I'm glad I just re-read the thread. Get it and enjoy it. It's my first nano coated, ed af-s lens and VR - it's my first taste of that and it's brilliant. I've only rented the 24-70 a couple of times but here's my tuppence worth.
I'll chime in although I haven't been shooting a 24-70 but used a 50/1.4d and 85/1.8d and 28-105d - and an 18-35d and a 105/2.5Ai - 6 months ago I sold the lot and bought a 24-120/4 to use on my D700 with a view to picking up some primes as funds allow. As it is, I'm looking at either a Sigma 12-24 or 14-24 for real estate as my priorities are shifting towards real-estate from portraiture but still getting occasional auto/vehicle gigs and events.
I shot a wedding with the 24-120 and a sigma 50/1.4 and used flash a lot more than I'd have had to with a 2.8, but it's a stylistic thing and maybe I should use more or less anyway.The stop of DOF that you gain with the 2/8 zooms adds a lot to event image qualityWith f/2 one can get acceptable people shots in candlelight pretty much, but by f4 the shutter speeds and ISO are maxed beyond what a candid human will freeze for - but all this is mitigable to an extent if flash is used. In this case one's only losing a stop of ambient to the 24-70 by choosing the 24-120 -
But I also shot a couple of weddings with a 24-70 and 70-200 and there's a lot to be said for faster apertures. At all focal lengths you end up with exactly twice as much noise
and twice the DOF as soon as you become ISO limited, ie you're shooting wide open and a slow as you dare and losing DR and details. I'd like a set of f/2 primes - 'that's it!' Maybe just a 35 and a 105..
Something I find hard to explain is the overall impact of the relatively deep DOF at f/4. It wasn't until going and plugging the figures into a calculator and realizing that the DOF was essentially the same at 120/4 as 50/1.4 and 85/2 (or thereabouts, I may be a third of a stop out but it's about that) at the same subject distance that I went for it and sold my primes. I cant's get the same framing but it's all swings and roundabouts from here.
There was a Sigma 12 - 24 in the shop today - Brand new, I'm just loading some sample shots now - I got distracted in my testing by a woman who was considering a 24-105/4 for her new canon 5D, to shoot kids indoors without a flash.It was my fault - I always interfere with people going about there business. I said don't bother, get a 85/1.8. I may have lost my coffee privileges in the shop for a bit. If she'd had a D700 I would have said the same thing.
Trying to cut a long story short, for me, low light means no flash and the 35/2 is a lens I've considered as a flashless candid tool. Did I mention the 200/2 - with the vr that'd be a thing! Imagine if they made a 'prosumer 180/2 just for fun! The thing is, we tend to want the widest available apertures by default unless we require depth of field and there's adequate light to stop down for it.
In my opinion the IQ of the 24-120 is good enough for sure. I'm only chipping in here because I guess what I'm saying is that if 'low light' means 'no flash' then f/4 is too slow if you are ISO limited. That's the biggest hit to IQ. Having said all this, it would have to be a well lit event before I considered using no flash at anything slower than f/2 or thereabouts.
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