Now if there’s one thing that’s more important than the camera itself, it’s the lens. The better quality the ‘glass/ optics’ used the finer your shots will be. It is unbelievable the difference between mediocre & top quality glass.

A top top of the range lens will set you back anywhere up to £10k+ but for that you get optics of absolute premium quality. For us mere mortals however, we can obtain superb results with a lens of comparible type (i.e. telephoto, macro etc etc) for circa £300. My advice is to stick with the camera body manufacturer lenses as they are designed & built to perform optimally with your camera body. Don’t get me wrong, 3rd party lenses, such as Sigma for example make some exemplorary lenses which will satsify all but the top Pros who strive for the purest quality.

Lenses come in all shapes & sizes & you need to think carefully about what type of lens you want & for what purpose. Ideally you need to have 3 different lenses in your kit bag, namely:

	1) Telephoto (adjustable focal length of between 70-300mm).
	2) Fixed lens (50mm) – ideal for portrait shots.
	3) Macro lens (perfect for close up photography).

Personally I have 5 lenses which incorporate variants of the above. Mostly I use the telephoto as this covers most applications & the particular lens I use has anti-vibration technology built in which really does work & compensates for those amongst us who have a little natural hand shake (godsend if you ask me).

Perhaps my most favoured lens is my 100mm Macro lens, again with anti-vibration technology. Along with my tripod, I can focus in on say an insect & get pin sharp images with the insect’s ‘gauze’ detail on it’s eye filling the frame…absolutely amazing…this level of detail cannot be achieved without a macro lens (there are other ways like using the lens back to front but that’s another topic altogether).

The aperture range of a lens refers to the amount that the lens can open up or close down to let in more or less light, respectively.  Apertures are listed in terms of f-numbers, which quantitatively describe relative light-gathering area (depicted below).

Note: Above comparison is qualitative; aperture opening (iris) is rarely a perfect circle,
due to the presence of 5-8 blade-like lens diaphragms.

Note that larger aperture openings are defined to have lower f-numbers. As a rule of thumb, the lower the number a lens is capable of, the more you’ll pay for it. Lenses with larger apertures (smaller f-stop numbers) are also described as being “faster,” because for a given ISO speed, the shutter speed can be made faster for the same exposure.  Additionally, a smaller aperture means that objects can be in focus over a wider range of distance, a concept also termed the ‘ depth of field’ which I mentioned in another post..

Portrait and indoor sports/theater photography often require lenses with very large maximum apertures to allow the use of faster shutter speeds and/or narrower depth of fields.  The narrow depth of field in a portrait helps isolate the subject from their background.  For digital SLR cameras, lenses with larger maximum apertures provide much brighter images through the viewfinder which is an absolute must for nighttime or low light photography.  The other advantage is a wider aperture provides the camera’s systems better ability to provide faster and more accurate auto-focusing without the need for supplementary or secondary lighting .  Manual focusing is also easier because the image in the viewfinder has a narrower depth of field (thus making it more visible when objects come into or out of focus).

It should also be noted that generally, the better quality the lens & the better the optics, the heavier the lens becomes. So when choosing a lens, purpose, cost & weight need to be considered.