The same SLR design developed for film, has been adopted for many semi/professional and professional digital SLR cameras –

Some people confuse lens interchangeability for SLR - SLR stands for Single Lens Reflex - viewing system and a camera is either of this design or not –

Within digital SLR camera design there are several types - cameras with fixed lens and more professional interchangeable lens models like the one above - that allow the lenses to be changed. Which is the best?

Often it comes down to personal preference - but the main thing is to identify what style of camera you need. Like cars - there is no need to get a grunty 4x4 to pick up the shopping or buy a smart car to crash through the bush or a formula one to crawl along a congested freeway.

While interchangeable lenses might appear desirable, the facility can present problems. You will also find with SLR digital cameras with interchangeable lenses the ccd is vulnerable to dust problems.

Any dust that gets on the sensor can sometimes stay there and turn up on in the same position on every image until you clean it off. Where as in a similar SLR interchangeable lens film camera – if dust gets on the film it tends to fall off or move as we transport the film to the next frame, so while you might get the odd piece of dust on one frame it tends to clear itself over time. But with the digital version if dust participles get inside they tend to stick to the ccd sensor and stay there.

Cleaning the ccd can be tricky – the sensor is quite delicate and once damaged any aberrations will show up on every image. At times it might even require a professional clean which can cost as much as $35 a time. As dust tends to fall downwards, If you can change the lens holding the lens in a lower position than the body – if you have a lens brush and dust it off just before you change it – you will find you can reduce the dust problem. On the other had if you hold the body with the opening facing upwards to place the lens on – you will find there is more chance of dust falling into the body. You can also buy thin computer and electronic cleaning hoses from an electronics shop - that fit onto a vacuum cleaner – these can be good to get inside the body to suck up dust - but be gentle and don’t use the brush to clean the ccd – usually the bristles are too course.