OneButton relies on two basic values which are related to each sensor - pixel size and focal length. These values help the software compute the correct distance from the sensor to the ground and determine the correct ground resolution of each pixel - or how many ground units (ft/m) each pixel in the image covers.
Sensor sizes are expressed in inches notation because at the time of the popularization of digital image sensors they were used to replace video camera tubes. The common 1" circular video camera tubes had a rectangular photo sensitive area about 16mm diagonal, so a digital sensor with a 16 mm diagonal size was a 1" video tube equivalent.
Sizes are often expressed as a fraction of an inch, with a one in the numerator, and a decimal number in the denominator. For example, 1/2.5 converts to 2/5 as a simple fraction, or 0.4 as a decimal number. This "inch" system brings a result approximately 1.5 times the length of the diagonal of the sensor.
Example dimensions can be found in this table:
|Type||Diagonal (mm)||Width (mm)||Height (mm)|
|1" Sony RX100 and RX10, Nikon CX, Samsung NX Mini||15.86||13.2||8.8|
|1.5" Canon PowerShot G1 X Mark II||23.36||18.7||14|
|1/1.2" (Nokia 808 PureView)||13.33||10.67||8|
|1/1.7" (Pentax Q7, Canon G10, G15)||9.5||7.6||5.7|
|1/1.8" (Nokia N8) (Olympus C-5050, C-5060, C-7070)||8.93||7.18||5.32|
|1/2" (Fujifilm HS30EXR) (Espros EPC 660)||8||6.4||4.8|
|1/2.3" (Pentax Q) (Sony Cyber-shot DSC-W330)(gopro hero 3) (Panasonic HX-A500)||7.66||6.17||4.55|
|1/2.3" (Sony Exmor IMX220)||7.87||6.3||4.72|
|1/2.5" (Nokia Lumia 1520, Sony Cyber-shot DSC-T5)||7.18||5.76||4.29|
|1/3" (iPhone 5S, iPhone 6 )||6||4.8||3.6|
|1/3.2" (iPhone 5)||5.68||4.54||3.42|
|1/3.6" (Nokia Lumia 720)||5||4||3|
|1/6" (Panasonic SDR-H20, SDR-H200)||3||2.4||1.8|
|2/3" (Nokia Lumia 1020, Fujifilm X-S1, X20, XF1)||11||8.8||6.6|
|35mm full-frame, (Canon EF, Nikon FX, Sony α, Sony FE, Leica M)||43.1–43.3||35.8–36||23.9–24|
|APS-C (Sony α DT, Sony E, Nikon DX, Pentax K, Samsung NX, Fuji X)||28.2–28.4||23.6–23.7||15.6|
|Blackmagic Cinema Camera EF||18.13||15.81||8.88|
|Blackmagic Pocket Cinema Camera & Blackmagic Studio Camera||14.32||12.48||7.02|
|Blackmagic Production Camera/URSA/URSA Mini 4K||24.23||21.12||11.88|
|Blackmagic URSA/URSA Mini 4.6||28.2||25.34||14.25|
|Canon EF-S, APS-C||26.82||22.3||14.9|
|Four Thirds, Micro Four Thirds ("4/3", "m4/3")||21.6||17.3||13|
|Leaf AFi 10||66.57||56||36|
|Medium-format (Hasselblad H5D-60)||67.08||53.7||40.2|
|original Sigma Foveon X3||24.9||20.7||13.8|
|Pentax 645D, Hasselblad X1D-50c||55||44||33|
|Phase One P 65+, IQ160, IQ180||67.4||53.9||40.4|
Once you have the sensor dimensions, look at the image dimensions (width and height in pixels that can be found in the image metadata) and use the following steps to calculate the pixel size:
1. Take the value in the "Width (mm)" column and divide it by the width in pixels. This is called "pixel size x".
2. Take the value in the "Height (mm)" column and divide it by the height in pixels. This is called "pixel size y".
3. Calculate the average between the two values - ("pixel size x" + "pixel size y") / 2. The result is the pixel value which you need to put into the "pixel size" field when creating a project in OneButton.
Some sensor manufacturers may refer to this value as "pixel pitch" and give the actual value in microns. In this case, do not follow the instructions above. Convert the microns into millimeters (by dividing by 1000) and enter the result in the "pixel size" text box.
Here is a link to the sensefly sensor: