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Oly 17mm snap focus - how does it work?

Discussion in 'Native Lenses' started by Ted, Nov 3, 2014.

  1. Ted

    Ted Mu-43 Regular

    79
    Oct 10, 2014
    Tasmania, Australia
    Theo B
    Hey guys, so I've just today grabbed the Oly 17mm 1.8 (and the 45mm!) and am a bit confused by the snap focus. I'll mostly be using auto focus anyway, but it'd be nice to at least know how it works! I'm going to assume the front numbers are the aperture, and the back numbers are the focal distance, but the aperture numbers go in both directions? Not sure what I'm meant to line up where.

    Also, I know f8 is meant to be the 'go to' for street photography, is that the same with m4/3 or can we get away with f4 for the same DOF as f8 in full-frame. Is my understanding there correct? Sorry for the super newb questions!
     
  2. Rudy

    Rudy Mu-43 Veteran

    449
    Jan 24, 2013
    Oakland, CA
    The f-stop numbers go in both direction as they show you the range that will be in focus for those f-stops.
    For example if you focus to 3m (red mark in the center) then at f/22 everything from about 1.5 m to infinity will be in focus.
    Since everything is really crammed this isn't really all that useful. You can't really see the range for more reasonable f-stop numbers...
    Rudy
     
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  3. Ted

    Ted Mu-43 Regular

    79
    Oct 10, 2014
    Tasmania, Australia
    Theo B
    That made complete sense, thank you so much! If only you wrote the user guide (which explained nothing) :wink:
     
  4. Vivalo

    Vivalo Olympus Loser

    931
    Nov 16, 2010
    Finland
    You can not change the aperture value from the lens, you can only change the distance of best focus. The distance scale on the lens is very simple. As you described on front side you have a red line and aperture values on both sides of that. Behind (or below) those aperture values you have your distance readings, meters marked white and feet marked orange. Lets say you know you want to focus one meter away from the camera, then all you have to do is to set the one meter mark aligned with the red line above it. Whatever aperture you are using, anything that is one meter away from the camera is in focus. But if you are using for example f11, then everything in that scale between the f11 marks are also in focus due to the larger DOF. That is why the f-numbers are there. You can also also use it outdoors so that you set your aperture to f5.6 and the right side aperture line over the infinity distance marking. That way (when using aperure f5.6) you have everything from roughly 5 meters to infinity in focus, as it is in the scale between f5.6 markings. And yes, the old full frame "go to" aperture f8 can be translated to new m4/3 "go to" aperture of f4, due to the larger DOF provided by the smaller sensor. Personally I prefer f5.6 or f8 though.
     
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  5. RickinAust

    RickinAust Mu-43 Regular

    119
    Feb 9, 2013
    Australia
    As described above by Vivalo the in focus range is determined by the f stop and the actual focus distance to subject. A neat trick is to pre focus at the hyperfocal distance so that everything just in front of the subject focus distance to infinity is in focus, just Google hyperfocal for an explanation or have look at the following link.
    http://www.dofmaster.com/dofjs.html
    I have the 12mm which is similar and I have a table that shows for each f stop the hyperfocal distance and the so called near limit, the far limit is infinity, I sometimes refer to this to set up the camera. Saves having to fiddle around just point and shoot.
     
  6. Lionroar

    Lionroar Mu-43 Rookie

    24
    Nov 10, 2014
    I love the 17mm f/1.8 lens, but more for the field of view and the cool lens hood rather than the snap focus which I never used and don't think I ever will, but some people seem to like it.