Compared to a unifocal lens, a zoom lens
also has several drawbacks as well. There are disadvantages of using a
zoom lens, and following are some of the problems:
1. Compared to most unifocal lenses, zooms are larger, heavier and more
2. In general, filters and other accessories are also larger, heavier
and more expensive.
3. Maximum apertures are smaller than those of similar sized unifocal
lenses. Most lie somewhere between f/3.5 and f/4.5 with a very few
being just a bit faster. In some zooms the maximum aperture gets even
smaller as the longest focal length is reached.
4. Except for some with so called "macro-focusing" modes, zooms do not
focus as close as unifocals. Even the close focusing zooms, with their
bulk and weight, cannot match the optical performance of unifocal macro
5. A zoom lens, especially in the wide angle range, cannot be corrected
for certain aberrations as well as a unifocal lens. Negative (barrel)
distortion at the shortest setting and positive (pin cushion)
distortion at the longest setting are found to some degree in every
6. Because zooms contain a larger number of glass elements, they tend
to have more flare (light bouncing around inside the barrel and
degrading the image). Since lens hoods for zooms have to be kept small
enough to prevent their cutting into the image corners at the shortest
focal length, they are not very effective in controlling stray light.