Originally posted by Neville I have a Pentax DA 55-300mm zoom lens, which has served me well with my wildlife photography and track athletics events.
However, I am intrigued by the SMC Pentax DA* 300mm F4 ED (IF) SDM prime lens, and the reviews are all very good.
The problem is that the prime lens is more than triple the price of the zoom lens.
I would like some opinions as to whether the cost warrants the benefits of getting the prime lens. In other words, I need to justify the outlay to my better half...
If price is the problem we cannot help you.
The Da*300 is one stop faster, so the lens need to be bigger and correction is more difficult to accomplish. Using a tele zoom lens on the extreme end is never the sweet spot of that lens. So, yes the DA* is worth it, but only a 300mm lens will not be enough for changing situations. You will want a second lens as well - like the DA*200. Or you have a closer look at the DA* 60-250. A stop faster than the 55-300, DA* features and 250 should be long enough for regular track and field. Ger a monopod as well.
F*300 and FA* 300 are often overpriced and offer less features than the DA*, F 4.5/300 can be found at decent prices, but old and used.