Is there any negative effect when using conversion lenses?
“Vignetting” usually appears in using most of the tele lenses but only happens when the lens is zoomed at wide position. This is normal though because it is meaningless to use a tele lens to shoot at wide zoom range. Barrelling effect can be avoided if the same mounting size or above of the camera lens is used. It is recommended to take off the UV or protective filter on the camera lens before using the conversion lens in order to further enhance the optics performance.
