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02-26-2010, 08:31 AM   #1
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How do you use the DOF scale?

How do you use the DOF scale?
Whats with those apertures, the red line, ft & meter


Last edited by rustynail925; 04-21-2010 at 09:20 AM.
02-26-2010, 08:38 AM   #2
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The red line indicates the selected focus distance (just over a meter I guess). The numbers next to the red line refer to the aperture and so you can see/predict what will be in focus. In the shown picture (with and aperture of 5.6[edit: oops, should be 8]), from about .75 meters to infinity.

If you close the aperture to f/22 and set the focus distance to about .5 meters (maybe .75), anything from .3 meters to infinity will be in focus (estimation).

[EDIT]
removed text refering to crop factor
[//EDIT]

Last edited by sterretje; 02-26-2010 at 04:17 PM.
02-26-2010, 10:14 AM   #3
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Decide what DOF you want, what range of stuff you want to have in focus. Using those paired f-stop marks, decide what aperture will give you that DOF range. (The red focus mark is now actually a hyperfocus, a pre-focus, but don't worry about that.) Just tell yourself, I want DOF to be 3 feet to infinity, or 2 to 10 feet, or whatever. Set those distance marks against the paired f-stop marks, dial-in that aperture, and you're ready to go.

NOTE: If infinity is really important to you, set the outer edge of the infinity mark to just inside its f-stop mark. This reduces your near DOF slightly, but ensures that you're crisp all the way out to forever. If the near edge of the range is more critical to you, set the near distance mark to just inside ITS f-stop mark. In other words, err on the side of caution.
02-26-2010, 10:52 AM   #4
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nice lens in image, the DOF scale show between 8 lines, meaning f/8, DOF is from ~0.75 meters to infinity on meters distance scale, and from ~2 feet to infinity on feet distance scale.

02-26-2010, 11:28 AM   #5
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Adding to RioRico's comments and observing the good practice of having 2/3rds of your effective DOF in front of a subject, I like to set the focus distance to a subject and then shift the lens slightly so that more of the foreground is in focus while sacrificing a little bit on the infinity side. It's pretty obvious on the DA15 above that there is an increasing rate of change to the distance scale as distance increases (as to be expected) but, still, infinity on that DA15 includes pretty much everything from maybe 10 FT and beyond, especially on a wide angle lens like a 15mm.

If you take a nice portrait of someone while outdoors and there is somethng in the foreground you want in focus who cares if a cloud in the sky beyond is slightly soft?
02-26-2010, 11:46 AM   #6
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Does anyone know if the DoF scales on the DA lenses are based on the 1.5x crop sensor? I just recently learned that the DoF scale on the old full frame lenses assumes a full frame sensor, and should be decreased by a factor equal to the crop factor of the sensor. This is due to different sizes of the Circle of Confusion.
02-26-2010, 12:07 PM   #7
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QuoteOriginally posted by devorama Quote
Does anyone know if the DoF scales on the DA lenses are based on the 1.5x crop sensor? I just recently learned that the DoF scale on the old full frame lenses assumes a full frame sensor, and should be decreased by a factor equal to the crop factor of the sensor. This is due to different sizes of the Circle of Confusion.
Shouldn't matter. The only thing that changes with the crop is your field of view. It does NOT change the lens characteristics. 1 foot or meter is 1 foot or meter no matter where or how you measure it.

02-26-2010, 12:17 PM   #8
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QuoteOriginally posted by devorama Quote
Does anyone know if the DoF scales on the DA lenses are based on the 1.5x crop sensor? I just recently learned that the DoF scale on the old full frame lenses assumes a full frame sensor, and should be decreased by a factor equal to the crop factor of the sensor. This is due to different sizes of the Circle of Confusion.
Crop factor is irrelevant. Crop factor refers to the FOV, the Field of View -- that is, the angle that the lens sees. DOF is determined ONLY by the aperture and focal length of the lens, and the distance to the subject. A smaller sensor or frame just means that you (and the camera) see a narrower slice of what's out there -- it doesn't change the depth relationships.

Say you have a 100mm lens, aperture is f/11, subject is 12 meters (40 feet) away. You use the same setup on 8x10 and 4x5 view cameras (wide), 645 and 6x9 MF cameras (nearly normal), 35mm FF and HF (same as APS-C) cameras (tele), and a 110 SLR (long tele). Because of the different frame sizes, the FOV angle changes greatly -- but the DOF remains exactly the same, from 7m (23 ft) to 30m (100 ft). All that changes is the width of what's captured.

EDIT: Darn, JeffJS, ya beat me to it! I shouldn't have stopped to look at a lens. ;(

02-26-2010, 12:26 PM   #9
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QuoteOriginally posted by RioRico Quote

EDIT: Darn, JeffJS, ya beat me to it! I shouldn't have stopped to look at a lens. ;(
Don't worry about it.. Sometimes it takes a few posts to get a point across. Mine wasn't totally helpful except to say No Affect on the scale, yours went into explaining focal lengths in general. It actually took me awhile to grasp the concept of why a 50mm on a medium format camera was a wide angle and normal on a 35mm camera.. Image Circle which affects everything else including DOF. Doesn't CHANGE the DOF, just how much of it you see in the final image.

02-26-2010, 01:22 PM   #10
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QuoteOriginally posted by RioRico Quote
DOF is determined ONLY by the aperture and focal length of the lens, and the distance to the subject.
This is not correct. You are completely ignoring the circle of confusion as a factor.
Circle of confusion - Wikipedia, the free encyclopedia
02-26-2010, 02:52 PM   #11
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>> DOF is determined ONLY by the aperture and focal length of the lens, and the distance to the subject.

QuoteOriginally posted by krb Quote
This is not correct. You are completely ignoring the circle of confusion as a factor.
Realistically, i.e. what the photographer can control, the CoC is a function of aperture and frame-to-subject distance (focus) -- that's 2/3 of what makes DOF. I can't deal with the cited factors (Visual acuity; Viewing conditions; Enlargement from original image to final image) when I'm composing, exposing, or developing-editing the picture. I *can* increase the CoC by stopping down too far (diffraction effects) or too little (softness), and/or focusing badly; and I can decrease CoC by focusing crisply and choosing a sweet f-stop. I can manipulate apparent sharpness somewhat in PP. But I can't control a viewer's eyeballs, and where and how she places them. Not my department.
02-27-2010, 07:13 AM   #12
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How do you compute the hyperfocal distance?
02-27-2010, 08:39 AM   #13
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Search for wiki hyperfocal distance

Or use Online Depth of Field Calculator
02-27-2010, 10:30 AM   #14
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Thx for the link.. Still cant get it exactly how to compute for the hyperfocal distance..
if you are shooting landscapes at what point do you focus to get more dof?
02-27-2010, 10:37 AM   #15
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Example

for this pic where would i focus to have the maximum dof
and where isl the hyperfocal distance ?
@f8, 115mm
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