What's the lighting going to be like in the penthouse? If it's lower light then the 50mm 1.4 will be a great choice. If the light will be good throughout, Sigma makes an 18-125mm OS lens that has looked really good so far, but it will need good light. Shoot in AV mode in the lowest aperture you can. Press halfway down on the shutter and check the shutter speed it sets. Most likely you will need to keep increasing the shutter speed until you get around 1/60 speed.
Remember that shooting in RAW will require you post process. The colors and sharpness won't look good until you do some work on it. Here is a good video tutorial that you can look at for a workflow.
http://www.nobsphotosuccess.com/tutorial/introtutwmv/introtutwmv.html
Hi, I'm relatively new to dslr ownership & photography. I've got a Canon XSi (aka 450D) with the 18-55mm f3.5-5.6 IS (kit) lens & a Canon 55-250mm f4-5.6 IS lens. My daughter will be a flower girl in a wedding on the fourth of July. The reception will be in the penthouse of a catering hall with great views of the Manhattan skyline and the fireworks display. I would love to be able to take just one lens with me to use all day on photos of the bride and her bridesmaids (and flower girls, of course!), through the wedding, reception and fireworks as well. I don't expect either of the lenses I currently have to do the trick, but I've got a couple of other lenses in mind; Canon 50mm f1.4, Canon 28-135mm IS f3.5-5.6, & the Tamron 18-250 f3.5-6.3. In general, I like the idea of getting a "walk-around" lens with a wide range & plan to get one in addition to the 50mm eventually. So basically this question is which would be more versatile/practical for that day.
Alternatively (& much lighter in weight & bulk), I also have a Canon S5 IS camera. The idea of taking the S5 is tempting, since I'll be carrying whichever camera I take in my purse all day long(!), but I'm leaning more towards the XSi because of image quality.
Any helpful suggestions will be appreciated.
Thank you.

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