Rebel XTI - shooting in Aperture priority Av Mode

Discussion in 'Canon EOS' started by kiranshankar, Dec 10, 2006.

  1. Hello,

    I am learning to shoot with my new XTI, Prior to this I had a Canon Powershot
    A620. In my P & S I used to shoot most of the pictures using Av mode. I could
    easily over ride the Shutter speed setting which the camera used to display and
    then take pictures, Which was helpful as I did not have to use tripod most of
    the times. But I am trying to figure out is there a way to over ride the Shutter
    speed whiich is displayed in the view finder when I am taking picture using AV
    mode. Most of the time i end up with blurred pictures because when I click the
    camera always waits for the time displayed before exposing the picture.I figured
    out from this forum that I can override flash firing by putting something in
    hotshoe. is there some trick to over ride shutter delay or should i shift to
    manual setting?

    If i go with basic zone( Portrait, Landscape, Av, Tv etc) Do I have to go with
    cameras setting?

    Kiran Shankar
  2. Just hold down the Av +/- button while using the main dial. You should see the exposure compensation bar on your lcd become highlighted and the shutter speed will change.
  3. Thanks Mike, I got what you mentioned. But my problem is I want to take that shot at f3.5. I dont want to change the f3.5 but the view finder displays 4" shutter time for that aperture value. Is there a way I can change the shutter lag time ?

  4. I'm not sure what you mean by lag time. Are you just trying to adjust the shutter speed? When you're in Av mode, adjusting the main dial will set your aperture, then you depress the shutter button halfway to calculate the shutter speed. After the camera chooses a shutter speed, you can hold down the Av +/- button (at the top right of the lcd screen) while adjusting the main dial to put in exposure compensation. That will change the shutter speed without changing the aperture.

    Also, if you're trying to take handheld shots in low light, you might also want to experiment with increasing the ISO setting.
  5. Shutter speed of 4" means the shutter open for 4 seconds. You are not seeing shutter lag time. At that speed you can't have a moving subject and needs a tripot if you don't plan to use a flash.
  6. I think the easy answer is to just use Manual mode. You can then set both your desired aperture value and shutter speed. There are some terminology problems in your post that are confusing people. As was mentioned before, the shutter speed displayed is the actual exposure time and not a "lag time". Also, keep in mind that the purpose of Aperture Priority mode is to allow the photographer to choose the aperture value he wants while the camera automatically sets the shutter speed to obtain a "correct" exposure. By choosing this mode, you implicitly agree to have the camera set the shutter speed for you. One way to override this is to use exposure compensation as was mentioned by someone who posted earlier. It seems to me, though, that it might be easier for you to simply use Manual mode.
  7. Thanks for all the response guys. With DSLR in the basic shooting mode the camera makes sure that the picture taken comes out well. I guess I should stick to Tripod while I am taking picture using Av mode else I might have to play with manual setting.

    I will have to explore my camera more.

  8. Kiran, it would be a good idea to explore the manual that came with your camera. It can answer most of your questions. People coming into DSLRs from P&S tend not to spend much time with their manual as they're used to having the camera do most of the work for them. You'll find that is not the case with the xti. Good luck.
  9. You want to control aperture and shutter speed ... that's what manual mode is for.
  10. Just to sum up your exposure modes:

    P: Camera sets both aperture and shutter speed. You have the option to do one or both of the following overrides:

    1. Move the camera's target exposure away from optimum (over/under expose).

    2. Adjust the combination of aperture/shutter speed: say double the exposure and half the aperture.

    For hassle free exposures in everyday situations, espeicially where you have to shoot fast, this is a good way to go.

    Av: You set aperture, camera sets shutter speed. (Options sim. to P)

    Use this mode where you want a specific aperture.

    Tv: You set shutter speed, camera sets aperture. (Options sim. to P)

    Use this mode where you want a specific shutter.

    M: You set both shutter speed and aperture. Camera shows a bar-and-pointer display of how your current settings compare to optimum exposure.

    Manual mode can give you ultimate control, or can be very frustrating, depending on circumstance. If your lighting is fairly constant, and you're not rushed (your subject is not going to take off on you), and you are getting frustrated by the camera's errant exposure assessments, then setting the exposure manually, metering on what's important, taking a few test shots, adjusting, is going to give *you* ultimate control.

    You also have options for *how* the camera determines exposure:

    Evaluative: Supposedly the "smartest", assesses the whole scene. One drawback, it locks exposure at time of assesment (shutter half-depressed), so if you pan, it could be way off.

    Center-weighted: Considers most of the frame, with preference for the center, and ajusts as you pan. This is what I use mostly. I don't like the way evaluative locks, so use this as a consequence. I do wish Evaluative had the option to turn off locking.

    Partial: A "fat" spot meter, similar to above.

    Finally, you can shift the overall light sensitivity of the camera, regardless of the metering mode, by adjusting the "ISO" setting. I don't remember (or really care) what this stands for. In essence it behaves like choosing fast vs slow film. A higher ISO number will make your camera more light sensitive, with downside of increased "noise" in your pictures. I find 400 a good compromise for most situations.

    Bottom line: Go through the manual, trying everything with your camera. Practice, practice. FWIW, that's where I'm at: I'm by no means comfortable with all the controls yet.
  11. Guys,

    Thanks a lot for the response. Special thanks to Mendel Leisk for putting down the steps in detail. Now my bible is the manual. I will get back to you guys if I need any more help.

  12. Kiran;

    There is lots of good stuff in the manual.

    A few things to remember;
    1) For me. . it was easier to learn how the "creative modes" (Av, Tv, M) performed, than it was to learn what the "basic modes" (portrait, sports) performed.

    2) In the creative modes, the camera is not mistake proof. If you try to take a day exposure for 6 seconds with a wide open shutter and nothing in focus. . .the camera will let you do that.

    3) Learn the relationship between aperture, shutter and ISO. You need to set two parameters, and let the camera solve for the final element using the built in light meter.

    You always set the ISO manually (100, 200, 400), controlling quality. Sometimes, you will find that you need to increase ISO to allow the camera to calculate a reasonable shutter/aperture value.

    In Av mode (aperture value mode), you set aperture and ISO and the camera picks shutter speed.

    In Tv mode (time value mode), you set shutter and ISO and the camera picks ISO.

    In M mode (manual), you set all three parameters and the camera meter readings are ignored.

    Smaller aperture value implies greater depth of field, but more light will be required to expose the image (higher ISO and longer shutter). Remember the 1/f rule (if you have a 100mm lens setting, any image with a shutter slower than 1/100th second will show motion blur)

    Once you learn this. . .everything follows.

    4) And it is rare to ever have enough light. Seems like you can never take a F8 image with 1/500th shutter speed at ISO 100. The flash unit is a friend, but a high maintenance friend (takes alot to make it work well)

Share This Page