That is where the manufacturers printed material falls short in providing detailed information. The manual is full of missing details that would make it more useful to newcomers to digital photography. The camera is basically a handheld computing device that can capture light impressions and record them. With that in mind we need to remember the authors of the manufactures products are engineers and write like everybody already knows all about the industry and it's workings.

In the practical art of using a computing device, you notice some odd behavior of the device during operation, you can observe, record the events, analyze the behavior, and come to some conclusions with the end product (poor focus, wrong focus on subjects, etc).

When observing the auto focus activity (in multi-focus points), you notice more than one focus point turning red, you know the camera cannot decide which point you want and will average between the lighted points. OTOH, if one of the focus points turns red and it is not your principle subject, you should know to select another focus point.

All of this is just a small part of controlling the capture of your image, and allowing you to take control over your camera and the image it captures for you. It is also called Artistic Control, and in some Canon models is used in the Creative Mode to assist the photographer. But, you need to experiment with the focus mode selections, and the creative modes to get the best out of your camera.

One of the more popular methods of artistic control is to set the camera for Av (Aperture Value), Focus Mode = center spot, and ISO=200. The camera will meter the exposure and set exposure with shutter speed, when you lock focus on your principle subject (depressing the shutter button half way), you can compose your image in the viewfinder, and full depredd the shutter to capture the image.

Michael G

OK,
Sorry if I misjudged your comment. But if you read my comment it refers to the quality of cropped pictures taken with a bridge camera (which I have) vs. a dslr and a dslr lens (which I have). My point is that if you want to compare quality of output you need to compare both setups with a similar mm lens (which I have done) and then crop the photo to see how much detail is actually captured when you zoom in to 100% of what the sensor captured. I also said if you compare uncropped photos, it would be hard to tell the difference. But if you crop (in my example from a pic of a squirrel in a tree, crop to just the face and whiskers of the squirrel), you will find out what your setup (camera and lens) can and cannot capture.
I don't know how to make it any clearer than that. You came back with I ought to consider framing the subject better, which makes no sense to me whatsoever. Now you are talking about sensors not being being judged on the basis of different lenses. Once again I have no idea what your point is or how it addresses my comment or even the OP's original question.
Bob