# Camera Specifications computing focal length and f/#

1. Jul 2, 2013

### thiirane

So I have come across a specification of a narrow field of view camera. The specification states
FOV=2x2
resolution=<.1m at 1 km

If I assume a 1K sensor at 9micron pitch and an aperture = 3.7cm

I have resolution at .013 m

Chip size = 9.2mm

Focal length is 6.167E5mm?? can this be right? Also f/#=1.6E4

Do I have the formulas correct

f/#=Focal Length/Aperture

Focal Length=Aperture/2*tan(IFOV)

2. Jul 3, 2013

### Andy Resnick

Can you provide additional information- for example, the field of view = 2x2 what- radians, degrees, other? Any specific information on the lens?

Alternatively, do you have a product ID/name?

3. Jul 3, 2013

### thiirane

Hi Andy,

Actually the only thing specified is the IFOV, FOV and resolution at 1Km I think it is up to the supplier to design the rest. FOV is degrees. I assumed a sensor 1K sensor at 9 microns.

4. Jul 5, 2013

### Andy Resnick

It's still not entirely clear- are you specifying a sensor, a lens, or an integrated sensor+lens? The IFOV and FOV specs define the sensor array size (I also got a 1k x 1k array), but the resolution spec involves a lens (which will operate at f/15 at a magnification of 1*10^-6, according the spec and assuming you are using visible light), and combining everything indicates a 400mm focal length lens, if the pixel size is 9um.

Note- imaging over 1 km distance is complicated by atmospheric distortion, you are unlikely to meet your resolution spec unless your application is able to avoid this. Some friendly advice- providing the OP specs to a supplier will result in an irritated supplier.