I want a new lens, but idk nothing! :/ Help

Although "only 2mm" difference. 2mm difference is far more significant at the wide end than at the tele end.

On your Kit zoom take a test shot at 18mm and then 20mm and look at the difference. Then do the same at 55mm and 53mm. Its a much larger percentage change.

You will see that a small change in mm at the wide end makes a big difference.

With the UWA filter and the 16mm lens you will have a 12mm lens. This is what I use when I want really wide shots.

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Ben Williams - UK
http://www.flickr.com/photos/hertsjoatmon/
NEX 5N / E 18-55. E 16. UWA. Fisheye. Sigma 19. / Minolta MC 50 1.4. Tamron 90 2.5 Macro. Vivitar 100 3.5 Macro. Soligor 135 2.8 / Raynox DCR-250 / 49mm CP filter / Spare battery / LIM's flash bounce. Film canister diffuser / OPTECH wriststrap
Nikon V1 / N1 10-30. N1 30-110 / Franiec Grip.
Sony TX10.