Some cameras incorporate a light or infra red beam to assist the autofocus system, other cameras use the ‘pop-up’ flash for assistance.
Aperture ( f number)
The aperture on a camera lens allows more or less light to fall on the sensor, commonly known as ‘ f ‘ numbers, the larger the ‘ f ‘ number the smaller the ‘aperture’ (lens opening). A smaller lens opening (large ‘f’ number) has the effect of giving the image more depth in terms of sharpness, which is important in macro photography.
When a camera is set on ‘aperture priority’ it enables the user to set the aperture to the best setting for the image being taken, in the case of intra oral images this would be the largest number i.e. smallest lens opening or aperture. ‘Aperture Priority’ would be the setting of choice for Digital Compact Cameras.
In this mode the camera sets everything for you, all you need to do is press the shutter. This is not a good setting for intra oral in particular.
Auto White Balance
Different types of light have different colour temperatures, the eye tends to compensate for this so we are seeing ‘natural’ colours in most lighting conditions. When you set your camera to Auto White Balance the camera automatically adjusts the white balance to match the true colour of the subject.
Many cameras have the facility to ‘bracket’ either exposure and/or white balance, this means the camera will produce 3 images at slightly differing exposure or white balance settings, for you to choose the best.
Custom settings allow you to set frequently used settings to memory and use those settings whenever necessary. Cameras usually have at least 1 custom setting, some have 2 or 3.
Digital zoom extends the ‘Optical zoom’ range of the camera by zooming in electronically on the image. These images can be pixelated (individual pixels can be detected in the image). Because the camera is enlarging the centre of the image, just like enlarging a 35mm picture the user will get a ‘grainy’ result. Images can be cropped on the computer to achieve the same effect.
Sometimes referred to as a speedlight, this is usually your main source of light for dental photography. Some cameras allow you to vary the light output of the flash.
On all Digital SLRs and many compact cameras the area where the camera focuses can be set, cameras will default to the centre setting, but for intra oral, mirror shots in particular it is useful to be able to dictate where the camera focuses.
Most digital cameras have many more functions than any 35mm equivalent ever had. Functions are the cameras capability to perform tasks and generally make photography easier for the user i.e. Auto White Balance
This is the fitting often found on top of many cameras, it’s primary use is for attaching additional flashguns or power packs for accessories such as ringflash.
35mm film was graded in ‘sensitivity’, as in Kodak Gold 200 and Kodak Gold 400. The 200(ISO) was a better quality (definition) film than the 400 but less sensitive to light, so if you were off on holiday to sunny destinations the 200(ISO) would be good, whereas if you were wanting to take interior shots without using flash 400 would be better.
Joint Photographic Experts Group, the most popular and widely use image file format. It is called a ‘lossy’ compression file but does the compression of files very well. Settings of choice on many cameras would be the highest jpeg setting available, often designated as superfine or fine. Once the image is loaded onto your PC each time it is opened and SAVED, the image is recompressed which will degrade the image, ALWAYS MAKE A COPY TO WORK WITH!
This mode will naturally assume you are taking a landscape, often focus is set on ‘infinity’ and aperture is quite often a small number i.e. larger lens opening. Focus and aperture are set this way because the subject is a distant shot , and also little depth of focus is required.
Officially macro refers to life size or 1:1 images, macro in real terms refers to close up photography, majority of digital compact cameras have a macro setting. For taking intra oral images it is essential that a camera is able to take ‘close up’ images. The common icon to depict the macro setting is the ‘tulip’. Some cameras will have a macro mode as well as a ‘tulip’ setting, this is not a good idea to use as it often disables the flash and endeavours to get as close as possible to the subject to achieve maximum magnification. This is explained more on the techniques pages.
Cameras with manual control give you the ability to override camera auto or programme settings, for most applications in Dentistry this is essential to get good consistent results.
This refers to the number of pixels a camera uses to produce it’s images, the more pixels the better resolution an image should have.
As with mobile phones the quality of these movies are improving, though if you want to make a movie buy a video camera, if you want high quality stills..buy a still camera. Some cameras now have the ability to record in HD…well worth looking at.
Night Scene Mode
With this setting the camera uses the flash but also uses a slow shutter speed, this has the effect of lighting the main subject, say a friend and then the slower shutter speed also records the surrounding area thus giving a more balanced exposure i.e. not too dark or too light. As a slow shutter speed is used you will need to ask your subject to keep still and also may need some support for the camera to stop shake.
Unlike ‘digital zoom’ this moves the lens elements to zoom in on the subject with little loss of detail.
With this setting the camera will choose a large aperture i.e. small number, to render the background out of focus, thus often giving a pleasing effect.
This mode sets everything for you but does allow some degree of ‘tweakin’ by the user, unlike ‘Auto Mode’which doesn’t give any user adjustable options.
Picture quality setting on cameras usually refer to the jpeg cmpression settings, such as Superfine, Fine, Normal (Canon PowerShot G6). This setting should not be confused with ‘Resolution’.
RAW doesn’t actually stand for anything other than it is the raw image data that is recorded and saved. Unlike jpeg any processing is applied post photography, whereas jpegs are processed at the time of photography
Resolution is measured in Megapixels, this setting on your camera should be set to it’s highest! Why pay for 10 Megapixels and then set your camera to use only 5 or less?
This is rated as an ISO setting, details of which can be found in this glossary under ISO
If taking photographs without the use of flash, the shuutter speed setting is critical if you are to avoid camera shake. Shutter priority can be used when photographing x-rays.An x-ray is flat and requires little depth of focus, but because you are not using flash the camera needs to either be on a tripod or set to a shutter speed that will not invoke ‘camera shake’, hand held photography is difficult for most at speeds below 1/60th second.
This mode aids the taking of Panoramic images by shooting overlapping frames.
TIFF(Tagged Image File Format)
This is a file format option that was available on many of the earlier cameras, it tends not to appear on the newer models. Unlike JPeg, a TIFF file is uncompressed and therfore by definition produces a higher quality image. The file fomat still has it’s uses though, if you have edited a jpeg in Photoshop, an option to retain the quality and not recompress the image on saving, would be to save as a TIFF. TIFF files are generally very large.
Setting white balance on your camera alters the colours of your image. Most of the time ‘Auto White Balance’ works well. If you are howevre getting inconsistent results in terms of colour rendition when using flash for intra oral images, a change to ‘speedlight’ balance often helps.