cos4 law
Without vignetting, irradiance of peripheral is still very small, cos4θ (θ is the half of angle of view)Distance from the film to the lens 1/cosθ (effects
square)The aperture of the lens seems ellipse (1)Incoming ray to the film is oblique(1) totally, cos4
θ
1
1/cosθLens is far fromthe lens (square)
Lens is tiltedfrom the film
Incoming ray is oblique
Telephoto lensRear principal point is in front of the lens. Front part of the lens has converging effect, and rear is diverging. (definition of telephoto lens)
Wide-angle (retro-focus)
It is used if the back-focus (mechanical clearance behind of the lens) must be long
For SLR or 3CCD cameras
Rear principle point is behind of the lens. Front part of the lens has diverging power, and the rear elements is converging.
3CCD camera
Prism for color separation is placed between the lens and the image sensors
Little loss of energy Lens design is
limited
AF SLR (1)
Contrast methodTwo images are
captured for different distances
Lens is moved to maximize the contrast
Pentax ME-F(1981)
Symmetric type lens
Standard lens (normal angle of view) Wide angle lens without the requirement
of long back focusCompact cameras“range finder” camera
Distortion-sensitive applicationsScan lens of Copy machine, FAX
Symmetric lens(2)
Design is almost symmetric to the aperturePerfect symmetric lens is not so common for
photographic lens, but used for scannersTransversal aberration can be cancelled out
• Distortion• coma• Transversal chromatic aberration
2.1cm F4
2.5cm F4
2.8cm F3.5
3.5cm F2.5
Zoom lens
Order and distance of diverging and converging power much affects to the focal length Moving the elements to change f
Telephoto lensRetrofocus lens
Example of zoom lens
Aberration of each group must be conpensated independently
Canon zoom lens 35-70mm F2.8-3.5 (1972)
Teleconverter(1)
Diverging lens begind the master lens extends the focal lengthAperture is same larger F no.
The principle of the rear-converterrear-converter
Master lens
Front converter Attached in front of
the lensPopular for video
cameras (lens is fixed to the body)
F no. is not changed
Converter itself has no diverging / converging effectCalled “afocal”
tele
wide
Master lens
Master lens
Front converter
Front converter
Telescope(1) – opera glasses
Attaching front tele-converter for eyeballGalilerian (= Galileo type) terescope
f1
f2
Lens of the eyeeyepiece
Objective lens
Telescope(2)
Both objective and eyepiece is converging lens Keplerian (=Kepler type) telesclope Image is inverted Maginification ratio : (both Galilean / Keplerian) (focal length of objective)/(focal length of eyepiece)
f1
f2
Lens of the eyeeyepiece
Objective lens
Loupe
Transfer near object to farIn general, image is supposed to be at 250mm
(distance of distinct vision)Magnification (using thin lens law)
1/x – 1/250 = 1/f , M= 250/x M = 1 + 250/f
250
x
Lens of the eye
Loupe
Microscope
Magnified image by objective lens is observed using loupeImage is invertedMagnification ratio : Magnification ratio of objective lens
x magnification ratio of eyepiece
Lens of the eyeeyepiece
Objective lens
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