I read a few post about how good the 22mm is and 15-45mm kit lens is so so. I decided to do a A-B comparision with my own lenses. The attached two croped pictures are at pixel level, taken with flash at 1/200 to minize hand-shaking. 22mm is at f4 and the kit lens is also at about 22mm at f 8. ( both are supposed at optimum f stop for best performance) I cannot tell the difference between them. My not so good eye site?? Please look at both pictures and tell me which lens is used
I would expect just about any reasonably modern lens to produce a pretty sharp image at f/8, and particularly if you are looking near the centre of the image. Lenses don't usually get a good reputation based on their performance at f/8 (unless perhaps f/8 is at or near their widest aperture, which is becoming a more relevant consideration with lenses for mirrorless systems than it was pre-mirrorless). Lenses tend to get a good, or bad, reputation for their sharpness at wider apertures, perhaps for being sharp across the whole frame (although how important sharpness towards the edges is may be arguable if a lens is likely to be used for something like portraits) and/or for a range of other characteristis such as bokeh, control of chromatic aberations, vignetting, auto-focus speed and reliability, minimum focus distance, etc. There is more to a lens than sharpness. In the end, the whole package is important, including things like size and weight, and the intended use of the lens.
If you want to compare your two lenses, I would start by comparing the sharpness of shots taken at their widest apertures (so f/2 on the 22mm prime and the widest aperture the zoom can manage when it is at 22mm), comparing shots taken at their widest common aperture (so stop down the 22mm prime to the same aperture that is the zoom's widest aperture when it is at 22mm), and perhaps comparing shots when both lenses are at f/8. Look at the sharpness towards the edges as well as in near the middle. I would also take some shots against strong backlighting to compare colour fringing on high contrast edges and metal/reflective surfaces, and some shots with a reaonably out of focus background to compare bokeh (more complex backgrounds, eg foliage, tend to show up differences in bokeh more than simple backgrounds). Test the auto-focus as best you can. There are a million other tests you could do too. And think about how and when you might use a lens (eg the fact the 22mm is so small and light may or may not be significant to you).
Another approach is simply to look at a bunch of photos taken with each lens displayed how you usually display photos (eg on a screen of a certain size, in a print of a certain size, etc) and ask yourself if you see a difference. If you don't, that's fine. You can certainly make an argument that the internet often over-states the practical differences between lenses by obsessing over differences which appear only in limited conditions and/or are unlikely to be noticed when a whole image is viewed in the way it is likely to be viewed (ie on a particular type and size of screen or print). There will almost certainly be differences between two lenses, but how much practical difference those differences can be harder to quantify (and the answer will depend on a number of factors, including how the images will be view, eg the larger an image is displayed, the more likely it is you will notice issues).
To answer you question about the two pictures you posted, image B looks a little sharper or perhaps higher contrast to me. My guess if image B is the one shot at f/8, so in this case the zoom. I won't be shocked if I am wrong though, and I agree there isn't much difference between the two images. I don't find that very surprising though given they were shot at f/4 and f/8, and particularly if you are looking near the centre of the image and the prime is the one at f/4.
