Digital Camera Lenses

Lens Protection, Filters, Supplementary Lenses and accessories. Lens Hoods.

Lenses need to be treated with care and consideration if they are to give of their best. Dropping them, knocking them, getting them wet, scratching the front element etc, are all acts likely to lead to them ceasing to work properly, if at all, or give poor images if they do. A scratch on the front element of a lens usually renders it useless, unless it is very minor, as it introduces reflections into the image besides degrading the image quality where the scratch is. For this reason a general action many photographers take with their lenses is to permanently keep Ultra-Violet [UV] screw on filters fitted on the front. 

The Ultra-Violet filter is regarded by many as a universal standard fitment for SLR lenses. As well as offsetting the effects UV light has on an image - distant views can have a blue cast and look hazy - these colourless filters also protect the lens front element from scratches and dirt. Unlike most other filters they don't stop any visible light from entering the lens [most filters - depending on the type -  reduce varying amounts of visible light from entering the lens resulting in slower shutter speeds]. Cheap to purchase in relation to the cost of a lens, they can easily be replaced should damage occur to them, without the lens being affected.

Many photographic outlets recommend the use of 'skylight' filters instead of UV's and say they do the same job. They don't. Skylight filters reduce the blue cast caused by UV rays not by blocking them, but by altering the image colour. They have a slight pink hue and add a warm cast to images and are in fact a very weak 'warm up' filter. They do not cut through distant haze.

Recently we have also seen a new range of 'digitally optimized' UV filters arrive apparently specially made for digital lenses, and at between two and three times the price of 'normal' UV's. This seems to us a load of nonsense. UV's stop UV light, that's all, nothing more, nothing less.

Nearly all SLR lenses, and quite a few on digicams, are fitted with screw threads on the ends just in front of the front element to enable all types of filters and other accessories to be used with them, square filters systems and ring-flash units for example. There are one or two exceptions, extreme wide-angle or fish eye types often do not have filter threads as using filters with them is not feasible, vignetting would result. Filters have identical threads to those fitted to lenses so other filters and accessories can be fitted onto them in the same way they fit the lens. 

Here are shots of a UV filter, a lens as purchased, a filter in place on the lens, and a manual ring-flash unit on the front of a macro lens.

Unfortunately it's not usually possible to fit UV filters for protection on many digicam lenses because of the general method of their construction and use. Most digicam lenses retract into the camera body when not in use, to protect them and reduce the size of the camera. They telescope out for use when the camera is powered up. Some, such as this Pentax Optio model, have lens protection blinds that close over the lens when the camera is not in use protecting it against scratches. Of course this means that to keep the lens protected the camera needs to be turned off and on in between use. Not much of a problem if there is a large time gap between use, but frustrating if it's measured in minutes rather than hours. If the camera is allowed to go into the 'sleep' mode many have, where the camera powers down without retracting the lens, and is 'woken' up by pressing any button, whilst this means the camera reacts more quickly and power is saved by not moving the lens, the downside is the lens is vulnerable to knocks.

There are some Digicams that are supplied with or can use lens adaptors. This is very useful as usually it means that supplementary lenses, filters, and other accessories can be used with them in the same way as with SLR's. Here is one such camera, the Epson 3000z/3100z. 

As you can see the adaptor is a tube that fits over the lens like a sleeve and screws into the camera body. It is shown here fitted with a UV filter. The adaptor, with filter, is kept permanently in place and means the lens is protected at all times. The camera can be left to go into it's 'sleep' mode with no danger of the lens being knocked. 

Sometimes it is possible to buy supplementary lenses to fit a digicam's zoom lens, which provide either a wider or longer view. Usually these are made by the camera maker but there are some independent makers such as Raynox which also produce these lenses. Here is one such lens, a 1.8x telephoto converter, complete with adaptor to enable it to be used with the Epson 3000z/3100z. Different adaptors are provided depending on the camera to which the lens will be fitted. Sometimes, as in this case, the lens converter and adaptor combine to make rather a large fitment on the front of a digicam. Regrettably there is no thread provided to enable a UV filter to be fitted.

Unfortunately using such supplementary lenses does not always provide the versatility that you might expect, indeed their usefulness can be extremely limited. On the Epson whilst it does provide the equivalent of a 189mm focal length when the camera lens is zoomed to it's maximum, that's all you can use it for. It does not alter the whole focal range by 1.8x. You can't use it with the camera's lens at other focal lengths or the shot turns out as if it has been taken through a tube, as in the second shot. It does serve to show that camera lenses produce circular images though! You can always crop the image of course, but then you could in all probability have got the same size of final image just by using the standard camera lens on it's own.

However you can use certain other fittings with the basic adaptor and here is a view of a manual macro-flash unit fitted on the camera via the adaptor. To use an external flash like this the camera does need to have a flash hot-shoe and a manual/external flash mode - all points to bear in mind when buying a digicam.

Lens Hoods

Increasingly many DSLR lenses and some digicams are being supplied as standard with lens hoods. Sometimes these are simple screw-in circular types but with lenses that cover a wide angle dedicated bayonet type 'petal' shaped versions are often now used. 

The basic principle behind the use of a lens hood is that it helps to stop extraneous light from hitting the lens front element at an oblique angle causing flare and image degradation. This mostly occurs when taking shots at an angle to the sun's position in the sky which is at 90° or less to the direction of the lens.

They are of use not only with lenses that cover wide views but longer focal lengths too, and you often find that the expensive fast aperture long telephoto types that have very large front elements have very large built-in lens hoods as part of the overall design.

However whilst the use of lens hoods has always been recommended, until more recent times very few were made to suit individual lenses and even fewer lenses were supplied with them as standard. As a result there are a number of 'standard' screw-in lens hoods made to suit any lens according to it's filter size. Generally they come in two types to cover normal focal length and wider focal length lenses, and they are usually made in either rubber or metal. Whilst they are perhaps not quite as good as a hood dedicated to the particular lens they are better than not using a hood at all. 

Hoya, the well known makers of high quality camera lens filters make a multiple purpose rubber hood which they call the wide lens hood. This is a screw-in type that can be altered to suit the focal length of the lens by pulling it in and out. It has three positions. Wide, Standard, and Tele. Here are some shots of it. Very useful at around £10.