Understanding Camera Lenses: Decoding The Ti 5 Label

Camera lenses are full of abbreviations, number ranges, and acronyms. The Canon EOS Rebel Ti, released in 2002, was a film camera and the first in the Rebel T series. The T in the Canon EOS Rebel series doesn't stand for anything in particular. The Canon EOS Rebel T5i is the second newest version of the Rebel series to hit the market. It is a great camera for beginners with easy-to-use functionality and impressive stills and videos.

Focal length numbers

Lenses with different focal lengths offer varying angles of view and magnification. Shorter focal lengths provide a wider angle of view and less magnification, making them ideal for landscape photography. Longer focal lengths, on the other hand, offer a narrower angle of view and higher magnification, which is why they are favoured for sports or wildlife photography.

When choosing a lens, it's essential to consider the focal length numbers. Lenses can be categorised into two main types: prime and zoom. Prime lenses have a fixed focal length and are known for delivering high-quality images with wider apertures. Zoom lenses, on the other hand, offer variable focal lengths, making them more versatile and reducing the need for multiple lenses.

The Canon Rebel T5i, for example, offers a range of lens options. The Canon 18-55mm STM kit lens is a popular choice, providing smooth and quiet video capabilities. Another option is the Canon 18-135mm STM, which offers a longer zoom range and is excellent for video as well.

In addition to focal length, other factors such as aperture, lens version, focusing motor, stabilisation, and filter diameter also come into play when selecting a lens. These specifications collectively influence the characteristics and capabilities of the lens.

Understanding focal length numbers and the various lens options available is key to capturing the desired images in photography.

Aperture

The size of the aperture is expressed in 'F numbers', for example: F/1.4, F/2.0, F/2.8, F/4.0, F/5.6, F/8.0, F/11.0, F/16. F numbers represent the diameter of the aperture as a ratio to the focal length of the lens. Therefore, the smaller the number, the larger the aperture, and the greater the amount of light which is able to pass through.

The aperture you choose will also alter the exposure of your images by making them brighter or darker. A large aperture will pass a lot of light, resulting in a brighter photograph. A small aperture does the opposite, making a photo darker.

Lens diameter

The lens diameter of a camera lens refers to the physical measurement of the diameter of the front-most part of the lens. This is different from the focal length of a lens, which is what people are referring to when they mention a 50mm or 70-200mm lens. It is also different from the aperture settings of a lens, such as f/1.8 or f/5.6.

The lens diameter is usually measured in millimetres and can be found engraved on the front of the camera lens or on the side near the top, where the lens filter is screwed on. It is often marked with the diameter symbol followed by a number, for example, ø52 or ø77. Some common sizes for the diameter of DSLR lenses include 49mm, 52mm, 58mm, 62mm, 72mm, and 77mm.

The lens diameter is important when it comes to buying filters, lens caps, or hoods, as these accessories need to fit the specific diameter of your lens.

It is worth noting that the lens diameter is related to the focal length and maximum f-number of a lens. The f-number is calculated by dividing the focal length by the aperture diameter. Therefore, a larger lens diameter on a lens with the same focal length will result in a smaller maximum f-number, allowing more light to enter the lens and potentially improving image quality. However, when comparing lenses of different focal lengths, the diameters do not necessarily indicate better image quality, and it is more important to consider the f-numbers.

Lens speed

Advantages of Fast Lenses

Fast lenses come with a few advantages:

• They allow you to use faster shutter speeds. This is especially useful when shooting handheld or moving subjects in low light.
• They create shallow depth of field effects. The wider the lens aperture, the shallower the depth of field, resulting in a highly blurred background.
• They enable hand-held shooting in more situations, such as in cathedrals or museums, where tripods are not allowed or practical.

When to Use Fast Lenses

Fast lenses are particularly useful in certain genres of photography, such as:

• Wildlife photography
• Portrait photography
• Sports photography
• Photojournalism

Disadvantages of Fast Lenses

While fast lenses offer these advantages, they also come with some drawbacks:

• They tend to be more expensive than slow lenses.
• They are often heavier and bulkier, making them more difficult to work with, especially when you need to carry equipment for long periods.
• They may be unnecessary for certain types of photography, such as landscape or architectural photography, where slower lenses can still produce good results.

Examples of Fast Lenses

Some examples of fast lenses include:

• Canon EF 50mm f/1.8 II
• Nikon AF Nikkor 50mm f/1.8D
• Leica Noctilux-M 50mm f/0.95 ASPH

While fast lenses offer many benefits, such as faster shutter speeds and shallow depth of field effects, they also come with increased cost and weight. Therefore, it is important to consider the specific needs of your photography before investing in a fast lens.

Image stabilisation

There are two types of image stabilisation: lens-based and in-camera. Lens-based stabilisation uses a floating lens element that is electronically controlled and shifted in the opposite direction to any camera shake recorded by the camera. In-camera systems, on the other hand, physically shift the image sensor to compensate for camera movements.

Lens-based stabilisation tends to perform more smoothly when using longer focal length lenses. However, it is not available as an option for all lenses and adds to the cost. In-camera stabilisation, on the other hand, works with any lens that can be mounted on the camera and is, therefore, a more cost-effective option. Nevertheless, it is less effective when using longer focal length optics compared to lens-based stabilisation.

When using a tripod or similar stable platform, it is recommended to turn off image stabilisation to avoid creating a feedback loop, where the camera's stabilisation system detects its own vibrations and starts moving, introducing blur into the images. Additionally, image stabilisation can negatively impact battery life, especially with larger lenses and sensors, as it requires more energy to move them around.

Overall, image stabilisation is a valuable feature for photographers, especially when shooting handheld in low-light conditions or with longer focal length lenses. However, it is important to consider the limitations and potential drawbacks of this technology to utilise it effectively.

Frequently asked questions