video camera lens fundamentals carlo beltrano
TRANSCRIPT
Video Camera Lens Fundamentals
Carlo Beltrano
www.canonbroadcast.com
LENS SELECTION CRITERIA
• What is the application? (studio, field, news, copy stand, etc.)
• Which camera model? (mount type, CCD size, 16:9/4:3)
• What VIEWING ANGLE is required? (wide, telephoto)
• How much of a ZOOM RATIO is required/desired?
• How will the lens be controlled? (manually, controls, remotely)
VIDEO LENS SPEC
20X8
FILM LENS SPEC
8~160mm
ANGLE OF VIEW
Determined by: Lens Focal Length & CCD size
Angle of View = 2tan-1 Image size (CCD or film)Focal Length X 2
Standard Image Sizes
2/3” CCD (4:3): 8.8mm X 6.6mm
2/3” CCD (16:9): 9.59mm X 5.39mm
1/2” CCD: 6.4mm X 4.8mm
35mm Movie: 24.92mm X 18.67mm
35mm Still: 36mm X 24mm
w
h
ANGLEHorizontal 1/2" Video (4:3 CCD) 2/3" Video (4:3 CCD) 2/3" HD Video (16:9) 35mm Still(in degrees)
[ccd width of 6.4mm] [ccd width of 8.8mm] [ccd width of 9.59mm] [gate width of 36mm]
82.2 3.7 5.0 5.5 20.6 77.3 4.0 5.5 6 22.5 63.2 5.2 7.2 7.8 29.3 61.9 5.3 7.3 8 30.0 51.2 6.7 9.2 10 37.5 43.6 8.0 11.0 12 45.0 35.5 10.0 13.8 15 56.3 29.8 12.0 16.5 18 67.6 27.0 13.3 18.4 20 75.1 22.6 16.0 22.0 24 90.1 21.7 16.7 22.9 25 93.8 18.2 20.0 27.5 30 112.6 15.6 23.4 32.1 35 131.4 13.7 26.7 36.7 40 150.2 12.2 30.0 41.3 45 168.9 11.0 33.4 45.9 50 187.7 10.0 36.7 50.5 55 206.5 9.1 40.0 55.1 60 225.2
FOCAL LENGTH
Focal Length and Image Size
VIDEO LENS NOMENCLATURE
J11aX4.5 BIRS J = 2/3” CCD IRS = w/ 2X
YH = 1/2” CCD VRS = w/ 0.8X WRS = w/ 2X & 0.8X KRS = none
B = compensated for prism
4.5 - 50 mm
9 - 100 mm (with 2X)
FNO =f
DThe smaller the FNO, the brighter the image
F-number vs T-number
FNO =
TNO =
TNO = 3
aperturefocal length
FNO
Transmitance %X 10
example
TNO =F2.8
86%X 10
2/3” LENS OUTPUT
11 mmDiameter
2/3” CCD (4:3 only)
2/3” CCD
(8.8 x 6.6 mm)
Lens image
11 mmDiameter
2/3” CCD vs 1/2” CCD
2/3” CCD (8.8 x 6.6 mm)Lens image
11 mmDiameter
1/2” CCD(6.4 x 4.8 mm)
2/3” CCD (16:9)
16:9 CCD
(9.59 x 5.39 mm)
Lens image
11 mmDiameter
2/3” 16:9 CCD (4:3 mode)
4:3 mode(7.19 x 5.39 mm)
Lens image
11 mmDiameter
Fixed 4:3 CCD
4:3 CCD (8.8 x 6.6 mm)
11 mmDiameter
Lens image
11 2 23
16:9 CCD
Switchable CCD in 16:9 Mode
16:9 mode
Lens image
11 mmDiameter
11 2 23
(9.59 x 5.39 mm)
1 1
4:3 mode
Lens image
11 mmDiameter
2 232 23
Switchable CCD in 4:3 Mode
(7.19mm x 5.39mm)
11
16:9 / 4:3 lens compensation
With 0.82X
Lens image reduced by 18.5%(9mm Diameter)
2 23 11 2 23
Lens image11 mm Diameter
11
Lens image reduced by approx. 20%
16:9 / 4:3 SWITCHABLE LENSES
J17aX7.7 WRS
J11aX4.5 WRS
J22aX7.6 WRS
16:9 / 4:3 SWITCHABLE LENSES(BOX TYPE)
• image size is 11mm diameter for both formats
HDTVlenses
vs.SDTV(NTSC)lenses
• Red and Blue abber. correction is better on HDTV lenses
• prism compensation is different between the two
• tracking error is minimized on HDTV lenses
• overall resolution is better on HDTV lenses
RGB OFFSET (2/3” LENSES)
10 um
5 um
NTSC
HDTV
When an SD lens is used on an HD camera, the MTF is greatly reduced when an image is slightly out of focus.
The amount by which an image is out of focus which causes only a 10% MTF loss in SDTV, causes a 50% MTF loss in HDTV.
MTF: HD vs SD
Depth of Field
Depth of field = x FNO x distance2
(focal length2) - (x FNO x distance)
permissible circle of confusion
Behind Object
for 2/3” ccd, =ccd diagonal
# of raster lines
for SDTV, = 0.021 mm
for HDTV, = 0.010 mm
for 16mm, ~ 0.009 - 0.012 mm
Range Calculator Test Q1
Find the focal length required to satisfy the following conditions:
• width of stage to be in the frame: 10ft
• distance between camera and stage: 70ft
• camera: 2/3” 4:3 ccd
Range Calculator Test Q2
How far back (distance) from a stage must a camera be placed in order to satisfy the following conditions:
• the full stage set height of 40ft must fill the frame (vertically),
• for maximum depth of field, the widest part of the lens is used: in this case an 8mm focal length,
• you are using a 2/3” 4:3 ccd camera.
Q & A