Digital SLR's

The main advantage of using a Digital SLR is one of extra versatility. Unlike digicams with their fixed lenses, DSLR's can be tailored for a wider variety of specialist tasks, by changing their lenses to suit particular circumstances. Another benefit is that they can be used, in most cases, with existing 35mm film SLR lenses and other system accessories, flash guns, tele converters, extension tubes, bellows units and so on, giving a wide choice and a measure of continuity and familiarity for those with present film SLR systems. They are also quicker to use, mainly because their designs are similar to film models and use the same basic methods of operation, but also because they generally have higher specifications.

They can take shots as they write files to memory, due to the larger amounts of RAM fitted, and access to their modes is generally by dials and buttons located on their bodies, although many newer DSLR designs now work in much the same way as digicams, with access to their modes through the rear LCD screen menus. The continued use of individual dials and buttons, along with the provision of a top-plate status information LCD becoming restricted largely to the higher specification professional DSLR's.

All of this is of course reflected in their price, which is considerably more than digicams although much cheaper than in the recent past, and ranging anywhere from around £400 up to £6000. It is only in the last few years that prices of the cheapest models have dropped to levels the ordinary person can consider paying, firstly dropping below the £2000 mark, and then £1000. 

Early models

The first Digital SLR's were big, heavy and very expensive. They were bought mainly by the  newspapers who had started the moved into DTP (desk top publishing), and needed to be able to compete with the other types of media, Radio and TV, on an equal footing by reporting news as quickly as possible. Cost was therefore not of prime importance, speed was, and being able to take pictures and send them back to the newspaper's picture desk via a laptop and 'phone line within minutes, from around the world, became possible using a digital camera. Kodak were at the forefront of  DSLR development and produced models using both Canon and Nikon lens mounts, the two makes most used by professional newspaper photographers. Both these companies now make DSLR's targeted at the professionals working in this and similar fields and below are a couple of views of one past Nikon model, the 4mp D2H. It used a new type of sensor developed by Nikon to enable fast shooting rates, and had 8 fps capabilities as a result. In common with quite a few cameras of this type it has a substantial body with a large integral vertical grip on the bottom for housing batteries and using the camera in the portrait position. There is another additional housing which can be fitted on the bottom, this being for the wireless transmission (wi-fi) of images. Cameras like this have transformed coverage of sports such as football for newspapers, as images taken right up to the end of the game can be used, which was not always the case in the past.

Nikon D2H  4mp DSLR

The latest models of this type to arrive (2007) are the Canon 10mp 1D mk3 which can take 10mp images at a blistering 10fps, and the Nikon 12mp full frame D3 at 11fps. Well in excess of anything available in the past in respect of film cameras let alone digital models. They are also cheaper than past top pro DSLR's, but at around £3000, still well outside most photographers reach.

Present day DSLR's

Nowadays the use of DSLR's has spread far and wide as the benefits of their use become apparent and their costs reduce, and they are finding favour not only with professional's but amateurs as well. Virtually all current DSLR's use existing 35mm lens mounts so they can be used with the large range of 35mm film lenses currently available and made in the past [Fuji using the Nikon mount], as well as the new digital lens designs being introduced to suit the smaller sensor sizes often used. An exception is the 4/3rds system from Olympus, which uses a new lens mount and lenses specially developed for this standard, along with a smaller than usual sensor size.

The main principle behind the 4/3rds standards is that it is a 'common' standard to which any maker using them will comply, so that camera bodies and lenses from different sources will be interchangeable, and used with each other. Whether this system will succeed in being widespread depends on how many makers join it. Kodak and Olympus started it along with Fuji, although it was initially only Olympus who produced 4/3rds cameras and lenses. It was hoped that as more companies joined the 4/3rds group further camera bodies and lenses would follow. This has happened, but not to the extent expected. Sigma have made a few lenses, and Leica and Panasonic some cameras and lenses, but apart from Olympus none seem really committed to it. It is seen, rightly or wrongly, as being the Olympus 4/3rds system, which rather restricts is adoption by others. This is besides the smaller than normal sensor size adopted, which is a considerable drawback in the eyes of many.

Apart from a few cameras which have sensors the size of a 35mm film frame - called 'full frame' sensors - all the rest have sensors which are smaller. This means the focal length of any lens used on these cameras is effectively multiplied by between 1.3x and 2.0x depending on the make, the smaller sensors 'cropping' the centre of the image the lens produces, making wide-angle lens photography more difficult, but increasing the magnifying power of telephoto's. However, even when lenses made to suit the smaller sensor sizes are used, the focal lengths used are different to that used in the past with 35mm cameras for the same field of view. This has led, and still does, to some confusion amongst users as to the focal length/field of view combination, which differs according to the size of the sensor, just as it does for digicams. Please refer to   Digital Camera Lenses   for more details.

While virtually all digicams still currently use CCD sensors there are an increasing number of DSLR's that now use the CMOS type.  Historically CCD's have been used in imaging applications because of the uniformly high standard of information they can provide, which has been far superior to that from CMOS sensors. However CCD sensors are expensive to produce and attempts to use CMOS sensors, which are far cheaper to manufacture, have been made in order to bring camera costs down. Canon have been at the forefront of this, developing and making their own CMOS sensors, which have proved to give high image quality. Nikon, Sony and Pentax now all produce DSLR's using CMOS sensors as well as CCD's, and it seems fairly certain that eventually all DSLR's will use the CMOS type.

Foveon have developed a further type of CMOS chip using three layers of pixels, and this is currently used by Sigma in their D-SLR's..

One main benefit most DSLR's and some digicams have, is the ability to be 'upgraded' by their owners via 'firmware' updates released by the manufacturers, which can be downloaded from the  internet and then installed. This enables a camera maker to fix any 'bugs' found with it systems after release, and to provide purchasers with some assurance that the expensive camera they have bought can be kept up to date with the latest specifications. An important consideration in view of the speed with which the current camera technologies are being improved. 

At the present time sensor resolution varies as widely as price, from the 4.7mp resolution of the Sigma SD14 to the 21mp that the Canon 1Ds mk3 provides. Most DSLR's currently now use 10/12mp sensors, a jump from the 6/8mp sensors of the past, with some of the latest offering 14mp.

Basic entry level DSLR's

It was in 2003 that Canon stunned the photographic world with the first DSLR to sell for less than £1000, the 6mp 300D. They achieved this by a combination of a reduced specification and a cheaper all-plastic body. There was for example no individual control over metering modes and limited flash modes with external flashguns. It also took several seconds to power up when switched on. Since then all makers have released cheaper entry level DSLR's and the price at which these now sell has continued to fall, as have all DSLR prices.

Here are two views of it. As you can see it looks just like a film SLR. Indeed you really need to look on the back of most DSLR's these days to see the rear LCD screen to know it is a DSLR and not a film SLR, so alike are they in design.

Canon 300D 6mp DSLR

Part of the reduction in cost has been achieved by designing these DSLR's to work in similar ways to most digicams, with access to most of the changes that are made to the camera via the rear LCD screen. Although this does reduce in some ways the speed with which they can be used, and some features found on better specified models are of course absent, none the less they still offer higher quality images and more versatility than digicams thanks to interchangeable lenses, along with better, quicker, and more accurate AF.  They also respond much more quickly.

New Standards - Single battery and instant response

Pentax set some new standards with the introduction in autumn 2003 of the *ist-D, being smaller than normal with instant start up and response times, and using just 4AA batteries. At the time many DSLR's used two sets of batteries, one to power the normal camera side with another for the digital elements. Most makers were soon forced to introduce new models with similar standards, and most makers entry level DSLR's are now of a similar size and use just one battery.

Here are two views of the original *ist-D, which remains the smallest fully featured professional DSLR to have been made, and the first of the *ist-D series. Some lower spec models, the *ist-Ds/2 and DL/2 followed. Pentax have now moved on to the 'K' series featuring anti-shake sensors. The replacement for the *ist-D, the 10mp K10D was broadly similar in design but regrettably rather larger.

Pentax *ist-D 6mp DSLR

Anti-shake sensors

Another latecomer to the DSLR scene who also set a new standard was Konica-Minolta, their Dynax 7D DSLR featuring a anti-shake sensor similar to those they had developed for their prosumer digicams. A cheaper DSLR, the 5D arrived later. One of the advantages of using a anti-shake sensor mechanism in the camera body is that it works with any lens fitted on the camera. No special lenses are needed and it's compatible with all lenses the camera can work with, old and new. As with many DSLR's, whose designs are similar to previous film SLR's from their makers, the design of the 7D and 5D are reminiscent of previous recent Minolta SLR's. Here are two views of the 7D.

Konica-Minolta 7D 6mp DSLR

One point of note is that the basic rear design of all DSLR's is broadly similar, with the the LCD being on the left with its control buttons running down the outer edge, and a control dial/jog wheel being to the right. Most DSLR's now also have 'shooting priority', so even if you are reviewing shots taken you can still press the shutter and get an instant response. This was again something introduced by Pentax with the *ist-D  that all have followed.

It is interesting to note that although Konica-Minolta no longer produce cameras, all camera making assets being acquired some time ago by Sony, the cameras produced by Sony, particularly the DSLR's, bear an uncanny resemblance to past Minolta designs in general appearance and in the methods of working, the placement of buttons dials etc.

Sensor cleaning and Live View.

Nothing really stands still for long and new DSLR developments are always occurring. Olympus have been responsible for introducing some with their 4/3rds DSLR's that have subsequently been adopted by others. A problem that affects DSLR's is dust/dirt adhering to the sensor surface, or rather the surface of the special filters fronting the sensor, and thus degrading the image quality, larger particles appearing as 'blobs' in the image. It happens with all digital camera sensors to a certain degree, but is a particular problem with DSLR's because of the removable nature of their lenses coupled with the flapping of the mirror assembly in the mirror box, which in combination accelerates the ingress of dirt.

Olympus came up with the idea of separating the filters from the sensor and subjecting them to sonic frequency vibration causing most dirt particles to fall off, being collected by a sticky pad underneath. They called this SSWF - SuperSonic Wave Filter. Although most other makes have followed with similar ideas, adding anti-static coatings into the mix, Nikon being the exception to date with respect to vibration cleaning, it is still accepted that the Olympus system works better than any other.

The latest development to arrive has also been originated by Olympus, live view, using the rear LCD digicam style to view a shot before taking. While slower to use than an optical viewfinder and using a considerable amount of power, it is nonetheless useful for those engaged in studio work and other situations where looking through the viewfinder becomes difficult or awkward. Again Olympus's latest DSLR, the pro spec E3, is best placed to take advantage of this option, having a twist and flip rear LCD, which few other live view enabled DSLR's have at present but are certain to adopt in the future.

Like the EVF viewfinders fitted to many digicams these additional specifications are welcome and useful but have a large impact on battery life, the extra power drain being considerable.