CDD28 said:
I am wondering if there is a significant IQ difference between the Mk1 and Mk2 lenses?
You may have seen my write-up on choosing between the two elsewhere. Since CR seems to not allow links to other photo-sites I'll just post the text here. As you will see raw IQ is no reason to go for the MKII. Good luck with your choice!:
"I have had my new EF 300mm f/2.8 IS L ii for six months now. This review will focus on a specific question; should current owners of the EF 300mm f/2.8 IS L "upgrade" to the mark ii version?
The short answer is "no". But there are other reasons than "upgrading" to consider, and a special case for those who shoot film. So read on.
Picture Quality
Stunning. But not anymore than its predecessor. Frankly, you would be hard pressed to see the difference. It's there. And I know some tell-tale signs pixel peepers can look for. But no one can seriously argue that's its worth an upgrade for the picture IQ.
Autofocus speed
Same thing as before. I've seen claims the new lens is faster. Well, mine is not. Definitely not. I shoot a lot of tracking shots, and just as before I take 3 to make sure 1 is spot on. That's still pretty fast. And its quite impressive for all the glass that needs to move around - just not lightning fast.
IS
Here you get a noticeable upgrade. At least one stop. Also it settles faster. There is a new setting type "3" mode IS, which I personally prefer for most sports type shots. But remember that if the shutter speed is high enough its even better to turn off the IS. Finally, its somewhat less noisy than the original, which could be an important reason for film makers to upgrade.
1.4x
A slight advantage for the newer model. If I shot birds for a living maybe a consideration. But then I would certainly go with a 400mm - so not sure how important this is (YMMV). I do not use 2.0x so no comments on that except to note that several reviews mention the mark ii as a slight upgrade.
Handling & design
This is where I feel I got the most from the upgrade. Its only a little lighter, but its just that much lighter to make a difference when you are hauling it for several hours. Also, the recessed buttons are so much better. I hated it when the old ones got pushed accidentally - and it happened too often to me. The new focus function is highly useful for filming. Pre-focussing is the same, and I'm personally not a big fan of Canon's implementation now or then. I disliked the new foot design when I first used the 200mm f/2.0 IS L ii, but on the EF 300mm f/2.8 IS L ii it feels "right" because I always use it with the foot on. I also use the 90 degree clicks to position the lens, a nice, practical design detail. The hood is slightly different and handles better, but there still that awful knob to contend with.
Conclusion
As an upgrade the better IS implementation and improved handling does not match the significant price differential between the original and the mark ii. At least not for photography. If using extenders is very important to you - than just maybe. Maybe. However, if you're shooting film - go for it if you can.
The market place seems to confirm this answer. Judging from review counts on the net and the flickr pool for this lens not that many EF 300mm f/2.8 IS L ii's are flying off the shelves. I also seldom see any of these in the wild - not even at sports events. Probably a side effect of the brutal cost cuts in the traditional news industry.
But there is more to the story. The original EF 300mm f/2.8 IS L is getting older every day. Some are still relatively new, but a lot are getting ready for their 10.th anniversary. With the very good used prices you can still get for your original lens and factoring in the cost of one major repair such as the IS will bridge a lot of the gap. In addition one day Canon will not repair these anymore - just ask 200L IS L f/1.8 owners about that sad scenario. And you get a short but welcome guarantee period that could be useful.
Remember that not even Canon lenses last forever. And IS lenses simply tend to fail more than non-IS lenses.
There is still some time for current owners to enjoy their original lens. Just remember to check the market place so you are not caught off guard and miss the boat when used prices begin to drop faster. If Sigma pulls off a great 300mm f/2.8 OS with three years warranty as they have just announced - that could hurt the old used lens prices a lot."
