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Old Nov 6, 2004, 8:01 AM   #1
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Justa quick question.......

I came across this article and it sounded like a great rule of thumb to be able to make easy use of the hyperfocal distance on a lens. However when I went to look at my lens (the Canon ef 28-135 IS) it doesn't have the f-numbers marked on a scale below the distance meter.

Is the article wrong about finding the hyperfocal distance in this way?And doesn't the "A-Dep" mode onthe Eos10d perform the exact same function anyway?
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Old Nov 6, 2004, 10:15 PM   #2
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It depends on the lens... the Sigma EX's have the same f-numbers markings

-> or you can use this on-line calculator to find the hyperfocal distance for any lens: http://www.dofmaster.com/dofjs.html
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Old Nov 7, 2004, 5:55 AM   #3
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Thanks for the info NHL.

I was asking because it sounded like such an easy way to make use of a complex but usefull property of a lens.

I suppose I could always make out a table of different focal lengths and f-numbers to carry around in a note-book. But even that isn't as easy as matching up the infinity mark with the f-number.......

:idea:

Or I could make my next lens pruchase a Sigma lens.......
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Old Nov 7, 2004, 6:15 AM   #4
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... Or you can put a masking tape on the 'useless' IR marking on the lens barrel with your own f-numbers! It sure is ugly, but that'll work :idea:
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Old Nov 7, 2004, 9:47 AM   #5
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I had thought about doing something like that - but I have no idea how far apart I should space the f-numbers. And it seems to me that having inaccurate numbers would be of a lot less use then not having the hyperfocal distances marked out at all.
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Old Nov 9, 2004, 7:34 PM   #6
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Hyperfocal distance is a somewhat dated theory of DoF application that madesome assumptions in order to be useful. In practice, it still wasn't as useful as one might have hoped. This theory is based on an assumption of "acceptable sharpness", and you, your application, and your print size make a difference in what is "acceptable sharpness". This makes "correct" DoF markings on lenses marginally useful.

Here's a good on-line source for alternative focusing techniques that can be useful and yield better results. Unfortunately, it's not entirely simple.IMO it is reliable and informative.

http://www.trenholm.org/hmmerk/download.html

I think that like the author, you're likely to be disappointed in many cases if you try to apply the old hyperfocal theory directly to current resolution and enlargement sizes.

The author still states that tradiational DoF theory can't be entirely wrong, simply based on the volume of work for which it's been applied. He offers more insight and alternative techniques.

DSLR's give a great opportunity in themselves for furthering this knowledge for oneself. The 20D for example allows quite usable tethered mode shooting -- you can shoot, and then immediately view your full size results on a computer (laptop), assuming that you've got that computer, connections, and enough power handy.

Especially if you have a decent view from a window, you can do such experimentation easily at your convenience at home.
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Old Nov 11, 2004, 7:23 AM   #7
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Thats an interesting Booklet and the explanations of optics are good to know.

For all the complex mathmatics he uses to make his explanations what it all boils down to in the end is that wide angle lenses should be focused at infinity with a large-ish f/number to get acceptable sharpness from foreground to infinity.

I'll try that out nest time I get the chance to shoot landscapes. At the moment the weather is too dull, overcast and the rain a little unpredictable to be out shooting.
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