Canon Rebel XT I can't change aperture or shutter speed in manual mode

On right hand top of the camera there is a Mode dial. Move the dial to Av (aperture priority) then rotate the wheel in front of this dial to set the F stop. The shutter speed will automatically adjust by the light meter.

You need to understand the relationship and teractivity of aperture, shutter speed and iso. In Av mod, you choose the aperture and the camera makes thw shutter speed agjustment, In Tv mode, you set the shutter speed and the camera makes the aperture adjustment, In manual, you have to set both shutter speed and aperture manually. If the ISO mode is set to AUTO, the camera chooses the sensors sensitivity to light automatically. Change to specific ISO
(200-400 for daylight and 799-1600 for night). Take a picture in AV mode and note what shutter speed the camera chose. Then switch to TC mode choose the same shutter speed and see if camera chose the same aperture(f-stop) you chose in first shot. Change to Manual and choose same f-stop and shutter speed the camera chose for you in the other modes. Compare all three photos. They should be almost if not exactly the same exposure wise.
In Tv mode choose a dlowers shutter speed, In Manual choose a combo of slower shuuter and wider f-stop(smaller number). Read your manual.

If your camera is a Rebel XS you should have a dial on the top right with a series of letters and icons. To set your camera so you manually control the shutter speed turn this dial too "TV" (Time Value). This setting will allow you to select the shutter speed and the aperture will open or close to achieve the correct exposure. The "M" is (Manual) where you would select both the shutter speed and aperture "AV" is (Aperture Value) where the user selects the aperture they want and the shutter speed increases or decreases to obtain a proper exposure. The "P" (Program) mode allows the camera to automatically select the shutter speed and aperture

Check to see that both cameras are set to the same settings. For example, turn both cameras to manual and set them both to the same aperture, ISO, and shutter speed. This could account for the difference in brightness if one is set to be more light sensitive than the other.

There isn't enough light for that scene. 1/13th of a second is the fastest at that ISO (automatically set by camera in Basic Mode) and Aperture (auto set by camera too, in Basic Mode) that the camera can handle to provide a reasonably exposed image. Try using Tv on the Mode Dial, set a higher ISO (trade off is image noise) of around 800-1600 or even 3200 if available on your camera. Set shutter speed at 200-1000 (1/200th to 1/1000th of a second) and see if it freezes your subject. An external flashlight with hi-sync mode would help in this situation if the subject is not too far away.

Suggestion.... try to reset all settings to default. See what happens then.

Use Av mode to change the aperture.

If you want to do this in Manual, where you rotate the wheel to change the shutter timing, press the Av button on back whilst rotating the wheel to change the aperture.

http://web.canon.jp/imaging/eosd/eosdigital4/specifications.html

First off, welcome to the world of photography! Good luck and have fun!!!

Like any slr, you have the option of Manual exposure. I'm not familiar w/ modern Canons (I use Nikon). According to this page, however, you also have aperture priority and shutter priority. I'm pretty sure ALL modern Canons have bracketing modes as well (Use this for HDR).

I couldn't find the 450 manual (I'm assuming Canon's web devs are behind), but I did find the instruction manual for the 400 :

http://gdlp01.c-wss.com/gds/0900000357/EOSDRXTi400DIM-EN.pdf

Should be similar, probably w/o some of the functions. Although you SHOULD have a book w/ your camera ;). Read it thoroughly.

Ok, according to the 400 manual, put your camera into Manual mode, then adjust the regular dial to adjust shutter speed. Then, to adjust aperture, hold in the A/V button while you adjust the same dial.

Like I said, may be a bit different. I think the dial may even be digital buttons rather than analog...

hope this helps!!!

The settings in Auto Mode are factory set. If you want to adjust exposure and shutter speeds then you will have to shoot in Manual Mode (TV=Shutter Priority, AV=Aperture Priority, M=Full Manual)

It does different things depending on the camera settings and only works in the creative zone settings not the automatic settings.

In AV mode it changes the aperture
In Tv Mode it changes the shutter speed
In M mode it changes the shutter speed unless the AV button is pressed when it then changes the aperture