I am actually in a bind myself, having gotten into Nikon gear with the D700 mostly for its great high ISO performance; thought of selling my 5D, but it’s this particular 100-400L lens has me hesitating – at least until I find an appropriate replacement for it on the D700.

A couple data points, this is 1/4 of the frame of a magnolia shot at 400mm 1/400 F5.6 ISO 1000
http://www.flickr.com/photos/nycandre/3452707338/
And at the short end, 100mm at 1/200 F5.6 ISO 1600 (handheld!)
http://www.flickr.com/photos/nycandre/5634034954/

I’ve been tied between this lens and the Canon 100-400 L lens for over a month now, as both are the same price here… As far as I can tell the Canon is just a tad sharper, but only just. I’m primarily a wildlife/nature photographer and I wanted something with nice reach, so the extra 100mm on the Sigma was interesting to me. I’m not sure if the opportunity is available to you, but if you ever get the chance to play with the Canon lens, I’d love to see what you had to say about it in comparison to this lens!

I write in a “I’m an average consumer, not a reviewer” style because, well, I’m an average consumer, not a reviewer. I know enough to know that I don’t have the technical knowledge to give a proper review, so I’ll stick to what I know (my own uninformed opinion). So I’m glad that it’s taken that way, with, I hope, the appropriate gain of salt. I’ve never used a Canon SLR, but have heard nothing but great things about their lenses, so I’d be surprised if the Canon wasn’t excellent… —Jeffrey

I just got back from prague and half of the old town square had green plastic and scaffolding around it for repairs. I framed photos to not include it. When I was in Japan last year, I had the same issue with some of the temples. It’s sometimes a real challenge to frame a shot that feels natural or intentional with so many distractions that can occur. That is one reason I enjoy street or urban photography so much (and why I loved Tokyo) – the distractions become the photo.

Mostly it’s because I use Nikon’s “Auto ISO” function, which allows me to set a maximum shutter duration, and it’ll push the ISO up to maintain that maximum shutter duration as needed. The problem is this Auto ISO feature is designed for use with prime lenses. Rather than a maximum shutter duration, it would be much more useful if Nikon were to allow the photographer to set a focal-length multiplier used to compute the maximum shutter duration (e.g. “2″ would mean that a 50mm focal-length would result in a maximum duration of 1/100th of a second). This would be helpful for users who change lenses often, and super-duper helpful for users with a zoom lens. But since Nikon doesn’t have this common-sense feature, I have to pick a setting that will work with any focal length I might be using, which on this day was in the range of 50mm – 500mm. So, I likely set a maximum shutter duration of 1/500th and just went with it. Actually, if Nikon is listening, it’d be good to have two of these focal-length multipliers: one for VR, and one for non-VR. —Jeffrey

John

Phone, wallet, sun glasses, house keys, and GPS unit. Maybe a hat, too. —Jeffrey