iStockphoto Photography Standards: Lighting
Lighting is probably the single most important aspect of photography, and is a huge topic. Every picture you take depends on good light. Mastering the basics of photographing a well-lit subject will help make your images useful for designers in everyday applications. When you know the basics, you can begin to explore the more dramatic possibilities of light: how the angle, power, and warmth of light effects your subject, stimulates emotions, and expresses your creativity.
Understanding light is a lifelong project. For beginning photographers, the key subjects are:
- Proper exposure
- Using and adapting to different light sources (natural and artificial)
- White balance
- Unexpected problems: Lens flares, reflections, and chromatic abberation
Let's explore these topics by looking at a few examples that aren't acceptable for our standards: shots that cannot find their warm home at iStock and need more technical improvement before being accepted into collection.
Exposure is the amount of light that you allow into your camera when you take a picture. Too much light makes a photograph overexposed. Too little makes it underexposed. These are among the most lighting issues people face.
In an overexposed photo way too much light comes through the aperture, completely blowing out the highlights, washing out the colors, and flattening the surfaces. What few shadows are left are harsh. You've essentially burned the image away, leaving only a few light and color values behind.
In an underexposed image like this one, not enough light has made it through the lens, which means that there just isn't enough information coming into the camera. Everything is flat and dull, and only the strongest colors are able to make any sort of impression. Shadowed areas become completely lost.
A properly exposed image has the right mix of shadows, highlights, and middle ranges. It is sharp and in-focus up close, the colors are rich and accurate, and we haven't lost detail in the shadows or highlights.
Exposure is controlled by 3 variables:
- Aperture: The aperture is the opening that lets light pass through from the lens to your sensor or film. The wider your aperture, the more light will be allowed in to strike the film or digital sensor. Light is measured in 'F-Stops', where the lower the F number, the more light is coming through your aperture.
- ISO: This is the measure of light-sensitivity of your camera medium. The term comes from film, where different 'speeds' of film were more or less sensitive to light, with low ISO numbers (100-200) being less sensitive, and suitable for well-lit situations, and higher ISOs (400 and up) being more sensitive and intended for low-light or fast movement. With your digital camera, you can change the ISO depending on the circumstances without running down the street to buy a whole new role of film. Generally speaking, in the controlled environments of stock-shooting, we are almost always using ISO 100, to get the best possible quality. Use higher values in dark rooms, night-time environments, or to catch quick action.
- Shutter speed The longer your shutter stays open, the longer your sensor is exposed to the light, and the more accurately it will reproduce — if everything in the frame stays still. Long exposures allow for better reproductions in low-lighting situations, with little possibility of the subject moving around. Fast exposures are necessary to capture objects in motion.
There are three ways to manage these variables and expose your picture. You can set your camera to an Automatic mode and let it take care of everything. Basically, the camera's brain will meter the available light, and then set its own exposure accordingly. This will let you shoot a lot, quickly. However, your camera is prone to making mistakes. Automatic modes include the fully auto mode (e.g. the green box on Canon) as well as ‘scene types’ (e.g. portrait, sports, landscape) and P mode.
A better option is to choose either manual or a semi-manual mode, meter the light yourself, and set your own exposure.
Aperture Priority (AV or A mode on camera)
Aperture priority is a great semi-manual mode to start with when moving away from automatic modes. It allows you to select the aperture you want, giving control over the depth of field*
of the image, while the camera looks after the required shutter speed. You still have some manual adjustment of the shutter speed by using exposure compensation.
A small F number will give a shallower DOF, faster shutter speeds and mean focus is more critical. A larger F number will give a larger DOF, slower shutter speeds and more latitude for small focus errors.
- Set your ISO. Is there a strong light source, like a flash, strobe light, or sunshine? You can probably use ISO 100. If you're in a darker setting, or plan to photograph something in motion, try a higher ISO.
- Select the aperture number you wish to shoot at depending on if you want a shallow or wider DOF. (Check the shutter speed the camera is going to use through the viewfinder. Is it too slow to handhold? If so you might need to bump your ISO speed up.)
- Focus the camera and take the shot.
- Review the image on the LCD and check the historgram.
- If the image is under or overexposed dial in exposure compensation and reshoot.
- With experience, you'll learn when you need to add compensation before the shot.
Shutter Priority (Tv or S mode on camera)
Similar to aperture priority mode, in shutter priority mode you select the shutter speed that is important to you and allow the camera to choose the aperture. The aperture can still be overridden by means of exposure compensation.
This mode is useful when you want to freeze action or produce motion blur, with DOF being less important.
- Set your ISO.
- Select the shutter speed you wish to shoot at depending on if you want to freeze or blur the motion. (check the aperture the camera has selected)
- Focus and take the shot.
- Review the image and check the histogram.
- Dial in exposure compensation and reshoot if needed.
- Learn when you need to add compensation before you shoot.
Full manual (M mode on camera)
Full manual mode gives you ultimate control over your capture. The exact order you set the ISO, shutter speed and aperture will depend largely on the shot you are trying to capture. Where depth of field (DOF) is critical you should set the aperture first, if shutter speed is more important set this first. Of course most of the time aperture and shutter speed are both important. Set them both and then vary your ISO to suit the exposure. Like everything in photography, practise and experimenting is the best way to learn to take full advantage of the power manual mode offers.
- Set your ISO.
- Set the aperture you wish to use depending on the DOF you want to achieve. A small F number will give a shallow DOF and larger F numbers give a larger DOF.
- Press the shutter button half way down and the camera will show you if the shutter speed needs to be faster or slower on its exposure level indicator. This indicator’s location depends on the camera. Normally it’s visible along the bottom or side of the viewfinder as a marker on a + or – scale.
- Adjust the shutter speed until the exposure level indicator is zeroed. You’ll often want this above or below zero depending on scene you are shooting e.g. in snow the cameras meter will be fooled and try to make the snow grey, set your exposure 1 stop higher than the meter says.
- If you can’t get exposure level indicator zeroed for your desired aperture/shutter speed combination you may need to adjust your ISO up or down to compensate.
- Focus. Shoot. Check Histograms.* Adjust. Reshoot. Repeat.
A note on metering modes
Using the correct metering mode is critical to getting an accurate exposure from your camera. For most shots Evaluative or Matrix metering is probably a good starting point. But there are times when Partial or Spot will give much more accurate results. For example, imagine a person standing in front of a bright light or window. With Evaluative/Matrix metering the bright light will be taken into account causing the subject to be underexposed. With Partial or Spot metering however, only the focus point will be taken into account, giving the correct exposure on the subject. (Note on some cameras spot metering only works on the centre focus point, meaning you must meter there then recompose with the metering ‘locked’).