When im downloading pictures from canon rebel xti to macbook i use iphoto. but sometimes when i drag the photos from the camera to my library is makes doubles! why?!

Alright, I have the manual… but I just don't understand it. :[
I know that it is fully manual and has automatic settings, but the manual that it came with is just comics on how to use it which consist of "Turn the focusing ring to focus until the circle in the middle is a complete circle!"

Like what are the f/stops and apertures?
How can I find out what type of Focusing Screen I have?
Where do I find the shutter speed setting/set it?
How do I know if my Light Meter is center weighted?
How do I find out if my camera has a depth of filed preview button on it?
What is a leaf shutter?
How do I know if my camera has a focal plane or leaf shutter?
Since I have automatic capabilities, how do I know if the automatic exposure control is aperture priority, shutter priority, or both?
What is a "Hot Shoe"?
What is the metering system?
How do I know if I have more than one metering thing?

Hi guys, quick question, I'm planning to get a Canon 450D with a lense 17-85mm f4-5.6 IS USM, I'm a newbie so I don't master all the information/ guidelines and all of that. Was just wondering if the Canon EOS 450D is compatible with L-Series lenses like the EF 24-70mm f/2.8L USM? Any downsides? Thanks a lot guys.

pictures in dark club during concerts, with clear and bright results WITHOUT using flash?

i am looking for a spare battery but really a battery charger for my canon sd900 camera. i really need to know where i can go 2 purchase one before i got 2 sixflags w/ my friends. i have looked on walmart & other electronic store sites, but since this camera isnt brand new they dont have anything i can work with..PLEASE HELP!!

I guess what I'm really asking is will a normal circular polarizer work on a Digital SLR?
I'm not too familiar with cameras and accessories. :d

i have a 400D and i want to start airial shots and shots of birds from far away, where are the cheapest lenses? and the best for around £100 links are welcome!
please help/

I have owned my Canon XTI for about 6 months. Mine came with the typical efs 18-55mm kit lens and while it takes decent photos, it is not great in low light. I also have the Canon 50mm 1.8. It is great in low light, but is not wide enough for many shots.

I use my camera for an extremely wide variety of occasions and activities (hiking, weddings, cycling, sporting events, and just everyday events. I would like good walk-around lens and a telephoto.

I have been looking at:
Sigma 17-70mm F2.8-4.5. If I were to purchase that lens, I would probably get the Sigma 70-300mm F4-5.6 to go with it.

Or I could just get the Canon EF-S 55-250mm f/4-5.6 IS to go along with my 18-55 kit lens, but I am not happy with my 18-55mm in low light… especially during times when I don't want to use a flash.
Great suggestions, but I am not really happy with having just the 18-55 kit lens as my walk-around lens. Maybe I should just get something like the Canon 28-135? I could always get a proper telephoto lens later. I am doing Ragbrai (bike ride across Iowa) in a few weeks, and would like one main lens to use for the week long event. The 18-55 is just not versatile enough.

model mp160 or mp150
I don't want a take home kit.
I'm sure Walgreens doesn't do Canon brand. And spending a couple bucks isn't an issue.
I'm sure Walgreens doesn't do Canon brand. And spending a couple bucks isn't an issue.

What is the best Canon DSLR for under about $700.

Also, what's the best Canon standard zoom lens for it?