Camera/Video

CCD DSPlux

3.6 mm f/1.2

70 deg.

1/3”

Definitionsradiometric vs. photometric

• Photometry is just like radiometry except that everything is weighted by the spectral response of the eye

• Luminance (cd/m2)-Describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle.

• Luminous flux (lm)- The measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.

• Lux (lx = lm/m2)-is the SI unit of illuminance, and measuring luminous flux per unit area.

QUANTITY RADIOMETRIC PHOTOMETRICQUANTITY RADIOMETRIC PHOTOMETRIC

power watt (W) lumen (lm)

power per unit area W/m2 lm/m2 = lux (lx)power per unit solid angle W/sr lm/sr = candela (cd)

power per area per solid angle W/m2-sr lm/m2-sr = cd/m2 = nit

Illuminance of surfaces illuminated by:(Power/Area, Intensity)

0.0001 lux -Total starlight0.002 lux -Moonless clear night sky0.01 lux - Quarter moon0.27 lux -Full moon on a clear night1 lux - Full moon overhead at tropical latitudes

Focal length-f

The focal point of a lens is defined as that point at which rays from infinity (parallel rays) impinging on the lens are focused. The focal length is the distance of the focal point from the center of the lens.

F number• In optics, the f-number is given by f/D where f is the

focal length, and D is the diameter of the entrance pupil

• Ex. f =100 mm and D = 25 mm 100/25 = f/4 • Ex. f= 200 mm and D = 50 mm 200/50 = f/4 • The 200 mm lens's f/4 opening is larger than that of

the 100 mm lens but both will produce the same illuminance in the focal plane when imaging an object of a given luminance.

FOV (Field of View)• FOV underwater• Angle of coverage (FOV)• α = 2*tan-1(d /2f)• Note small f large α

α=80° Field of View α=8° Field of View

Snell’s LawDiagonal coverage of lenses on the 35mm formatThe refractive index of (sea) water was taken to be 1.339 for underwater (UW)

Focal Length (mm)

Coverage in Air (degrees)

Coverage UW (Flat Port) degrees

19 97.42 68.2720 94.49 66.5124 84.06 60.0028 75.38 54.3430 71.59 51.80

α' = 2 sin-1[ Sin(α/2) / nw ]

The port itself has no effect on the angle of coverage (although it does alter the effective position of the lens entrance pupil as seen from outside the housing). Derivation

CCD-Charged Coupled Device

Type Aspect

RatioDiameter (mm)

Diagonal(mm)

Width (mm)

Height (mm)

1/3.6” 4:3 7.056 5.00 4.00 3.00

1/3.2” 4:3 7.938 5.68 4.536 3.416

1/3” 4:3 8.467 6.00 4.6 3.6

The type designation harks back to a set of standard sizes given to TV camera tubes in the 50's. These sizes were typically 1/2", 2/3" etc.

Depth of Field

Image distance vs. object distanceIf the object becomes closer to the lens, the image moves further away from the lens and becomes larger.

If one moves a real film plane back and forth a bit, a range of object distances remains in acceptable focus, this is the depth of field

One can change the depth of field by changing the focal length or aperture size of the lens. The width of the non-converged beam for the near-tree image becomes much less, and can be made too small to notice. Then both trees will be in acceptable focus.

Focus the camera on the far tree. Near tree out of focus

CCD-Charged Coupled Device

• CCD Overview• Animation• DSP-digital signal

processing

The signal processor within the camera receives the information from the charged coupled device, or CCD, and combines it into video frames

Some CalculationsOutland UWC-325/p

• Focal lengthf=3.6 mm f/1.2 Using f/1.2=f/D and solving for DD= 3.6/1.2= 3 mm• FOV α = 2tan-1(d / 2f)=2tan-1(6/(2*3.6)) = 79.61o

Notice that a small f gives a larger FOV• Underwater FOV using nw=1.339α' = 2sin-1[ sin(α/2) / nw ]=2sin-1[sin(80/2)/1.339]= 57.3 o

High-definition video or HD video is any video system of higher resolution than standard-definition (SD)

video, and most commonly involves display resolutions of 1,280×720 pixels (720p) or 1,920×1,080 pixels

(1080i/1080p).

640 x 480 Pixels with 4:3 Aspect Ratio

1920 x 1080 Pixels with 16:9 Aspect Ratio

Camera

• Outland Technology• Seaview• Remote Ocean System• Insite• GoPro• GoPro 3D• Camera Potting• OceanPro HD

• Deepsea Power and Light

• Lights-camera-action

Glossary

• f = F number• f= focal length• D = diameter of apature• α = Field of View in air (FOV)• α’ = Field of View in water• d = diagonal of imaging device