CAMERA BASICS Stops of light A stop of light isn t a quantifiable measurement it s a relative measurement. A stop of light is defined as a doubling or halving of any quantity of light. The word stop is pervasive in photography. Mostly it is used in regards to setting exposures. Opening up a stop means you are letting more light in and closing down a stop this means you are letting less light in. Two ways we control this is 1) Shutter speeds and 2) Apertures - Most new cameras display either ½ stop or 1/3 stop increments. In some cameras you have the ability to set the camera to function in ½ or 1/3 increments. It is important to know the increment system that your camera is set to and to understand that only full stops half and double the light. The meter display in your camera is also divided into stops. Cameras vary in the way they display the metering information but in general, most display a range of plus two stops and minus two stops in half-stop or third-stop increments. Exposure In photography this word simply describes the overall amount of light that hits your sensor. There is no absolute correct exposure your camera s meter and histogram will help you find an exposure that gives you a good range of tones from light to dark but the only correct exposure is the one that you want as it will greatly effect the look of your image. 1
Variable shutter speeds what they are and why we have them The Shutter controls the amount of time that light hits your sensor. Shutter speeds describe that amount of time. We have variable shutter speeds to control the amount of light in each exposure (it does this in combination with Aperture). The shutter speed you choose also controls the depiction of motion in your images, faster shutter speeds freeze motion and slower shutter speeds create motion blur. Shutter speeds are actually fractions but some cameras do not have the 1/ represented. Full stop shutter speed increments are as follows: 30 15 8 4 2 1 2 4 8 15 30 60 125 250 500 1000 etc Full stop means that each number is half or double the amount of time (and therefore light) as the number next to it the means full seconds the rest are actually fractions as follows: 2 1 ½ ¼ 1/8 1/15 1/30 1/60 1/125 1/250 1/500 Unless you see after the number, the larger the number the faster the shutter speed or the shorter amount of time that the shutter is open - a 1/500 of a second is faster (a shorter time) than a 1/30 500 is faster than 30 Because most digital SLRs have either ½ or 1/3 stop increments your number sequence might look something like: 4 5 6 8 10 13 15 20 25 30 40 50 60 80 100 125 160 etc these are 1/3 stop increments with the full stops underlined 2
Variable apertures what they are and why we have them The aperture controls the amount of light that hits the film or sensor by essentially adjusting the size of the opening in the lens. So we have variable apertures (also called f-stops) to control the amount of light in each exposure (it does this in combination with shutter speed). By changing the aperture you make the opening bigger or smaller letting in more or less light. Changing the aperture also changes the way a photograph looks by changing the depth of field in an image. Depth of Field is a zone of apparent focus in a picture. It is apparent because a lens only focuses at one point and has a plane of focus parallel to the plane of the sensor (the back of your camera). Depth of Field means that it looks like there s more in focus than there really is. This area of focus extends in front and behind the true point of focus. Aperture or f-stop numbers are a little confusing. Technically they are ratios of the lens focal length to the size of the aperture opening. You don t need to know this to make good pictures and control your aperture though what you need to understand are the following two points: 1) As the f-stop number increases, light entering the camera decreases because the opening gets smaller. 2) As the f-stop number increases, depth of field increases. Here are typical full stop f-stop numbers (they vary from lens to lens in terms of the start number and end number): f/1.4 f/2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 f/22 f/32 3
Like shutter speeds, when using full stops, the amount of light is halved or doubled when moving from one f-stop setting to the one next to it. Remembering that the larger numbers give us a smaller opening, moving from f/11 to f/8 lets more light in (one stop more - the light is doubled you are opening up a stop). Conversely if you move from f/4 to f/8 you are closing down by two stops, decreasing the amount of light by half and then half again (f/4 to f/5.6, f/5.6 to f/8). big opening small opening f/1.4 f/2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 f/22 f/32 shallow depth of field long depth of field Just to confuse matters more, most of your cameras will have ½ or 1/3 stop aperture settings as well it is important to know that moving a ½ stop with the aperture does not double or half the light, only moving a full stop aperture setting will do that. Having ½ or 1/3 stop settings just gives you more incremental control over the light. The following are 1/3 stop increments (with the full stops underlined): f/4 f/4.5 f/5 f/5.6 f/6.3 f/7.1 f/8 f/9 f/10 f/11 4
Aperture/shutter speed relationship equivalent exposures To have full control over your exposure (how much light hits your sensor) and to have full control over how your photograph looks (depiction of motion and depth of field) you set the shutter speed and aperture (you must be in Manual shooting mode to do this). Here is where we see the idea of equivalents. In any given set of lighting circumstances you have many shutter speed and aperture choices that could work for example: If you receive a good exposure with: f/8 at 1/60 You could also use any of the following combinations, as they will all result in the same amount of light hitting your sensor: Big opening Shallow depth of field small opening long depth of field f/2 f/2.8 f/4 f/5.6 f/8 f/11 f/16 f/22 f/32 1000 500 250 125 60 30 15 8 4 fast shutter speed frozen motion slow shutter speed blurred motion In the above scenario, as you move from left to right with your f-stops, you are halving the amount of light with each change 5
and with your shutter speeds, as you move from left to right, you are doubling the amount of light with each change. So f/8 at 1/60 gives the sensor the same amount of light (exposure) as f/2.8 at 1/500 and the same as f/16 at 1/15 th. Of course this relationship changes with different lighting conditions. You can also see that you have more sets of usable shutter speed/aperture combinations (especially in low light situations or situations where you want a very long depth of field) if you use a tripod (due to the longer shutter speeds). So how do you choose which combination to use when? It depends on how you want to depict motion and what kind of depth of field you want in the photo. If you are shooting a landscape with nothing moving, your first consideration would usually be aperture to determine depth of field. An image with everything sharp and clear from front to back would require shooting in the f/22 f/32 range with an appropriate shutter speed. For a shallow depth of field you would be working more in the f/2 f/5.6 range. If you are working with a moving subject, then the shutter speed would usually be the first consideration. To depict the motion as frozen, you would be working in the 1/250 and faster range (depends on the speed of your subject). To create a blurred motion image you would be working more in the 1/30 and slower range (again depends on the speed of the subject). 6
ISO what it is and how to use it Films are rated by how sensitive to light they are - this is called ISO - and in digital photography the same idea applies (in fact when you increase the ISO on a digital camera you are actually boosting the signal amplification of the sensor). In both cases, the higher the ISO the more sensitive the film/sensor is to light. Typical ISO numbers are: 50 100 200 400 800 1600 3200 When using a higher ISO it means you need less light to make the same exposure than you would need at a lower ISO setting, for example: 200 ISO is more sensitive to light than 100 ISO, meaning at 200 ISO you need less light to make the same exposure that you would make at 100 ISO half as much light - or one stop less. ISO is subject to the doubling and halving described in photography as stops. So another example: When shooting at 100 ISO you need two more stops of light for any given exposure than you would need if you were shooting at 400 ISO (100 to 200, 200 to 400 = 2 stops) and three more than if you were shooting at 800 ISO (100 to 200, 200 to 400, 400 to 800 = 3 stops). What this means practically is that at higher ISO numbers you can use faster shutter speeds than at lower ISO numbers. In 7
low light situations this can mean the difference between being able to take the shot or not (or having everything look totally blurry because at the lower ISO, the shutter speed needs to be so slow). For example: @ 100 ISO and f/2, if you need a shutter speed of 1/30 then @ 200 ISO and f/2, you could use a shutter speed of 1/60 and @ 400 ISO and f/2, you could use a shutter speed of 1/125 The trade-off is that with film, using a higher ISO means that the grain of the film is larger and therefore can become visible. The visible grain is more pronounced as you enlarge the print. In digital the same thing happens but is referred to as noise. Noise appears as random colors and is best described as splotchyness and is particularly visible in darker areas and areas with less detail like a sky. Digital cameras are getting better at eliminating the noise at higher ISO. With digital you can change the ISO from one shot to another, which is a huge advantage over film. With film every roll was a specific ISO and had to be shot at that ISO (you could do something called pushing the film shooting it at a higher speed than the film was rated for but you still had to shoot the whole roll this way). 8
Most of your cameras will have an auto ISO setting but I suggest you set it manually for each situation. It is important to remember if you can not get your shutter speed fast enough for a shot, depending what ISO you are at, you may be able to work at a faster shutter speed by increasing your ISO. Four Main Shooting Modes: 1) Program identified with a P this is the shooting mode with the least control for the photographer when you push the shutter release button, the camera automatically meters the scene and chooses a shutter speed and aperture. So the camera is deciding how motion is depicted, what kind of depth of field the image will have and how light or dark the image will be (the exposure). 2) Manual identified with an M this is the shooting mode that gives the photographer the most control. The photographer meters the scene, chooses a shutter speed and an aperture before making the photo. The photographer determines the exposure 100 % - how dark or light the scene looks as well as depiction of motion and depth of field. 3) Shutter Priority identified with TV (stands for time value) or S this is one of two shooting modes that gives some control to the photographer and some to the camera. In shutter priority, the photographer sets the shutter speed and meters the scene, the camera then chooses and sets an aperture that will give a good exposure. So the photographer is determining the depiction of motion but not the overall lightness or darkness (the exposure). 9
4) Aperture Priority identified with AV or A - this is the second shooting mode that gives some control to the photographer and some to the camera. In aperture priority, the photographer sets the aperture and meters the scene, the camera then chooses and sets a shutter speed that will give a good exposure. So in this mode, the photographer is controlling the depth of field but not the overall lightness or darkness of the scene (the exposure). White Balance (WB) White balance is a camera setting that adjusts for lighting in order to make white objects appear white in photos. This is more difficult than it might seem due to the fact that light cast from different sources is different in color (technically called temperature). Light is rarely truly white in nature. The light from an incandescent or tungsten bulb, for example, is orange/red in color, while light from the sun is relatively blue. A proper white balance setting in a camera will prevent, for example, a white bed sheet in a photo from appearing orange in color when it is being illuminated by an incandescent bulb or slightly greenish from a fluorescent bulb. Most of your cameras will have an auto white balance setting, which will work fine in most situations. However most auto white balance settings have trouble with incandescent as it results in a very strong orange/red cast. When shooting in this kind of light you should manually change your white balance to match the light source. 10
Another time that auto WB has a hard time is when there are many light sources. You may want to try a shot and see how your camera handles the mixed light source situation first but if you are not happy with the result you can do a custom WB. This usually involves photographing a white piece of paper or object with the mixed light sources reflecting off of it. Different cameras have different ways of creating a custom WB so look this up in your manual. Essentially though, by photographing the white paper with the mixed light sources all falling on it, you are telling the camera how to make white look white under that particular light. Focal Length The focal length of a lens is the distance, in millimeters, from the optical centre of the lens to the focal plane (film or sensor) when the lens is focused at infinity. The focal length determines our field of view. Focal length choice affects the look of your image in a number of different ways: 1) Magnification of subject 2) Degree of horizon visible 3) Perspective shift (how the subject looks in relationship to the background) 4) Depth of field 11
First the basics: Focal length is divided into three categories, wide angle, normal and telephoto or long. For 35 mm film size (and the equivalent digital sensor size): Wide angle is 16 35 mm Normal is 50mm Telephoto or long is 85-200 mm Over 200 is very long or extreme telephoto 1) & 2) Magnification and Degree of horizon visible 50 mm sees 45 degrees of the horizon and magnifies X 1 100 mm sees 22 degrees of the horizon and magnifies X 2 200 mm sees 11 degrees of the horizon and magnifies X 3 24 mm sees 90 degrees of the horizon and magnifies X 1/2 15 mm sees 120 degrees of the horizon and magnifies X 1/3 3) Perspective shift This refers to the shift in the space of a photograph created by different focal length lenses. Wide angle creates a deep space and telephoto creates a shallower space. This can best be seen rather than described. In the following example the photographer changed the focal length and the camera/subject distance to keep the subject the same size in the image. Notice not only the shift in the degree of horizon visible but also the way the background appears in relationship to the subject. 12
28mm 50mm 100mm 200mm (images by Ross Cornish) 13
4) Effect on depth of field Wide angle lenses allow for a greater depth of field than telephoto. Telephoto is often used for portraiture so that the photographer can fill the frame without being right in the subject s face also the shallow depth of field brings the viewer s gaze right to the subject by blurring out the background. Wide angle is often used in landscape photography so that more of the scene can be captured and a long depth of field used for maximum clarity. Note: When you are working in full manual and metering each shot it is important to remember to meter after setting your focal length when shooting with a zoom lens (a lens that has more than one focal length, a lens that has only one focal length is called a prime lens). The reason for this is that with most zoom lenses (except very expensive ones) you lose aperture settings at the extreme ends of your focal length range. As you zoom long (also called zooming in higher focal length numbers) you lose your more open aperture settings (smaller numbers). As you zoom wide (also called zooming out smaller focal length numbers) you lose your more closed aperture settings (bigger numbers). For example with my zoom the range changes from: At 28mm focal length (wide end) f/3.5 f/22 At 105mm focal length (long end) f/4.5 f/29 14
Note: Digital magnification factor/crop factor its effect on understanding focal length This refers to the fact that most digital sensors are not as large as one frame of 35mm film. Because focal length has to do with area of coverage, (field of view), you have to use a mathematical equation to figure out your true focal length if you have a crop frame sensor in your camera. Your manual should refer to either a magnification factor, or lens conversion number or crop factor. If for example your lens conversion number is 1.6, you take the focal length of the lens and multiply by 1.6 to know the true focal length. This is not something that you always need to think about but it is good to know your true focal length so that you know what really is wide and really is long. For example, on my digital camera a zoom that states 28mm- 105mm is really (with a 1.6 lens conversion) a 45mm-168mm. It is also important to know this when you are buying a new lens so that you know what you are really buying. Metering To engage your meter, depress the shutter release button slightly. You must be pointing the camera at the subject during the metering to get a correct reading. It is best to read your meter through the viewfinder, not on the back of the camera, although it is typically displayed in both places. 15
Metering in full manual: The important thing to remember, when working in full manual, is that when you set one of your exposure controls, (aperture or shutter speed), you have to then engage the meter and then adjust your other control and zero out the meter. (This is the case most of the time, however, there are some times when you will want to over or under expose on purpose.) There will be times when you will not be able to get the settings that you want and may have to readjust the first control that you set. For instance if you set your shutter speed to 1/2000 to capture some motion and you have your camera wide open, say f/2.8 but there is not enough light you can increase your ISO to get a bit faster but if there is still not enough light you may have to decrease your shutter speed. So you need to have time to work in manual. Determine what is most important, depiction of motion or depth of field and set the corresponding control first, then meter and set the other. Mind over meter: As mentioned there are times when you will want to over or under expose on purpose. You can do this in the Manual shooting mode, or you can do this in Aperture Priority and Shutter Priority shooting modes using your Exposure Compensation Feature (when using this feature make sure to always turn it back to zero after taking the shot). You may want to do this simply to achieve the look that you want you may want a darker or lighter subject than what you meter tells you is correct. 16
But there are also two specific times when you have to practice mind over meter if you want your image to look like it does to your eye. These two times are when you have an overly bright scene or an overly dark scene and has to do with the way that your meter functions. In brief, everything in the world reflects light to different degrees light things reflect more light and dark things reflect less light (as they absorb more of the light that falls on them). In most scenes all the objects reflecting light when averaged out reflect 18% of the light this is referred to as 18% grey (or middle grey). Your camera meter works from the assumption that you are photographing an average scene and therefore functions by reading the light in a scene and giving you a reading that will result in a correct exposure at 18% reflectance. This means that if you have an overly light scene, for example a white cat in the snow, it will look grey and if you have an overly dark scene, for example a black cat on a black couch it will look grey. This is more apparent with overly light scenes. To correct this in full manual you specifically overexpose by a stop or two for an overly bright scene and underexpose by a stop or two for an overly dark scene by changing either your shutter speed or your aperture setting. With the overly light scene, when you over expose you are letting more light hit the sensor and so instead of the snow looking grey it will look white. With the overly dark scene, when you under expose you are letting less light hit the sensor, so the scene will look black instead of grey. When using the Exposure Compensation feature to do this, if you are in Aperture Priority, the camera changes the shutter speed by as many stops as you choose 17
and when you are in Shutter Priority the camera changes the aperture setting by as many stops as you choose. Histogram: The histogram is a handy tool to help you understand this and check your exposure. A histogram is basically a graphical representation of the amount of pixels by tone. In your display mode you can choose to see the histogram for each image that you take. There is no correct way that a histogram should look each image s histogram will look different. The left side is the darkest tones, and the right side is the lightest tones. If the graph goes off the scale at the right side you are missing highlight detail and if the graph goes off the scale at the left side you are missing shadow detail. In digital it is harder to deal with missing highlights as there is simply no information there. Missing detail in shadows can sometimes be fixed in post-production but missing highlights are very hard to recreate. If you are shooting in a tricky lighting situation, with overly bright or dark objects, you may want to take a few test shots and then check the histograms to make sure you are not missing tones (especially with overly light). 18
Metering modes: Another time that your camera meter has trouble is with backlit subjects there are two ways to achieve detail in a subject when it is back-lit. 1) Working in Manual shooting mode, you can move up, fill the frame with the subject (ei a person s face), meter, set your shutter speed and aperture and then move back and shoot the scene, leaving the settings where they are. 2) The second way is built into your camera and requires you to change your Metering Mode most cameras now have different ways to meter a scene the factory setting is usually called matrix or evaluative and measures the whole scene and averages it. There are usually two others, centreweighted and spot. They are just as they sound centreweighted gives more weight to the centre of the scene and spot metering will specifically measure one area (most cameras allow you to choose where the spot is). You usually see less of a difference with centre-weighted than with spot. Experiment with your camera s different metering modes but remember to change back to Matrix or evaluative for most situations. Other Film/sensor limits: It is important to know that film and digital sensors have limits in terms of how they deal with extreme ranges in light. In 19
terms of stops, we can see details in a much broader range of light than film and sensors. This is why, in extreme lighting situations, such as a sunset or sunrise, an image will not show as much detail in the highlights and shadows as what you see with your eyes. Our eyes typically see a range of light from dark shadows to bright highlights of about 12-14 stops. Slide film can only see a range of about 4 5 stops of light. Digital and negative film see about 6 7 stops of light (although digital is getting better all the time). This range of light is called latitude. The important thing is to understand that when photographing in situations when the light range is extreme, you have to choose where you want to see detail in the image. When photographing a sunset, if you want to see the colour in the sky then meter the sky. If you want to see the detail in the ground, then meter the ground. Experiment with the next extreme range of light situation that you come across by taking multiple shots metering different areas of the scene. Fill Flash One way that you can reduce the difference in the range from highlights to shadows is to use your flash as a fill light. When you are working on a bright sunny day, the highlights and shadow details are so far apart that you tend to lose details. If you move into the shadows, the image can look dull. One way to compensate for this is to shoot with your flash on so that it functions like a fill flash. To do this shoot in A/P with the flash turned on. This will fill in the shadows. Just be careful that your shutter speeds don t get too fast as most cameras have a 20
maximum shutter speed at which they can balance flash (usually around 1/125 or 1/250). Your camera will probably indicate this somehow. My shutter speed number indicator flashes if it gets too high with the flash engaged. Some cameras can adjust the brightness of the flash or have different settings for their flash. Experiment with these to see which work well as a fill flash. Focus It is important to know how to focus your camera in manual focus mode as in low light situations your auto focus might not work. Some cameras will not allow a shot to be taken if the camera cannot auto focus. Look in your manual at the focusing section and practice manual focusing. Also most cameras allow different ways of focusing and allow you to shift the point of focus to different areas of the image. 21