Photography 101.4 - Exposure and Stops

Photography 101.4 – Exposure and Stops

Photography 101 - Exposure and Stops

The following post is from Australian photographer Neil Creek who is part of the Fine Art Photoblog, and is developing his blog as a resource for the passionate photographer.

Welcome to the fourth lesson in Photography 101 – A Basic Course on the Camera. In this series, we cover all the basics of camera design and use. We talk about the ‘exposure triangle’: shutter speed, aperture and ISO. We talk about focus, depth of field and sharpness, as well as how lenses work, what focal lengths mean and how they put light on the sensor. We also look at the camera itself, how it works, what all the options mean and how they affect your photos.

This week’s lesson is Exposure and Stops

So far we have covered the basics of turning light into an image, starting with the concept of the pinhole camera, then introducing lenses and how they focus light, and last time about how the qualities of the lens affect the size and brightness of the projected image. So far this has all been pretty theoretical, but it’s important groundwork to helping you internalise how the camera works. When you know these basics, you can get to the solutions of photographic problems that much faster.

Play iconSome Housekeeping

Lesson naming
I’ve updated the naming scheme for this series to include the lesson number as a “point” value after 101. This will help you keep track of where you are up to in the series.

What happened to aperture?
Last time I said that this lesson would cover aperture and stops. I think introducing exposure and stops as a concept is important enough to dedicate a whole lesson to. Aperture will be now be discussed in Lesson 5.

This lesson we’re finally going to start getting a bit more practical. You will learn about the brightness of light, and how it is controlled. Of all the fundamentals of photography, this is probably the most important to understand, and can be the most intimidating because of the terminology used. But fear not! The mysteries of exposure and stops are about to be revealed!

What is “exposure”.

In the simplest terms, exposure is: “is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph(Wikipedia).

Whether it is a digital sensor chip or grains of chemically dosed silver on a film, it is the same thing. The greater the amount of light that falls onto a particular region of the photographic medium, the brighter that part of the recorded image will be when reproduced, whether on screen, print or slide.

Play iconPlay iconWhat We’ve Covered

Lesson 1
Light and the Pinhole Camera
Lesson 2
Lenses and Focus
Lesson 3
Lenses, Light and Magnification

The variation of brightness in the real world is absolutely huge, much more than you might think from your subjective experience of it. A subject lit by the midday sun on a beach looks over four thousand times brighter to your camera than the same subject lit by the quarter moon! (

Brightness is measured in “Exposure Value” or EV.

You might recognize this acronym from your camera’s settings or manual. An EV of 0 is defined an image exposed for 1 second at f1. Steps of one up or down from zero are a change in the light by a factor of two. So an EV of 1 is twice as bright, EV 3 is eight times as bright, and EV -2 is one quarter as bright.

Exposure variationsFig 1.4.1: From a base exposure, the exposure is increased and decreased in one stop steps to +/- 4 stops.

The “Stop”

A step up (doubling) or down (halving) by one EV is called a “stop”.

If you only come away from this lesson having learned one thing, it is this. Photographers talk about light and exposure settings in terms of stops. In photography a stop can refer to different settings in any of the three points of the exposure triangle (more below). One of the most important and useful things you can learn as a photographer is to get an intuitive feel for light levels.

I’m not suggesting that you should be able to walk onto a location and immediately be able to assess the EV of the light and determine the correct exposure settings (although some very experienced photographers can do just that!) – that’s what your exposure meter is for. However, if you can learn to look at a photo you have taken on the back of your camera, and see that the exposure needs to be increased by say 2/3 of a stop, then you will become a much more efficient and successful photographer.

Controlling Exposure

To accommodate the huge variety of brightness levels we see in the real world, we need to be able to control how much light gets to the camera’s sensor. We do this by adjusting one or more of the three points of the “exposure triangle”. These three points are ISO, Shutter and Aperture.

The aperture is an adjustable iris or opening that can be made wider to let in more light, or narrower to let in less. The shutter is the “gate” that allows light onto the sensor, and it can be left open for different lengths of time, to let the sensor collect more or less light. Finally, the ISO once referred to the sensitive to light of the film in the camera. In digital cameras it refers to the “gain”, or amplification of the information collected by the sensor. In film days, changing ISO meant changing films. Today the ISO can be easily adjusted with a dial.

The Exposure TriangleFig 1.4.2: The exposure triangle.

Each of these points will be the subject of future lessons in Photography 101. For now, you need to know that they are there, and that they all work together to control the exposure. At the centre of the exposure triangle is your camera’s light meter. It is by reading this that you determine how to set each of the three points. We’ll cover that in a future lesson as well, probably in Photography 102 – A Basic Course in Taking Photos.


Each method of controlling exposure does so in a different way, and as such, has a different effect on the character of the resulting photo. Increasing the shutter speed reduces the light, and freezes motion. Decreasing it allow more light in, but blurs movement occurring while the shutter is open. Closing the aperture decreases the light, but increases the depth of field, meaning sharp focus over more of the image. Opening the aperture lets in more light, but decreases the depth of field, meaning a narrower window of sharp focus. Increasing the ISO amplifies the light collected, but also amplifies the random noise in the chip, which can become visible in photos at higher settings.

It’s important to note that all of these effects can be used for creative purposes in photography. Having a narrower depth of field for example can be an artistic effect in a portrait, a slower shutter speed can convey a feeling of movement. Taking a good photo is the result of the conscious choice of the three points on the exposure triangle in order to get a well exposed image which has a character pleasing to the photographer. Adjusting the settings is a balancing act that affords huge creative options to the photographer.


  • Put your camera into manual mode, and find the controls to adjust each of the three exposure triangle points: ISO, Shutter and Aperture.
  • Set your camera to full auto, find various scenes, and “half press” the shutter and see what exposure settings it recommends. Now go to manual, make the settings using the manual control and take the photo. Repeat until you feel comfortable adjusting the manual settings.
  • Using the technique above, see what the camera recommends for various scenes, then adjust the photo up or down one stop of exposure with each of the exposure controls. Note the difference in the appearance of the resulting photos.
  • For those already familiar with manual control, find difficult, high contrast scenes (eg: a wall with a window outside, or under a shady tree on a sunny day). Shoot the scene on auto, then looking at the result, try to guess how much you need to adjust the exposure manually to see detail in the over or under exposed areas. Practice to see how close you can get just by estimating.
  • Apply these lessons artistically. Experiment with deliberately over or under exposing photos (high and low-key photos) or tweaking the auto exposed settings to emphasise otherwise under or over exposed areas.
  • If you wish to share your homework photos, upload them somewhere (eg: your Flickr account) and post a link to them in the comments on this post below.


Next Lesson

Photography 101.5 – Aperture
An overview of the first point on the triangle: aperture, including creative applications.

Any Questions?

I want to help my students learn, so I am always happy to answer any questions you may have. I’d also love to make friends with you, and perhaps talk about better ways to teach what I know, and learn more myself. So far I have been answering questions posted in the comments on each lesson. This time I’d like to experiment with using Twitter to take your questions and suggestions. So if you’d like to tweet me, then please feel free to add me to your twitter ‘following’ list:

Follow me on Twitter, username: neilcreek

I also strongly encourage you to participate in some extra curricular activities to develop your photography skills, and the monthly photography projects I run at my blog are ideal for this! While you’re there, please feel free to check out some of my other photography posts, and if you like it, please subscribe to my feed! I also am part of the Fine Art PhotoBlog, where I sell my photography as high quality fine art prints along with six incredibly talented photographers.

See you next lesson and good luck with your homework!

Read more from our category

Neil Creek is a professional photographer from Melbourne, Australia. He has been shooting with a DSLR since 2004, and blogging about his experiences since 2006. Neil has authored five ebooks and a video training course, all designed to help others improve their photography. View Neil's folio at his home page. Learn about his publications here.

Some Older Comments

  • mckinney landscape design} November 20, 2011 10:34 pm

    Thanks my photography!

    Wow, this blogpost let wangle a reward for the sterling orientation posted!

    You all sure like to argue about this topic. See how long this thread is????

  • Ilana October 13, 2011 03:20 am

    Are there sessions beyond 101.8? Is there a way to notify me when there is a new class? Is there an advanced (or next ) level?

  • chaCharles October 12, 2011 08:14 am

    Amazing Thanks so much for the help(: Cant wait to do my homework this weekend!!!A

  • Ilana July 25, 2011 05:39 am

    Thank you for your effort and time. The tutorials are super! I like the mathematical flavor of them as well. Your current change of the titles makes my life a lot easier and I can track my progress much better. Is there a way to send an e-mail when you post a new tutorial...?? ... I know it may be time consuming, so if this is the case, I'll continue to search the web for the new material.

    Best regards,

  • Gabriel Hudelson March 12, 2011 05:52 am

    Thank you much for taking the time to tutor aspiring light painters like yours truly!

  • Tiffany November 11, 2010 02:06 pm

    I have just found this sight and the lessons, and was wondering since its been so long if I should even bother doing the homework section and posting it. or should I just go on to the new stuff you guys are writing about.

  • Kenneth Dreyer September 20, 2009 05:36 pm


    We've written about photography exposure over at as well, for those of you who are interested in a bit of extra reading on this topic:

  • jared strugala August 1, 2009 12:49 pm

    i dont get EV stops.. like if you wanted your picture brighter, then why wouldnt you just changed your speed to lower? like EV stop and shutter seem like they do the same thing to me..

  • Raj July 17, 2009 05:13 pm

    Best photography lessons ever....and I've bought many books.

  • Celine Ellis February 13, 2009 08:39 pm


    Im taking a photography course at the minute and these tutorials are just genius for getting me through the mechanics of photography!

    i hav done a fair bit of the homework suggestions for the class but there a re a few bits im going to try this weekend!

    keep it up


  • Ricardo July 17, 2008 01:43 am

    Great post!
    i am a freshman, so a lot to lern :)

    how do i find 101.5 and further lessions?

  • sharaf June 9, 2008 12:42 am

    valuble information though they are the basic stuff. Technical know how is important, because the f/ stops are just a mechanical input, but they have enormous aesthetic implications in the photograph you're making. Whether you want lots of depth of field or a shallow depth of field. Exposure values, shutter speeds, all those sounds daunting but now I know I have to learn it in order to be fluid with them. Which then enables me to speak with a much louder voice!
    This is what I have been talking about a while back.

  • Mathieu June 7, 2008 08:42 pm

    Great post, exactly what you need to understand all those terms when you are a beginner! I now know what a stop is! =)

  • Mandy June 7, 2008 05:47 pm

    Great lesson, I'd heard of the exposure triangle but didn't properly understand it. This has made it a lot clearer, Thanks.

    I'll have to try out this twitter thing!

  • kristarella June 6, 2008 09:42 pm

    Sweet! Looking forward to the homework!

    So... 0EV = f1@1sec, xEV = 2^x amount of light on the sensor. This would mean that it's entirely relative to the situation you're in, the brightness associated with 0EV will change every time you change times or locations or weather conditions... this doesn't make a whole lot of sense to me...
    Looking at Gordon's cheat sheet (thanks, I've only had a brief look, but it's great so far) he's got EV referring to the scene itself. So did you mean that 0EV is the "correct exposure" and therefore if your scene has an EV of about 15 (bright sunny day, for example), you need to dial down 15 stops to get the right exposure?

    I'm gonna read Fred Parker, but feel free to let me know if what I said is on track. :)

  • Lia June 6, 2008 05:08 pm

    thanks so much for this. I can't wait to do my homework this weekend :)!!!

  • Jas June 6, 2008 04:40 pm


    i tried to follow you at twitter for no success. How do you do it??

    When trying to find you it tells me to enter your email address which i guessed as being

    Thanks / Jason

  • Paulo Jordao June 6, 2008 02:44 pm

    Thanks for the tips.. I will check you on Twitter
    Paulo Jordao

  • ditch_azeroth June 6, 2008 12:38 pm

    nice read. when i started, i went A>P>Tv/Av - i would check what the exif and see how the camera set it. i would make some adjustments in manual and here i am ^_^

  • Neil Creek June 6, 2008 11:43 am

    @Rafael Thank you very much :) I agree that a picture is worth a thousand words, especially when explaining abstract concepts, so I've put a lot of work into the illustrations for the Photography 101 series.

    @xportebois I believe what you are describing there is stopping down the lens to prevent the light from travelling through the edges of the lens, which is where (typically on lower quality lenses) the optical quality of the glass is not as good. It is true that most lenses are less sharp at their widest aperture settings, it's certainly not universal, and it isn't essential to close the aperture by as much as two stops all the time. Sometimes, to get the shutter speed to an acceptable level, you have to open the lens to its widest or risk not getting the photo at all.

  • Martin June 6, 2008 11:39 am

    @xportebois: for many lenses, saying you should stay 2 stops above the max aperture is probably valid.
    However, it's certainly not true for all lenses, and many lenses are very sharp even at max aperture.

  • xportebois June 5, 2008 05:38 pm

    Great lesson, I would like to read it before :)
    Nevertheless, I want to underline that there is another "problem" than depth of field when you play with the aperture : if you use your lense full open, it may result in a little blurred photograph (like in macro photo).

    It was really painful for me to solve this problem, to understand from where it came ; PhotoNewt helped me well on this (see this thread in the forum : )
    So when playing with the three parameters, if it's commonly known to be careful with too high ISO (noise) or too slow shutter speed (motion blur), be also aware to stay something like 2-stops above the maximum aperture.

  • Rafael June 5, 2008 01:28 pm

    Hey Neil.

    Awesome lesson. I must say that your "exposure triangle" image is a great didactic tool, and really set the info into my mind.

    Great to have you back. Cheers, Professor!


  • Gordon McKinney June 5, 2008 12:24 pm

    @Neil, no problem. Please link to the PDF direct or my blog as you see fit. That PDF is a great collation of a lot of collective knowledge.

    Have a great week, G. :o)

  • Neil Creek June 5, 2008 10:52 am

    Thanks everyone for the comments! It's great to be back in the classroom :)

    @taryn I look forward to seeing your homework :)

    @pablo I'm glad you like the lessons, but they are a LOT of work! I aim for weekly, but I have a very hectic life, so I'm sorry but you'll have to settle for "as often a I can manage".

    @Gordon Wow, an excellent resource that goes very well with this lesson. I may well link to it in a future lesson, so thank's for bringing it to my attention.

    @W. Michel I intend to mention this relationship in the next lesson on aperture, where those figures are most relevent :)

    @Darren Thank you very much! It's a rare honor for you to comment ;) I'm glad you enjoyed the lesson!

  • Darren June 5, 2008 10:43 am

    welcome back Neil - this is one of your best lessons yet!

  • W. Michel Kiteley June 5, 2008 08:27 am

    Perhaps someone should mention that the square root of 2X (as in the formula of the area of a circle) is actually 1.414 and that should be familiar in a string of numbers like 1.0, 1.4(14), 2.0, 2.8(28), 4.0 and 5.6(56) etc.


  • Teewinot June 5, 2008 08:10 am

    Excellent lesson, thanks!!

  • boris June 5, 2008 04:25 am

    Well done, thank you - I look forward to the following lessons.

  • Chris Bergman June 5, 2008 04:19 am

    Yay manual mode! I will defeat you yet, camera.

  • ebradlee10 June 5, 2008 03:51 am

    Well this is just awesome. I've always judged light by sight, with wildly varying degrees of success. Thanks for this simple & insightful tutorial.

    I just initiated a follow of you on Twitter. My twalias is ebradlee10.

  • Gordon McKinney June 5, 2008 02:56 am

    Checkout my Photographic Cheat Sheet, it sums up Exposure, f/stop, shutter speed and more!

  • pablo June 5, 2008 01:50 am

    great stuff. I just wish the lessons were here more regularly. what about having the photography 101 every wednesday???

  • cabrown June 5, 2008 01:05 am

    Welcome back, Neil. :D

  • taryn June 5, 2008 12:52 am

    i can't wait to try out my homework. thanks for this post. i've been wanting to move away from aperture setting and into manual. we'll see how i do.