What am I doing wrong? Aperture Priority Mode on Canon DR XT

Discussion in 'Digital Photography' started by odinsride, Jul 28, 2007.

  1. odinsride macrumors 65816

    odinsride

    Joined:
    Apr 11, 2007
    #1
    I am new to SLR photography, and was trying to figure out the Av setting on my camera. I bought the field manual and was reading that you can change the aperture to make the background blurred or in focus.

    Well I tried this Av mode just now with a big styrofoam cup on my desk and my speaker about 3 feet behind it.

    First of all, I could never get the speaker to be in focus at all, no matter what Aperture I set.

    Secondly, every shot I took turned out blurry, because the shutter speed was slow in this Av mode and I couldn't hold the camera still.

    I tried using the flash, increasing the ISO, everything. But I keep ending up with shots where everything is blurry, even the main subject.

    What gives? In auto mode I always get clear pics. Are the manual modes really the way to go?
     
  2. robbieduncan Moderator emeritus

    robbieduncan

    Joined:
    Jul 24, 2002
    Location:
    London
    #2
    Are you sure you're setting the aperture correctly? To get selective focus like you are describing you want the lens open so small aperture numbers. This should result in faster shutter, not slower, making hand holding easier.
     
  3. odinsride thread starter macrumors 65816

    odinsride

    Joined:
    Apr 11, 2007
    #3
    Well I was really just experimenting right now. I wanted to see if I could get everything in the scene in focus if I wanted to. I'm setting the aperture just as the manual describes. Even at the lowest aperture the shutter speed was too slow for me to hold the camera still.
     
  4. Kamera RAWr macrumors 65816

    Kamera RAWr

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    #4
    How close are you trying to focus to the cup? Perhaps it can't focus because you're too close? Perhaps the reason the speakers in the background are never in focus is because when you have a lower f/number it's probably blurring the background and when you have a higher f/number, depending on lighting, maybe the shutter speed is too slow to hand hold a sharp shot. Just my .02 :eek:
     
  5. Kamera RAWr macrumors 65816

    Kamera RAWr

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    #5
    What lens are you using, just out of curiousity?
     
  6. robbieduncan Moderator emeritus

    robbieduncan

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    Jul 24, 2002
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    #6
    If you want everything in the scene in focus you need a small aperture (so a big aperture number). This lets less light into the camera making the shutter speed slower. If there is not enough light available you won't be able to hand-hold. That's just the way it is.
     
  7. odinsride thread starter macrumors 65816

    odinsride

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    Apr 11, 2007
    #7
    I was sitting about 3-4 feet from the cup, zoomed in to just the top half of it. It appeared to be focused in the viewfinder, hell the AF thing even beeped.
     
  8. odinsride thread starter macrumors 65816

    odinsride

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    Apr 11, 2007
    #8
    Just the DR XT kit lens...18-55m I believe.
     
  9. Kamera RAWr macrumors 65816

    Kamera RAWr

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    #9
    Hmmm... in what kind of lighting are you trying to shoot?
     
  10. odinsride thread starter macrumors 65816

    odinsride

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    Apr 11, 2007
    #10
    Well it's still daylight outside but I also had my lamp turned on (to the right of where I was shooting from).
     
  11. Kamera RAWr macrumors 65816

    Kamera RAWr

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    #11
    I suppose the best I could say is to post a pic or two with EXIF data... other than that, I'm not completely sure what the problem is :eek:
     
  12. robbieduncan Moderator emeritus

    robbieduncan

    Joined:
    Jul 24, 2002
    Location:
    London
    #12
    OK, what focal length are you using?

    I've set up a little scene with a cup close to the camera and a speaker behind it (the cup is about a foot from the camera, the speaker around 4 feet further on). Using a 35mm lens the speaker is pretty much in focus (and the cup too) at f20. It's noticeably out of focus at f8. At ISO 200 in the amount of light in my room right now f20 is a 13 second exposure. At ISO 1600 that drops to 2 seconds. Neither is hand holdable (I'm cheating and using a tripod).

    Without moving the tripod and switching to a zoom lens at 17mm I get an exposure of under 1 second and the entire scene is in focus at f20. At 85mm the exposure goes to 1.6 seconds and the speaker is out of focus at f20...
     
  13. odinsride thread starter macrumors 65816

    odinsride

    Joined:
    Apr 11, 2007
    #13
    Well I already deleted the pics since nothing turned out, and now I'm charging the battery, but I'll try messing with the settings again tomorrow and post the results. Thanks
     
  14. odinsride thread starter macrumors 65816

    odinsride

    Joined:
    Apr 11, 2007
    #14

    I tried shooting at 55mm. I should have written down the settings I tried. I'll do that once my battery is charged and I try again. Thanks for the help
     
  15. odinsride thread starter macrumors 65816

    odinsride

    Joined:
    Apr 11, 2007
    #15
    Ok here's some shots I took.

    First image (low aperture number)

    http://www.flickr.com/photos/sitheris/933955366/

    Camera: Canon EOS Digital Rebel XT
    Exposure: 0.077 sec (1/13)
    Aperture: f/4.5
    Focal Length: 34 mm
    ISO Speed: 1600
    Exposure Bias: 0/2 EV
    Flash: Flash fired

    Orientation: Horizontal (normal)
    X-Resolution: 72 dpi
    Y-Resolution: 72 dpi
    Date and Time: 2007:07:28 08:46:21
    YCbCr Positioning: Co-Sited
    Exposure Program: Aperture priority
    Date and Time (Original): 2007:07:28 08:46:21
    Date and Time (Digitized): 2007:07:28 08:46:21
    Shutter Speed: 242512/65536
    Metering Mode: Pattern
    Color Space: sRGB
    Focal Plane X-Resolution: 3954.233 dpi
    Focal Plane Y-Resolution: 3958.763 dpi
    Compression: JPEG
    Image Type: Canon EOS DIGITAL REBEL XT
    Owner Name: unknown < P d
    Camera Serial Number: 2520718507
    Custom Functions: 20, 0, 256, 512, 768, 1024, 1280, 1536, 1792, 2048
    Model ID: 2147484041
    Tag::Canon::0x0013: 0, 159, 7, 112
    Tag::Canon::0x00AA: 10, 463, 1024, 1024, 644
    Image Width: 3456 pixels
    Image Height: 2304 pixels
    Macro Mode: Normal
    Image Quality: Fine
    Canon Flash Mode: On
    Continuous Drive: Single
    Focus Mode: One-shot AF
    Canon Image Size: Large
    Easy Mode: Manual
    Contrast: High
    Saturation: High
    Sharpness: High
    Metering Mode: Evaluative
    Focus Range: Not Known
    Canon Exposure Mode: Aperture-Priority AE
    Lens: 18 - 55mm
    Max Aperture: 128
    Min Aperture: 304
    Flash Activity: Flash did not fire
    Photo Effect: Off
    Color Tone: 0
    Focal Type: Zoom
    Scaled Focal Length: 34
    Focal Plane Size: 907 x 605
    Flash Guide Number: 2097168
    ISO: 1600
    Measured LV: 65508
    Target Aperture: 22.62741699797
    Target Exposure Time: 0.077616113254593
    Flash Guide Number: 2047.96875
    F Number: 4.5
    Camera Type: EOS Low-end
    Auto Rotate: None
    Image Width: 3456
    Image Height: 2304
    Image Width (As shot): 3456
    Image Height (As shot): 2304
    Shutter Count: 7172
    Color Temperature: 5200°K
    Sensor Width: 3516 (52-3507 used)
    Sensor Height: 2328 (19-2322 used)



    Second Image (High aperture number)

    http://www.flickr.com/photos/sitheris/933955242/

    Camera: Canon EOS Digital Rebel XT
    Exposure: 2.5 sec (5/2)
    Aperture: f/20
    Focal Length: 34 mm
    ISO Speed: 800
    Exposure Bias: 0/2 EV
    Flash: Flash fired

    Orientation: Horizontal (normal)
    X-Resolution: 72 dpi
    Y-Resolution: 72 dpi
    Date and Time: 2007:07:28 08:44:46
    YCbCr Positioning: Co-Sited
    Exposure Program: Aperture priority
    Date and Time (Original): 2007:07:28 08:44:46
    Date and Time (Digitized): 2007:07:28 08:44:46
    Shutter Speed: -86634/65536
    Metering Mode: Pattern
    Color Space: sRGB
    Focal Plane X-Resolution: 3954.233 dpi
    Focal Plane Y-Resolution: 3958.763 dpi
    Compression: JPEG
    Image Type: Canon EOS DIGITAL REBEL XT
    Owner Name: unknown < P d
    Camera Serial Number: 2520718507
    Custom Functions: 20, 0, 256, 512, 768, 1024, 1280, 1536, 1792, 2048
    Model ID: 2147484041
    Tag::Canon::0x0013: 0, 159, 7, 112
    Tag::Canon::0x00AA: 10, 599, 1024, 1024, 571
    Image Width: 3456 pixels
    Image Height: 2304 pixels
    Macro Mode: Normal
    Image Quality: Fine
    Canon Flash Mode: On
    Continuous Drive: Single
    Focus Mode: One-shot AF
    Canon Image Size: Large
    Easy Mode: Manual
    Contrast: High
    Saturation: High
    Sharpness: High
    Metering Mode: Evaluative
    Focus Range: Not Known
    Canon Exposure Mode: Aperture-Priority AE
    Lens: 18 - 55mm
    Max Aperture: 128
    Min Aperture: 304
    Flash Activity: Flash did not fire
    Photo Effect: Off
    Color Tone: 0
    Focal Type: Zoom
    Scaled Focal Length: 34
    Focal Plane Size: 907 x 605
    Flash Guide Number: 2097168
    ISO: 800
    Measured LV: 65508
    Target Aperture: 16
    Target Exposure Time: 0
    Flash Guide Number: 2047.96875
    F Number: 20.2
    Camera Type: EOS Low-end
    Auto Rotate: None
    Image Width: 3456
    Image Height: 2304
    Image Width (As shot): 3456
    Image Height (As shot): 2304
    Shutter Count: 7172
    Color Temperature: 5200°K
    Sensor Width: 3516 (52-3507 used)
    Sensor Height: 2328 (19-2322 used)


    The first turned out okay, but the second one is blurred. Any suggestions?
     
  16. miloblithe macrumors 68020

    miloblithe

    Joined:
    Nov 14, 2003
    Location:
    Washington, DC
    #16
    f/20 is pretty high. I think the kit lens might get soft overall at that kind of aperture.

    Also check out this site:

    http://www.dofmaster.com/dofjs.html

    at 34mm and f/20 focusing 3.5 feet away:

    Subject distance 3.5 ft

    Depth of field
    Near limit 2.61 ft
    Far limit 5.32 ft
    Total 2.71 ft

    In front of subject 0.89 ft (33%)
    Behind subject 1.82 ft (67%)

    only things 1.8 feet behind the subject should be in focus.
     
  17. odinsride thread starter macrumors 65816

    odinsride

    Joined:
    Apr 11, 2007
    #17

    Thanks for the link and explanation. Still have a lot of learning to do I guess. :p
     
  18. beatzfreak macrumors 6502

    Joined:
    Jan 11, 2006
    Location:
    NYC
    #18
    If you're hand holding at 2.5 sec shutter speed, it will be blurry. Set the camera on something solid and use the self-timer.

    Also, your metering mode is evaluative, try changing it to partial. Check the manual to see how to do this.
     
  19. seenew macrumors 68000

    seenew

    Joined:
    Dec 1, 2005
    Location:
    Brooklyn
    #19
    to check and see what your aperture is going to leave in focus, there is a button on the bottom right side of the camera, right where the lens connects, that when you push it, the aperture closes down, but it doesn't take a picture. Hold this down to see how the picture will be focused.
     
  20. odinsride thread starter macrumors 65816

    odinsride

    Joined:
    Apr 11, 2007
    #20
    One thing I've noticed is that on Av mode, I get a much lower shutter speed than on Full Auto mode, using the exact same shot and aperture. Apparently Full Auto mode is making adjustments to the settings that I'm not in order to get faster shutter speed. What am I missing? I set the ISO as high it goes and still can't get the shutter speed as high as full auto mode.
     
  21. robbieduncan Moderator emeritus

    robbieduncan

    Joined:
    Jul 24, 2002
    Location:
    London
    #21
    Either:

    1) It's not using the same aperture (check the details)

    2) It's using a different metering mode which results in a different exposure calculation.

    3) It could be intentionally underexposing a bit and using the exposure compensation to bring it back up

    4) Probably other stuff I've not thought about
     

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