Well, the 55-250mm from canon is definitely a challenge to shoot with... I will dissect #2 as an example.
for satisfactory sharpness, f/8 is required. This creates an undesirable ISO setting of 500. That is in order to achieve a relatively high shutter speed of 1/1250 sec to freeze the motion of the bird in flight and counteract my shaky hands. Now that the photo is taken, the real fun begins. Even at f/8, the lens is not overly sharp. I apply the following settings: USM sharpening, radius 2px, amount 150, threshold 200 (the second and third settings, I have found to be arbitrary and dependent upon the editing software you have chosen). The photo is now close to the sharpness that I like. The exposure must now be adjusted. This photo was ever so slightly underexposed. Tone curve is adjusted to compensate and add contrast where I want it. Compression time. Highlight and shadow compression are applied to even the lighting across the scene. The photo is noisy. Noise reduction is implemented to counteract this. Since this photo included a large amount of blue sky and green foliage, I decided to use an abnormally large level of color boosting.>SNIP>