Understanding Photography Exposure
As photographers, we are truly artists of a different kind. We strive to use both hemispheres of our brains to make a two dimensional image appear three-dimensional. To do this we use various techniques of composition, color, posing, shadow, and light. This last is sometimes the most forgotten and yet the most important. We tend to forget the technical aspects of exposure and focus on the other aspects of composition, posing, and colors, but we often leave the camera do the technical work for us when it comes to the exposure. One of the things we can do to help make our pictures better is to take the camera off the ‘auto’ setting and put it on ‘manual’.
When we put the camera on ‘manual’, we have full control of the settings. To make the photograph look the way we want it to look, we will need to control three basic aspects to get a good exposure. The word dates back to the pre-digital era, when light was exposed through the aperture of the lens onto film, creating an image. These three basics are shutter speed, ISO, and aperture (F-setting/F-stop). All of these settings can have a dramatic impact on the way our photographs appear.
The exposure triangle will help you imagine shutter speed, aperture and ISO together. And help you understand interaction between these elements to produce final image. Take a look once now, and also once after reading this article fully.
Shutter Speed
Technically, the shutter is the mechanical contraption that allows light to enter the body of the camera and onto the film or in the digital realm, the sensor. The length of time that the shutter remains open determines, in part, how much light the sensor (or film) receives. Shutter speeds are typically measured in fractions of a second for most photographs. The standard shutter speed is 1/125 of a second. A fast shutter speed will help to capture time. By this, I mean that a fast shutter speed will catch quick action and ‘freeze’ it. A slow shutter speed will allow for moving objects to be blurred by their motion. There must always be a connection between the amount of light on your subject and the shutter speed. If you are under very bright conditions, a high shutter speed will help to limit the amount of light and capture very sharp and detailed images. If you have little light, a fast shutter speed can be the cause of an under-exposed image. Fast shutter speeds will help you freeze the propeller of a helicopter in flight. Slow shutter speeds can give you the light streaks of a car passing by without the car being ‘visible’ in the photograph. Combining various shutter speeds with camera movement can keep a fast moving object (like a race car) in focus, while the things around the car will appear blurred by the motion of the camera movement.
ISO
ISO: 3200 (pixilation you see is called noise)
Aperture
The aperture on your camera is nothing more than an iris that is set to allow the light in through the lens and onto the digital image sensor. These settings are usually called F-settings or F-stops. The term F-setting comes from the idea of focal length of the camera in comparison to the opening of the iris. Without getting overly technical, the aperture controls the amount of light coming in through the lens, and how the focus will act in terms of depth of field. We will go into depth of field more in a moment. The higher the F-setting number (F/18) the smaller the opening in the lens and the less light will affect the image sensor. The smaller the F-setting number (F/2.8) the larger the opening in the lens and the more light will affect the image sensor. Small openings produce crisper images while larger openings will help to ‘soften’ them a bit. Keep this in mind when shooting so you can achieve your goals with the shot.
Depth of Field
The term depth of field is used to describe how large or small of an area will be in focus. In a picture where the foreground is out of focus, the mid-ground is in focus, and the background is out of focus, we can see the affects of depth of field. This can help us as photographers draw attention to the areas of the photograph we desire without having to change the overall setup of the shot. In some cases, we might have a very busy background that will likely detract from the subject of our shot. If we could blur the background enough to keep it from being distracting while keeping the subject in crisp focus, we will be successful in our shot. The depth of field is dependent upon a couple of things. First the aperture and second the focal length (zoom) of the lens. If I were to use a small aperture number, like F/2.8 in combination with a 70-200mm lens zoomed in to 100mm I could effectively put the background out of focus and keep the subject in focus. In some cases, it might be a bit bright to have this large of an aperture. In such circumstances, you could use a filter called a Neutral Density filter. These filters will change the amount of light entering the lens as if you had a smaller aperture set on the camera. You would be ‘fooling’ the camera into thinking there was less light.
In order to take good pictures, we should always be concerned with lighting. The idea of exposure on your camera is the concept capturing light. As you can see, aperture, ISO, and shutter speeds all inter-relate to achieve a good exposure. Think of keeping one constant and the other two as variables. The easiest thing to make the constant is the ISO and then use a light meter, either hand held or the one built in to your camera, to achieve proper exposure. Once you start getting the hang of exposing properly on manual, then you can begin to expand your horizons to achieve dramatic lighting, motion blurs, and other things. Take some time to get to know your camera and its capabilities. One of the great things about digital is that there is no cost involved in practicing. Try to get various exposures through different combinations of settings. Make a log or diary of your shots and their settings. You will probably not need to write the settings down as the information is recorded in the EXIF data on each digital image, but keep in mind what you are trying to achieve and why it happens. The more control you can achieve, the better your pictures will be in the long run.
There are 15 comments on this post.
Trackback URL | Comments RSS FeedISO is not greek, but rather an acronym from the International Standards Organization that sets the standards for film or digital sensor speeds.
see http://en.wikipedia.org/wiki/Film_speed
Hi Nic, I’m glad you are reading my articles
Regarding your comment, I’m aware that ISO means International Standards Organization, but I’m also aware of the fact that this name was chosen because of its Greek translation.
Taken from the organization website itself:
http://www.iso.org/iso/about/discover-iso_isos-name.htm
“Because “International Organization for Standardization” would have different acronyms in different languages (“IOS” in English, “OIN” in French for Organisation internationale de normalisation), its founders decided to give it also a short, all-purpose name. They chose “ISO”, derived from the Greek isos, meaning “equal”. Whatever the country, whatever the language, the short form of the organization’s name is always ISO.”
@Nic
p.s. In my academic career I’ve noticed that professors and teachers don’t trust wiki as a source for credible information. While wiki is an awesome place to gain general knowledge, unfortunately some of its articles lack preciseness.
In academia, there is nothing better than a direct source, and this is how I try to write most of my articles.
Discount Wiki if you will, but it has far more people involved with peer review than most text books. Case in point, in the textbook for a college photography class I’m taking, I’ve found five rather glaring errors, and I’ve only skimmed the book. Wikipedia had correct examples of each. And years ago, when taking electrical engineering classes, I had a 5th edition text where we would often spend five to fifteen minutes each class correcting it. In once case, a section on diodes referenced the wrong illustration, and left classmates completely stumped. I explained to one student the text was wrong, and now she is an Assistant Professor running the robotics lab at MIT.
I’d like to think that academics can always do better, but we really have to take each author’s work at its own merit.
Wikipedia is not without fault either, as some niche topics can gain enough support with the review system to push their own agenda. Look up kibibyte. I agree we need a new prefix to describe the quantity of 1024 bytes, and kilo should revert to the standard 1000 multiplier from the metric system — but Kibi and Mebi are not at all in common use. Wiki, most likely following members of the IEC who wrote the proposal, implies it is.
I agree with you completely. Now that you mentioned it, I remember studying from an economics textbook 14th edition, still full of typos and theory controversies.
In any case, lets keep discussion close to the topic of the post…
I actually like the story where ISO came from, and agree with their logic (to keep it universal). But let’s keep in mind that ISO is a worldwide standards organization, not just a film/sensor speed specification. ISO does administer a spec for film speed (adopted from the ASA, which is now ANSI – American National Standards Institute), but they also propose and administer hundreds of other specifications for testing and standardization of other topics.
That said, photographers probably only know ISO as a camera setting and it’s unlikely they run across other ISO specifications, unless there some for photographic paper or related equipment issues (?). Outside of engineering circles, I don’t know of any.
A quick search of “Photography” on the ISO website shows 78 specifications! Seems they define everything from photographic paper to how to record sound!
nic »
Hi Sandro,
To change the subject if I may?
I am letting you know I am enjoying the content of your newsletters and as a relatively inexperienced photographer I find them pertinent and informative.
That’s great
thanks!
hello sandro, your blog is very helpful. thanks for this post, i’m looking forward for more tips that you will be sharing and can help new generation photopgraphers:)
Hello, I am also a rookie in photography, I used to just press the shutter button, that’s how good I was. But now, I am really learning a bunch of stuff which I intend to try in my next shots. I honestly don’t like reading but I couldn’t stop reading this one. Thanks.
hi, i think this site is amazing, it tells you what you need to know in seconds. how a the speed of the cameras shutter can change the blur of the photography, to make the one thing stand out, truly amazing.
hi, im rebecca ive been reading your latest updates and am intrested in how the shutter can change even the blur of the image. thanks
hi sir sandro!!! i really appreciate this article, especially i’m a newbie. simply informative.