# Forum

### Author Topic: Wrong calculation of sensor X/Y res  (Read 5296 times)

#### Gall

• Jr. Member
• Posts: 85
##### Wrong calculation of sensor X/Y res
« on: May 03, 2016, 05:58:56 PM »
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

• Agisoft Technical Support
• Hero Member
• Posts: 14927
##### Re: Wrong calculation of sensor X/Y res
« Reply #1 on: May 03, 2016, 06:00:42 PM »
Hello Gall,

Can you send a sample image to support@agisoft.com?
Best regards,
Alexey Pasumansky,
Agisoft LLC

#### Alexey Pasumansky

• Agisoft Technical Support
• Hero Member
• Posts: 14927
##### Re: Wrong calculation of sensor X/Y res
« Reply #2 on: May 04, 2016, 10:46:35 AM »
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.

Best regards,
Alexey Pasumansky,
Agisoft LLC

#### Gall

• Jr. Member
• Posts: 85
##### Re: Wrong calculation of sensor X/Y res
« Reply #3 on: May 04, 2016, 12:01:31 PM »
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

• Agisoft Technical Support
• Hero Member
• Posts: 14927
##### Re: Wrong calculation of sensor X/Y res
« Reply #4 on: May 04, 2016, 12:20:45 PM »
Hello Gall,

26.666 pix in cm means that there are 2.666 pix in mm, not 266.66.
Best regards,
Alexey Pasumansky,
Agisoft LLC

#### Gall

• Jr. Member
• Posts: 85
##### Re: Wrong calculation of sensor X/Y res
« Reply #5 on: May 04, 2016, 12:30:21 PM »
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.