Camera Lenses and Optics - What You Should Know About Focal Length

Camera Lenses and Optics – What You Should Know About Focal Length

A zoom lens is one of the key features that you will need for your professional photography business. You will need to know that most compact digital cameras have optical zoom lenses. An optical zoom lens can magnify and broaden a scene that you want to photograph. This would be ideal for when you are not in a position to move closer to your subject or by including your subject more into a frame by making the camera versatile. It will give you great flexibility in your shooting and the bigger your zoom rage, the greater your flexibility would be.

Focal Lengths

High End Digital CamerasCameras with zoom have their focal lengths specified by comparison with the focal length of a 35mm film camera. The focal lengths are indicated on the camera lens in millimetres. This might sound a bit technical, but all you need to know is the description of lenses or cameras using terms such as two times (2x) or four times (4x) abbreviated. The wider the focal range the bigger the abbreviation becomes and the deeper the lens can magnify. Let’s use an example to make this clearer. If a digital camera has a zoom lens of 35 to 105mm, the focal range would be a 3x the optical zoom lens. This is because the biggest focal length is three times the lowest focal length. 35 x 3 = 105.

A 28 to 112mm lens would then be four times (4x) the focal length. 28 x 4 = 112. You can now find cameras with ultra zoom lenses 60x its focal length. The most common zoom lenses on a digital camera are the 3x or 5x zoom lenses.

Optical Zoom Or Digital Zoom

Digital cameras have features called digital zoom. This would enable to enlarge a portion of the sensors image electronically to create a zoom effect. By using the lens to magnify a scene will make the optical zoom work and it uses the whole sensor for an image and will keep the image quality and resolution. When using digital zoom, it enlarges only a small area which is the central portion of the sensor. This will then produce block or grain images that should be avoided when quality prints are going to be made.

Fixed Lenses Explained

Sigma DP2A zoom lens on a camera is basically a standard feature. Consider an alternative when using a fixed lens camera when you want to start a professional photography business.
Having looked at the flexibility of a zoom lens and what it can offer you, but with a fixed lens on a digital camera there are a couple of benefits which are not available on a zoom lens.
The benefits are optical quality and compact size. A Sigma DP2 is a great example.

Fixed Lens Advantages

You will find better optical quality results in a lens as it is a specialized lens that does not have a zoom function. If zoom takes place in a lens, compromises are made in designs which affect the optical quality. There are no compromises made in a fixed lens camera. It only has one focal length, which is usually a wide view of 28 to 35mm. This means that the lens is specially made for that length and making it much sharper and brighter than the zoom lens. Battery power last longer on a fixed lens camera.


Fixed lens cameras might seem expensive due to the cost that goes into their optics and that they are premium models. There are also few fixed lens cameras on the market that can also make them pricey. It does not have the flexibility of a zoom lens and is a result of people living with the compromises in a zoom lens camera.

The Cheaper Option

There are cheap models that you can take a look at on the market as they tend to use digital zoom to make of for the lack in an optical zoom. With cheap fixed lens digital cameras, you can bet that you will get worse optics and poor image processing. Avoid buying these type of cameras.


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