Lenses / Re: Canon Announces Two New EF Ultra Wide-Angle Zoom Lenses and White EOS Rebel SL1 Digital SLR Came« on: May 16, 2014, 06:55:02 PM »
f/2.8 is not that thin DOF as you go to UWA. A 50 mm FL at 6 feet away f/2.8 gives DOF 0.78 ft (very thin, and difficult to manage), whereas a 24mm FL gives 3.4 feet, which is more than enough. At 15 feet away for a group, 24mm lens gives a whopping 36 feet of DOF. The razor thin concern doesn't apply at ultra wide.
An extreme example here: 24mm f/1.4 at 15 feet still has a DOF of 11 feet (but Canon's 24 1.4L is very soft in the corners at 1.4, different issue).
16mm f/2.8 at 6 feet away still has a very easy to manage DOF of 11 feet. Even as close as 3 feet, gives about 2 feet DOF.
So, f/2.8 really can help indoor photography for ultrawides without causing DOF problems.
yea. so f/2.8 can help isolate the subject from the background as well. in your example, the DOF extends from about 2 feet in front to 9 feet behind, which may be pushing it for subject isolation but still doable (you would more likely be stepping back and zooming in to 21 mm for example, for better results -- But to continue the example: at f/4 (still 16mm and subject distance of 6 feet) you loose almost all hope of subject isolation from the background because everything 34 feet behind the subject is in focus. so in this particular example, the f/2.8 lens has a hope of capturing a venue feature like a candelabra or whatever, with some isolation from the background, but the f/4 lens has little hope. I doubt very many people/group shots are taken at 16mm and 6 foot distance... but I'm not a wedding 'tog so I'm open to correction here