What's wrong with my camera?

Discussion in 'Beyond the Basics' started by thafat1, Dec 14, 2004.

  1. thafat1

    thafat1 TPF Noob!

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    http://www.thafat1.com/messup.jpg

    I have a Canon EOS Rebel G with a Canon 28/80 lens. I've had problems with photos coming out with a part of the picture completely black. It's only in dark/indoor photos though. I recently took a roll of film: a few outdoors and the rest indoors. Every indoor shot had about 3/4 of the picture black. It has happened with my current lens and with an old Sigma 28/80 lens. I use a cheap shoe mount flash too.

    The link above is an example of what has been happening. If I remember correctly, I took almost a whole roll at a shutterspeed of 500 and an apature at about 4.0 (it went to that automatically when i set the SS to 500).

    I take lots of high speed action shots of BMX riding. I need the picture to freeze the guy and bike and be clear and crisp while he is in fast motion.

    Any help is appreciated. Thanks in advance.[/url]
     
  2. MDowdey

    MDowdey Guest

    im not for certain but it looks like a flash problem. is the room that black when you are taking the shot?


    md
     
  3. thafat1

    thafat1 TPF Noob!

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    the room is dark, but not black.

    it has done it w/ the shoe mount flash and the in-camera flash.
     
  4. MDowdey

    MDowdey Guest

    usually with flash sync problems you get a curtain of black. i could be wrong here, but i would focus on light in the room.


    md
     
  5. Big Mike

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

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    That is exactly what will happen when you use your flash with a shutter speed faster than the camera's flash sync speed.

    The shutter on these types of cameras opens in two flaps, one up and one down. They don't open at exactly the same time. The flash burst is about 1/10,000 of a second so if it fires while only half of the shutter is open...you get half of an image on the film.

    Check your manual for the max sync speed. Probably 1/90 or 1/125 for an EOS Rebel.

    If you want to freeze the action when shooting bikes...use the flash at the max sync speed. The very fast light burst will freeze the action. If you use a slower shutter speed with the flash, you will get a sharp image and some motion blur...this can be a cool effect but your camera probably does not have 2nd curtain sync so the effect will look weird.

    Another option is to use a fast lens and or fast film and no flash.

    good luck
     
  6. Cole_Alex

    Cole_Alex TPF Noob!

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    Here is the same response I gave you on the other forum. :D
    --------------------------------------------------------------------------------
    i'm not sure I'm qualified to answer this as a pro but as an amature here I go.

    It sounds like to me you are running into a flash sync issue. Let me explane

    Your camera has a flash sync speed defined for what speed you can take a flash picture and it be exposed proporly. how this works is your camera has 2 curtins that move out of the way to let light hit and expose the film/ccd. when you take a picture the 1st curtin moves out of the way to let light in...then after a tiny fragment in time(what ever your shutter speed is set to) the 2nd curtin moved to block the light from exposing....thus giving you the propor exposure.

    Now how your flash works with this.

    When you press the shutter button the 1st curtin moves out of the way and starts exposing your film/ccd. Then right before the 2nd curtin moves into block the light the flash is fired exposing your film for just a little bit before the 2nd curtin blocks all the light. this gives you a correct exposure for using flash.

    Now how this works with the sync speed. The sync speed is the fastest speed you can use on your camera with a flash because of mechanical ability. when you have the shutter speed set above your flash sync speed and you press the shutter then the 1st curtin opens but the 2nd curtin starts to close before the flash gets a chance to expose all of your frame. So what you end up with is a picture where you only have 1/2 of a flash exposure. Now depending on how dark the room is and what your apature settings are then you may end up with a picture that ony has 1/2 or some other size (depending on shutter speed) exposed.

    when you use really fast shutter speeds the 2 curtins are actually never letting all of the frame exposed at one time. its like a slit of light moving over the frame. Like the light on a copy machine. because of this the flash canont expose the whole frame at once.

    Now this is the problem with using a faster shutter speed that what the camera is able to sync at.

    You can use the camera with a slower shutter speed and be ok. Here I will explane.

    If your camera has a sync speed of say 1/125th then you can set your shutter speed to 1/60 and be ok. This is called dragging the shutter. by draging the shutter like this the camera will open the 1st curtin and start exposing the frame. the flash still doesn't fire until just before the 2nd curtin closes but sence more time has gone by then your picture will have a lighter background because it has allowed more ambient light to expose your frame.

    Some cameras might have trouble with this also.

    NOTE: some cameras have options to modify when the flash will fire, wether it be with the 2nd curtin or right after the 1st curtin opens. I am only covering the 2nd curtin sync in this msg.

    I hope this helps and if I posted somthing wrong please some one correct me.

    Thanks
    Alex
     

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