Compare Sensor Sizes
Compare Sensor Sizes is a free, open source tool to easily compare multiple digital camera sensor sizes, celluloid film formats and lens image circles – graphically as well as in tabular form. Usually all data of sensors and lenses come directly from the respective manufacturers. The database will be continuously extended this way.
In addition to the comparison function and the usability as a trustworthy, sortable database, one of the most useful features is the possibility to check which lenses cover which sensors and to what extent. If a lens does not yet appear in the list, you have the option of specifying an individual image circle in millimeters, which is then displayed.
You can also switch to the real physical sensor sizes in the graphical view, if you specify the size of your screen in inches.
The tool should also bring clarity to diffuse terms like Large Format, Full Format and Full Frame, which do not denote standardized sizes and are used differently depending on the manufacturer.
The value of pixel density – that is the number of photosites per given sensor area – helps to quickly determine which sensor will have the highest resolution with a given lens image circle. For example you want to shoot on old 16mm lenses and still cover a 4K sensor area? Then just sort the camera models by "Density" and immediately you will see the most suitable models first.
Compare Sensor Sizes is optimized for desktop and also usable on mobile. An app might follow if there is demand.
Some lens data comes from Florian Milz' Lens Coverage Tool.
Why does sensor size matter?
Imagine the sensor as a canvas in front of you. The larger the sensor, the larger the angle of view (field of view) for a given focal length and distance to the subject. Therefore to get a desired angle of view, you can move closer to the subject or use a longer focal length compared to a smaller sensor size. Either way this means the depth of field becomes shallower as a result. So with the same angle of view, distance to subject and aperture, you’ll always get shallower depth of field the larger the sensor size.
In addition to that a larger sensor means additional area for more photosites (more pixels) or bigger photosites (brighter pixels) or a bit of both.
Lastly the sensor size determines the set of lenses one can use, if full sensor coverage is desired.
Image Circle vs Illumination Circle
The Image Circle of a given lens is defined as the area within which the manufacturer guarantees a defined optical quality performance.
The Illumination Circle or Circle of Illumination of a given lens is defined as the area within which there is still light, but of undefined quality. Vignetting, chromatic abberations, loss of sharpness, etc. can appear.
Image Circle and Illumination Circle are often used interchangeably, which can lead to confusion.