Not operator error. Perhaps the lens has been reassembled incorrectly, for example, with an element reversed. Does it show signs of having been opened up, burr marks etc?
Even if it is toast, you might want to hang on to it as a soft-focus lens. I "made" a soft focus lens from a magnifying glass, a T-mount, and a toilet paper tube that gives similar results.
As stated, this looks like one (or more) of the elements is in backwards. I learned years ago to mark the outside surface with a Sharpie. Once, someone sent me a 50/2 Summicron with three groups inserted backwards. That took a lot of trial and error to correct. Which lens is this? Perhaps looking at the optical formula will help determine which element is reversed. The Canon 100/3.5, 135/3.5, some others- the rear element is easy to put in the wrong way.
thanks for the replies. the lens is a Canon FD 28mm 2.8. I'll have a look tonight to see if it looks like it was opened up. I'd like to see if i can put it back together properly if it can be saved.
I cannot find the optical formula for that lens- not given by the Canon Museum. The rear element would be my first suspect.
It certainly would not pay to have it fixed by a pro, since you can buy it very cheaply from places like KEH LINK Canon 28mm F/2.8 FD Mount Lens {52} at KEH Camera On the other hand, even if you fouled up getting it back together, it's not much at stake. Here is a lens diagram which should be close at least: from Canon FD 28mm wideangle lenses