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Depth of Field Calculator

PocketPC Depth of Field

Focus Meister is a Shareware tool, running on the PocketPC platform, that produces a table with depth of field information for any given focal length of lens. It is possible to set 4 separate focal lengths and quickly switch between them, allowing an easy comparison between lenses.

Focus Meister will operate on PocketPC machines running either PPC2002 or PPC2003. PPC2002 XScale users should download the ARM version, and also install the Microsoft .NET Compact Framework. Users of PPC2003 users should download the ARM4 version.

Register Now!		Download the Trial		MS .NET Compact Framework (for PPC 2002 users)
To ensure a secure payment, you will complete payment through PayPal. Once payment is confirmed you will follow instructions to obtain your unlock code		We recommend that you download the trial version first, to ensure that the software works on your machine. The trial version is limited to 1 focal length and will display data for a limited number of apertures		For users of machines running PocketPC 2002 (ARM processor), you will need to download the Microsoft .NET Compact Framework. Users of PocketPC 2003 2003 do not need the framework, as it is included in the OS
$4.99		Free		Free
		Size 95 KB		Size 1.0MB
		ARM ARM4		ARM ARM4

Entering New Data
To begin using Focus Meister, you first need to enter your lens focal lengths and COC – which is discussed below. At this time, Focus Meister allows you to preset 4 focal lengths - these should correspond to the lenses you have, or if zooms are being used, the widest and furthest focal lengths, and equally spaced points in between. For example, if you own a 28-135 zoom lens, you could set up the 4 focal lengths as 28, 65, 100 and 135 - this will give you a close table no matter what length you choose to zoom to on this lens.

COC is an acronym for "circle of confusion". This refers to the largest size a circle can be in order for the human eye and brain to see it as a dot - rather than a circle. If you consider that light falling onto the film or sensor in a camera is in fact many circles of light (formed by the near circular aperture) and that the further away from being focused on the film or sensor the circles are, the bigger the circles are, then you can appreciate how it is important to specify the largest size circle to be seen as a dot when calculating what appears in focus. Naturally, the largest size is a debatable issue, and also relative to the distance it is being viewed from. It is taken that a circle of 0.2mm viewed from 25cm is seen as a dot. This would simulate holding a photo print in the hands at normal viewing distance. If it is then taken that the print is 10x8 (larger than average for a print held in the hands - therefore erring on the side of quality) it can be calculated how big this 0.2mm circle would be on the film or sensor before enlargement. In the case of a 35mm system, the circle size equates to 0.023mm.

To calculate for systems other than 35mm, you will need to find the dimensions of your recording media, i.e. either the film or sensor dimensions, and note the smaller of the two dimensions for use in the following equation to give COC:

COC of 8x10 print x smaller dimension of your media / smaller dimension of 8x10 print

An example of a Canon EOS10D, which has sensor dimensions of 22.7x15.1mm (the sensor dimensions can usually be found in the Specifications section of the user manual), and taking an acceptable figure of 0.2mm as the largest circle size on an 8x10 (203.2x254mm) print, the formula produces this result:

0.2 x 15.1 / 203.2 = 0.015mm

Finally, enter the focus distance, which is the distance from the lens to the point you are focusing at. This can be easily changed afterwards by selecting Input - Edit Input.

Hyperfocal Distance
Each table shows, for a given focal length, its hyperfocal distance at each f-stop. If a lens is set to focus at its hyperfocal distance, then all objects between half this distance and infinity will appear in focus on the image. As a lens’ hyperfocal distance varies with aperture, each full f-stop is included in the tables. For ease of use, the near field point (the closest point appearing in focus) is also shown. An example of a 100mm lens at f8 gives a hyperfocal distance of 83.4 meters. The table shows this, and that the near field point is 41.7 meters - hence all objects between 41.7 meters and infinity will appear in focus, with a 100mm lens set to f8 and focused at 83.4 meters.

Near Field and Far Field
When a given lens is focused at a given distance, any object at that given distance will be in focus. However depending on the focal length, the focus point distance and aperture, a certain distance in front and behind this focus distance will also "appear" in focus. In fact it is truly not in focus, but it is as close as to not be noticed by the human eye (see COC above). The total distance between the closest and furthest point appearing in focus is called the depth of field. The closest point appearing in focus is referred to as the near field point and the furthest point at which objects appear in focus is referred to as the far field point. Each table shows, for the specified focal length and focus distance, the near field and far field points for each full f-stop. An example of a 100mm lens focused at 5 meters and with an aperture of f8 shows that all objects between 4.72 and 5.31 meters will appear in focus.

Saving Multiple Configs
Focus Meister allows you to input four separate focal lengths, and rapidly call up the table for any of these four. If you have a large number of focal lengths, or multiple systems, you may also save and re-load different input settings. By default, Focus Meister remembers the last input setting you used.