When To Change White Balance
First things first: white balance has nothing to do with caucasians on stilts. No, white balance affects how your camera's sensor captures color.
Here's a (potentially) surprising fact: all light is NOT the same color.
The reason that this might be surprising is because our eyes automatically adjust to different lighting conditions so that we are able to see "natural" colors all of the time. Without a camera in your hand, morning light looks an awful lot like mid-day light.
But the color of light changes throughout the day, and it especially changes when you're taking photos in shade, overcast conditions, or under artificial lights.
The Color of Light
In the early morning hours, natural light is cooler and objects photographed with your digital SLR will take on a faint blue hue. Right around mid-day, the light takes on a neutral tone, but as the day wanes toward dusk, light becomes warm and you'll notice more orange and red in your photographs.
If you're ambitious enough, you can do the following exercise: pick a day when you don't have anything planned.
Get up in the morning before the sun comes up, set up your camera and tripod and take a photo of some outdoor subject (any subject you like really). Here's the hard part: take another photo of the exact same subject from the exact same position every two hours for the rest of the day.
What this sequence will show you is that the color of light changes as the day goes along and these color shifts can have an impact on your photos.
White Balance to the Rescue
The white balance setting on your digital SLR is meant to counteract these color shifts. When the white balance is set to AUTO mode, the camera is trying to determine the lighting conditions and then set the white balance so that the colors in your photo don't appear to have any tint.
An extreme example of this is when you take photos lit by tungsten light (regular old run-of-the-mill lightbulbs) or by fluorescent light.
Tungsten light adds a strong orange cast to colors, while fluorescent light makes everything look a sickly green. If you were taking portrait photos with these types of light, your subject's skin tone would not look natural at all.
When To Change White Balance
While many digital SLRs are quite good at guessing the lighting conditions, sometimes it's a better idea to take matters into your own hands. This is why white balance can be changed manually.
For example, shade tends to make colors look soft and muted. But if you're taking photos in shade and set your white balance to "shade" then suddenly those colors will look rich and saturated. When taking photos under tungsten light, set the white balance to "tungsten" to make sure that all colors look normal.
I've already touched on some of them, but here's a list of the most common digital SLR white balance settings: AUTO, natural (daylight), shade, overcast, tungsten, fluorescent and flash.
Many cameras also have a "custom" white balance setting, but this is only necessary if you want to be 100% sure that the light striking your subject is not affecting the colors in any way (in other words, it's used more by professionals than the everyday photographer).
ISO
What is ISO?
| ISO Sensitivity | Auto; ISO 100, 200, 400, 800 equivalent |
ISO sensitivity expresses the speed of photographic negative materials (formerly expressed as ASA).
Since digital cameras do not use film but use image sensors instead, the ISO equivalent is usually given.
What ISO denotes is how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations.
And, where you would have needed to physically change to a different roll of film if you wanted a different ISO speed, digital technology allows you to simply dial one in. In this way, you can record images taken at different ISO speeds on the same memory card.
ISO Speed & Exposure
ISO speed affects the shutter speed / aperture combinations you can use to obtain correct exposure.
Suppose your digital camera's light meter warns you there is not enough light to correctly expose a scene. You could use the on-board flash, but let's suppose again it's not allowed (like in a concert or indoors recital).
You would then need to use a higher ISO. Set on "ISO Auto" mode, your digital camera will automatically select a higher ISO. Otherwise, you can manually select the next higher ISO and see if the increased sensitivity allows you to obtain a correctly exposed picture. If it does, you can now take a correctly exposed picture.
Similarly, if you find the camera is using a shutter speed that is too slow (1/60 sec. and slower) to handhold the camera steady and shake-free (thus resulting in blurred pictures), and you cannot open up the aperture anymore, and you do not have a tripod or other means to hold the camera steady, and you want to capture the action, etc. etc. -- then you might select the next higher ISO which will then allow you to select a faster shutter speed.
ISO Speed & Noise
However, all this increase in sensitivity does not come free. There is a price to pay with your image appearing more noisy.
See, when you boost the sensitivity of your image sensor by selecting a higher ISO, the image sensor is now able to record a fainter light signal. However, it is also true now that it will record fainter noise, where noise is any signal that is not attributed to the light from your subject. Remember that an image sensor is still an analog device and it generates its own noise, too! The increased sensitivity allows the image sensor to record more light signal and more noise. The ratio of light signal to noise (S/N ratio) determines the "noise" in your resultant image.
An image sensor is usually calibrated so that it gives the best image quality (greatest S/N ratio) at its lowest possible ISO speed. For most consumer digital cameras, this value will be expressed as ISO 50, ISO 64 or ISO 100. A few digital cameras use ISO 200 as their lowest ISO speed.
Just as with its film counterpart, an image sensor will exhibit "noise" (comparable to "graininess" in film) at the higher ISO speeds. Unlike film, where graininess can sometimes contribute to the mood of the image, noise produced by an image sensor is undesirable and appears as a motley of distracting coloured dots on your image.
ISO Speed & Image Sensor Size
The size of the image sensor determines the ISO speed range that a digital camera can use without suffering from undue noise. One reason for this is because the pixels on the larger image sensor can be larger and therefore receive more light, and thus have a greater signal-to-noise (S/N) ratio (for more information on noise, see our tutorial: What Is... Noise?).
If we take two image sensors, each with 4 megapixels resolution, but of different sizes, the 4 megapixels image sensor that is smaller will exhibit more noise at higher ISOs than the larger one.
 1/1.8 in. (7.2x5.3mm) |  APS-sized (23x15mm) |
| 4 million tiny pixels crammed into a 1/1.8 in. image sensor cannot compete in image quality with 4 million large pixels on an APS-sized image sensor. | |
Most consumer digital cameras use 1/1.8 in. (and smaller) image sensors, so noise at high ISO is a problem. Though they will allow you to use a high ISO (such as ISO 400), the resultant image will usually be very noisy.
A digital SLR (dSLR), on the other hand, uses a large image sensor, usually full frame (24x36 mm) or APS-sized (half-frame). Noise is rarely a problem and the use of a high ISO 400 results in images with barely noticeable noise.
Practical Considerations
You obtain the best image quality by using the lowest ISO possible on your digital camera. If you want to ensure your digital camera always uses the lowest ISO setting, switch the ISO setting from the default "Auto ISO" (this setting is usually found in the Menu) to the lowest possible on the camera, say ISO 50.
- If you mostly take pictures where there is enough light for a correct exposure, i.e. sunny outdoors, then using the lowest ISO on your digital camera will give you the best image quality your digital camera is capable of.
- If you want to take pictures indoors where light may not be sufficient and in other low-light situations, then you would need to supplement existing light with flash or studio lights. Either that, or select a higher ISO. Of course, depending on your digital camera, a higher ISO may mean a noisy image.
- A large image sensor (APS-sized and larger) means that you are able to use a high ISO speed without unduly worrying about noise. This means that you can take pictures in low-light situations without your pictures being under-exposed. It also means that in situations where it is required, you are able to use a fast enough shutter speed to prevent camera shake. All, again depending on your camera, without much noise.
Until consumer digital cameras start adopting the larger image sensors, noise will continue to be an ever present fact of life at high ISOs.
Another category of digital cameras for advanced amateur photographers -- commonly known as "prosumers" (professional consumers) -- attempt to bridge the gap between consumer and professional digital cameras by using a slightly larger image sensor (at 2/3 in. or 8.8x6.6mm).
However, the "megapixels race" has meant that ever more pixels are being crammed into a small area. Where before there were 5 million pixels on a 2/3 in. image sensor, now we see 8 million pixels crammed on the same sized image sensor. It is therefore not surprising that noise remains a problem. And which is why you should not be fooled by the "more megapixels is better" mantra.
A little bit of noise may not be a problem depending on the size of your prints or images for display. There are also a number of noise reduction software (Noise Ninja, Neat Image) that you can use to clean up the noise, though there's quite a bit of post-processing work involved, and you might want to reserve this for the special pictures you want to print large format.
If it is a matter of choosing between not being able to take a picture and suffering a noisy image, I'd rather be able to take the picture at a high ISO and then try to clean up the noise afterwards in a noise reduction software.
But remember, to be able to do this, your digital camera must allow you to select a high ISO (ISO 400, ISO 800). Some entry-level digital cameras have only one ISO, usually ISO 64 or ISO 100.
Is There A dSLR In Your Future?
If you definitely must take noise-free low-light pictures and therefore need to be able to use a high ISO speed, then you need to consider digital SLRs with their large image sensors. Just remember, though, that a dSLR usually requires a higher level of proficiency in using the camera and adjusting exposure than a point-and-shoot consumer digital camera does.
Recap
- ISO (equivalent) speed on a digital camera gives an indication of the sensitivity of the image sensor.
- The best image quality is usually obtained at the lowest ISO setting on your digital camera.
- If by adjusting the shutter speed / aperture combinations you cannot obtain a correctly exposed picture (usually in low-light situations), then you may want to select the next higher ISO.
- However, remember that using a higher ISO usually results in noisy images on consumer digital cameras.
- Use a high ISO if it is a choice between missing a picture and being able to capture an image -- even if it means you need to spend time cleaning out the noise in post-processing using a noise reduction software.
- If you leave your camera on "Auto ISO" and if you find that most of your images are noisy, then perhaps you are taking most of your pictures in low-light situations where the camera has automatically selected a higher ISO.
- If you are printing mostly 4x6 in., you may find the noise is not evident in the prints (and so you don't need to worry about noise at high ISO) though they may be visible at original sizes on screen.
BULB MODE
What is Bulb Mode?
BULB mode (or BULB setting) is a shutter speed setting that gives you complete manual control of the duration of your shutter speed. Most often it’s used for shutter speeds of more than 30 seconds. Please refer to your instruction manual on how to set BULB mode. For most DSLRs, you first have to be in manual (M) mode to set BULB. Once in manual mode, dial down your shutter speed all the way to 30 seconds. After 30 seconds, dial it down once more and you’ll find BULB. Once you have it set, you’re ready to go!
In most cameras, BULB works by pressing and holding the shutter release until you’ve had the the desired shutter time (or when you finger gets tired!), then let go to close the shutter. You can image that if you want a 5 minute exposure, you’ll need to find another way.
Equipment
That’s where remote triggers come in very handy. I showed you a variety of trigger options in my Intro to Macro Photography tutorial but you don’t need fancy wireless options like the Canon LC-5 or the Nikon ML-3. I would suggest a wired option like the Nikon MC-30 or the Canon RS-80N3. Depending on the trigger you purchase, you’ll have the option of locking it so all you need to do is press, go have a double mocha latte mochino cream thing-a-ma-gig, come back and press again to close the shutter. If you don,t have that option, gaffer tape is a cheap alternative.
Another advantage to remote triggers is that they prevent camera shake when pressing the shutter button.Needless to say that another very important piece of equipment is a tripod. If you’re shooting outside and you’re leaving your camera unsupervised, I would suggest a heavier tripod or adding sand bags… just in case.
One of the downsides of shooting digital is battery life. Long exposures take lots of battery juice. Just one long exposure can drain a fully charged battery! No kidding. So if you’re planning on doing lots of BULB shots, you might consider investing in a vertical grip like the MB-D80 for Nikon D80 or D90 bodies or the BG-E2N for Canon 30D, 40D and 50D. What the vertical grip does it that it lets you put 2 batteries in it for double the juice.
When to use BULB mode?
The most obvious reason to use BULB mode is for exposures of more than 30 seconds like shooting night skies to get the star trails or dramatic moving clouds.But it doesn’t always have to be for exposures of more than 30 seconds. It could just be for total control of when the shutter opens and closes. Great examples of this are shooting fireworks. The timing needs to be just right to get the best looking “bangs” and “poofs”.
1st OUTDOOR SHOOTING
D60 | F 5.6 | 1/60SEC | ISO 400
D3000 | F 5.6 | 1/60SEC | ISO 200
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