This calculator allows you to input two different camera/lens systems and then to calculate various resolution parameters for the two systems. You may use the drop-down menus for the camera and lens choices, or, if you know the physical parameters for the camera and/or lens, you may input them directly. Some of the cameras in the drop-down have integrated lenses; the lens information is automatically filled in for those cameras. You will note that the focal length of integrated-lens cameras listed on this page is the actual physical focal length, not the "35-mm equivalent."
Once you have the camera/lens systems set up to your satisfaction, press the "Calculate!" button. This calculator uses JavaScript; you may need to adjust your browser security settings for it to work.
| Sensor 1 | Sensor 2 | |
|---|---|---|
| Micrometers per pixel | TBD | TBD |
| f/ratio diffraction limit | TBD | TBD |
| Lens 1 | Lens 2 | |
|---|---|---|
| Diameter, mm | TBD | TBD |
| Angular resolution, arc-seconds | TBD | TBD |
| Airy radius, micrometers | TBD | TBD |
| Camera 1 | Camera 2 | |
|---|---|---|
| Lens 1 | Lens 2 | |
| Arc-seconds per pixel | TBD | TBD |
| Image size, degrees | TBD | TBD |
| Effective pixel resolution | TBD | TBD |
| Effective megapixels | TBD | TBD |
| Effective arc-seconds per pixel | TBD | TBD |
Current camera and lens marketing (especially in the high-end bridge camera market) is focused on "megapixels" and "35mm equivalent lens focal length" as the metrics by which image quality may be judged. The laws of physics, though, constrain the actual resolution delivered. This calculator shows those constraints and allows you to compare two camera+lens systems.
First, the lens itself constrains the resolution. A given diameter lens delivers a maximum resolution, typically measured in arc-seconds In addition, the f/ratio of a lens dictates the physical Airy Disk size in micrometers. The higher the f/ratio, the larger the physical Airy Disk size is. Perhaps surprisingly, a larger lens with the same f/ratio as a smaller lens will have the same Airy Disk size as the smaller lens. This calculator uses the Rayleigh Critereon to calculate the resolution limit. This means that the full physical resolution is dictated by the radius of the Airy Disk.
Second, a given sensor will have a certain pixel size, measured in micrometers. The lens Airy Disk may be bigger or smaller than the pixel size. If the Airy Disk is smaller than the pixel size, then the effective resolution is not constrained by the lens, but only by the physical sensor pixels. However, if the Airy Disk is bigger than the pixel size, then the lens constrains the resolution, and the effective resolution will be lower than the physical sensor resolution.
The calculation of Airy Disk size and diffraction limit depends on the wavelength of light being gathered. Green light (with a wavelength of 550 nm) is typically used for these calculations with today's sensors, since it is in the middle of the visible spectrum, and since a typical RGB camera sensor has twice as many green pixels as red or blue pixels.
Note that lens and sensor aberrations and imperfections may further degrade actual delivered resolution. In addition, many sensors have an antialiasing filter in front of the pixel array which will further reduce delivered resolution.
These calculations assume a monochromatic grid. Consumer digital cameras typically use a 2x2 Bayer color filter grid on top of this to extract color data. This complicates the calculation, since any particular wavelength is only sampled at 1/2 the frequency of the overall grid. To somewhat account for this, select the "Use Bayer Quads" checklist, and all of the calculations will be done for the (larger) 2x2 Bayer quad array. This can have a substantial difference on the f/ratio diffaction limit.
The rows of the tables are therefore as follows. The "Sensor calculations" table contains the rows:
The "Lens calculations" table contains the rows:
The "System calculations" table contains the rows:
Ross Cunniff, June 16, 2022, rcunniff@gmail.com
This calculator and associated files are licensed under the MIT public license:
Copyright 2022 Ross Cunniff
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