I do not know, if this is the right place to ask a question from fellow photographers.

I have a Sony DSLR F-828. Good one.

But, I have a problem. When I take pictures with full zoom, ( optical zoom only ), I find that the pictures quality suffers.

The sharpness suffers. Even during sun light shots, with ample ambient light, my picture remains poor quality. I have taken shots of sun set, and get disappointed when compare my pictures with those which are already on dreams time.

Can some one please give me some reason on it?

The image here is not mine, but this is what i like, and I want to take pics like this.