Originally posted by axl So what I'm thinking?:
DA*200 -
smallest, lightest, but shortest. Even with TC only 300/4. Good IQ plus WR, SDM. And it's the cheapest.... but would it be long enough???
DA*300 -
daydrem for me. With TC = 450/5.6. Still WR, SDM. Great IQ and not too big and heavy. Downside? cost!!
DA*60-250/4 -
a good option. WR, SDM. Decent range (375/5.6 with TC) + flexibility of the zoom. Downside - super expensive.
Sigma 100-300/4 EX DG -
I had one for a week. Stunning IQ IMO. Great range, but no WR and SDM. And bigger than the others.
Forget about the DA*200mm, because of the bad purple fringing. 200mm is not that much for wildlife either.
Among the lenses in your list, I would go for the DA*300 because it will offer you the best image quality in a relatively small package. As this is a top quality lens, you will be able crop your pictures if you need more reach, or to use a 2x teleconverter.
From a practical point of view, my personal limit to transportability is a 300/4 lens. Anything bigger will not fit in a normal photo bag and will require a large tripod, which means that it will not get carried more than a few hundred meters from the car. So, yes, in theory the longest lens is the better one for wildlife but to me a good 300mm is much more usable than anything longer. And with the resolution offered by modern digital cameras, I can zoom 3X by cropping into a picture while retaining more than acceptable quality.
I can walk all day long with the Pentax F*300/4.5 or Leitz Telyt 400/6.8 in my bag, because they are reasonably small and light. On the other hand, my Tamron 300/2.8, Tamron 200-500/5.6 and Takumar 500/4.5 only get used for the occasional moon shot or for shooting birds across the yard. And I won't ever try crossing an airport checkpoint with my Novoflex 640/9 in the bag! For your info, here's a picture of its little brother the 400/5.6, the 640mm being much longer:
Photo credit:
Horst Neuhaus
Cheers!
Abbazz