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04-16-2007, 06:38 AM   #1
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A perplexing focus question (to me anyway)

I've come across this problem quite a few different times and have managed to "muddle thru" by guessing but I'm hoping there is a better method than pure guess, or even worse "you'll learn by experience". My experience with "you'll learn by experience" is that I experience more failures than not!
Anyway here is the problem. I'm shooting with a new DA lens, one without either aperture ring or DoF markings. I set a fairly narrow aperture (for sake of argument say f16) as I want a wide DOF. So where do I set my focus point? Let's also say for sake of argument, that the DOF preview is too dark for me to really discern how much of the exposure will be in focus (I shoot with a DS so I don't have the luxury of the "digital preview") So do I focus on the foreground? Background? Middle? Middle back? Middle fore? Where? Looking thru the viewfinder is no help, I've got not dof markings to guide me, what do you more experienced photographers use?

NaCl(I've encountered this problem more than once, and I hate "guessing" )H2O

04-16-2007, 06:41 AM   #2
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The actual focus plane should be about 1/3 of the way into the "in focus"area. That has been a rule of thumb for over thirty-five years that I know of, and probably for the last hundred years.
04-16-2007, 06:56 AM   #3
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Solution: Canon's unique DoF Priority Mode! ;-)

BTW, as we are Pentaxian, if you have a pocket PC, try to download a DoF calculator, then you'll have a DoF scale and you know roughly where you should put your focus scale at :-))

QuoteOriginally posted by NaClH2O Quote
I've come across this problem quite a few different times and have managed to "muddle thru" by guessing but I'm hoping there is a better method than pure guess, or even worse "you'll learn by experience". My experience with "you'll learn by experience" is that I experience more failures than not!
Anyway here is the problem. I'm shooting with a new DA lens, one without either aperture ring or DoF markings. I set a fairly narrow aperture (for sake of argument say f16) as I want a wide DOF. So where do I set my focus point? Let's also say for sake of argument, that the DOF preview is too dark for me to really discern how much of the exposure will be in focus (I shoot with a DS so I don't have the luxury of the "digital preview") So do I focus on the foreground? Background? Middle? Middle back? Middle fore? Where? Looking thru the viewfinder is no help, I've got not dof markings to guide me, what do you more experienced photographers use?

NaCl(I've encountered this problem more than once, and I hate "guessing" )H2O
04-16-2007, 09:58 AM   #4
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Bingo!

QuoteOriginally posted by Dana G Quote
The actual focus plane should be about 1/3 of the way into the "in focus"area. That has been a rule of thumb for over thirty-five years that I know of, and probably for the last hundred years.
Thanks Dana, that is exactly what I was looking for, a nice straight forward "rule of thumb" that is easily applied. So middle foreground it is. Thanks!

NaCl(or to be more exact "near middle foreground" )H2O

04-16-2007, 10:07 AM   #5
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QuoteOriginally posted by RiceHigh Quote
Solution: Canon's unique DoF Priority Mode! ;-)

BTW, as we are Pentaxian, if you have a pocket PC, try to download a DoF calculator, then you'll have a DoF scale and you know roughly where you should put your focus scale at :-))
RH, don't have a pocket PC, don't even want to own a pocket PC. And the last thing I want to do is to whip out ANOTHER electronic gizmo and start calculating away while shooting.

NaCl(but thanks for the input)H2O
04-16-2007, 01:51 PM   #6
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I agree that a DOF calc on a PDA might be a bit much.

However, a small (4X6 index card) chart might be of help, if you want to be a bit more precise about things. Charts are really suited to one focal length, (because otherwise you might need to carry a poster!), so if you've got a prime or find yourself shooting at X mm frequently, it wouldn't hurt to make one.
04-16-2007, 01:59 PM   #7
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Hi Salty,
Here are some links that might be of some use to you.

Photo Critique, DOF Chart
Custom Depth of Field Chart
Hyperfocal Distance Chart - DOFMaster
Focus Pocus: Outsight Photography Depth of Field Calculators

Google DOF chart and you'll get a ton of links.
04-16-2007, 02:18 PM   #8
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QuoteOriginally posted by bdavis Quote
I agree that a DOF calc on a PDA might be a bit much.

However, a small (4X6 index card) chart might be of help, if you want to be a bit more precise about things. Charts are really suited to one focal length, (because otherwise you might need to carry a poster!), so if you've got a prime or find yourself shooting at X mm frequently, it wouldn't hurt to make one.
Thanks Beth, but I actually was thinking of the "kit" twins, DA 18-55 and the DA 50-200, I've encountered this with "bode o dem" as some say here in the Bronx. The reason I finally brought it up was that I was wandering around my sisters property on the edge of her swamp, (I refuse to call it a wetlands...too many letters to type) taking pictures of the flora sprouting further in. Silly me I had forgotten water proof foot wear so was limited to using my DA 50-200 to get close enough. Several times I wanted to get two different plants that were some distance from each other. Fortunately it was bright enough to narrow my aperture to f11 or even f16 but the quandary was where to focus? Front plant? Back Plant? halfway between? etc. And I was using all kinds of different focal lenghts but mostly somewhat near the middle of th zoom. I've come across the problem before with both lenses and have always guessed. With Dana's rule of thumb I don't have to do that any more. I try to make the aperture narrow enough so there is some room to play with.
The card is a good idea but I'd have to have a bunch of them to cover the zoom range, and I don't want to fumble with cards any more than I want to fumble with a pda. I'll probably make up one for my FA 50mm 1.4 tho, that will also cover the short end of the DA 50-200 and the long end of the DA 18-55.

NaCl( limited application but good idea)H2O

04-16-2007, 03:09 PM   #9
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Hey, its cool. If you don't want to carry cards, don't carry cards. I noted that they do have a somewhat limited application, however, you can make them work with zooms.

I've got a 24-135 zoom on the camera right now. I've also got cards for 30 mm, 50, 75, 100, and 125. You don't have to be super precise, and if the hamster upstairs is running on the wheel, you can take a good stab at what f13 will give you between 30 and 50, 75 and 100. You don't have to carry that many cards at all, and you'll know, okay "I have X # of feet to work with".

Admittedly, I do have them on 3X5 index cards, because I'm young (and fabulous ) and my eyes aren't completely shit. I can use the back of (one of) them to set my white balance, and I've considered laminating them and carrying a wet-erase marker to make notes (but considering that I've already scrawled on them in pencil, I suppose I'll just continue to do that).
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