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Thread: focus at infinity?

  1. #1
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    Default focus at infinity?

    Hihi!

    I knoe that focus at infinity is for far away objects...such as landscapes? But in wat situation can you actually use focus at infinity? As in how far is considered far?

    Suppose i haf a tree 5m in front of me...does it make a difference if i focus on the tree...or i focus to infinity?

    I'm oso thinking more of concerts...suppose i haf a cam which haf difficulty focussing in low lights...can i just set it to focus to infinity all the time and just shoot without bothering bout focus lock?

    Thanks!!!

  2. #2

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    usually more anything at 30m or more from u is taken as "at infinity" ^_^

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    Sorry, chup in a bit...

    How does hyperfocal focussing differ from focussing at infinity? Is the depth of field larger when using hyperfocussing techniques than simply focussing at infinity?

    Thanks!

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    there are detailed arguments that conclude that hyperfocussign gives u the maximum range of DOF, there are other studies that claim other wise...actually even if thay are correct to any extent, well our eyes wont really see much diff unless u intend to be very very meticulous (which i dont recommend, due to a pragmatic and time saving point of view ), it like the issue with DOF preview: press the button and the aperture blades stop down, viewfinder gets so dim that u cant even really see clearly, let alone judge the range of DOF that u want to be accdeptable...so, at the end fo the day, it really really doesnt matter loh (well, there r better thingsd to do, like swimming! ;-) ^_^

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    Senior Member Kit's Avatar
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    A simple explaination. Hyperfocal focussing does not focus at infinity. It focuses on a spot some in front of the camera to give good DOF for foreground objects but at the same time, the background is still in focus. E.g. on a Canon 20mm f/2.8, when using f/8, the hyperfocal distance would be around 1m and anything in front of your camera that falls within the range of 0.7m to infinity would be in focus.

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    Senior Member Kit's Avatar
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    Hyperfocal focussing is useful as you can preset the lens focus for fast snapshots as long as you can the object distance fairly accurately. Try it on scenes with layers(with foreground and background). Compare the shots focussed at infinity, you'll definitely see the difference, even with DOF preview.

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    Ah, thanks for the explanations! So hyperfocussing will get you more foreground DOF as compared to focussing at infinity right?

    I find that my eyes aren't very sharp...when stopping down in DOF preview, things which I think are in focus aren't...so trying to get a way to ensure sharpness when I need it and not on the camera's AF. Thanks!

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    Senior Member Kit's Avatar
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    If you use hyperfocal focussing and know your lenses well enough, you don't even have to use DOF preview anymore. Just compose and shoot. If want to be a bit more kiasu, focus with a smaller aperture mark than the aperture you're using. E.g. if you're using f8 to shoot, focus using say..... the f11 mark on the lens.

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    I see I see...so I basically have to make sure that I'm within the hyperfocussing distance and just shoot lar? Thanks!

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    Senior Member Kit's Avatar
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    Hmm...... first you have to decide how far is your foreground objects is roughly. That will help you select the appropriate aperture. If you want to play safe, focus using the aperture that is a stop smaller than the chosen aperture to take the picture. So the aperture you use to shoot and the aperture mark on the lens you use to focus is different.

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    hmm..guess I have to test it out soon. Being a film shooter, this sort of blurness issue very gek sim when you see your attempted 'artistic' shots going haywire cos it's out of focus...

    Thanks!

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    Senior Member Kit's Avatar
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    Yes, the best thing to do is to try it out.

  13. #13

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    Quote Originally Posted by Kit
    A simple explaination. Hyperfocal focussing does not focus at infinity. It focuses on a spot some in front of the camera to give good DOF for foreground objects but at the same time, the background is still in focus. E.g. on a Canon 20mm f/2.8, when using f/8, the hyperfocal distance would be around 1m and anything in front of your camera that falls within the range of 0.7m to infinity would be in focus.
    Does hyperfocus work on all lenses?

  14. #14

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    Quote Originally Posted by phantasia
    Hihi!

    I knoe that focus at infinity is for far away objects...such as landscapes? But in wat situation can you actually use focus at infinity? As in how far is considered far?

    Suppose i haf a tree 5m in front of me...does it make a difference if i focus on the tree...or i focus to infinity?

    I'm oso thinking more of concerts...suppose i haf a cam which haf difficulty focussing in low lights...can i just set it to focus to infinity all the time and just shoot without bothering bout focus lock?

    Thanks!!!
    The only time I focused at infinity was for the following shot of the heavenly stars which I took up in a mountain in Nepal... Exposed the film for 13 mins, aperture at f3.5, in almost total darkness (and cold) late at night...

    Jia Wang... "A photo is only as beautiful as the photographer's eyes can see."
    My Eyes ;)

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    Cool! But it looks a bit shaky (as in the star trails aren't truly circular...)

    mikedsjr: I believe hyperfocussing techniques can be used on all lenses, but most modern zoom lenses does not provide a DOF scale on the lens, making it hard to use this technique.

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    most,if not all NIKON lens have HF marking.

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    Quote Originally Posted by kex
    most,if not all NIKON lens have HF marking.
    Erm, my 28-80G and 75-240D doesn't, but my 3 primes does. I don't know about the higher end zoom lens though. Guess I should change my statment to 'some modern zoom lens lack DOF markings..'

  18. #18

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    what's hyperfocal focussing???

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    Quote Originally Posted by clive
    usually more anything at 30m or more from u is taken as "at infinity" ^_^
    Doubt that. Depends completely on what lens and what aperture you're using. With a 400mm lens at f2.8 for instance, your DOF at 30m is only from 29.5m to 30.5m. Easy to see that if you just focus at infinity, something just 32m away won't be in focus. Stopping down to f5.6 changes that to 29.1m to 31m in focus, still not sharp enough.

    I've explained this already before on this forum when some time ago at national day someone suggested shooting planes in flight just by focusing at infinity. Not going to work.

  20. #20

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    Quote Originally Posted by phantasia
    Hihi!

    I knoe that focus at infinity is for far away objects...such as landscapes? But in wat situation can you actually use focus at infinity? As in how far is considered far?

    Suppose i haf a tree 5m in front of me...does it make a difference if i focus on the tree...or i focus to infinity?

    I'm oso thinking more of concerts...suppose i haf a cam which haf difficulty focussing in low lights...can i just set it to focus to infinity all the time and just shoot without bothering bout focus lock?

    Thanks!!!
    at 5m, focus at 5m. if not, use zone focussing to get apparent sharpness.

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