Lens Questions/Tamron 17-50

[Daniel Browning]

Q1. EF24-70mm has a horiz view angle of 84 degree vs.EF 17-55mm has a horiz view angle of 68 degree:

That's only true if the 24-70mm is used on a full frame camera (e.g. 5D2). When you put it on the 50D, the angle of view is not 84 degrees, but much narrower.

a)Isn't it shorter focal length gives wider angle of view?

Yes, that's correct.

b) if I have a 24-70, then it covers what I can take with 17-55?

No.

c) why 24-105 doesn't provide horz view angle in its spec? At least I can't find it.

You will find the answer to that question here:


http://community.the-digital-picture.com/blogs/news/archive/2009/09/22/new-site-feature-lens-specifications-and-measurements.aspx

Q2. If I want to take pictures of my 2 yr old kid indoor, assuminghe is not that cooperative in keepingstill,is it qualified as "freezing action in low light" and thus I need to consider f/2.8?

Yes and yes.

Q3. If I use a flash with a non-f/2.8 lens, can I achieve "freezing action in low light"and for the situation I mentioned in Q2 above?

Yes.

Q4. I saw posts mentioning Tamron 17-50mm f/2.8 with its price much lower than EF 17-55. I assume it is compatible with 50D?

Yes.

Any people used this before can give me more insight comparing with EF 17-55 or even EF 24-70 (w/o considering the extra 20mm focal length)... I am not a professional and thus not really looking for poster size IQ.

The EF-S 17-55 has better manual focus features, much quieter autofocus, better resale value, and better image quality in some ways, to name a few differences. I still prefer the Tamron 17-50 because of the value. I suggest reading Bryan's reviews for each lens, that should give you a very good impression of each lens.

Q5. I am considering the following 2 combinations:


a) 50 f1.8 + Tamron 17-50 (low light & wide angle landscape) + EF 24-105L (general use, travel)


b) 50 f1.8 + EF 24-70 (worrying a little bit heavyto carry around formy kid, and travel)

I suggest option "a", for the ability to use wide angle as well as higher quality. But instead of the 24-105, I would suggest a different lens such as the 55-250 IS or 70-200 f/4 L IS, the latter of which will blow away the 24-105.