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| Impressionist Painting Effect FZ1000 Subject 1.3 kilometers from the camera over ocean and beach, I-Zoom at E800mm. Strong atmospheric distortion. |
In the good old days of film there were not many sizes from which to choose. Most people used 35mm film which was actually 35mm wide, and I suspect many would have been only vaguely aware that any other size existed.
However since the beginning of digital photography there has been a profusion and confusion of sensor sizes. Adding to the muddle, camera makers got into the habit of naming their sensor sizes in the most bizarre way. They used as reference the diameter of a notional cathode ray tube which would have been required in the 1950's to incorporate the particular sensor. To make matters worse they described this in inches then expressed the dimension in a weird inverted fashion like [1/1.7 inches]. Nobody presented with this bit of nonsense would have the faintest clue how large the sensor might actually be.
Maybe the manufacturers were deliberately obfuscating the size issue, perhaps to divert consumer's attention from the fact that most digital cameras used a sensor very much smaller than the imaging area given by 35mm film.
There is a simple, useful alternative namely to designate a sensor by it's diagonal dimension. Lets' see how this works in the table below:
| Sensor Type | Aspect Ratio | Nominal Dimensions (mm) | Diagonal (mm) | Area (squ.mm) | Focal length Factor |
| Medium Format | Various | Various, about 44x33 | Various about 55 | Various about 1452 | Various about 0.78 |
| Full Frame | 3:2 | 36x24 | 43 | 864 | 1.0 |
| APS-C Sony et al | 3:2 | 23.5x15.6 | 28 | 367 | 1.5 |
| APS-C Canon | 3:2 | 22.3x14.9 | 27 | 332 | 1.6 |
| Four Thirds, Micro 4/3 | 4:3 | 17.3x13 | 21.6 | 225 | 2.0 |
| One inch | 3:2 | 13.2x8.8 | 15.9 | 116 | 2.7 |
| 2/3" | 4:3 | 8.8x6.6 | 11 | 58 | 3.9 |
| 1/1.7" | 4:3 | Various about 7.5x5.6 | Various about 9.3 | Various about 42 | 4.6 |
| 1.2" | 4:3 | 6.4x4.8 | 8 | 30 | 5.4 |
| 1/2.3" | 4:3 | 6.1x4.6 | 7.7 | 28 | 5.6 |
So, instead of calling the sensor in the Panasonic FZ1000 and several other cameras, "one inch" which means nothing it can be described by the diagonal which is 15.9mm which is at least something real and useful for those consumers who might want to know the size of the sensor in their camera.
I really don't know why this simple naming system has not become universal, it seems so completely obvious to me. Not to others apparently.
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