife and baby/infant/child photography (from the time they walk, until they quit running) is about getting as close as possible and using the Telephoto to close that last little bit of distance.
Or buying that $8000 telephoto at 800mm.