Single lens reflex camera

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.         

                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.