When a sensor is advertised/sold as 1/2.3″ most people would think that is the diagonal of the sensor. Well it is NOT! It might even vary drastically between manufacturers.
For historical reasons the diameter of a fictitious Vidicon tube with the same active area is what is advertised!!
![ccdsizes[1]](https://eskerahn.dk/wp-content/uploads/2015/05/ccdsizes1.gif)
From http://www.dpreview.com/news/0210/02100402sensorsizes.asp
Unfortunately, it is even more confusing than that…
The same article also has a table, that I have expanded with two ratio columns. Some intermediate rows also added (data via wiki).
(And removed some columns to make it less confusing)
| Sensor | Asp | Width | Hight | x*Full | Factor adver. to real diag. |
| 1/3.6″ | 4:3 | 4.000 | 3.000 | 1/72.0 | 0.71 |
| 1/3.2″ | 4:3 | 4.536 | 3.416 | 1/55.8 | 0.72 |
| 1/3″ | 4:3 | 4.800 | 3.600 | 1/50.0 | 0.71 |
| 1/2.7″ | 4:3 | 5.270 | 3.960 | 1/41.4 | 0.70 |
| 1/2.5″ | 4:3 | 5.760 | 4.290 | 1/35.0 | 0.71 |
| 1/2.3″ | 4:3 | 6.160 | 4.620 | 1/30.4 | 0.70 |
| 1/2″ | 4:3 | 6.400 | 4.800 | 1/28.1 | 0.63 |
| 1/1.8″ | 4:3 | 7.176 | 5.319 | 1/22.6 | 0.63 |
| 1/1.7″ | 4:3 | 7.600 | 5.700 | 1/19.9 | 0.64 |
| 1/1.6″ | 4:3 | 8.080 | 6.010 | 1/17.6 | 0.63 |
| 1/1.5″ | 4:3 | 8.800 | 6.600 | 1/14.9 | 0.65 |
| 1/1.2″ | 4:3 | 11.000 | 8.250 | 1/9.53 | 0.65 |
| CX | 3:2 | 13.200 | 8.800 | 1/7.44 | |
| 1″ | 4:3 | 12.800 | 9.600 | 1/7.03 | 0.63 |
| μ4/3 | 4:3 | 17.300 | 13.000 | 1/3.84 | |
| 4/3″ | 4:3 | 18.000 | 13.500 | 1/3.56 | 0.66 |
| APS-C | 3:2 | 25.100 | 16.700 | 1/2.06 | |
| APS-H | 13:9 | 29.200 | 20.200 | 1/1.46 | |
| 35 mm | 3:2 | 36.000 | 24.000 | 1.000 | |
| 645 | 4:3 | 56.000 | 41.500 | 2.690 |
Note that the actual sensor diagonal is approximately 2/3 (63% -72%) of the advertising figures!!
A 1/2 “sensor is thus effectively only about 1/3″ or 8mm
But to add to the confusion factors vary between models and manufacturers!
Examples
| Manufacturer / Model | Adver. | Width(mm) | Height(mm) | Real Diag.(mm) | Factor adver. to real diag |
| FujiFilm / F50,60,100,200 | 1/1.6″ | 8 | 6 | 10 | 0.63 |
| FujiFilm / F30, 31 | 1/1.7″ | 7.44 | 5.58 | 9.3 | 0.62 |
| FujiFilm / F900 | 1/2″ | 6.40 | 4.80 | 8.00 | 0.63 |
| Sony /RX100 | 1″ | 13.2 | 8.8 | 15.9 | 0.63 |
| Sony / IMX220 | 1/2.3″ | 6.30 | 4.72 | 7.87 | 0,71 |
So Sony’s sensor called 1/2.3″ is only 1.6% less in diagonal than what FujiFilm call 1/2″ !!!
Said otherwise Fuji could call Sony’s sensor a 1/2.03″, OR Sony could call Fuji’s 1/2.26″
So be REALLY careful when comparing sensor sizes that you look at the actual area in use!! – if you can get the correct info from the manufacturer!!!
As the factor used can vary with as much as 14% (matching 30% in area) it is easy to make wrong assumptions, and many sites do, assuming that e.g. all sensors called 1/2.3″ has the same actual size. There are NO reason to assume that – unfortunately…
See also this post on the Megapixel craze