Rectangle in viewfinder ?

Discussion in 'Photography Beginners' Forum' started by Sirene, Aug 24, 2009.

  1. Sirene

    Sirene TPF Noob!

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    1.What is the rectangle that I can move in the live viewfinder of my camera ?
    Is it the equivalent of the AF points in the regular viewfinder ?
    If so then it is even more useful as it can be moved more than the fixed points you have to choose from ?
    Oh and is it for spot metering as well ?

    2.When shooting a landscape, how do you know which af point to choose ?

    3.What is focusing on infinity ?

    4.Do you select a focus point everytime ?

    5.When does manual focus is necessary ?


    I understand the idea of focusing, but when applying that knowledge with my camera, I'm lost, I wish there was a video explaining it all.

    Thanks for all your help !
     
    Last edited: Aug 24, 2009
  2. musicaleCA

    musicaleCA TPF Noob!

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    1. The manual should explain this.

    2. Meh. Shooting landscapes is done at infinity anyway.

    3. Hyperfocal distance - Wikipedia, the free encyclopedia

    4. Usually I just set it and leave it to suit my current needs. Sometimes in other situations I leave it on full AF, sometimes I have to switch between them all. It's all very dependant on the situation.

    5. In very low light, or when the AF can be fooled (e.g. when you need to focus on something that has little or no contrast for the AF processor to use for it's calculations). Or, for the really picky, when the AF is slightly off and you can actually notice it in the viewfinder...for those with super-sharp eyes. MF can also be handy on lower-end bodies that don't have excellent continuous AF (AF Servo on Canon cameras).
     
  3. Steph

    Steph No longer a newbie, moving up!

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    Well not always. If you want to have something close to you in focus and keep the background in focus, infinity focusing won't do. That's when you need to use the hyperfocal distance. Focusing on infinity and hyperfocal distance are two different things.
     
  4. Dao

    Dao No longer a newbie, moving up!

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    +1
     
  5. Dao

    Dao No longer a newbie, moving up!

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    Question #5

    Besides what musicaleCA had said, sometimes I use manual focus ...

    - When shooting macro type photos.
    - When I need to take a series of photo of a stationary object. So I do not need to wait for the AF (esp with low ambient light flash type photos and camera on tripod)
    - Wide view landscape type shots.
     
  6. Sirene

    Sirene TPF Noob!

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    Ok so my manual tells that the rectangle is for af, but I don't get why the rectangle can go to more places on the scene than the AF points in the regular viewfinder do..... ?
    I get what focusing on infinity is, but how do you focus on infinity with your camera ?
    Does full AF mean all the Af points ?
    What do you mean you set it and leave it to suit you current needs, don't we have to change the af point between all of our shots ??
    Is it me or is manual focusing seems so much easier....

    Wow, I have a lot to learn, I get what focusing is but I don't know how to apply the knowledge to my T1i

    Do you guys know any links to a detailed article on how to focus with Canon or a video....

    Thanks again.
     
    Last edited: Aug 24, 2009
  7. musicaleCA

    musicaleCA TPF Noob!

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    Well, that's because when you are looking through the viewfinder, the AF sensor (and mirror) are locked down, so the camera uses that. The AF sensor is very accurate, compared to the contrast-detection via the sensor in Live View. When the mirror is locked-up, the camera can't use the AF sensor, so uses simple contrast detection, and thus you can move the box wherever you want on the screen. There should be a custom function you can change to set it so that it locks-down the mirror when you focus in Live View and uses the AF sensor.

    Turn the focus ring until it reaches infinity.

    Yeah, that's what I meant.

    Sometimes the situation warrants setting your AF point manually. That's for times when you have, well, time. But say I'm running around on the street, and don't have a clue what the next shot will be; I set the camera to be close to the exposure I expect, at an aperture I want, and let the camera use all AF points. Works like a charm most of the time, unless I'm trying to shoot through passing people, in which case I flip-off AF and use manual focusing to quickly nab the shot.

    Only with experience. The AF sensor is pretty darn accurate, and will almost always be faster than you.

    *sets-up the Samanax signal*
     
  8. Sirene

    Sirene TPF Noob!

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    Great Musicale, that helps me a lot, I'm sorry for being such a newbie, but reading and the internet are my ressources, so sometimes I don't get how to apply an option or a feature to my camera..

    So would you say, most of the time people simply let the camera set on all of the AF points ? Can this way takes sharp images ?

    So when shooting a landscape you're better of using manual focus then all of the AF points ?

    Why would you focus and lock with the center AF point when you could simply choose the right af point ?

    I feel that this focusing thing would take a lot of time when taking pictures, or do you with experience get really fast at choosing the AF mode and then the AF point ?

    Thanks so much again !!
     
  9. Dao

    Dao No longer a newbie, moving up!

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    I usually use the center AF point only. Focus and re-compose type case.
    In some occasion, I will select a particular focus point such as shooting a stationary object.


    You may want to read more about Depth of Field (DoF) as well as Hyperfocal distance.
     
  10. Sirene

    Sirene TPF Noob!

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    Do you guys really see a big difference when choosing a specific AF point, as opposed ot full af points ?
     
  11. Sirene

    Sirene TPF Noob!

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    Like I said, why would you focus and lock with the center AF point when you could simply choose the right af point ? I wonder ...

    Thanks in advance
     
  12. musicaleCA

    musicaleCA TPF Noob!

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    The theory goes that the centre AF point is most accurate (which it is) and thus will focus better. However, because you reposition the camera, you have to adjust the focus again manually before you take the shot, particularly when your DoF is shallow. This is because the angular movement of the lens moves the focal plane behind where you originally focused, and thus requires that you pull back the focus ring. In such cases, it is generally better to just stick to using the other focus points, and not waste time messing with manual focus (of course, this changes on lower-end bodies, where using MF to pull back the focus can be preferable in some situations, dependant on one's MF experience and ability).
     

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