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Thread started 14 Jan 2016 (Thursday) 06:02

# Focal depth?

Jan 14, 2016 06:02 |  #1

So where can i find the math that will tell me how deep of area will be in focus at different aperatures and other variables

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Jan 14, 2016 06:14 |  #2

You wanted the math, so here it goes:

You need to know the CoC of your camera, Canon APS-C sized sensors this number is 0.018, for Nikon APS-C 0.019, for full frame sensors and 35mm film the number is 0.029.

The formula is for completeness:

CoC (mm) = viewing distance (cm) / desired final-image resolution (lp/mm) for a 25 cm viewing

got this of the net

Old but still trying to be young at heart

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Jan 14, 2016 06:18 |  #3

or you could just download an app to your phone. I use one that I think is called Depth of Field.

yeah, I gots some stuff.

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Jan 14, 2016 06:22 |  #4

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Jan 14, 2016 06:22 |  #5

Lookin more for how deep of a area will be in focus in front and behind point of focus

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Jan 14, 2016 06:27 |  #6

faw67 wrote in post #17857651
Lookin more for how deep of a area will be in focus in front and behind point of focus

You mean you did not want to work thru the mathematical formula on the nature of the universe, why there is air, and the existence of time?? Tch, tch. Imagine that.

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Jan 14, 2016 06:33 as a reply to  @ Picture North Carolina's post |  #7

Lol not really
It all depends on what makes the women happy

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Jan 14, 2016 06:34 |  #8

Dof calculator does what i need thanks

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Jan 18, 2016 20:07 |  #9

faw67 wrote in post #17857651
Lookin more for how deep of a area will be in focus in front and behind point of focus

Yes, we understand. But the question you are asking is a very complex one, and there are a lot of parameters and variables that need to be specified in order to get an absolutely accurate answer. Otherwise, the DOF calculator will just fill in default values for you and you may not get an answer based on your exact usage and/or output and/or needs.

"Your" and "you're" are different words with completely different meanings - please use the correct one.
"They're", "their", and "there" are different words with completely different meanings - please use the correct one.
"Fare" and "fair" are different words with completely different meanings - please use the correct one. The proper expression is "moot point", NOT "mute point".

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Jan 19, 2016 11:19 as a reply to  @ Tom Reichner's post |  #10

It actually gave me what i wanted

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Jan 19, 2016 13:38 |  #11

faw67 wrote in post #17864412
It actually gave me what i wanted

There's one thing that you must understand. That's he fact that the numbers in almost any depth of field calculator are basing the results on several assumptions. The assumptions include:

All images are expected to be viewed at some standard size (typically 8"x10" or 8"x12").

All images are expected to be viewed at some standard distance.

All persons viewing the image have a certain visual acuity.

How do these variables affect you? If you make prints or display images on a screen at some other size and/or have people view the images at some other distance and/or have folks with super-sharp or blurry vision, the perceived depth of field of your images will be different from what the calculator showed you.

Skip Douglas
A few cameras and over 50 years behind them .....
..... but still learning all the time.

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Jan 19, 2016 14:03 |  #12

SkipD wrote in post #17864650
There's one thing that you must understand. That's he fact that the numbers in almost any depth of field calculator are basing the results on several assumptions. The assumptions include:

All images are expected to be viewed at some standard size (typically 8"x10" or 8"x12").

All images are expected to be viewed at some standard distance.

All persons viewing the image have a certain visual acuity.

How do these variables affect you? If you make prints or display images on a screen at some other size and/or have people view the images at some other distance and/or have folks with super-sharp or blurry vision, the perceived depth of field of your images will be different from what the calculator showed you.

And yet it works for most people.

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Jan 19, 2016 14:42 |  #13

gonzogolf wrote in post #17864677
And yet it works for most people.

The calculators give results that show folks roughly what to expect of course. However, some people have complained that they did not get what they expected and usually it's because they were using a different set of conditions when analyzing the results.

Skip Douglas
A few cameras and over 50 years behind them .....
..... but still learning all the time.

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Jan 19, 2016 14:53 |  #14

SkipD wrote in post #17864741
The calculators give results that show folks roughly what to expect of course. However, some people have complained that they did not get what they expected and usually it's because they were using a different set of conditions when analyzing the results.

The problem is that many come here asking a simple question, they get treated to a thesis that still doesnt answer their questions, and they leave intimidated. Its like asking f8r directions and being told you simply cant get there from here.

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Jan 19, 2016 15:41 |  #15

In response to the 'debate' between SkipD and gonzogolf..."Certs is a breath mint, Certs is a candy mint"

The problem of DOF is that most folks do not understand the underlying assumptions, so they jump very quickly to wrong conclusions. Ergo the debate. Neither are totally wrong. Oversimplify, jump to bad conclusions. Explain sufficiently, intimidate those expecting a simplistic answer.

Let me throw out these points, raising the question to the OP about whether or not there is real value in knowing the actual DOF numbers,
"Why even bother with a DOF calculator?!"
If you know 11' - 30' at a certain aperture when your 100mm lens is focused at a certain distance (let's say 17' for discussion) at a certain aperture...

• ...can you even know WITH ACCURACY where is 11' , and where is 30' and where is 17' ?!?!?!...and do you know with any certainty that objects of interest are actually all within the DOF front to rear distances?!?!
• ...your lens distance scale on a 100mm AF lens ends at 10' and there are no distances marked between 10' and Infinity!
• If you do not print an 8x10" print, but only print a 4x6" print, your DOF values are invalid!
• if you print anything larger than 8x10" for a wall print, your DOF values are invalid!
• When your lens is a shorter FL, like the 17-55mm, your distance scale runs out of distances even sooner, by 5'... you nave nothing between 5' and Infinity...so knowing DOF distances are even lower in value and nearly useless.

You need to give me OK to edit your image and repost! Keep POTN alive and well with member support https://photography-on-the.net/forum/donate.p​hp
Canon dSLR system, Olympus OM 35mm system, Bronica ETRSi 645 system, Horseman LS 4x5 system, Metz flashes, Dynalite studio lighting, and too many accessories to mention

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Focal depth?
AAA
 x 1600 y 1600

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