Originally posted by JohnBee I know there are alot of oppinions here but I'm going to go out on a limb and say that birding really starts at or around 600mm.
Whatever the case, if I was a birder, I would likely shoot with a different kit(Canon most likely).
Hope this doesn't come across as provocative, but that's my opinion on the issue.
I beg to differ. birding does not start at 600mm
go back to the math.
image size = subject size * focal length / subject distance
while it looks like yes longer is better. consider shooting a bird like a chickadee, which is only about 100mm long.
If you want to fill a frame (and being a pentax forum, consider ASP-C) at 24mm (ill call this 25 to make the math easy) the ratio of focal length to subject distance is 1/4
getting close is much more cost effective than getting a long lens, assuming the long lens can focus that close in the first place.
also note that the weight of any 600mm lens plus the tripod, means that you are staked out in a blind, and stationary. in that case, you probably don't need 600mm at any rate.
sure, for big birds, you can be 10x further back, but those birds are generally easy to shoot.
and just to be clear, the following, which I have posted before was taken with the FA28-105F4-5.6 at 105mm, and was taken totally in the wild.