This document discusses different types of camera lenses including their focal lengths and uses. It describes telephoto lenses as having narrower angles of view and longer focal lengths than standard lenses, used for magnifying subjects. Wide angle lenses are described as having short focal lengths from 20-35mm, providing more depth of field and showing expanses. Zoom lenses allow adjusting the focal length while prime lenses have a fixed focal length. Proper lens care and cleaning is also discussed.

1. Lenses
By: Amit Chawla

2. Focal Length
 Focal length = distance from the optical center
of the lens to the focal plane (target or "chip")
when the lens is focused at infinity. It is
generally measured in millimeters.

3. Angle of View
 It is directly associated
with lens focal length.
Longer focal length (in
mm), narrower the angle
of view (in degrees).
 When you double the
focal length of a lens,
you double the size of
an image on the target;
and vice versa.

4. Classification of Lenses
Lenses
Telephoto
Normal Like binoculars
Wide
45 to 55 85 to 300 mm
20 mm to 35
13 to 18 mm 400 to 1000
Super wide Extreme/super tele
8 mm fish eye

5. Telephoto
 Taking pictures through it is like
using a telescope - it magnifies
& makes everything look larger.
 They are having narrower
angle of view and a longer focal
length than standard lens.
 For 35mm cameras:
– 70-120mm are short telephotos
(often called portrait lenses)
– 135-210mm are moderate
telephotos
– 400mm or more as extreme
telephoto lenses.

6. Telephoto Lens - Uses
 The main use of telephoto
lenses is enabling you to
select a small part of the
subject - to pick a detail.
 To give greater emphasis
to the subject
 To create artistic impact by
getting the background
blurred.

7. Telephoto Lens – Word of Caution
 Telephotos magnify camera shake as
well as the subject, so one needs to
use fast shutter speeds.
 The slowest speed that is
recommended for use is 1/focal length.
 With a 500mm lens, 1/500 or faster,
with a 135mm, 1/125 or faster.
 Tripod use is very imp if you need
slower speeds

8. Portraits (70-120 mm )
 Short telephoto lenses
are especially useful for
impressive. The
working distance you
need with them gives a
natural looking
perspective & makes
whole of the person's
face sharp.
105 mm pic

9. Moderates (135mm to 210 mm)
 Moderate telephoto
lenses are great for
picking out details and
Isolating Subject from
distracting material.
 You need to focus with
care.
 Limited depth of field

10. Extreme Tele (400 mm onwards)
 They are used for specialist
purposes such as sports & wild-
life. With 35mm, a 400mm lens
lets you stand on the boundary of
a pitch and photograph action in
the centre.
 Extreme telephotos are much
easier to use when the action will
occur in a predictable place .

11. Wide Angle Lens
 A short focal length lens. For a common 35 mm
format, a common wide angle is 28 mm.
 Wide angle lens have considerable depth of field.
 Show expanse
 Are useful when space in limited
 Are useful when one doesn’t have time to focus
every time
Wide Angle Super Wide Fish Eye
20 – 35 mm 13 – 18 mm 8 mm

12. Wide Angle Lens
v/s

13. Wide Angle Lens
Wide angle is easier are easier to work with due to:
 Less Camera Shake
 More Depth of Field
 Everything comes in reasonable focus
Wide angle lens is ideal for
 Landscapes & Architectural photography
 For achieving distortion
 For a newness in perspective
 To catch a glimpse of interiors

14. Examples of usage of Wide Angle Lens

15. Examples of usage of Wide Angle Lens

16. Effect of Changing Lens
Photos below were taken by 35 mm camera at constant distance from subject.
28 mm lens 50 mm lens
70 mm lens 210 mm lens

17. Classification of Lenses
 Prime Lens & Zoom Lens
 With Prime Lens, focal length of lens cannot
be varied. Prime lenses are more predictable
in their results. Prime lenses also come in
more specialized forms, like, super wide
angle, super telephoto, etc. They also give
lesser distortion.

18. Classification of Lenses
 Zoom Lenses came into common
use in the early 1960s. Before then,
cameras used lenses of different
focal lengths mounted on a turret on
the front of the camera, as shown
on the right.

19. Classification of Lenses
 Zoom lenses use numerous
glass elements, each of which
is precisely ground, polished, &
positioned & can be
repositioned to change
magnification of lens. On zoom,
these lens elements move
independently at precise
speeds.

20. Zoom Ratio
 Zoom ratio is conventionally used to define focal
length range for a zoom lens. If the maximum range
through which a particular lens can be zoomed is
10mm to 100mm, it's said to have a 10:1 (ten-to-one)
zoom ratio. But this does not shows that what is the
minimum and maximum focal length of lens. A 10:1
zoom lens could have a 10 to 100mm, or a 100 to
1,000mm lens, & the difference would be quite
dramatic.

21. Lens Care
 Sloppy lens changing and storage is a primary factor
that helps dust to invade camera and pictures.
 Cleaning of lens - occasional thorough 'scrub‘ apart
from regular cleaning with a dry cotton piece of cloth
of a requirement. Using a specially developed brush
for the same is not a bad idea.
 Using a UV or skylight filter.
 For as long as possible, the lens should be kept
away from dust, smoke and moisture.