How SLR Cameras are better than Compact Cameras

SLRs are big, heavy and expensive when compared to compact digital cameras.

So wouldn’t you be better off with a compact? Well, not necessarily.

This page outlines the key differences between the two, and will hopefully show you that there are good reasons why keen photographers carry bulky SLRs around with them!

It’s difficult to pin down just one advantage of digital SLR cameras, because there are so many of them. Here are some them:

1. ADVANTAGE OF DIGITAL SLR CAMERAS: PHOTO QUALITY

Many compact cameras these days have a huge number of megapixels. More in fact than a lot of digital SLRs. You could be forgiven for thinking that this must mean better photos?

Unfortunately you’d be wrong. More megapixels doesn’t equal better quality. The problem is the image sensors on compact digital cameras are just too small. When 10 million pixels are crammed onto them the individual photosites on the sensor are too small, and too close together.

This closeness and their size means they suffer from interference. When you look at photos closely they have speckles on them. This is called digital noise. The effect is worse in low light.

The lack of noise in photos is one advantage of digital SLR cameras when it comes to picture quality, but not the only one. Another advantage is SLRs’ ability to shoot in RAW mode.

By shooting in RAW mode the camera captures more detail, and allows for far more flexibility when it comes to editing photos later on.

Overall photo quality is one advantage of digital SLR cameras over compact digital cameras.

2. ADVANTAGE OF DIGITAL SLR CAMERAS: SPEED

When I talk of “speed”, I am referring to the speed of camera operation.

There are a number of factors that contribute to the overall speed of a digital camera.

First, there is the speed of focusing. When composing a shot, cameras clearly need to focus first.

In any given situation a digital SLR camera will focus on the subject faster than a compact digital camera.


This speed advantage of digital SLR cameras is even more obvious in low light conditions.

Second, there is the frame rate. Frame rate is the number of frames per second a camera can take.

Digital SLR cameras are usually good at taking a sequence of photos of a moving subject; and will be able to keep re-focussing as the subject moves too. Have a look at the photo below to see the effect.

Another element of speed is how long the camera takes to switch on. With a digital SLR, especially the more recent Nikons and Canons, as soon as you turn the switch, it’s on. That’s it. No lens to extend. No motor whirring. It’s just on, in an instant.

If you are interested in capturing a moment, this “on” speed might be the difference between getting your shot, and missing out. This is a definite advantage of digital SLR cameras.

A final note on the speed of operation is the speed of zooming. When a compact camera zooms the motor whirrs and the lens slowly extends. Digital SLRs don’t work in this motorised way. You zoom the lens by turning the lens barrel. This gives you an instant zoom.

With this type of manual zooming it is also easier to nudge the zoom in or out a little if you need to – just a little flick of the wrist is all that’s needed, and you’re there.

Speed of operation is therefore a clear advantage of digital SLR cameras over compact digital cameras.

3. ADVANTAGE OF DIGITAL SLR CAMERA: FLEXIBILITY


With a digital SLR you have the choice of hundreds of different lenses and a huge range of flash options.

Why should you care about the lenses, after all, compact digital cameras come with good zoom lenses, don’t they? Well, yes, they do. But the quality of the lens is poor in relation to the lenses available to digital SLRs, and there is no comparison when it comes to aperture.

Lenses on digital SLRs have wide apertures, much wider than the zoom lenses on compacts. This provides two advantages of digital SLR cameras over compacts.

First, this means that shutter speeds can be faster because more light can enter the camera.

Second, it means you are able to control the depth of field in your photos. A shallow depth of field is particularly flattering in portrait photography, and is impossible to achieve with a compact camera because the lenses just aren’t up to the job.

And then there’s the flexibility of the flash on offer. The small flash on top of compact cameras is no match for the powerful flashguns that are available for digital SLRs.

Not only are flashguns more powerful, but they also able to “bounce” the flash off of ceilings and walls. This diffuses the flash, and eliminates red eye.

Shutter Speed

In photography, shutter speed is the length of time a shutter is open; the total exposure is proportional to this exposure time, or duration of light reaching the film or image sensor.

Factors that affect the total exposure of a photograph include the scene luminance, the aperture size (f-number), and the exposure time (shutter speed); photographers can trade off shutter speed and aperture by using units of stops. A stop up and down on each will halve or double the amount of light regulated by each; exposures of equal exposure value can be easily calculated and selected. For any given total exposure, or exposure value, a fast shutter speed requires a larger aperture (smaller f-number). Similarly, a slow shutter speed, a longer length of time, can be compensated by a smaller aperture (larger f-number).

Slow shutter speeds are often used in low light conditions, extending the time until the shutter closes, and increasing the amount of light gathered. This basic principle of photography, the exposure, is used in film and digital cameras, the image sensor effectively acting like film when exposed by the shutter.

Shutter speed is measured in seconds. A typical shutter speed for photographs taken in sunlight is 1/125th of a second. In addition to its effect on exposure, shutter speed changes the way movement appears in the picture. Very short shutter speeds are used to freeze fast-moving subjects, for example at sporting events. Very long shutter speeds are used to intentionally blur a moving subject for artistic effect.

Hight Shutter Speed

Low Shutter Speed

I shot these pics during Shrikhand Trek in Himachal Pradesh.

What is Aperture in Cameras?

In optics, an aperture is a hole or an opening through which light is admitted. More specifically, the aperture of an optical system is the opening that determines the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are, which is of great importance for the appearance at the image plane.

F-STOPS:

* F-stop: Focal length/Diameter of the selected aperture.
* F-stop: Bigger the number smaller the aperture, smaller the number bigger the aperture.
* With every opening of aperture by one full f-stop, amount of light coming in the camera becomes twice of the previous stop.

The aperture stop of a photographic lens can be adjusted to control the amount of light reaching the film or image sensor. In combination with variation of shutter speed, the aperture size will regulate the film's degree of exposure to light. Typically, a fast shutter speed will require a larger aperture to ensure sufficient light exposure, and a slow shutter speed will require a smaller aperture to avoid excessive exposure.

* Reducing the aperture size increases the depth of field, which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus.
* In general, the smaller the aperture (the larger the number), the greater the distance from the plane of focus the subject matter may be while still appearing in focus.

Aperture priority is a semi-automatic shooting mode used in cameras. It allows the photographer to choose an aperture setting and allow the camera to decide the shutter speed and sometimes ISO sensitivity for the correct exposure. This is sometimes referred to as Aperture Priority Auto Exposure, A mode, Av mode, or semi-auto mode.

Prime lenses have a fixed focal length (FFL) and large aperture and are favored by professionals, especially by photojournalists who often work in dim light, have no opportunity to introduce supplementary lighting, and need to capture fast breaking events.

Zoom lenses typically have a maximum aperture (minimum f-number) of f/2.8 to f/6.3 through their range. A very fast zoom lens will be constant f/2.8 or f/2, which means the relative aperture will stay the same throughout the zoom range. A more typical consumer zoom will have a variable relative aperture, since it is harder and more expensive to keep the effective aperture proportional to focal length at long focal lengths; f/3.5 to f/5.6 is an example of a common variable aperture range in a consumer zoom lens.

The amount of light captured by a lens is proportional to the area of the aperture, equal to:

Where f is focal length and N is the f-number.

The focal length value is not required when comparing two lenses of the same focal length; a value of 1 can be used instead, and the other factors can be dropped as well, leaving area proportion to the reciprocal square of the f-number N..

If two cameras of different format sizes and focal lengths have the same angle of view, and the same aperture area, they gather the same amount of light from the scene. The relative focal-plane illuminance, however, depends only on the f-number N, independent of the focal length, so is less in the camera with the larger format, longer focal length, and higher f-number.