Originally posted by aaronjamesgray
Thank you Igor. I'd love to have a good telephoto prime but it's not in the cards in the moment. Do you think the 100 would be worth shooting with there? I should note also that I'll be in the crowd, not up close, but not too far either.
You can always crop and the 100mm is plenty sharp, but to get a "large" sharp shot of a couple of torsos and some sweat/teeth flying =), I think it may be a bit on the borderline with a 100 on a K5 16mpix even with cropping.
But I'm no expert on these shots, haven't done a lot of similar so better wait for someone more knowledgeable =). (For example my guess would be that the 100 wide open+crop would give you similar if not better shots than the 18-200@200@6.3, but I've got no experience from that particular lens, and it was a couple of years since I had a K5 and 100mm (not the II), so I think others will have more valid thoughts).
But if the K5II is similar to the K5 in focusing, I'd say not to use AF but pre-focus manually and shoot when the action happens at the distance you've focused on, othewise the af will delay your shots, miss some in time and some in focus. (And if the lighting allows you to use a F-stop/iso/shutterspeed combination that allows for a depth of field that captures a lot of the ring, all the better). Also if you have a memory card that allows it it's better to do some "pray and spray" for maximum number of keepers rather than being selective about framing etc. and getting a good percentage but low total overall.
While talking about manual focusing and lba =), if I may give one suggestion in that direction it could be the Pentax-M 200 F4. I think it can be had for $50 if lucky or up to twice that if in a hurry (without having checked, I might be somewhat off), but while manual it's ok sharp even wide open, especially on aps-c (I think the PF score is perhaps a bit low just because f4), and at f4 not superfast but more total resolving power vs distance/light than you have now I think.
Now wait and let someone that actually knows something give some advice =)
Edit: Seems the M 200mm F4 can be had for as low as $25 in the states if lucky, or less than 50 at least, so might be an option!