I have had this for a couple of weeks and would like to share my impressions. Anyone that is interested in this lens has probably read the relevant technical reviews by now anyway.
Compared to the 100L macro it doesn`t look a lot longer or thicker, but there is definitely a noticeable difference. Its also a fair bit heavier.
The way I use the 100 macro is to rest it in between my thumb and pointer and my hand, its very comfortable, feels natural and allows for really steady shots and minor adjustment of the focus. Unfortunately even though the focus ring is in the same spot it doesn`t work for the 70-300L, because you cannot use the zoom from there and any movement affects your focus. It took me a while but I now hold it between the two rings and its not a problem, its better that way for fast movement/panning and fast action shots. But I still think that due to the weight of the 7D it would have been better to have reversed the two. Would be interesting to see how the balance is on a 550D for example.
My best mate has the 100-400L, so I know how much bigger and heavier it is and its one of the reasons I chose this lens. Its all-round portability, better IS and better weathersealing. Also I am chasing the kids often and needed a larger general purpose Zoom. I may well have bought this if it had been updated, newer IS, weathersealing etc.
I seriously did consider the 70-200 F4 L, but its not that much different to this one, its lighter but longer and its 100mm shorter zoom. I was really worried that I should have bought this lens instead, as its known for its quality. Funnily enough, having a cropped body, if this lens was a 50-200 F4 , I would have bought it. Anyway I took a bit of a gamble, because I still wanted a reasonable zoom length for wildlife photography or bird nerding as my wife calls it, but it needed to be as good as the 70-200L F4.
I am going to buy some bigger zoom lens in future, but I cannot justify the expense at this stage.
As far as dof is concerned, I spotted this as I was washing the car today. A nice big Huntsman spider was hanging on a thread and I focused on his rear end as I liked the way he was hanging of the spiderweb. I actually picked him up by the thread and moved him later.
F5.6, at 269mm, 1/400, iso 400. I also dialled in a bit of neg exposure, the reflection of car window wasn`t helping. There seems to be a fair bit of jpg compression going on here, these should be really sharp.
then the spider itself. 1/250 f5.6, at 300, iso 400 with flash.
I am happy with these shots, it has taken me a while to get these, bloody rain. Heard something about wettest Summer in recorded history on the radio.
Australian Wood Duck, at 300, ISO 100, F 5.6. at 1/400
Kookaburra at 300, iso 125, F 5.6, 1/500
ISO 100, F5, at 200. 1/640
I will add more pics, when the weather improves, I am especially keen to add birds in flight. The fast focusing system is what I bought the 7D and this lens for.