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stacker:docs:tables:macromicrodof [2019/12/15 03:26] rjlittlefield |
stacker:docs:tables:macromicrodof [2020/01/07 18:24] (current) rjlittlefield add formulas for DOF calculations |
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- Adjust step size if desired, so as to give more overlap between focus bands and/or choose values that are simple to use with your setup. Many people like to use about 0.7 times the values given in these tables. | - Adjust step size if desired, so as to give more overlap between focus bands and/or choose values that are simple to use with your setup. Many people like to use about 0.7 times the values given in these tables. | ||

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**Step 1: Determine Magnification From Frame Width** | **Step 1: Determine Magnification From Frame Width** | ||

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^ 1.4 mm | 13 | 16 | 26 | | ^ 1.4 mm | 13 | 16 | 26 | | ||

^ 1.0 mm | 18 | 23 | 36 | | ^ 1.0 mm | 18 | 23 | 36 | | ||

+ | Numbers in the above table can be reproduced as magnification = SensorWidth / FrameWidth . \\ | ||

+ | Example: Frame width 70 mm on full frame (sensor width 36 mm) computes as magnification = 36 / 70 = 0.5143 . | ||

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**Step 2: Determine Aperture and Step Size** | **Step 2: Determine Aperture and Step Size** | ||

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^ 14 | //0.010 mm // | //0.020 mm // | //0.040 mm // | //0.079 mm // | //0.16 mm // | //0.31 mm // | //0.65 mm // | //1.2 mm // | | ^ 14 | //0.010 mm // | //0.020 mm // | //0.040 mm // | //0.079 mm // | //0.16 mm // | //0.31 mm // | //0.65 mm // | //1.2 mm // | | ||

^ 20 | //0.0097 mm // | //0.019 mm // | //0.039 mm // | //0.076 mm // | //0.16 mm // | //0.29 mm // | //0.62 mm // | //1.2 mm // | | ^ 20 | //0.0097 mm // | //0.019 mm // | //0.039 mm // | //0.076 mm // | //0.16 mm // | //0.29 mm // | //0.62 mm // | //1.2 mm // | | ||

+ | Numbers in the above table can be reproduced by the formula DOF = (0.0022*N*N*(m+1)*(m+1))/(m*m) , where N is the F-number and m is magnification. \\ | ||

+ | Example: F-number 5.6 and magnification 0.50 computes as DOF = (0.0022*5.6*5.6*(0.50+1)*(0.50+1))/(0.50*0.50) = 0.6209 . | ||

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^ 3.5 | 0.00072 mm | 0.0014 mm | 0.0029 mm | 0.0056 mm | **0.011 mm ** | **0.022 mm ** | **0.046 mm ** | //0.087 mm // | | ^ 3.5 | 0.00072 mm | 0.0014 mm | 0.0029 mm | 0.0056 mm | **0.011 mm ** | **0.022 mm ** | **0.046 mm ** | //0.087 mm // | | ||

^ 5.0 | --- | 0.00069 mm | 0.0014 mm | 0.0028 mm | **0.0056 mm ** | **0.011 mm ** | **0.023 mm ** | //0.043 mm // | | ^ 5.0 | --- | 0.00069 mm | 0.0014 mm | 0.0028 mm | **0.0056 mm ** | **0.011 mm ** | **0.023 mm ** | //0.043 mm // | | ||

+ | Numbers in the above table can be reproduced by the formula DOF = (0.0022*N*N)/(m*m), where N is the F-number and m is magnification. \\ | ||

+ | Example: F-number 5.6 and magnification 0.35 computes as DOF = (0.0022*5.6*5.6)/(0.50*0.50) = 0.2760 . | ||

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- | This final Table 2-C is for users of microscope objectives. In this case, step size is determined almost entirely by the NA rating (Numerical Aperture) of the objective. | + | \\ |

+ | This final Table 2-C is for users of microscope objectives. In this case, step size is estimated entirely from the NA rating (Numerical Aperture) of the objective. | ||

__**Table 2-C**__ -- //Determine DOF (step size) from Numerical Aperture (NA)// | __**Table 2-C**__ -- //Determine DOF (step size) from Numerical Aperture (NA)// | ||

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| 0.5 | 0.0022 mm | | | 0.5 | 0.0022 mm | | ||

| 0.55 | 0.0018 mm | | | 0.55 | 0.0018 mm | | ||

+ | Numbers in the above table can be reproduced by the formula DOF = 0.00055/(NA*NA) . \\ | ||

+ | Example: NA 0.25 computes as DOF = 0.00055/(0.25*0.25) = 0.0088 . | ||

- | Notes: You may be surprised that there's nothing in these tables about circle of confusion (COC), like you'd find in most DOF tables. That's because COC is essentially bundled into your choice of aperture. Once you've chosen the aperture setting, then using the numbers in these tables will guarantee that you won't see “focus banding” no matter how good a camera or lens you're using, or how closely you choose to look at the captured images. The math underlying these tables makes assumptions that are reasonable for most lenses, then proceeds using a math formulation that is based on wave optics and guarantees no more than 1/4-lambda wavefront error for green light at the worst focus distances. Roughly speaking, this corresponds to no loss of fine detail and no more than 26% reduction of MTF at any spatial frequency. Send email if you want more information. | + | \\ |

+ | \\ | ||

+ | **Notes:** You may be surprised that there's nothing in these tables about circle of confusion (COC), like you'd find in most DOF tables. That's because COC is essentially bundled into your choice of aperture. Once you've chosen the aperture setting, then using the numbers in these tables will guarantee that you won't see “focus banding” no matter how good a camera or lens you're using, or how closely you choose to look at the captured images. The math underlying these tables makes assumptions that are reasonable for most lenses, then proceeds using a math formulation that is based on wave optics and guarantees no more than 1/4-lambda wavefront error for green light at the worst focus distances. Roughly speaking, this corresponds to no loss of fine detail and no more than 26% reduction of MTF at any spatial frequency. Send email to [[support@zerenesystems.com]] if you want more information. |