Week 5: Exposure continued – the zone system

What is the zone system?

The zone system was originally created by Ansel Adams and Fred Archer, for black and white film and paper photography, as a way to guide exposure for there aesthetic results.  The scene was divided into various photographic elements which were separated out by their relative brightness.  As we discussed last week, there is only a certain range of brightness that our camera’s can see.  This brightness range is what the zone system is designed to help us recognize.  The zone system helps us to recognize the limits in the capabilities of our camera’s and as a result helps us to find ways to overcome these limitations.

Enough of why, let’s get to what the zones are.

In the days of black and white film there were actually 11 zones defined, but current digital technology does not really allow us to use nearly this much tonal range.  In current digital camera’s we can use about 5 of these zones effectively.  Each zone represents one full stop of exposure.  Actually, last week with our assignment with the wall photographs we were effectively looking at the range of these zones.  We were also looking at how to use them, when we talked about our exposure compensation.

Lets take this basic look a little further, and actually define these zones in our images.  In this discussion keep in mind that this is a tool to help us understand our photographs, not a photographic result. When you expose for colors and tones you want them to appear the way they were when we saw them so to make this easier we define them.

Since we are only looking at 5 zones lets start with the lowest at zone 3, this is our black wall.  It’s not really black is it? It is black with detail.  That detail is what we want in our photographs (usually), because we want our photographs to give the impression of blackness, when we see “blackness” with our eyes there is detail there.  In our photographs we usually want to show some detail in the dark area’s.

The next step up is zone 4.  Here we are looking at our dark tones and colours, like navy blue’s, and deep forest greens, chocolate browns.  These colours are rich and deep, and if we photograph them it is important that they show as these colours

Zone 5 is our mid tones, these are the average colours, sky blue, bright red, lawn green — this is our middle grey that we have already discussed.  These are the colours that our camera’s are designed to give us right away without adjustment.

Zone 6 represents our bright colours.  Zone 6 is for pastels, like bright yellow, baby blue, pink,

Zone 7 is our whites.  Whites with detail, like the blacks, the detail is important.  With our eyes, when we look at something bright and white like snow we see more than just a blank whiteness we see the detail and texture of the snow, and in our photographs we usually try to show this as well.

Knowing the zones is great, but . . . ?

How do you use them?  Lets go back a little to using our meter.  The zones, are represented by stops of exposure. Zone 3 are objects that should be 2 stops underexposed, Zone 4 should be one stop underexposed, zone 5 should be exposed exactly right at zero, zone 6 should be overexposed by one stop, and zone 7 should be overexposed by two stops.  Now you are just checking colours (or tones of brightness of those colours) and adjusting your exposure accordingly.  Move your camera around your scene and check the exposure levels in it,  start with something in the mid-tones — set your exposure for that and lock it in (either using manual exposure, or with your exposure lock), now point your camera at the white area’s, are they no more than two full stops over exposed? If so, great, if not then you know that in your final image you will not have much detail in your white area’s.  Now check the blacks are they no more than two stops under exposed? If they are more you will not have detail in your blacks.

If you want detail in your blacks then you may have to bring your exposure up a little bit, if you want detail in your whites, you may have to lower your exposure down a little.  It all comes down to what the subject of your image is and what you want your photograph to show your viewers.  Maybe the detail in the black does not matter, maybe the detail in the whites does not matter, maybe they both matter.  What the zone system does is help you understand the choice you are making.  The zone system helps to show you what will and will not be exposed properly in your images, and when you may need to change the framing of your composition to make your image work.

Don’t forget, this shows you the limits of your camera with the light the way it is, but it does not show you the limits of what you can photograph, you may just have to get more creative.  Can you add some light to your dark area’s to decrease your contrast?  Can you use a fill flash, or a reflector/ Can you take away some light from your bright area’s? Can you use a diffuser to tone down the light, or close a curtain? Do you need both the bright sky, and the dark cave to show the scene? Can you come back at a different time of day? Can you take a HDR composite image?

For now lets focus on the different zones, and let’s think about keeping our image tones in the range that our camera can see, from two stops under exposed, to two stops over exposed, we will look at different problems and solutions later.  If you do not fully understand yet ask some questions, tomorrow we will start with the assignment.

For some more information on the zone system try the wikipedia article: http://en.wikipedia.org/wiki/Zone_system

Happy shooting

Jason

Week3: Shutter speed assignment

So I hope that I didn’t totally overload you with yesterdays post.  It was a little long — so if I lost you, I apologize.  There is a lot of information there, so while you are completing this assignment don’t be afraid to refer back to that post.  Hopefully, you will find this assignment interesting.

If you have a dog this will be really easy.  Otherwise, go to your local dog park.  What we are looking for is something to photograph that, well, runs, and quickly.  If you don’t have a dog or a dog park you can even do this on the side of the highway taking pictures of the cars driving by, but I find dogs are much more fun.

Set your camera to shutter priority mode.  Start with a fairly slow shutter speed 1/15th of a second.  Now if you can get into a position, where the dogs will be running past you.  Follow along with your subject with one of your focus points on the dogs shoulder,  as the dog runs by pan along with it.  Photograph, as fast as you can, keeping pace with the dogs speed.  Do this for several sets of photos.  Then move up to progressively faster shutter speeds, doubling the shutter speed each time you change until you’re down to your largest f-stop.  You can also increase your ISO, so that you can get progressively faster shutter speeds.  If you have any questions — just let me know.

Simple.

Week 3: Experimenting with Shutter Speed

Shutter Speed – Framing the 4th dimension

When we look at the world around us, it is in constant motion.  Things happen not  in 3 but in 4 dimensions.  To take a good photograph of our subject we must choose  both where and when to frame our subject.  A photograph frames a subject in both time and space.  When we frame our photographs, we are taking our subject from the real world and separating it from its environment.  Composition, is how we choose to arrange the elements of our photographs.  We are choosing not just what to photograph, but when to photograph it.  This goes back to an earlier discussion on “the golden hour” in a previous post about lighting.  We are also changing how long we photograph our subject for.  This is our shutter speed.

Shutter Speed – the duration of our exposure

From the standpoint of the exposure triangle, shutter speed is purely a matter of how long we allow light to enter our camera, and subsequently how bright we choose to make our exposure.  But changing our shutter speed changes much more about how we compose our images than how dim or bright they are.  Changes in shutter speed can have a dramatic impact on how we perceive an image.  Because we are taking our subject out of context in time, we have to choose how we want to convey the dimension of time in our photographs, similar to how we would portray depth and perspective of the third dimension on a two dimensional print.  We can’t actually show motion (unless we are using the movie function on our new camera), so we must convey the feeling of motion (or stillness) within the frame of our photograph.

OKAY in plain English — Shutter speed goals

1. Freeze camera motion.  You know the photographs where you just can’t figure out why things are just a little bit out of focus.  You know that you took the time to focus your camera correctly but everything is a little bit fuzzy (or a lot fuzzy).  If you are hand-holding your camera, there is a certain amount of camera motion that you impart on the image.  You breathe, and you have a heart beat, and you sway in the breeze, and your hand shakes because you are excited or nervous.  If you have to hand-hold your camera, for whatever reason there is a general rule of thumb — your shutter speed should be at least equal to the focal length of the lens you are using (don’t forget the focal length multiplier effect of many digital cameras).  If you are using a 50mm lens on a 1.6x camera body – the actual focal length is closer to 85mm so your minimum shutter speed for handholding should be 1/85th of a second.

2. Freeze subject or background motion.  Sometimes you don’t want to convey motion in your subject.  Most portraits for example we want a nice clear precise representation of our subject.  You will want to use a faster shutter speed to freeze the motion of our subject. This will really depend on how fast your subject is moving, a race car for example will need a much higher shutter speed than say someone walking. Start with 1/200th of a second and go faster if necessary.  Check out the following Flickr group for some idea’s: Stopping Time

3. Motion blur.  At other times, we want to portray that our subject is in motion.  Take a race car again as an example — if you take a photograph with a fast enough shutter speed, it will not look like the car is moving at all, but is this what you want to convey in your image?  If it is, it might be a whole lot easier to take a photo of the car while it is sitting still.  Choose a slightly lower shutter speed and you may get only some parts blurred in the motion — the spinning wheels maybe, or go slower and move the camera with the image, and with some practice you may get the background completely blurred and the car mostly in focus.  This will give the impression of motion.  Start with a slower than usual shutter speed and experiment. Take a look at the flickr group for some inspiration: Deliberate Motion Blur

As with our discussion of aperture  there are many different factors to consider.  Like the rest of photography the shutter speed you decide to use has to be balanced with other factors in your image such as your ISO and your overall exposure but you are in control of framing your subject in time — so think about what you want to convey.

For some inspiration follow the links above to the flickr groups.  Tomorrow we will start with an assignment to practice with the effects of shutter speed in our photographs.

Aperture – the trade off

I understand how difficult it is working with only one piece of the exposure triangle.  We are trying to control only one aspect at a time for the exposure of your images.  But the goal of these exercises is to understand how each piece of the exposure puzzle fits together.  Unfortunately you must be prepared (as my wife so frustratedly declared), that as you choose one aperture it necessarily forces you to choose (or the camera to choose) a corresponding ISO and/or a corresponding shutter-speed.  Always remember, that your choice of aperture is always a trade-off.

Using a small aperture, with your extended depth of field, what portion of the depth of field is increased?  Where is your depth of field added to, the foreground or the background?  It really depends on where, in your photograph, you are focusing in the first place.  It also depends on the focal length of the lens you are using.  I could go over so many different formulas to discuss depth of field and where and how.  For now just concentrate on changing the depth of field and using the depth of field preview button to check.  Concentrate on your composition, not the mechanics of the camera.

A few more things about depth of field

How is it going with the depth of field assignment?  Working here in Smithers I have been reminded about a few things with depth of field.  When you look through your camera you can’t tell what the actual depth of field is going to turn out like in your final image. While you compose your image, the camera holds the aperture on your lens open as wide as it can until you take the picture, then as you press the shutter release button it closes the aperture down to the setting you want, opens the shutter and takes your exposure.  Instead of just guessing at what your final depth of field will be, there is a way, on most digital SLR’s to check, the depth of field preview button.  You will likely have to look in your manual for this, but on Canon models the button is on the camera on the lower side near the base of the lens barrel, on the left hand side (when you are taking a picture).

The button near the lens base on the right hand side of the picture is the Depth of field preview button, check your camera manual to find yours

Using this button is simple.  Set your aperture, compose your picture, press the button and look through the viewfinder.  Keep in mind, that, if you are using a small aperture your screen may get very dark.  Remember, this is what closing down your aperture actually does — it lets less light onto your image.  But if you look very closely you can see what in your image will actually be in focus in your final picture.

Week 2: Assignment — aperture

So,  hopefully you didn’t have any difficulties with my directions (it seems my wife felt my wording was somewhat comical).  Here are the results of our test shots we were using a Canon Xsi with a 17-85mm lense set at  a focal length of 56mm.  So what are the differences between the images?

f32 and 8 seconds

f11 and 1.0 Second

F5.6 and 1/4 Second

We were focused on the salt shaker in the middle of the objects.  With the lower ambient light levels we had to use a tripod to get steady shots.  There are two main things that happened with the images.  At the very small aperture (f32 you can clearly see both the foreground and back-ground images are in focus (as well as the background plug-in, and the fridge and well, just about everything).  As you move to larger and larger apertures, less and less of these things are in focus, at f5.6 there is much less in focus.  Look at how less distracting the background in the f5.6 image.  An f4 or larger also has much less in focus.  If your image needs the information in the background use the small aperture.  If not, use the large aperture.

What else changes between the images?  In fact, it is not actually evident in these images but if you look at the exposure information the image, the difference is there.  The shutter speed.  Changing your aperture will always make a corresponding and opposite change in shutter speed.  Always keep in mind that the two are related.

Now to move on a little further we are finally moving on to this weeks actual assignment.  Use your aperture.  Take your camera out to an area where you usually like to take photos.  A park or a section of the city — anywhere that you find interesting subjects to photograph.  But go over several days and photograph the first day with a large f-stop (remember small aperture).  You may need to increase your ISO speed or more effectively use a tri-pod in order to deal with the slower shutter speed.  Shoot so that what you have in the photograph is supposed to be in your picture.  A large f-stop will require you to really concentrate on your foreground and background.

The following day work exclusively in a small f-stop (a large aperture).  Use this f-stop to help isolate your subject in your images.  When you change your f-stop you change how you photograph.  Learn, what the different f-stops do in your photographs and pay attention to the differences.  Soon you will be using this incredibly powerful tool to help improve your photographic compositions.

 

Good luck and happy shooting.

Week 2: Aperture — mini-assignment

Okay, so we’ve talked about the basic components of exposure now lets start to look at each in detail.  This week we are going to look at the effects of aperture.  So lets start with a small exercise.  Start by putting your camera into aperture priority mode (on a Canon this is the Av, setting on the dial).  Now, take three objects, about the size of a salt shaker — in fact salt shakers would be perfect. Now place them in a line near one end of a table, one closer to the camera, one about a foot further away, and another a foot further away again.  Now, with your camera set to it’s largest aperture (smallest f-stop number) take a photograph of the three shakers (make sure you can see all three).  Now set the camera to an f-stop somewhere in the middle take another.  Now the smallest possible aperture (largest f-stop number).  Now check the photographs, how are they different?

Week 2 – Introduction: Understanding exposure

It’s time to pick up our camera’s and start taking some pictures.  I will start with a discussion of the three basic components of exposure.  Exposure is the art of making sure the image we make in our photograph is the correct brightness to actually represent what we are photographing.  In fact we are able to make our photograph both brighter or darker than the actual image, and usually some parts of our image show up as brighter and others as darker.  This is an unfortunate characteristic of the sensors we use to take photographs.  For now, however, lets just take a look at the basic building blocks of our exposures: aperture (or f-stop), shutter speed, the ISO setting, and most importantly the amount of light available.  Though you can change all four of these factors, we will assume for the time being that we are working with natural light (not flash or strobes — we will get to these later), so we will focus on the first three, aperture, shutter speed and ISO.  This weeks assignment will actually focus on aperture but we will need to talk about all three so we have a basic picture of how they fit together.

The adjustment of these three factors adjusts the brightness of our image.  For a given amount of light in our environment there are combination’s of these factors that will work to make the exposure you want, and combinations that will not.  Given that you want a certain artistic outcome in your final image, if you choose any two of these, there will not be a choice in the third.  In fact, there are limits on all of them that may make the combination you want to use impossible.  You always have to balance these things together.  They each affect the amount brightness in your image in a different way. As well, each of them also have different secondary effects on our images.

1. Aperture or F-stop. The aperature is literally a tiny opening somewhere deep in your lenses that allows a certain amount of light to pass.  We can make this hole larger, or smaller in order to allow more or less light in for a given amount of time (shutter speed).  This hole is measured in a unit called the f-stop.  The larger the F-stop number the smaller the hole and the less light it will let in.  So an f-stop of 32 is actually smaller than an f-stop of 8.  The largest f-stop a lens has is often referred to as the speed of the lens.  A lens with a smaller f-stop number, a larger opening, is referred to as a faster lens — because it will allow us to use a faster shutter speed in a given lighting condition.  Aside from the amount of light that a given f-stop will allow onto our pictures, the aperture also affects the depth of field of our image.  Depth of field is how far into the foreground and background our photograph is in focus measured from the subject that is actually focused on. A smaller aperture will allow less light to expose our photograph but it will make more of our foreground and background in focus around our subject.  This may or may not be what we want.  If our background is distracting it may be better to use a larger aperture (smaller f-stop) to make sure it is not in focus.

2. Shutter speed.  This is how long we actually expose our image sensor to the light produced by the scene.  The basics are actually quite intuitive.  If you leave your shutter speed open longer more light will come in and your exposure will be brighter.  Keep in mind however, that if your subject moves during the exposure time it will cause the image to blur.  More importantly, if we move while the shutter is open our whole picture will blur.  A faster shutter speed will minimize this affect.  In general we want to use a shutter speed that is at least as fast as the focal length of our lens is long (don’t forget the crop factor of your camera).  So if your lens is a 200mm lens and you are using it on a 1.6x crop factor camera the actual focal length you have is 200*1.6=320mm so your slowest shutter speed you should try and handhold that lens at is 1/300th of a second.  If you want to use a slower shutter speed you will need to use a tri-pod or some sort of image stabilization system (available on lots of newer lenses)

3. ISO speed.  On a digital camera the ISO speed is how much amplification the camera applies to the exposure in the camera.  On a film camera it is how sensitive your film is to light.  A higher ISO setting is one in which your sensor or your film will make a properly exposed image for a lower amount of total light (ie shorter shutter speed, or larger f-stop, or smaller aperature).  Unfortunately, in both film and digital there is a negative impact to a higher ISO setting.  They are kind of the same thing (not really but similar).  A higher ISO film is grainier,  the “dots” that make up the image are larger, so there is lower resolution.  A higher ISO setting on a digital camera is “noisier”  there will be more individual pixels in the image which are over exposed or exposed in a weird color, in effect, there will be light colored specs in the darker portions of your image and your resolution is not as good.

So — how do the three of these things work together?  Lets simplify things a little.  You will usually want to use the lowest ISO setting you can which will allow you to set the other two where you would like.  When you are starting out, set your ISO as low as possible and check your exposure for the other two settings.  Can you get a fast enough shutter speed so that your image is sharp? Can you use the f-stop that puts everything you want in focus?  If not then you may have to increase your ISO — otherwise leave it where it is.  As for shutter speed and f-stop if one goes up the other will have to go down to maintain the same amount of exposure (brightness) in your picture.

Before we go any further you will want to ensure that you know how to adjust each of these settings on your camera. Grab your manual and look up a few things. What dials change f-stop, shutter speed, and ISO speed?  Do these dials change if you are in a different picture taking mode with your camera?  Tomorrow we will start our assignment by looking more precisely at the effect of aperture on our images — so make sure you understand how to put your camera in either aperture priority mode or manual mode, and how to read your in camera light meter to properly adjust for a correct exposure with different apertures (i.e. choose the correct corresponding shutter speed)

Until tomorrow — happy shooting