Luminous Landscape Forum

Equipment & Techniques => Cameras, Lenses and Shooting gear => Topic started by: ejnewman on April 03, 2013, 10:13:26 pm

Title: Calculating the exact size of a sensor
Post by: ejnewman on April 03, 2013, 10:13:26 pm

Does anybody know if its possible to calculate the exact dimensions of a sensor using the resolution and pixel pitch?

In theory this is all you need in order to calculate the area of a sensor to a very high degree of accuracy, only I don't know if pixel pitch includes the space inbetween each pixel or not...

Title: Re: Calculating the exact size of a sensor
Post by: ErikKaffehr on April 03, 2013, 10:47:14 pm

Hi,

Pixel pitch is the distance between pixel centers. So dimension is pixels x pixel pitch.

But you normally also find sensor sizes in the same data sheets that you find pixel pitch.

Best regards
Erik

Quote from: ejnewman on April 03, 2013, 10:13:26 pm

Does anybody know if its possible to calculate the exact dimensions of a sensor using the resolution and pixel pitch?

In theory this is all you need in order to calculate the area of a sensor to a very high degree of accuracy, only I don't know if pixel pitch includes the space inbetween each pixel or not...

Title: Re: Calculating the exact size of a sensor
Post by: ejnewman on April 04, 2013, 09:59:28 pm

Thanks. I find the information can sometimes vary depending on where you look. Is there a trusted resource that details sensor specifications accurately that can be trusted? For example last time I checked I found 2 different values listed for Canon 5D II sensor size online.

Title: Re: Calculating the exact size of a sensor
Post by: ErikKaffehr on April 04, 2013, 11:33:12 pm

Hi,

It depends on how exact you want to be. Different raw converter extract different number of pixels from the same raw image.

I presume that DPReview and DxO-mark have reasonably correct figures.

Best regards
Erik

Quote from: ejnewman on April 04, 2013, 09:59:28 pm

Thanks. I find the information can sometimes vary depending on where you look. Is there a trusted resource that details sensor specifications accurately that can be trusted? For example last time I checked I found 2 different values listed for Canon 5D II sensor size online.

Title: Re: Calculating the exact size of a sensor
Post by: ejnewman on April 05, 2013, 07:47:04 am

Thanks, yes I am going to assume DXO's pixel pitch spec is accurate!

Thanks for the help.

Title: Re: Calculating the exact size of a sensor
Post by: ejnewman on April 06, 2013, 09:40:23 am

This is what DxO state for the Canon 1Ds Mark II

Sensor Size: 36 x 24 mm
Resolution: 5108 x 3348 
Pixel Pitch: 7.05 µm

Firstly, the ratio of this sensor is specified as 3:2, but the resolution specified does not fit this 3:2 aspect ratio. Secondly, if pixel pitch is the distance measured from the centre of a pixel to the centre of the adjacent pixel (i.e. assume there are no gaps) then it can be assumed that to find out the size of the sensor you must run the following calculation:

Resolution x Pixel Pitch

This gives me a sensor size of 36.01 x 23.60 mm for this camera, which of course is different than what is specified by DxO.

So it seems there isn't an easy way to know how accurate this pixel pitch actually is? If I can assume it's accurate then I can easily just calculate the "effective" sensor size, for the 1Ds Mark II this would be 4992 x 3328 which would give me an "effective" sensor size of 35.19 x 23.46 mm. Or if running raw conversions through DCRAW which gives you more edge pixels so I would end up with an effective resolution of 5010 x 3336 which would mean a "effective" sensor size of 35.32 x 23.51 mm.

Interestingly digicamdb suggest a different pixel pitch. 7.21 µm:

http://www.digicamdb.com/specs/canon_eos-1ds-mark-ii/