Instruction: Answer the given question by extracting information from the supporting document.

Input:
Question: Will this lens be a great difference than the 17-40 f/4 for city night and indoor photography? Im using a 6D.
Document: I am not a professional photographer,  but I like to take high quality pictures of my family etc. I have a Canon 40D camera,  and to date I have been mostly using the Canon EF 28-135mm f/3.5-5.6 IS USM. Having just started to use these lens (EF 16-35), I am amazed by what I have been missing. Photography is all about capturing light, and these lens make a huge difference in terms of being able to take great indoor photos without a flash, you have to see it to believe it.
I had been contemplating which wide angle zoom to buy for some time now, I photograph weddings occasionally and need it for indoor shots as well as for street photography. I had had the kit wide angle zoom once in weddings and the pictures were substandard. The 17-40 4.0 is cheaper for sure but I decided this lens will be in heavy use for years, probably decades, so why not go for the big Kahuna. It was worth every dollar. Picture quality is as good as one can wish for, even in extreme wide end and all the way opened to 2.8!
The Canon EF 16-35mm f/2.8 L II USM Lens is perfect for the wide work outdoor landscape photography, indoor events such as stage work, parties, wedding and for other photojournalism needs.I spent months researching this lens. I debate between the cheaper 17-40L and the 16-35mm 2.8 II lenses. There is a big difference in price between the lenses. In the end, I felt that having the extra stop of light and wider angle was more important than saving a few dollars.
Images quite grainy at low light (compared to my 24-105 L at the same ISO)4. Expensive, twice as much as 17-40 but does not offer much benefit.5. Having problem lock on the focus with outer focus points at low contrast area, with my Canon 6D full frame camera.Final words: if you want to get the benefits of 28mm,  35mm, 40mm and 50mm f2.8 benefit, the lens to get is the 24-70 f 2.8, not this ultrawide lens.
The Canon E-82mm front snap-on lens cap will fit on this filter. Canon's instruction manual recommends the installation of a filter to complete the weather resistance of the lens. So, the Heliopan has not added any ghosting (yet) to night time images.At f/2.8, images in the viewfinder are bright, the autofocus is quick, and like the 17-40/4 the lens is mostly flare resistant. At 100% zoom in Canon's DPP, the images are class leading sharp at all focal lengths.
When compared to it's little brother, the 17-40mm f/4L, this thing is a beast! Even on a 1.6x sensor (7D) camera you get an astounding perspective. I can pretty much stand at the corner of a room and more than 80% of it in view. Great for indoor shots because you don't have to stand back to get the shot. And the wide 2.8 aperture is definitely more forgiving than the 4 provided by the 17-40mm, especially in low light conditions.
I am a wedding photographer with a extensive resume of weddings. I own a good bit of L glass that Canon makes and use them on a pair of Canon 5D's & a C100 Cinema camera.16-35 is a great sharp lens with a nice low light f/stop. I find myself never using my 17-40 LENS now. If you want that dramatic wide shot this is it. If you need to get a wider shot for your CROP sensor Cinema Camera, this is the solution.I rate this lens with 5 stars and is work every penny.
I'm a big fan of landscape photography and creating sunstars3) obviously, a stop faster, allowing for shots at night or indoors that otherwise would be impossible handheld4) 1mm on the wide spectrum is far more useful than 5mm on the long end.That said, it's highly arguable if it's worth paying twice as much for a very similar lens. For my needs, there was no question which lens belonged in my kit, but sometimes regret paying so much for it. The 17-40 is a much better value for the $, unless you absolutely need the widest, fastest, zoom lens in canon's lineup (as of march 2011).As much praise as I have for this lens, there are two things that fall short for me:1) Chromatic Aberation.
indoor cathedral, candle light @ 16mm, hand held, 1/4sec).I don't have any experience using the mkI, but I have traded my 16-35 II with a co-workers 17-40 for a few weeks and made the the following observations (on full frame):1) wide open, noticeably better performance in the corners on the 16-35 (all focal lengths), just a hair sharper in the center.2) sunstars are far more pleasant on the 16-35, and not as clearly defined on the 17-40 (even at f16).
I was debating between the cheaper 17-40L and the 16-35mm 2.8 II lenses. There is a significant difference in price between the lenses. In the end, I felt that having the extra stop of light was more important than saving a few dollars. After receiving the lense, I have been nothing be astounded by the quality of photos taken with this lens. Lens build and Image Quality are top notch. While I've seen the 17-40 produce high quality pictures, I wasn't about to sacrificy the F2.8 over the F4.For those not needing the extra stop of light and plan to do outdoor landscape photography, the 17-40 will work just as well.
Answer: Yes, it will make a difference.  Jumping from f4 to f2.8 will help you mainly in one of two ways depending on the nature of your shoot.  Either you will be able to drop your ISO to reduce the noise that comes with low-light/high-ISO photography, or you will be able to use a faster shutter to reduce motion blur.  That being said, this lens will HELP these problems, but not necessarily eliminate them.  It's up to you to decide if the difference is great enough to merit the price.  I would suggest renting it or borrowing it to see for yourself.  Good luck!