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Home → Cameras and Lenses

What is a DSLR (Digital SLR) Camera?

By Nasim Mansurov 97 Comments
Last Updated On April 3, 2018

DSLR stands for “Digital Single Lens Reflex”. In simple language, a DSLR is a digital camera that uses a mirror mechanism to either reflect light from a camera lens to an optical viewfinder (which is an eyepiece on the back of the camera that one looks through to see what they are taking a picture of) or let light fully pass onto the image sensor (which captures the image) by moving the mirror out of the way. Although single lens reflex cameras have been available in various shapes and forms since the 19th century with film as the recording medium, the first commercial digital SLR with an image sensor appeared in 1991. Compared to point-and-shoot and phone cameras, DSLR cameras typically use interchangeable lenses.

1) What DSLR Cameras Consist Of

Take a look at the following image of an SLR cross section (image courtesy of Wikipedia):

DSLR Cross Section

2) How DSLR Cameras Work

When you look through a DSLR viewfinder / eyepiece on the back of the camera, whatever you see is passed through the lens attached to the camera, which means that you could be looking at exactly what you are going to capture. Light from the scene you are attempting to capture passes through the lens into a reflex mirror (#2) that sits at a 45 degree angle inside the camera chamber, which then forwards the light vertically to an optical element called a “pentaprism” (#7). The pentaprism then converts the vertical light to horizontal by redirecting the light through two separate mirrors, right into the viewfinder (#8).

When you take a picture, the reflex mirror (#2) swings upwards, blocking the vertical pathway and letting the light directly through. Then, the shutter (#3) opens up and the light reaches the image sensor (#4). The shutter (#3) remains open for as long as needed for the image sensor (#4) to record the image, then the shutter (#3) closes and the reflex mirror (#2) drops back to the 45 degree angle to continue redirecting the light into the viewfinder.

Obviously, the process doesn’t stop there. Next, a lot of complicated image processing happens on the camera. The camera processor takes the information from the image sensor, converts it into an appropriate format, then writes it into a memory card. The whole process takes very little time and some professional DSLRs can do this 11+ times in one second!

The above is a very simple way to explain how DSLR cameras work.

To read a lot more about DSLRs, check out this great article at Wikipedia.

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Filed Under: Cameras and Lenses Tagged With: DSLR Camera, Photography Tips, Tips for Beginners

About Nasim Mansurov

Nasim Mansurov is the author and founder of Photography Life, based out of Denver, Colorado. He is recognized as one of the leading educators in the photography industry, conducting workshops, producing educational videos and frequently writing content for Photography Life. You can follow him on Instagram and Facebook. Read more about Nasim here.

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Kim
Kim
May 22, 2022 12:34 pm

Very helpful. Thanks!

1
Reply
Aman Kashyap
Aman Kashyap
November 28, 2021 1:57 pm

Its very helpful thank u so much

0
Reply
Sean B
Sean B
December 21, 2020 7:49 am

This really help for my class that im doing!

0
Reply
Raghu
Raghu
December 11, 2020 6:28 pm

Simple and neat to explaining how DSLR works !! Excellent work.

1
Reply
jeff jeff
jeff jeff
April 23, 2018 5:28 am

My name jeff

20
Reply
Jeff Reeeeeeeee
Jeff Reeeeeeeee
Reply to  jeff jeff
October 19, 2022 7:24 am

Real

0
Reply
Wendy
Wendy
December 23, 2017 11:37 am

Hello,
Love your site
Just got myself a cabin EOS rebel SL2 after thinking about getting a “real” cámara for almost 9 years.
I am a total beginner anfd looking forward to learning from you.
– Wendy

1
Reply
Binay Kumar Yadav
Binay Kumar Yadav
December 21, 2017 3:57 pm

Hi sir,
I am following your site since a week and I am loving it. Sir I wanted to buy Canon 80d with lens 18-135mm so can please brief me how it would or can I get any recommendation from you.
Thank you!

1
Reply
Mohiuddin
Mohiuddin
December 16, 2017 11:05 pm

Thanks for the simplified article, for news users like me

2
Reply
Siddharth Malkania
Siddharth Malkania
October 20, 2017 10:21 am

A very informative but more technical article. Does mirror-less camera function the same way? Is there any article based on mirror-less cameras? I would love to read it.

I also wrote about, how DSLR camera focuses and tried to explain it in more simplest way!
Please go through it and leave your feedback..
siddharthmalkania.com/how-d…a-focuses/

Regards,
Siddharth Malkania

1
Reply
Ardas Sandhu
Ardas Sandhu
May 18, 2017 8:22 am

This content has helped me so much for my finals. Thank you! :)
I am somewhat leaning towards photography, it fascinates me, any words of advice on what or who should i pursue?
I don’t have any point of reference, if you would be so kind to shed some light it would be very kind of you.

2
Reply

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