« on: July 23, 2014, 01:39:12 AM »
2.8 is fast enough for UWA - no point having a f/1.4 with tons of CA, coma effect and others, that would only be mild to tolerable above f/4..... sharp f3.5 with high iso is better than f2.0 images a lower iso I suppose.
I really don't know - maybe it's design/optical law restriction., and only can imagine either with huge front element (>95mm)
Certainly an F1.4 wide angle would not be feasible with cost to produce and front element size, but an F2 16mm for example would be the same focal length as the 16-35 F2.8 version 1 at it's widest, not have all the glass associated with a zoom, and just 1 stop faster...seeing as the 16-35 F2.8 version 1 has a 77mm filter size, I wouldn't think that while losing the zooming but making it a stop faster, we would then be talking about a front element greater than 95mm. I don't know the calculations involved for knowing exactly so this is just based on what makes sense to me.
Perhaps I did not elaborate as to what I meant by a good lens. Check out the price of a Zeiss 15mm lens, its not f/2, but it costs $5,000. Wide angle lenses are very difficult to build, and that extra stop comes at a huge price. I use a Canon 135mm f/2 for concerts and theater, I do carry my 16-35L, but its far too wide for almost of my stuff. I don't do astronomy, but wouldn't coma be a issue on a lens at f/2?
You can't base Canon lens prices on Zeiss lens prices. When does a Canon lens ever cost what it's Zeiss counterpart does? Canon's L 50 F1.2 costs $1,620 and the Zeiss 55 F1.4 otus costs $4,000. Yeah an extra stop is gonna cost more, but you have to be kidding to suggest that a 16mm or 18mm F2 L lens would cost $5,000. It's a Canon and not a Zeiss.
The 24 F1.4L is a super fast wide angle specialty lens and there is not a $3,000 surplus for the extra 2 stops compared to an F2.8.
I guess you don't get to shoot very close to the stage - when I shoot concerts I am either at the base of the stage or on the stage, and often use a fisheye lens at shows so the wider the better for some shots. With an F2.8 fisheye I struggle with shutter speeds though...F2.8 doesn't do it for dimly lit shows where I can't use flash even with an ultra wide angle. F2 would make a big difference (I've been a lot happier with F1.8 lenses, though even then I have to go to ISO 12,800. Thank god for the 5DmkIII. Point is every stop counts.