An Introduction To DSLR Photography

Thanks for taking the time to visit. You can start with the introductory article for amateurs below, "First Experiences with a DSLR" and its related pages, or use these links to explore other subjects:

UNDERSTANDING DIGITAL EXPOSURE:

Part 1: Exposure Reduction for Highlight Retention
Part 2: Digital Exposure & Noise
Part 3: When Blocked-up Shadows Aren’t Really
Part 4: Take a Balanced Approach to White Balance
Part 5: Dynamic Range
Part 6: Extending the Tonal Range
Part 7: What’s the Real Difference Between RAW and JPEG?

GENERAL:

1) COST-EFFECTIVE PHOTOGRAPHY
2) CONTROL THE RANGE OF FOCUS
3) IMAGE INTERPOLATION
4) LOSE THE DEAD SHOTS
5) SCANNING 35MM FILM
6) THE RAW vs. JPEG DEBATE…
7) IS PHOTOGRAPHY EASY?
8) MUST EVERYTHING HAVE AN ADOBE SLANT?
9) A CAMERA TO PAINT WITH
10) WHAT'S THIS COMPOSITION THING ABOUT?

First Experiences with a Digital SLR

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BEGINNER?

Where do you start with digital SLR photography?

It may seem simple enough at the very beginning—set everything to auto, point the camera at the subject and press the button. But get off on the wrong foot and you’ll have to backtrack at some stage.

Basically, a digital SLR (Single Lens Reflex) camera is a light-tight box crammed to the gills with very clever and expensive technology, and you can attach a wide range of lenses to it. Straight out of the pretty box it may come with a fairly basic zoom lens, but don’t assume that this would stop you taking arresting images with it.

Once the lens is attached to the camera, the new SLR photographer will need to insert a charged battery and a memory card on which new images can be stored. Today’s DSLRs produce fairly large images (measured in megabytes and pixels) so it’s wise to invest in cards that will hold quite a lot of images, say 4 gigabytes. Higher capacity cards are available and cost more but if anything goes wrong it’s easy to lose a very large number of images simply because they were all recorded on the one card. Perhaps several smaller cards are a better approach?

Typical contents in the DSLR body-only box, and there are plenty of lenses available

So with a suitable memory card and a fully charged battery in the camera the photographer is ready to shoot. And that’s very often where the disappointment begins! Poor images are usually the result of poor technique. It’s rarely the fault of the new camera. Understanding the basic controls of a DSLR will certainly boost confidence but images that are frequently blurred and improperly exposed will just lead to endless frustration and disappointment.

Understanding Lenses, Apertures and Hoods

A single lens reflex (SLR) camera allows the photographer to look through the lens and see what the camera will record. Manual or auto focus lenses are interchangeable on most SLRs. Wide-angle lenses (20mm-28mm) take in much more of a scene than a standard 50mm lens. The longer the focal length, the farther a lens looks into the scene.

Wildlife photographers will use 300mm-600mm lenses to bring subjects closer. Landscape photographers may use 20mm-35mm lenses or even wider. For taking portraits, focal lengths of 85mm-135mm are recommended. Shorter lengths distort features. A macro lens is designed for close-up photography. A zoom lens covers different focal lengths: 35-80mm, 28-105mm, 75-300mm, and so on. Quality zooms are expensive because they are faster (see below), are optically superior and are more robust.

The aperture of a lens is the hole through which light passes to reach the sensor or film. On SLRs the aperture setting is variable and is indicated by f-numbers: f1.4, f1.8, f2, f2.8, f4, f4.5, f5.6, f8, f11, f16, f22 (other f-numbers will appear on the DSLR's display). If a lens is set to f2.8 the aperture (hole) will be much larger than if the aperture is set to f11. If you set a lens aperture to its smallest number, the hole through which light passes will be at its widest . An aperture setting is often referred to as a stop and the the term stopping down means setting the aperture to a higher f-number (a smaller hole). Doing the opposite - enlarging the hole by selecting a smaller f-number - is called opening up.

Lenses are manufactured fast and slow: A fast lens has a large maximum aperture such as f1.8, f1.4, or even f1 (very expensive); a slow lens (a cheaper zoom lens, for example) will have a maximum aperture of around f4-5.6 which may be limiting at times if it's quite dull and you want to avoid the noise or grain associated with faster ISO settings such as 400 and 800.

Lenses deliver sharpest results a few stops down from the largest aperture. At wider apertures various aberrations reduce image sharpness, while at much smaller apertures sharpness is adversely affected by diffraction (the scattering of light through a small hole). Software techniques can accentuate the perception of image sharpness and help to counteract some of the deficiencies of less expensive lenses and their elements.

Always use a lens hood to protect the lens elements from bright light. If you use a lens without a hood, your images may suffer from the effects of non-image-forming light that reaches the sensor. A lens hood that is not compatible with the lens in use may encroach into the lens's field-of-view and darken the corners of your images.

So, what can we say about technique?

Well, at the very beginning it may help to understand what actually happens when you first press down on the shutter button to record a digital image. As we have seen above, light passes through an adjustable hole in the lens called the aperture. A mirror that lets you see through the lens when you look in the viewfinder swings up for a moment and a mechanical device known as a shutter makes a precise timed movement allowing the light that holds the focussed image to strike the sensor (see Nikon image below). The sensor sits just where the film did in a conventional camera.

In an instant the information gathered by the sensor is passed as a stream of electrical signals that are converted into digital data before being processed by an electronic imaging ‘engine’.

But if the scene being recorded is quite dull, the shutter will have to stay open longer to make sure the image is properly exposed. What happens then? If the photographer is holding the camera in his hands, many details in the scene may not be recorded in exactly the same position on the sensor because of unavoidable movement.

This problem is known as camera-shake.

It’s very difficult and often impossible to hold a camera still enough at longer exposures. That’s one reason why experienced photographers put a camera on a stable tripod so that nothing moves during exposure.

To put this information another way, it’s usually, but by no means always, bad technique to hold a camera in your hands in low light without using flash to illuminate the recorded scene. But as explained in the camera’s manual, by increasing the ISO number the camera’s electronics can be made more sensitive to light. At ISO 100 in low light there's every chance that the recorded image will be blurred if the camera is not on a tripod or some other solid support. Changing the speed to 400 may solve the problem.

The path of light through a DSLR before the mirror
flips up to let the light strike the sensor

A DSLR shutter unit and imaging sensor

Another factor that can cause or eliminate the blurring of the recorded image is the focal length in use. For example, a very wide focal length such as 17mm at ISO 100 may not result in a blurred image on a dull day simply because the enormous angle-of-view makes some movement of little consequence.

So a general rule-of-thumb is to make sure the shutter speed is slightly ahead of the focal length. If a lens is set to a focal length of 80mm make sure the shutter speed is set to a higher number, say 125th of a second. And even so, be sure to hold the camera as steady as possible. A zoom lens set to 300mm will need a shutter speed of around 500th of a second or more to guarantee sharp details in the image. Gusting winds can make these calculations less reliable.

Camera-shake is less noticeable in smaller prints, but on the computer where you see everything at full-size you may find that the image you considered sharp on the camera’s LCD screen is in fact blurred. If this is the case a larger print will only make it more obvious.

So we begin the see that proper technique is very important indeed. There’s no getting away from it. So when practising with a new camera for the first time, to avoid too many disappointments, it might be best to set the ISO to 400 if it’s a dull day and take plenty of images of family and friends, or simply go for a walk where you live.

If you don’t have a tripod yet, try setting the camera to its lowest ISO and choose aperture priority. Aperture priority allows you to select the lens aperture knowing the camera will choose the appropriate shutter speed. Set your SLR on a wall and make the aperture in the lens very small by choosing a number like 16 or 22 – remember: the bigger the number the smaller the hole. This will restrict passage the light and increase the exposure time. The movement of people and traffic will blur. If it's particularly dull they may even disappear. Flowing water will begin to look like candyfloss. And of course, you can go the other way: a higher ISO setting and a larger aperture will result in a quick exposure that will freeze most of the movement.

The new digital photographer should note that higher ISO settings (like 1600) can result in something called noise. It looks like tiny specks sprinkled here and there across the image, more noticeable in dull areas where there’s not a lot of detail. Try shooting a dull scene at the camera's lowest and highest ISO setting (you'll probably need a tripod). The difference can be striking, especially when viewed at at 100% on the computer screen. So for cleaner-looking images it’s preferable, if possible and appropriate, to use a much lower number like 100. Lower ISO settings will be beneficial during image processing too.

It’s also important to learn that a DSLR camera is always trying to average out the tones in any scene it records—it gathers them together and calculates an exposure that won’t make allowances for large expanses that are either very bright or very dull.

In other words a scene where a polar bear is (hopefully!) sleeping on snow will turn a disappointing grey if the photographer doesn’t override the camera’s settings and let more light in. At the other end of the scale, a black Labrador standing in the shade of very dark evergreen bushes will be overexposed because the camera will be aiming for a middle exposure and that will let too much light in.

Understanding Light Metering Systems

Modern consumer SLRs allow the photographer to use segment, partial and centre-weighted average metering; more expensive cameras include spot metering.

Segment (or Evaluative): the meter calculates exposure based on readings from different areas. The current exposure information is compared with evaluative metering data stored in the camera. The most appropriate exposure is calculated in an instant.

Partial: the meter takes a reading from about 10% of the overall image. This can be very helpful when the subject is mostly light or dark.

Spot: similar to partial, but reading taken from only a central 2 or 3% of the image area. Accurate if used properly.

Centre-weighted average: the meter takes a reading from the whole scene, but gives much more importance to the central area.

Flash

Daylight flash, or fill-in flash, is an excellent technique that can be used to bring out detail in shadow areas and put a sparkle into someone's eyes. The extra burst of light has little effect on the brighter areas of the subject but significantly lightens the darker areas. The camera, linked to a dedicated flashgun, controls the flash burst, ensuring proper exposure.

The Histogram

Histograms: The histogram readout depicts the brightness levels of the image, from the darker tones at the left to the highlights on the right. These histograms from SmartCurve also show how colour data is distributed throughout each image. The height of each peak indicates how many pixels there are for that particular brightness level. If a peak at either side of the histogram runs off the edge of the display then it's possible that image data has been lost: to the left indicates missing shadow detail and to the right, lost highlight detail.

In the context of exposures, it's very important learn all you can about histograms as quickly as possible. A histogram is a graphical representation of the distribution of tones in an image. You'll find them in software and on your DSLR's LCD display.

The histogram on the DSLR LCD display will help you judge if you have exposed an image properly. The readout depicts the brightness levels of the image, from the darker tones at the left to the highlights on the right. The height of each peak indicates how many pixels there are for that particular brightness level. When appropriate, expose so that more information is shown to the right of the display without data loss. This will make better use of the shadow and mid-tone areas of the scene.

So it's obvious there's a lot to learn, but good SLR technique is essential. With practice the new SLR shooter will quickly learn to avoid the typical frustrations that can quickly dampen enthusiasm.

Apart from good technique the new DSLR shooter needs to get the images on the memory card into a computer that’s reasonably powerful. Once there it will be necessary to edit them to make sure they look their best. A card reader is handier than connecting a camera directly to a computer.

The card reader is connected to the computer all the time, either as a built-in unit or by a cable that's plugged into a USB port. The card is simply inserted into it. The card will quickly show up as an icon which, when opened, reveals a folder or folders where the new images have been stored by the camera. These can be easily viewed and copied to a new location on the computer’s hard drive.