Have another cigarette, fella. You're going to make some oncologist rich.
Look folks, I'm a fan of old prime lenses--I even own an old zoom
from the late 1970s. And that's why I say: know the capabilities of
all your lenses--but especially old zooms.
When you change lenses, you reach for the best tool for the job from
those in your bag, right? (Otherwise, why change lenses at all? Just buy
a fixed lens camera with a modern zoom and have at it. Lots of good
pictures get taken that way.)
Zooms are not "just another lens". They are massively complex. The
ones made by paper-and-pencil design (before around 1980) ranged from
OK for some subjects to horrible--and everywhere in between. Other
than being available used for cheap, there isn't much to recommend them.
Possibly a 1970s zoom with particularly good mutli-coating might
have a lower flare than the most complex modern zooms (with 15 or more
groups!), but they only way to know would be to test it. Testing loss of
contrast due to flare is not easy. So I don't view this as reason for buying
a really old zoom.
Zooms made in recent decades are a totally different story. There's no reason
to suppose a zoom made in the last 30 years isn't just as good as one made
yesterday. There have been some minor improvements, but there has always
been a lot of variation between models.
If somebody has published tests of a lens you own, great!--read it. If not,
the only way to know immediately what you've got -- a servicable lens or
a paperweight--is to test it. Otherwise you'll find out one spoiled shot at a time.
Often abberations don't get noticed until it's too late to try a different lens.
Why take the risk? Using a zoom lens isn't
manditory. Why pick
such a complicated lens if you're on a budget? The only reason I can
think of is to shoot moving subjects or portraits (where unsharpness may
actually be a plus).
I tested my 1970s zoom. It's reasonably sharp, but has some distortation.
As a result, I use it for animals, waterfalls, clouds, some sports, etc.
These subjects can move, which makes a zoom worth the lower
image quality.
Were I not still using an old film camera sometimes, I would not own tis
zoom.
Sometimes the truth takes more than one word to express--which I know
taxes the attention of people raised by the TV...