Smart_Photography_-_September_2019

Name Resolution Abbreviation Scanning Frame

Rate (fps)

Full HD 1920 X 1080 1080p Progressive 24

Full HD 1920 X 1080 1080p Progressive 25

Full HD 1920 X 1080 1080p Progressive 30

Full HD 1920 X 1080 1080p Progressive 50

Full HD 1920 X 1080 1080p Progressive 60

Full HD 1920 X 1080 1080i Interlaced 50

Full HD 1920 X 1080 1080i Interlaced 60

HD Ready 1280 X 720 720p Progressive 24

HD Ready 1280 X 720 720p Progressive 25

HD Ready 1280 X 720 720p Progressive 30

HD Ready 1280 X 720 720p Progressive 50

HD Ready 1280 X 720 720p Progressive 60

UHD 3840 X 2160 2160p Progressive 24

UHD 3840 X 2160 2160p Progressive 25

UHD 3840 X 2160 2160p Progressive 30

Table 1: HDTV Standards

Not very long ago, if you had gone on a

vacation and if you wanted to take stills

as well as movies, you had to carry two

pieces of equipment — a still digital

camera (perhaps a D-SLR) and a video

camera. All that has changed, in fact

quite drastically, when Nikon introduced

the D90 which was the first D-SLR with

built-in video recording. Since then many

technological advances have occurred,

and excellent video capability is built

into every ILC (Interchangeable

Lens Camera, that is a D-SLR or a

mirrorless camera). In fact it is now a

part of the standard feature set that is

taken for granted.

Unfortunately, surveys show that few

still photographers, even serious ones,

take cognisance of video features that

are in their ILCs though they have paid

for them! This is a pity because modern

ILCs are capable of very high quality

video capture, far better than the earlier

video cameras. The reason for this is

not hard to understand. Video, as it

popularly said, is a ‘different ball game’!

It has its own terminology, menus and

parameters that you need to understand

and master. The setup is very different

from that of still photography.

We at Smart Photography always aim to

make things simple without confusing

readers with arcane details and jargon.

We hope to repeat this with our coverage

on video capture (or videography) with

ILCs. In this article, we wish to introduce

to you the process of video capture

and the various parameters you need

to know before you set up your ILC for

video capture.

Frame rate

This is a self-explanatory term and states

how many frames are recorded and

subsequently shown (say on a TV) in a

second. It is specified as ‘fps’, which is

the abbreviation for ‘frames per second’.

Now, let us see how continuous motion

is achieved. The truth is that the sense

of smooth motion is created due to our

perception. The motion you see on a

TV or in a theatre is made of several

still images (called frames), each taken

sequentially one after another. So, each

frame is one slice of time and thus will

be slightly different from the preceding

frame (unless you are taking a movie

of a perfectly still scene in which case

each frame will be the same). When

these sequential still images are shown

‘sufficiently fast’, then we will get an

impression of continuous smooth

motion. Why so? It is due to two

important phenomena called persistence

of vision and the phi phenomenon, but

we will not go into more details of these

due to lack of space.

The important point here is what

is ‘sufficiently fast’ or how high the

frame rate should be before we do not

detect any jerkiness? For humans, at

the minimum, it is 24 fps. Also, beyond

60 fps humans don’t experience any

further smoothness. The movies we

see in theatres are shown at 24 fps.

In our country TV broadcasts are at

several different rates – usually at 25

fps progressive (called 25p) or 50

fps interlaced (called 50i). More of

this shortly. These frame rates have

a relationship with our mains power

which is at 50 Hz.

Slow and fast motion: If a video is

recorded at a certain frame rate and

played back at the same frame rate,

then it appears normal as captured. If

the video is played at a rate less than

the recorded rate then the playback will

appear in slow motion as the display

time is stretched. For example, if the

capture has been made at 50 fps for 10

seconds and played back at 25 fps (at

half the fps), it will now show for 20

seconds, and everything will appear in

slow motion. The opposite will happen

when the played-back frame rate is

faster than the captured rate, though this

is seldom used.

Resolution

This defines the number to lines that

are shown on a TV. This is an important

parameter that determines the detail

that will be visible on the screen. There

are currently three broad resolutions in

use, called standard definition (SD), high

definition (HD) and ultra-high definition

(UHD) popularly known as 4K.

Standard Definition (SD): In our

country, colour TVs follow a standard

called PAL. This uses a resolution of 625

lines at 50 fps. This is called Standard

Definition. However, there is a catch

here. All the 625 lines are not displayed

at once. Only half, called a ‘field’

(composing of alternating lines) will be

displayed at a time and the second half

of the missing frame will be shown next.

This is why it is called ‘interlaced scan’

method. This is really a compromise as

at any instance of time, the resolution

(called temporal resolution) is only half

of 625! As opposed to this, ‘progressive

scan’ method shows all the lines at once

and thus gives a much better visual

experience especially when fast paced

motion (like sports) is being shown.

http://www.smartphotography.in September 2019 | Smart Photography | 93