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THE ROBIN

Jim McGovernDear wee robin, dear,
So snug in winter yet full of fear.
In summer green thou art in gear
With squabs three or four so near.
However safe they are to-day
They have enemies in their way
Here, there and everywhere.      Readmore

THE PILOT

Malachy McCullaghDown in the bright green grass I lie
And watch the planes in the clear blue sky,
I’ll be a pilot one day soon
And fly my plane straight up to the moon.The man in the moon will say to me,
Do stop and have a cup of tea,
And all the stars will sparkle by,
For I shall fly so high - so high.One morning I’ll start up my plane,
Fly round the world and back again,
And when I’ve seen all I can see,
I’ll come home to mammy and to tea.      Readmore

THE FOOTBALL MATCH

Michael McAliskeyI
The referee blew the whistle and
The ball was thrown in
The players jumped high for it
And were at it thick and thin.II
Down the field the ball went sailing,
Players striving main and might
But the kick was unavailing for
The umpire signalled wide.III
The forwards all were playing well,
The backs were well-behaved,
Then a sizzling shot was taken
But the goalie quickly saved.IV
‘Twas drawing near the close of play
And near the full time call
When little Dan Quinn, hurrah!
Jumped high to catch the bait.V
He soloed and he dummied,
He raced…     Readmore

SUMMER! SUMMER!

John NugentSummer! Summer!
The call of the plover!
When the lark cries
And Spring dies,
O Summer! Summer!Summer ways are here again,
When day lives till after 10 p.m.
While the honey bees work
And the hedge-sparrows chirp,
O Summer! Summer!Summer days, school is o’er,
September back to chore,
Sea waves roar,
“Golden Summer is no more”,
O Summer! Summer!     Readmore

SPRING?

R DoyleSleek, svelte, and long, the shimmers of sun
Slip and steal through the branches.
And the sky carries clouds that float and run
Propelled and pummelled by a young April breeze.A ripple of shiver creases the lake
Where the water bird settles,
And bright green fields sound the song
Of a new birth - promising, fruitful and young.And an old world listens
And understands - but does not feel.     Readmore

SPACE AGE

Joe McLoughlinI’m sure you’ve heard or read about,
The satellites in space,
How Russia and the United States
Are in the rocket race.To hear them talk it won’t be long,
The moon they will conquer soon,
And then what next will man attempt,
If he should reach that moon?Russia leads so far,
By their flights towards the moon,
And according to Khruschev,
They’ll be up again soon.If they do go up again,
Who’ll follow them but Colonel Glenn ?
And if he does he’ll be the toast,
Of more than American space men.      Readmore

FISHING

Eugene HughesUp the stream,
With rod and tackle,
To fish for bream,
Goes Bobby Mackle.Quickly throwing out the bait
He leisurely sits in wait,
For some unwary bream,
To break the placidness of the stream.The captured fish starts to plunge about
Alas, he’ll never get it out,
The fish it swims away,
But he says there’ll be another day.      Readmore

ESCAPE

R DoyleGrey smoke, blue grass,
A lift of wind,
Sky of brass.
In a long slope
Comes down a bird,
Alert, soft-falling
Down to earth in a spiral.Sharp eyes watching,
Dull heart longing,
Human heart lifting
In vain desire to imitate;
To be away, far separated,
Looking down
From some spire of height.     Readmore

TO COLONEL GLENN


John HannaO Colonel Glenn, you hero so bold
Remember this as now you’re told.
Next time you pass high over head
Think of me and my buzzing head
If you were here you’d quake and shake,
So drop a bomb just for my sake.I’d like to shout, I’d like to sing,
I’d like to dance out in a ring.
But I’m afraid I have to hurry,
In case the teacher’s in a flurry.
Still I’m made to laugh when I think of you
Out in orbit in the blue.      Readmore

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Home arrow 1991-92 arrow Articles arrow THE WORKINGS OF A CAMERA
THE WORKINGS OF A CAMERA PDF Print E-mail
Written by Dermot Cushnahan, U6

A camera is light tight box which has an opening covered by a lens in one wall. This lens forms a real image of the object upon a plate of film which is made of light sensitive material inside the box. A modern camera consists of housing (body), the film holder, the film feed mechanism, the lens, the shutter, the distance setting, the range finder and the view finder for composing the picture.

The simplest method of taking a photograph is by means of forming an image on a photographic plate or a pinhole (camera) diaphram, containing a hole about 5 mm in diameter on the front of the light tight box. On this principle it is possible to construct a ‘pinhole camera’.

From each point on the object a ray of light passes through the hole through lens and focuses on the film where it makes an image at that point. Each point of the object is admittedly projected onto the plate as a small elliptical spot or light and the adjacent ellipses merge together to form an image.

A pinhole camera needs long exposure time. It has a low speed lens. This type of camera needs two lenses to become sharper so it may have a two element lens

In more advanced cameras both the aperture and exposure time can be changed to suit light conditions (or the movement of the object). The lens in these more elaborate cameras usually consist of three or more elements.

Cameras using larger sizes of film are usually those which give a sharper image. Smaller cameras using small sizes or film (miniature) have optical advantage such as short focal lengths, large angular field (can take large photos at short distances) and of course the resultant advantages.

High class expensive cameras are equipped with coupled rangefinder interchangeable lenses and shutters with high speed (1/250 to 1/1250 of a second, enabling you to take photos of fast moving objects like cars and birds, leaving no blurred images. The twin lens reflex camera has a viewfinder and just the simplistic camera; the distance finder for the two is the same so that the sharply focused images which are formed on the screen of film is also focused on the plane screen of the viewfinder. The lenses of the two parts have exactly the same focal length. As a rule the viewfinder has a greater light transmitting power than the camera lens.

A single lens reflex camera has only one lens which serves for focussing the image on a ground screen. When the image has been focused, the deviating mirror set at 45° is swung upwards, enabling the image to be formed on the film. The aperture or stop value is set before the exposure is made and when the shutter is released the deviated mirror is automatically swung out of the way which is mounted directly in the front of the film (momentarily of course) exposes the film. Then the film is wound on for the following shot and the shutter is thereby automatically cocked. Then the mirror is lowered again for focussing the next object for photographing.

 

Last Updated ( Saturday, 15 December 2007 )
 
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