Infinity Focus Question

Discussion in 'Photography Beginners' Forum' started by decado, Oct 11, 2009.

  1. decado

    decado TPF Noob!

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    After taking some night skyline shots of Minneapolis I noticed I had a little problem. I manually focused the shots at infinity and they came out unfocused (not camera shake blurriness) and I was far enough away to get the entire skyline in the frame. I then went to test out my lenses to see what was going on in the daytime and I actually have to focus forward slightly in order to get the sharpest image. Is this supposed to happen or might there be a problem with my lenses? I'm using a Canon EOS500D and my lenses are the kit EF-S 18-55 f/3.5-5.6 IS and the EF-S 55-250 f/4-5.6 IS, I seem to have this problem with both.
     
  2. Derrel

    Derrel Mr. Rain Cloud

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    MANY lenses will focus past infinity! Strange but true. Not too many years ago, ALL of Nikon's AF-S lenses,all of them, focused past infinity.That peculiar behavor has now made its way into many other lenses. Very large, long telephoto lenses have focused beyond infinity for many decades, to allow for changes in the lens's focusing as the lens got hot in the sun; very large lenses like 300/2.8 and so on get pretty warm after a few hours in the sun on hot days.

    Focusing past infinity seems kind of odd, but it's something the manufacturers have begun doing on more and more zooms. For doing things like night fireworks or night landscape shots, the new breed of kit lenses is really a PITA; older prime lenses that stop right at Infinity are much easier to use in the dark. Canon, and Nikon's 18-55mm kit lenses both have really sloppy, hair-trigger manual focusing action,and neither is what I would call a first choice for nighttime work, but you go with what you've got,right?

    There is no problem with your lenses: this is the "new way" many zooms are being made. I find it rather disconcerting at times to have to visually confirm focus when I grew up with lenses where Infinity meant Infinity...
     
  3. mtfd635

    mtfd635 TPF Noob!

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    I remember from my Canon AE1 film days that I had to focus to infinity then back off a little.
    Practice with your lens in daylight, to infinity n then backing off to determine how much back.you'll notice a little sideways "L" next to infinity symbol, that is the 'range' for infinity which I understand compensates for hot/cold climes
     
  4. Plato

    Plato TPF Noob!

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    Many years ago, I had a telephoto lens that not only focused beyond infinity but the lens was actually marked that way! I think that it had something to do with adjustments necessary when using IR film.
     

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