Joel Leindecker Photography

Tutorials

Photography Basics: Shutter, Aperture, ISO

Posted by Joel on May 31, 2013 at 9:35 AM


Part 1: Understanding the camera

Digital SLR cameras are very technical systems, and if a person intends to use one to its full potential he/she must first understand how it works.  The first question to ask is what does SLR mean?  SLR stands for single lens reflex.  This means that there is a single lens inside the camera which reflects the actual view through a camera lens to the viewer’s eyepiece.  In simple terms, you see exactly what will be recorded in the image.  Below I have placed an image which shows the elements of the camera.

 (image from http://www.1derful.info/Words/Truth.htm)


As you can see from this illustration the blue mirror reflects the image through a penta-prism into the eyepiece.  This camera gives you a look at an image which a standard point and click camera cannot.  With a point and click camera you see a digital copy of the image which may not match the actual shot.

 
Another common question is how can you see exactly what is being recorded and still take a picture.  When looking through an SLR camera while taking a picture one will note two things:  the loud noise the camera makes, and the fact that the eyepiece goes black until the image is done being recorded.  These two parts work hand in hand; as the camera records the image the mirror lifts up, blocking the eyepiece, and exposing the sensor to the plane of view.  This is called the shutter release. The shutter lifts up allowing the sensor to record the image (this is also what creates the loud noise you hear).  This is the same for a digital camera and a film camera.  However, in new digital cameras there is no film strip; the sensor works as a digital film strip allowing for the picture to be viewed as soon as the memory card records it.


In the upcoming sessions I will detail the technical aspects of the camera, and how they can be manipulated to create intentional tricks and effects.  The elements which differentiate a photographer from a picture taker are distinct.  In this tutorial I intend to point out some methods which can be implemented in digital photography, to help you take more than just simple snap shots.  A picture taker will just point their camera at the subject and take a “snap shot” of the scene; a photographer will set up and capture a photograph of the same scene using distinct techniques.  This tutorial will enhance your skills and help you become a true photographer.


Part 2: Shutter Release

As I mentioned in the previous section, the shutter is the part of the camera which exposes the sensor to the scene you are trying to shoot.  If you were to think of human vision as a camera the shutter would be your eyelids.  When your eyes are open you are exposing the sensor (your brain) to the scene (the world around you).  However, our brain records images more like a video camera than a photographic camera.  Our mind is constantly processing what we see, and this creates the moving picture we see every time we open our eyes.  If you would like to simulate a photographic camera through vision try this:  close your eyes for a little while, and then open them for a fraction of a second before closing them again.  The scene which lingers in your mind is a still photographic picture.

Freezing Action
Why does this matter?  The answer lies in the effects generated through recording with a fixed sensor over time.  This effect is called a timed exposure.  The human mind records images at 60 frames per second, which means that with still images the human’s shutter triggers at 1/60 of a second.  When using a camera you can record “superhuman” results by using the shutter at a higher speed.  For example, if you look at a fan spinning it appears to be one solid ring, but you know that the ring you see is in fact separate blades.  They appear to be solid because of the speed at which you see them spinning.  By setting a camera’s shutter at 1/2000 of a second we can record motion which the human eye could never record.  Here is an example picture shoot at 1/500 of a second:


 
1/500 of a second is significantly faster than the human eye can record, but you can see that it still wasn’t fast enough to freeze the racket.  We see a blur where the racket and ball are, and this tells us that the racket was swung at a rate faster than 1/500 of a second.  If I were hoping to completely freeze the action I would have to retry the shot at a faster shutter speed.  Here is an example of action which has been completely frozen:


 
I was fortunate enough to have the opportunity to shoot a Michigan football game, and this image shows Fitzgerald Toussaint frozen in action as he breaks through the line against Minnesota.  This shot was taken with a shutter speed of 1/6400, which was fast enough to freeze the action.


Timed Exposure

We have discussed how to freeze fast action with a camera, and now we are going to look in the other direction.  The cool thing about having a fixed sensor is that it allows you to record a given scene over a longer timeframe than human eyes are able to see.  Have you ever taken a picture in low light just to find out that everything is blurry?  This blur isn’t because the shot was out of focus, it was because the shutter was triggering at a slower rate than you were able to hold your camera.  The subtle shaking of your hands altered the scene enough to make the shot blurry.   Fortunately, with the aid of a tripod and a shutter timer we are able to snap these slow shutters without moving the camera.  This can allow us to blur moving objects while keeping still objects in place.  


How can we use this in photography?  By showing motion in objects which appear to be still by the naked eye.  One common way this is used is by giving flowing water a silky look.  When we see water flow it looks choppy and rough.  As I mentioned before, our eyes see things at about 1/60 of a second.  At this speed we are able to see the little bubbles formed when water flows, and we are able to see the water droplets when they jump up from hitting objects.  More or less, this is what a waterfall looks like when we view it.  This shot was taken at 1/15 of a second, a little slower than human vision:


 
As you can see the water looks clumpy as it falls.  We can see bubbles along the bottom of the waterfall, and the water underneath looks rough.  Imagine if you were to view this waterfall over the length of a few seconds.  How would it change?  You would be able to see the flowing of the water, and the lines would be much smoother.  Let’s take a look at this same scene with a two second shutter:


 
In this shot the water has a nice silky look to it.  Also, because we were able to mount the camera on a tripod which remained still through the entire shot we were able to keep the background still by not moving the camera while the shot was being taken.


Part 3: Aperture
Now that we understand how a shutter works let’s look at the camera’s aperture.  An aperture is a part built into the lens of the camera which opens wide or small in order to allow either more or less light into the sensor of the camera.  If you were to think of the camera as a human eye the aperture would be the pupil.  If you are standing in a dark area your pupils get bigger to let more light in, and if you are looking at the sun your pupils will shrink to keep the access light out of your eyes.  Here is an example of what an aperture looks like:

This image shows how the aperture makes the normally large opening much smaller.  This particular aperture consists of five plastic pieces which create a pentagonal shape in the center.  When the image is actually taken the pentagram will appear to be a circle.  The tricky thing to remember about an aperture is that it also controls the focal plane for the shot.  What is the focal plane?  It is the area in the shot which is in focus.  The bigger the hole in the aperture the less you have in focus.  The smaller your aperture the more you have in focus.  Here are two shots which will help show what I mean.  Both shots focus on the crack in the center of the frame; the first shot uses a large aperture, and the second shot uses a small aperture.

Large Aperture:


 
Small Aperture:


 
You can see that the first image has significantly less area in focus than the second shot.  However, in order to compensate for less light getting in to the camera the shutter used on the second shot was open for far longer.  The first shot used a one second shutter, and the second shot used a 22 second shutter.


In an SLR camera the shutter is recorded in what is called an “F-stop.”  This refers to the ratio of focal length to the aperture diameter.  What does this mean?  It means that the further your subject is from the lens, the more you will see in focus.  The ratio between how much is in focus and the distance changed determines the number on the “F-stop.”  The easy way to think of this is the smaller your F-stop, the bigger your aperture hole.  The aperture range is dependent on the lens you have attached, but most lenses have apertures between f/2.8 and f/22.  You express the “F-stop” value by the letter “f” followed by a “/,” than you state the number of the aperture.

If I have a camera set to f/2.8 this is a large whole.  This will allow a lot of light in, which means I will be able to use a faster shutter speed.  Also, it will give me a shallow depth of field; this means I will have a small area in focus with a blurred background.

Photographers often use this with sports photography.  The goal there is to use the fastest shutter speed you can.  By using a large hole you allow a lot of light in, and this allows for faster shutter speeds.  Notice the photograph I have of the football game in the shutter speed section, the background is out of focus because I was shooting with a large aperture (f/4.5).


However, if I have a camera set to f/22 this is a tiny hole.  This means I will need to use a slow shutter speed to compensate for the lack of light; it will allow for a large area to be in focus though.  This is often used in landscape photography.  The goal with landscape photography is to have as much as possible in focus, and to get as clear of a picture as possible.  Most landscape photographers use tripods, and this allows them to open the shutter for as long as they need without worrying about the subject moving on them.  Notice the waterfall shot I have in the shutter speed section, the whole image is in focus because I used a small aperture (f/22).  This also helped prolong my shutter to allow for more water flow in the shot.

Part 4: ISO
Next I will talk about a tricky element of SLR photography called the ISO.  The ISO will determine how quickly your camera processes an image, and this will control how much light the camera absorbs in a given shot.  However, the quicker the camera processes the image the more noise (or digital pixilation) the camera allows in.  I look at this like reading a book.  You can skim through and just get the main ideas, or you can read through for content, and learn the subtleties in the writing.  The lower the number on your ISO the more details the camera processes, but this requires a slower shutter speed.  If you have the camera process the image fast you will get more noise, but you will be able to use a much faster shutter speed.  Most cameras have ISO ranges between 100-3200; if your ISO is set to 100 there will be little noise in the shot, but if your camera is set to ISO 3200 there will be far more noise.


If you are shooting in the daylight you will most likely be able to use a lower ISO.  Also, if you are shooting with a tripod you are able to use these lower ISOs.  Generally, landscape photographers use these lower ISO settings because clarity is their number one goal.  They use tripods, so it is not a problem to use slower shutter speeds.  Here is an example of a shot taken with a low ISO.  My camera offers ISO 50, and at this setting there is practically no noise whatsoever.  This shot was taken with a shutter speed of 1/125, an aperture setting of f/8, and an ISO setting of 50.


 
Some situations make you more limited on what shot settings you are able to use.  Often times if one is trying to photograph moving objects in low light settings they will need to increase the ISO to accommodate for the lighting.  If you do not have a tripod you will need to handhold the camera for the shot.  The slowest shutter speeds a person can hand hold are about 1/50th of a second, depending on the person.  If the lighting does not allow for speeds above 1/50th of a second you will need to increase the ISO until this speed can be reached.  


This is commonly needed when doing action photography.  If you need to freeze action the shutter speed needs to be quicker than the action you wish to freeze.  If you have the aperture as open as you can, the only way to adjust your shutter speed and still have the proper exposure is by adjusting the ISO.  Here is a shot I took with limited light.  This shot was taken in near pitch black, and it successfully froze the action of the bass player.  I used a shutter of 1/40th of a second, the aperture was set to f/3.5, and I adjusted the ISO up to 6400.  You will notice that there is far more noise than the previous image, but this is necessary if you wish to shoot in low light.


 

Part 5: Combining the Elements
Every shot is a unique photographic opportunity, and no two shots are the same.  By learning how to use the shutter, aperture, and ISO settings on an SLR camera one becomes able to capture any scene they encounter in a unique way.  As you approach a scene it is important to note which element is most important to you.  In this section I will pose three possible situations and explain how the three elements we have discussed can help capture the image desired.


Situation 1: Shutter Priority
Imagine you are visiting a nice picturesque park.  This park many wonderful hiking trails, and many people go there in the fall to view the leaves changing colors.  The scenic park also contains many beautiful waterfalls.  You decide to take some scenic pictures of waterfalls, and you grab your camera and tripod.  You reach a waterfall and you notice leaves circling in the water below.  It creates an opportunity for you to capture the motion of the water along with the waterfall.  If the shot were handheld you would freeze the water in the air and the leaves circling the water below would be frozen as well.  However, if you delay the shutter you will be able to catch the motion of the water.  By making the aperture as small as you can and dropping the ISO as low as possible you are able to extend the shutter longer.  With the camera and lens you are using you have the aperture set to f/22, and the ISO is set to 50.  This allows for a shutter speed of four seconds; enough time to show the motion of the water.  Here is the shot you create:


 
Situation 2: Aperture Priority
Imagine you are out for a hike with a nice telescopic lens on your camera.  You approach a clearing and hear a rustling off in the distance.  You look over and see a young buck deer standing off in the distance.  You bring the camera up as the deer approaches, and look through the viewfinder.  The deer is standing in a clearing with flowers and grass standing tall behind him.  You realize your camera is set to f/8, and with where the deer is standing this will make him blend with the background at that aperture.  With your current aperture setting your shutter is set at 1/15th of a second, which will not freeze the deer, and the ISO is set to 250.  You can either adjust the aperture or the ISO to get a better shot.  You decide to adjust the aperture to the lowest number you can.  With the lens attached you can drop the aperture to f/2.8.  This changes your shutter speed to 1/160th of a second.  This aperture and shutter speed combination will help freeze the deer's movements, and give you a nice blurred background.  You press the shutter release and snap the picture:


 
Situation 3: ISO Priority
It is night time, and you decide to take an image of the stars.  The stars are small and far away, and if you intend to correctly expose them you will need to use a high ISO.  You set the ISO nice and high to ISO 6400.  The stars are slowly moving through the sky, but if you want to capture as many as possible you need a fairly fast shutter speed.  However, it is still night, so you will need to set the shutter slower than you can hand hold.  You choose to set the shutter to six seconds, this is slow enough to allow light in, but fast enough to keep the stars from overlapping.  In order to get a correct exposure you set the aperture to f/3.5.  This is a large aperture, but the stars are so far away that you know the stars will be in focus.  Remember, the focal field grows the further away you get from the camera.  Here is the shot you take:


 


Part 6: Conclusion
Photography can be a fun hobby, and by understanding a few basic concepts one is able to fully explore the abilities of an SLR camera.  This tutorial has detailed the functions of a camera’s shutter release; teaching how to capture images which the human eye cannot view.  Also, this tutorial shows how to control the aperture; allowing a photographer to use depth of field to their advantage.  Finally, we have covered the basics behind a camera’s ISO settings.  We have learned how to control the ISO based off the available light in a given scene.


Now that you better understand how to use an SLR camera feel free to take this knowledge and create your own artistic images.  With these basic concepts one can create all sorts of artistic images.  Here are a few more shots I have taken, enjoy viewing them, and enjoy taking your own artistic images! 



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