Results 1 to 13 of 13

Thread: Focusing in low light

  1. #1

    Default Focusing in low light

    Hi guys

    wanna ask a noob question. Why is that my camera doesnt want to lock onto the subject when in low light conditions; i.e. it keeps trying to focus, and even when it does, I fully depress the shutter button but the camera refuses to take the picture?

    The funny thing is, when i shoot in portrait orientation using the shutter button on my batter grip, the camera takes the same picture right away.

    What gives??

  2. #2
    Moderator Octarine's Avatar
    Join Date
    Jan 2008
    Location
    Pasir Ris
    Posts
    12,388

    Default Re: Focusing in low light

    Quote Originally Posted by hyde9 View Post
    wanna ask a noob question. Why is that my camera doesnt want to lock onto the subject when in low light conditions; i.e. it keeps trying to focus, and even when it does, I fully depress the shutter button but the camera refuses to take the picture?
    Focus lock requires some contrast patterns where the focus sensor can pick up required information. If your camera is in AF mode it will not take the picture as long as there is not focus confirmation. Normal behaviour, explained in the manual.
    The funny thing is, when i shoot in portrait orientation using the shutter button on my batter grip, the camera takes the same picture right away.
    It seems that in portrait orientation one of the sensors at least can pick up some useful information. Do note that there are different types of sensors: cross-type and normal type (single orientation), cross-types will fall back to normal in low light / with slow lenses. That would explain why the AF sensor worked in a different orientation.
    EOS

  3. #3

    Default Re: Focusing in low light

    Hi bro thanks for your reply. But I don't really understand the sensor part.

    Am I right to say for the first part of my question, the camera will have to detect contrasting colours and also ensure that the apeture, shutter etc all provide enough light, then it will take the picture?

    But why does switching orientation help if the scene remains the same, e.g. the amount of light etc. Sorry I really don't uinderstand about the sensor thing u mentioned...

  4. #4

    Default Re: Focusing in low light

    if its realy low light, go to manual focusing, turn your focusing ring to infinity...

  5. #5
    Senior Member Diavonex's Avatar
    Join Date
    Sep 2008
    Location
    Admiralty
    Posts
    3,641

    Default Re: Focusing in low light

    Quote Originally Posted by hyde9 View Post
    ....The funny thing is, when i shoot in portrait orientation using the shutter button on my batter grip, the camera takes the same picture right away....
    The shutter button on the grip by-pass the shutter lock mechanism.

    If your camera have Focus Assist Light, turn it ON.
    Last edited by Diavonex; 2nd August 2010 at 04:16 PM.

  6. #6

    Default Re: Focusing in low light

    shutter lock? so you mean when i try to shoot in landscape there's a shutter lock that's why the cam refuses to take the picture?..

    cause i always thought it was because the area was too dark or the camera couldn't lock onto the subject..which was weird cause it not only was able to lock onto the subject in portrait but shoot as well

  7. #7
    Senior Member Diavonex's Avatar
    Join Date
    Sep 2008
    Location
    Admiralty
    Posts
    3,641

    Default Re: Focusing in low light

    You can try this to overcome the shutter lock; focus on something that is at the same distance from the camera as your main subject, but which is in better light and have better contrast. Depress shutter release half-way to lock the focus, then reframe on your main subject and take the shot.

  8. #8
    Moderator Octarine's Avatar
    Join Date
    Jan 2008
    Location
    Pasir Ris
    Posts
    12,388

    Default Re: Focusing in low light

    Quote Originally Posted by hyde9 View Post
    Hi bro thanks for your reply. But I don't really understand the sensor part.
    Read about Auto Focus and the technical details: Wikipedia: Autofocus
    Cambridge in Colour: Understanding Autofocus
    Am I right to say for the first part of my question, the camera will have to detect contrasting colours and also ensure that the apeture, shutter etc all provide enough light, then it will take the picture?
    Camera only has the detect contrast patterns. Then the autofocus can lock.
    The camera has a priority mode to ensure that the picture taken is properly focused. In AF mode (when the switch at lens or body is set to AF) the focus lock is compulsory before the picture can be taken. Simple logic, call it 'idiot proof' if you like

    But why does switching orientation help if the scene remains the same, e.g. the amount of light etc. Sorry I really don't uinderstand about the sensor thing u mentioned...
    Read about the AF sensors, link above. We don't know about your scene. But if there was any pattern then it was in a certain orientation (horizontal, vertical). With camera in landscape mode the pattern was 'invisible' to the sensor, in portrait mode the sensor is turned 90 degree and the pattern became 'visible'.
    Another example: http://electronics.howstuffworks.com/autofocus3.htm
    EOS

  9. #9
    Moderator Octarine's Avatar
    Join Date
    Jan 2008
    Location
    Pasir Ris
    Posts
    12,388

    Default Re: Focusing in low light

    Quote Originally Posted by Diavonex View Post
    The shutter button on the grip by-pass the shutter lock mechanism.
    I have serious doubts about this. Can you provide any source for that?
    EOS

  10. #10

    Default Re: Focusing in low light

    here are a few tips mostly using spot.

    if subject not moving, long exposure.

    if total darkness, aim at anything on subject that has some light and then crop for the composition you want.

    if camera doesnt fire, aim at something else close to original target.

    eg,

    Photographing a light saber fight after cosfest with the lights all off was quite an experience...(:
    Last edited by Reportage; 2nd August 2010 at 10:54 PM.
    You wont see me much less remember me but i am the guy who makes you look good.

  11. #11

    Default Re: Focusing in low light

    Thanks for the input guys. Didn't realise that even for something supposedly so simple,there is some serious tech going on! Gotta read up and shoot more man =)

  12. #12

    Default Re: Focusing in low light

    Quote Originally Posted by hyde9 View Post
    Thanks for the input guys. Didn't realise that even for something supposedly so simple,there is some serious tech going on! Gotta read up and shoot more man =)
    It seems simple to you *because* of all the tech behind it.
    Alpha

  13. #13
    Member enzeru21's Avatar
    Join Date
    Apr 2010
    Location
    upper thomson
    Posts
    1,493

    Default Re: Focusing in low light

    Focusing works by detecting contrast within your selected focus point, i.e. if you are using the centre focus point, then whatever you are pointing at has to have contrast. If you're pointing at a white wall or clear sky, the camera will not be able to figure out what is the distance between you and the object you are focusing at, and thus will not be able to focus.

    Similarly, if it's dark, naturally the contrast between things is much lower. It then becomes difficult for the camera to pick out the contrast in order to focus.

    The best thing to do is to (a) look for something with a high contrast to focus on (e.g. something lit by a lamppost) or (b) open your on camera flash and let the focus assist flash fire, then when it's focused, close the flash and take your photo

    ______________________________________________
    enzeru21 Canon 500D EFS 17-85mm IS | EF 50mm f/1.8 II

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •