I fully understand all the variables that go producing a quality image
I was just asking the question would it make an image look more professional
for arguments sake , if a competent photographer took the same image ,one with kit lens one ,with a better [not more expensive]
would you see the difference
I look at flicker with images of various lenses and its all there, colour ,sharpness, tones ect
I know its not all about the lens but there must be a percentage
I come from a trade background, so I know that if a use a certain piece of equipment, that it will produce a higher quality than something from aldi
im asking whether this translates to photography
It depends on the specific shot and conditions - for some cases, you will see very little, if any difference, for others, the difference in lens will make a visible difference.
The simplest example is down to aperture - with an f/2.8 lens you have the option to shoot at f/2.8, rather than f/4 (to take the average max aperture of your current lens).
This means more light captures in the same time - so you can shoot in lower light without having to raise the ISO - which can give an improvement in the image.
You will also have less DOF with a wider aperture, which will change the appearance of the image - good if that's what you want for a given shot.
Other improvements that affect the image are better lens coatings, etc, to reduce flare when shooting with bright light sources (such as the sun) in frame (or just out of frame).
As Phil mentioned, you might get faster, more precise AF - and an in focus shot is usually considered better than one where the subject is out of focus.
BUT - buying 'better' lenses is very much a law of diminishing returns.
The kit lenses today are, in the main, capable of taking decent quality images in a wide range of conditions.
As you look at progressively 'better' lenses the cost to get the extra capabilities, IQ, etc, cost more and more - depending on what you want to photograph, you might find investing an a different lens to compliment what you have (EG a 70-300, or a 50 f/1.8) will give you wider range of options than opting to switch your existing lens to a more expensive equivalent.