Single lens reflex camera
SLR(single lens reflex camera ) is a camera consists
of pentaprism and reflex mirror, that helps the photographer to view the
subject through the viewfinder as it will be captured on the film/Digital
sensor, thereby compose the image by seeing through the viewfinder. SLR camera uses a photographic film for
storing images which later postprocessed
in the lab to get the print of the image on the sheet. This kind of processing of
image has existed until digital technology have come to eradicate the complex
system of getting image prints by using
SLR camera.
How SLR camera shows subject on the viewfinder??
As I said above, there are two things that help you
to see the subject through your eye piece. They are Pentaprism and reflex
mirror. You can compose the elements of
the image manually only by using SLR or
DSLR camera. This the way DSLR camera vary from SLR camera. SlR uses photographic film as sensor elements
wherein the image gets stored. Whereas DSLR uses Digital sensor that stores
image on the Digital memory card. There is no much difference between them
except in DSLR, you can easily see the
image that has been taken instantly but In SLR you cannot see the image unless
you have processed the film negative in the lab.
Pentaprism?
It is used in the SLR camera to direct the beam of
light coming from the subject to the eyepiece where you can compose the image
by seeing your naked eye. But without
reflex mirror ,you cannot see the image through the eyepiece even with a help
of pentaprism. So reflex mirror is an
essential one. I will tell the how it functions later.
How pentaprism functions?
A pentaprism, as it name calls five sided optical
device uses two reflecting surfaces that rotates a beam of
light to 90 degress without changing the orientation of the image. It is as the same way when two mirrors placed
at 45 degrees . Both give the same
result .
Reflex mirror?
It is the mirror used in a camera that allows the photographer
to view the scene through the lens before taking the photograph. So with the help of pentaprism and reflex mirror the photographer can able to see the
subject has to be captured prior to taking the photograph. Normally this mirror should be placed at 45
degrees towards the light coming from the subject through the lens.
Let’s see the image below for understanding of this
concept. I explain step by step function
that happens in the camera when taking
the photograph.
Before explaining the concept step by step, know the
elements found in the camera. Almost all
the cameras have this elements. See the diagram above and this paragraph side
by side to know what are the elements are placed according to the numbers shown
above.
1. Lens/optical elements
2. Reflex mirror
3. Shutter door
4. Film sensor
5. Focussing screen
6. Condenser lens
7. Penta prism
8. Viewfinder.
2. Reflex mirror
3. Shutter door
4. Film sensor
5. Focussing screen
6. Condenser lens
7. Penta prism
8. Viewfinder.
Assume you are seeing through the viewfinder(8) for
taking photograph of some objects. You can see the object as the lens sees the
object. Both the image you are seeing
and the lens capturing are going to be the same. This is what the SLR camera
does and that we call it as manual camera. SLR camera provides either manual or
automatic. It is upto you to set the mode you want. But it is always recommended to set
manual mode to taking up the photographs, because that teach you the real
nuances of photography if you have practised it. Now lets look at the step by step explanation.
Step 1:
First, when you take the photo , the beam of light
coming from the subject through the Lens/optical
elements try to reach the sensor either film negative or digital sensor ( CCD ,CMOS
sensor).
Step 2:
Due to the placing of reflex mirror at 45 degrees in
between the sensor and the lens elements, the beam of light rays is reflected
by the mirror and fall on the Focussing screen(5).
Step 3:
After the light fall on the focussing screen, the
condenser lens (6) used to gather light and directed towards the pentaprsim(7).
Step 4:
In the pentaprism(7) , internal reflections takes
place as the light entering from one surface is reflected twice by the two
reflecting surfaces of pentaprism (you
can see in the diagram above, how light reflects in the pentaprism) and finally
the image appears on the viewfinder(8). You can see through it to compose your
image as you want to shoot.
Step 5:
After you are satisfied with the composed image in
the viewfinder, you can press the shutter button to take a snap. Shutter button is a button found in the camera
used to press for taking a snap.
Step 6:
When you are pressing the shutter button, the reflex
mirror moves at some angle towards the focussing screen that lets the rays of
light coming through the lens reach the
sensor plane(4) when the shutter door
opens. When you press the shutter button , shutter door(3)
opens normally and the light fall on the
sensor plane and the images stored on it
as it exactly shown on the viewfinder. Shutter door opening and closing is the vital
part as it calculates the amount of light it lets in.
Finally, the image get stored on the film negative
or sensor plane depending on the camera types.
So read this
steps as it is fundamental and must to know to learn photography.
SLR vs DSLR?
SLR camera – Film plane as its storage element
DSLR camera – uses digital sensor(CCD or CMOS type
of sensor) behind the shutter door that use to store image on the memory card.
