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Hyperfocal and Depth-of-Field Calculator

note 1: Calculations based on adequate focus for an 8x10 inch print. (Long considered the standard for depth of field) note 2: For digital cameras, enter actual lens focal lengths, not 35mm equivalent focal lengths. Select Format: 35mm 6x6cm 4x5in Digital LMF Enter Lens Focal Length: mm Enter Aperture f-stop: Focus at ft. for Depth of Field from ft. to infinity. (multiply feet by 0.3048 to convert to meters) For more film format options and the abilty to quickly customize, create and print concise, easy to read tables of hyperfocal distances, check out the Hyperfocal Distance Chart Maker.

Near Field - Far Field Calculator

note 1: Calculations based on adequate focus for an 8x10 inch print. note 2: Focus distances over several thousand inches can be considered infinity for most purposes. note 3: When solving for f-stop and focus if aperture result is unrealistic enter smallest aperture available and recalculate for near/far limits - reiterate as necessary - but there are limits! note 4: For digital cameras, enter actual lens focal lengths, not 35mm equivalent focal lengths. Select Format: 35mm 6x6cm 4x5in Digital LMF Enter Lens Focal Length: mm Enter f-stop and Focus Distance to Aperture f-stop: inches Focus Distance: inches - OR - Enter Near and Far Focus Limits to Near Focus Limit: inches Far Focus Limit: inches Depth of Field: inches (1 inch = 2.54 centimeters) Technical Note: The focus calculators assume a simple, single element lens with the focus distance measured from the center of the lens to the object. In reality, most lenses have multiple elements and we assume that the focus distance is from middle of the lens assembly (lens barrel) to the object. But at close focus this may be inaccurate because there can be several Principle Points of Focus. Precise close-up focusing requires determining these Points. For further information see the recommended reference below. For more film format and distance unit options PLUS the abilty to quickly customize, create and print concise, easy to read tables of focus limits, check out the Near - Far Focus Limits Chart Maker.

What is Depth of Field?

Knowing what will appear to be in focus (and what will be out of focus) is one of the most basic considerations when making any photograph. Although exact focus occurs only at the precise focusing distance, depending on film format, lens focal length, aperture size and focus distance, the apparent range of focus, or depth of field, can vary considerably. Additionally the size of a print made from the film will have an effect on this apparent depth of field. It should be noted that an 8x10 inch print has long been considered the standard by which most lens manufacturers base their depth of field guidemarks on. Without going into the physics involved, this apparent depth of field is due to an optical phenomena called circle of least confusion. When an object is at the exact distance the lens is focused, every point on the object will focus to a point on the film plane. When an object moves out of focus, on the film these points begin to grow and become circles. The farther out of focus an object is, the larger these circles become. But up to a certain point (again depending on film or electronic sensor size, lens focal length, etc.), these circles of confusion are unobtrusive (unresolved by the human eye) and the image appears to be in focus over a range of distances and has 'depth of field'.

Determining Depth of Field for Digital Cameras

The same factors that affect depth of field in film cameras apply to digital cameras too: aperture f-stop, focus distance, lens focal length, film format (essentially the size of the 'light recording area' whether a piece of film or an electronic sensor), and of course, the final print size (traditionally, 8x10 inch). But unlike film cameras which use a handful of standardized film sizes (35mm, 6x7, 4x5, etc.), digital cameras are being made with numerous different sized image sensors. This makes determining the all important Diameter of the Circle of Least Confusion parameter used in the calculations a laborious and ongoing task for each and every digital camera model! Fortunately, there's an easy "shortcut" that yields accurate results. Lens Multiplier Factor (LMF) In the specifications for the focal lengths of the zoom lenses in point-and-shoot digital cameras, most manufacturers also show an Equivalent 35mm Focal Lengths spec. By dividing the Equivalent 35mm Focal Length by the camera's Actual Focal Length we derive a number, The Lens Multiplier Factor, that can be used to interpolate an acceptable Diameter of the Circle of Least Confusion for use in depth of field calculations for our digital camera. For digital camera bodies that use interchangeable lenses the manufacturer usually specs this Lens Multiplier Factor. (A Nikon D100, for example, has a Lens Multiplier of 1.5, while Canon specs the EOS D1 as having a Lens Multiplier of 1.3.) Do the Math: LMF =   35mm equivalent focal length   camera's actual lens focal length Enter the Lens Multiplier Factor (LMF) for your digital camera into the corresponding Select Format box on any of the Focus Pocus calculators. IMPORTANT! Be sure to enter your digital camera's actual lens focal lengths in the calculators. DO NOT enter 35mm equivalent focal lengths! Example: In the specifications for an Olympus C-720, you'll see the zoom lens focal length spec is 6.4mm to 51.2mm. Right next to this is the 35mm equivalent focal lengths of 40mm to 320mm (Yikes! That's some zoom!). Taking the wide angle equivalent 35mm focal length value of 40 and dividing by the digital camera's wide angle focal length of 6.4 we get an LMF of 6.25. Or divide the 320 (35mm telephoto equiv) by 51.2 (actual telephoto focal length); it's the same number: 6.25. Hence, an Olympus C-720 has a Lens Multiplier Factor of 6.25 and it is this number you enter into the Digital LMF box on the calculators. Can't Find the Equivalent 35mm Focal Lengths for Your Lens? If you can't find a specification for the equivalent 35mm focal lengths for your camera's lens, there's another method - if you know the size (height and width) of the sensor in your camera. First, determine the usable diagonal length of the sensor in millimeters (see note below). (Remember Pythagoras' Theorem? --- height2 + width2 = diagonal2.) Next, divide 43.3 by this diagonal length. This yields the LMF for this camera to use in the calculators. LMF =                           43.3                          Diagonal Length of Image Sensor (mm) Enter the Lens Multiplier Factor (LMF) for your digital camera into the corresponding Select Format box on any of the Focus Pocus calculators. Important Note about Diagonal Length of Sensor: In investigating this approach, I discovered that the size many manufacturers spec for image sensors is not necessarily the portion of sensor area that is actually used to record the image. This makes this method highly suspect! If you determine the LMF for your camera this way, be aware that it most likely will be a very conservative number, meaning the usable depth of field available may be greater than the calculators indicate.

The Equations

Note 1: Based on acceptable sharpness for an 8x10 inch print. Note 2: Multiply Inches by 25.4 to convert to Millimeters. Divide Millimeters by 25.4 to convert to Inches. Hyperfocal Distance Setting focus at the Hyperfocal Distance gives maximum depth of field from H/2 to infinity. H = (L x L) / (f x d) Where: H = Hyperfocal Distance (in millimeters) L = lens focal length (ie, 35mm, 105mm) f = lens aperture f-stop d = diameter of circle of least confusion (in millimeters)       for 35mm format d = 0.03       for 6x6cm format d = 0.06       for 4x5in format d = 0.15 Near Focus Limit NF = (H x D) / (H + (D - L)) Where: NF = Near Focus Limit (millimeters) H = Hyperfocal Distance (in millimeters, from above equation.) D = lens focus distance (in millimeters) L = lens focal length (ie, 35mm, 105mm) Far Focus Limit FF = (H x D) / (H - (D - L)) Where: FF = Far Focus Limit (millimeters) H = Hyperfocal Distance (in millimeters, from above equation) D = lens focus distance (in millimeters) L = lens focal length (ie, 35mm, 105mm)

Recommended Reference

Applied Depth of Field, by Alfred A. Blaker, published 1985 by Focal Press, an imprint of Butterworth Publishers. Calculators Courtesy Thomas Hallstein / Outsight Photography PERSONAL USE ONLY no commercial or redistribution rights granted

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