Photography Calculators

This page contains several calculators of use to photographers. All of the calculators are written using Javascript, which means you'll need a Javascript enabled browser (IE/Firefox/Opera/Chrome/etc.) to use this page. It also means that you can download/save this page to your computer and use the calculators without being connected to the internet. Fields displayed on the left of the "compute" button are for user input. Fields on the right of the "compute" button are where the results are displayed.

This calculator computes depth of field, based on aperture, focal length, distance to subject and Circle of Confusion (CoC). A CoC of .03 is generally accepted as appropriate for a 35mm camera. For most modern digital SLR cameras with a "cropped frame" sensor (e.g. Canon 20D/30D/40D/50D/XTi/XSi/T1i, Nikon D40/D60/D90/D200/D300/D5000, etc.), a smaller CoC is probably more appropriate. Because the sensor size on these cameras is smaller than a 35mm negative, the image must be enlarged to a greater extent for any given print size. A CoC of 0.019 is a reasonable value for these cameras. For small, point-n-shoot digital cameras (e.g. Canon A650, Canon G9) with a 1/1.8" sensor (7.18 x 5.32 mm), a value of about 0.006 is appropriate.

The chart above is generated whenever the compute button is clicked. The x axis shows distance from the sensor, and the y axis shows "blur" measured in mm. The blue line shows how blurred a point source of light becomes on the sensor as its distance ("subject distance") from the camera varies, while the camera's "focus distance" remains unchanged. The closer the line to the x axis, the better focused the subject. When focus distance and subject distance are identical, the image is perfectly focused and the object is said to be in the "plane of focus", and there is no blurring. This corresponds to the point where the blue line touches the x axis. This should be the sharpest point in the image. As subject distance and focus distance diverge (i.e. the subject is moved in front of, or behind the plane of focus), the amount of blur increases, and the image becomes progressively softer/blurrier. The subject distances at which the blur is less than the amount specified as the Circle of Confusion (indicated by the red line) are within the "depth of field", depicted with a light blue shading on the chart.

Bluring can also be caused by diffraction, which causes light to become spread out as it passes through the camera's aperture. The smaller the aperture, the more softening/blurring. The green line shows the point at which the Rayleigh criterion diffraction limits the resolution of the image. Wherever the blue line drops beneath the green line indicates where diffraction limits the amount of perceived sharpness in the image.

This calculator computes the degree of parallax error that occurs when a camera is rotated around a point that isn't the nodal point. This is useful for photographers who take a sequence of images to be stitched into a panorama. The Nodal Point Offset field is the distance (in mm) between the actual point of camera rotation and the nodal point. The calculator computes how much two objects that are at different distances (i.e. one "near" and one "far") from the camera appear to shift in relation to each other as the camera is rotated through the specified angle. Put another way, if the two objects are perfectly aligned (so that the near object appears directly in front of the far object) before rotation, they will be seperated by the angular distance determined by the calculator after rotation. The result is expressed as an angular distance (in degrees), and the number of pixels. For any given angular shift, images with larger dimension (i.e. more pixels) and/or smaller fields of view will show a larger pixel shift.

This calculator computes the angular field of view for a lens of a specified focal length on a 35mm camera. For most modern consumer level digital SLR cameras, a focal length multiplier of greater than 1 is appropriate because these cameras have a smaller sensor than a 35mm negative. For these cameras a focal length multiplier of approximately 1.5-1.6 is appropriate. Note: This calculator assumes a standard width/height image ratio of 3:2.

This calculator computes the field of view, measured in feet or meters, for a lens of a specified focal length on a 35mm camera. For most modern consumer level digital SLR cameras, a focal length multiplier of greater than 1 is appropriate because these cameras have a smaller sensor than a 35mm negative. For these cameras a focal length multiplier of approximately 1.5-1.6 is appropriate. Note: This calculator assumes a standard width/height image ratio of 3:2.

This calculator computes the number of images and lens focal lengths required to create a mosaic image covering the same field of view as a single image. For any given field of view, overlap percentage, and focal length multiplier (1.6 for most modern digital SLR cameras) the calculator determines the focal length of the lens that is needed for each shot in a mosaic consisting of different numbers of images.

This calculator computes the equivalent lens focal length and aperture necessary to produce the same angular field of view and depth of field on two cameras with different sensor sizes. For example, a DSLR camera like the Canon T1i or Canon 50D (with their sensor sizes of 22.3 x 14.9mm) can be compared to a point and shoot camera like the Canon G9 (sensor size of 7.18 x 5.32 mm) or Canon G10 (sensor size of 7.60 x 5.70mm). The point and shoot camera needs a shorter focal length to achieve the same field of view as the DSLR, and does not need to stop down nearly as much as the DSLR to achieve the same depth of field. A 50mm lens on the Canon 50D, stopped down to F11, gives the same angular field of view and depth of field as the Canon G10 when its lens is set to 17.7 mm and stopped down to about F4.

This calculator also computes the maximum number of megapixels that the sensor can contain before becoming diffraction limited. In other words, for any given aperture and sensor dimension (in millimeters), this calculator computes the number of megapixels at which the system becomes diffraction limited...the point beyond which adding more megapixels to the sensor is futile, because those extra pixels do not resolve any more detail. Note: This calculation is based on a wavelength of green light (510 nanometers, approximately in the middle of the visible spectrum), and the Rayleigh criterion for calculating when objects are said to be "just resolved". More details about this here and here.