just got my rebel xti need some help

Discussion in 'Photography Beginners' Forum' started by bisdakr, Jan 13, 2007.

  1. bisdakr

    bisdakr TPF Noob!

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    hey guys, I just got my cannon rebel xti and in need of some help, i've read about aperature and shutter speed and all that, my question in when I take a picture do I just adjust everything(aperature/shutter/iso) so that my exposure is neutral? like for example, I was reading this one write up about aperature and shutter speed and it said f5.6 should have a shutter of 1/30 to get proper exposure, however when I take a shot in my cam 5.6 at 1/30 inside the house would be underexposed so I have to change the shutter to let more light in and inturn gets blurry at times. am I on the right track here?
     
  2. benwiggins

    benwiggins TPF Noob!

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    well lets start here: are you shooting in full manual?
    Av: aperature value-you set Ap. and the camera sets shutter
    Tv: time value-you set shutter speed and the camera sets Ap.
    M: manual- you set both.

    there isnt really a hard and fast rule in my opinion however because your ISO will afftect these settings immensly as will your available light. If you shoot Av or Tv then the meter setting you have it set on will also affect the reult. one thing to try is upping your ISO for the indoor shots or using a flash. that will allow faster shutter speed and less blur.
     
  3. bisdakr

    bisdakr TPF Noob!

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    im shootting in full manual. yeah I found that I would have to set my iso higher If i didn't want to use flash which created a lot of noise in the picture. I'm not sure if this is normal buy my lense(18-55 f3.5-5.6) will only open at f3.5 when its at 18mm at 55mm it will only go as far as 5.6 is this normal? in my sony dsc f717 I was able to do 99mm at f2.4.
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Welcome to the forum.

    It seems like you know the terms and have an idea of how they work. The next step is understanding how the exposure is made and how to use the camera's meter.

    There are three things that determine exposure. The shutter speed, the aperture and the sensitivity (ISO setting). You can't just pick a setting, or even read it out of a book. You have to use a light meter to determine the light that you are photographing in. Luckily, modern cameras have built-in light meters....that's how they know what to do when in the auto modes. Try putting your camera into P mode...and half press the shutter release. Do you see the settings pop up on the screen and in the viewfinder? Those are the settings that will give you an average exposure...in the light that you are shooting.

    To get started, it may help...if you just shoot in P mode and always take note of the settings that the camera is using. That will give you an idea of what you can do in the light you have.

    If you want to control your DOF (depth of field) then you would use Av mode and pick an aperture that gives you what you want. However, as you change the aperture, the camera will change the shutter speed to match. For every full stop that you change the aperture...the shutter speed must change by a factor of 2...so either 1/2 or double.

    If shutter speed is more important for your shot, then you can use Tv mode. This will let you pick a shutter speed and the camera will pick an aperture to match, for the light.

    When shooting hand held, the thing to think about is the shutter speed. To avoid blurry pictures, you will want to keep the shutter speed higher than the focal length (times 1.6). So if your lens is set to 50mm...then you will want the shutter speed to be at least 1/80 of a second.

    That's all well and good....but when it's not very bright (indoors for example)...it may be hard to get a good shutter speed. If you set a speed of say 1/90...(in Tv) the camera's meter will try to set an aperture to let in enough light. However, if it's too dark...the maximum aperture may not be big enough. If this is the case...I think the camera will flash the number to let you know.

    What you can do, is to use Av mode, and set the maximum aperture (lowest number)...then the camera will give you the fastest shutter speed that you can use for the light you are in.

    If this shutter speed is still to slow...then your next option is to turn up the ISO. You should keep in mind that the higher the ISO setting...the more noise that will show up in the images. You can get a pretty good shutter speed at ISO 1600 but the noise will really start to degrade the image quality. It's a trade off that you must decide.

    The best option is to use a tripod or something to hold the camera (without you touching it)...that way, you can keep the ISO low and the shutter speed won't matter.

    Sorry, that was a bit long....I hope it helps.
     
  5. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Yes, that's normal. That's the maximum aperture for that lens. It's not a very good lens in that regard. I suggest looking at a 50mm F1.8 lens. It's quite cheap but very good optically and the maximum aperture is F1.8...which will allow you to get much better shutter speeds in low light.
     
  6. bisdakr

    bisdakr TPF Noob!

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    oh okay, 55mm f1.8 where can I find these for best bang for the buck? also I was debatting drom d80 vs xti and d80 was sold out at circuitcity and 0% ended today so I made a quick choice. I'm planning to take picture of pretty much everything however I dont want to go out and buy 3-5 sets of lenses what would be an all around lense to get? thanks for the great info.
     
  7. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    A 50mm F1.8 lens can probably be found in any good sized camera shop. Or you can order one on-line. I suggest B&H or Adorama, both of which can be found on this site's 'links' page. You can get it for as low as $70 US.

    They are both good cameras...you got a good one...no need to second guess your choice.

    Well, if you want an 'all in one' lens...then you will be trading that for image quality and probably speed (speed meaning the maximum size of the aperture).

    What's your budget for a lens or lenses? The lens you have now, is actually OK...but not in low light. So if you combine that with a fast lens (like the 50mm F1.8) then that will be a good combination. Another option is to find a replacement for the lens you have now. You can get a lens with a similar focal range...but with a bigger maximum aperture. Sigma and Tamron both have 17 (or 18) to 50mm lenses with a maximum aperture of F2.8. I think they are around $500...which is actually a great price for a zoom lens with a maximum aperture of F2.8.
     
  8. bisdakr

    bisdakr TPF Noob!

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    allright thanks, I guess i'm second guessing myself because my buddy has a d80 which takes great pictures but then again he has upgraded his lense. the 50mm 1.8 should alow me to take pictures in low light situations, indoors and what not? In may I will be going home to phillippines and shooting a wedding, you think the 50mm f1.8 along with stock lense will do okay? I went to b&h and if a lense says 17-55 f2.8 does that mean that from 17-55mm the aperature stays constand at f2.8, this also means my focal point will stay at 2.8 and nothing larger? also if I buy a lense that is 17-55m f2.8 does it mean I can ony use f2.8 at 17mm?thanks for all the help this is a great site.
     
  9. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    It means that you have the option of using F2.8 all through the focal range. You can always use a smaller aperture (F5.6, F8, F11 etc.). This is much better than the lens you have, which has a maximum aperture of F3.5 at 17mm and a maximum aperture of F5.6 at 55mm.

    If the name of the lens has only F2.8...that usually means that you can use that aperture for the whole range. If the lens says F2.8-4.5....then the maximum aperture is F2.8 only at the wide end and F4.5 at the long end.

    17-50mm is the focal range...the zoom. You can always change that.
     
  10. the flying moose

    the flying moose TPF Noob!

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    thank you very much for posting that. i recently got myself a XTI and that info you posted saved me making my own thread.
     
  11. space

    space TPF Noob!

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    I'm in a similar position.. noob with a 400d :) Thanks Big Mike, your explaination was great, made me understand alot more :)
     
  12. bryanwhite

    bryanwhite TPF Noob!

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    I just got my 50mm f/1.8 a few days ago, and I can't stop singing its praises. Except, I can't sing, so when I do so I seem to clear the room.

    But honestly, I can't see myself taking that lens of my camera for a very long time.
     

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