Wrong calculation of sensor X/Y res

[Gall]

Hello,

I was new TIFF images (with complete EXIF data) and I noticed that the calculated Sensor X/ res are off.
My data (1280x960) has :

• FocalPlaneXResolution: 26.666665
• FocalPlaneYResolution: 26.666665
• FocalPlaneResolutionUnit: 3 (so cm)

I was expecting Sensor res as 266.66665 mm and a pixel size of 0.00375 mm but instead it shows 2.6666665 mm and a pixel size of 0.375 mm.

[Alexey Pasumansky]

Hello Gall,

Can you send a sample image to support@agisoft.com?

[Alexey Pasumansky]

Hello Gall,

Thank you for sending the sample image.

FocalPlaneXResolution means that the given number of pixels are present in the one FocalPlaneResolutionUnit, so the pixel size is 10 mm / 26.666 pix = 0.375 mm.

[Gall]

Ok but this result doesn't make sense.

sensor size = size / focal plane resolution so
sensorX = 1280 / (26.666 * 10) = 4.8 mm
sensorY = 960 / (26.666 * 10) =  3.6 mm
which is the size of my sensor. So we should have:
pixel size = sensor size / size
pixelX = 4.8 / 1280 = 0.00375 mm
pixelY = 3.6 / 960 = 0.00375 mm

Am I wrong somewhere?

[Alexey Pasumansky]

Hello Gall,

26.666 pix in cm means that there are 2.666 pix in mm, not 266.66.

[Gall]

Ho you're right, that's the part messing me up. So my file is actually off by a factor of 100.

Thank you Alexey.