Using Digital cameras – what do we need to know?
The most common sort of digital camera is the ‘point and shoot’ automatic type. Who can blame people for spending less than £100 to get an 8 mega pixel camera which takes nice pictures, automatically. Why would you want to spend £500 on a Canon/Nikon with the same number of mega pixels?
One reason is that the higher priced cameras allow you to buy extra lenses – telephoto or wide angle – and another is you get more control over the features of the camera – the dials settings and programmes.
For a standard landscape photo, you may not be able to tell which camera has taken it, but with other photos – close-up, low light, action photos etc – you will.
Having an expensive camera doesn’t guarantee good photos. All camera users can take better pictures if they practice with the camera and the settings
The best way to understand the use of the features of a camera is to give users various tasks [take pictures] which use those features, and then view and compare the results.
Some features are dependent on the settings of the camera. This may demand a reading of the camera manual! Even simple cameras have settings.
ISO settings – this relates to what was called film speed [ASA /DIN]. The human eye is incredibly sensitive to light levels though we are not too good in seeing in the dark. Film / Camera chips are not so sensitive and have to be manually set to bright or dark settings.
With film, highest quality pictures were obtained with slow speed film in bright conditions [100 ISO]. For action pictures [fast shutter speeds] or low light conditions we used fast film [400 ISO] but the quality suffered [grain].
Digital cameras have some kind of setting for ‘film speed’. Often it is done automatically, and they may expect you to make improvements to poor picture quality with Photoshop skills. Other cameras a have some kind of quality or speed setting – find it and use it once you have anticipated the lighting conditions/ action you are facing.
File size and frame size, mega-pixel choice – this controls the size and quality of each frame. If you want to print high quality pictures, you need to choose the biggest frame size and quality. If you do this you won’t be able to store so many pictures on your memory card. If you want pictures to be used in a computer application, shown on a laptop or projected with a multimedia projector, you need to choose smaller lower quality frames.
My 3.2 mp Canon Powershot offers me:
Picture size: pixels
2048 x 1536 [=3.15 million] – I am told I can get 24 pictures on the memory card
1600 x 1200 [=1.9million], and get 39 pictures
1024 x 768 [=0.78million], and get 69 pictures
640 x 480 [=.3 million], and get 155 pictures
I am also offered Superfine quality [155 pictures] , fine [ 253 pictures] or normal [436 pictures].
So what do you choose?
- If you want prints of highest quality/size, go for big pictures and highest quality – get a bigger memory card as you won’t get many pictures if they are this big.
- If you want to put pictures on the internet, or a small digital photo frame you need small pictures. You can also choose lower quality since the average computer screen has poor image resolution.
- If you use ‘digital zoom’ rather than the optical zoom, choose a higher quality setting than normal. Digital zoom is a cheat – it zooms in on the picture electronically. Don’t use it on low size/quality settings.
- If you want to take pictures at night, in low light or of fast action subjects, try to choose a fast [high] ISO setting if offered.
Simple cameras all record in a JPEG format – the most common format. Specialist cameras may ask you to make decisions about other formats – TIFFs and RAW etc.
These other specialist formats record more information in the picture and therefore a higher quality. Note – these files will use more memory space on your flash card.
[A note about memory cards – you should already know that they differ in their size which equates to the number of pictures they store. They also differ in the speed at which they store images – once you have pressed the shutter button – and users with fancy cameras taking high quality images will notice that they may have to wait several seconds before they are able to take another picture. These users need to get a memory card which has faster processing time – yes, they cost more].
Black and white / colour / enhanced colour – If you use Photoshop, you can convert your pictures to B&W or enhance them after taking them. If you know what you want [eg. B&W] you can choose this in advance [and save on memory space].
Programmes –
AUTO – this is the default setting. The camera makes a decision to set the camera to take the best picture it can. It will not be the ‘best’ if your pictures are taken in low light conditions or you are taking fast action subjects.
Aperture priority – this controls the aperture – which is the amount of light passing through the lens – it tries to give you as much light as possible. In dull conditions, you may want the shutter to open longer so that more light can pass through onto the chip, and therefore take better pictures in dull light. The problem is that a longer shutter speed leads to more camera shake – blurred pictures – and the need to use a tripod.
Shutter priority – this controls the speed of the shutter and tries to give you the fastest speed possible. This makes pictures of moving objects sharper. The problem with this is that you need a bigger aperture to get enough light. This option is easy on a bright day but not easy in dull light.
Your choice of programme / setting may effect the Depth of field – the amount of your picture which will be in focus, relative to distance from the camera. Wide apertures give smaller depth of field so accurate focusing will have to be more critical. Smaller apertures give greater depth of field.
Autofocus?
By default all digital cameras are set for autofocus, and if you want manual focusing you’ll have to select that [why would you want to?]. There are different kinds of focusing.
CAF – constant autofocus – with this on, your batteries will always be driving the focusing motor as it constantly re-adjusts the focus. It reads the focus of the area within the indicated area/s in the viewfinder. You will constantly be hearing the focus motor drive working every time you move the camera.
S-AF – this will adjust the focus only when you press the shutter button lightly. This uses up your battery power less.
Manual focus – you twist the lens, or press buttons yourself and view the effect in the viewfinder.
Macro focus – this is for close ups. The icon is a tulip. A normal lens cannot focus very close to an object. Macro does something to make this possible. Read your manual to find how close you can focus. Technically you may be able to press buttons to adjust the macro zoom. Usually you focus by moving the lens/camera closer/further to the object. If you have a big bright viewfinder you will be able to see when the object is in focus. You will not have much depth of field in macro – you may have to decide which part of the object you want in/out of focus.
A note about focus – depending on your camera. Automatic focusing does not always result in the correct part of your picture being sharp [in focus]. Generally speaking the camera selects the centre of the viewfinder for focus measurements, but what if your subject is not in the centre? Usually you can half press the shutter and the camera takes a reading – but not yet a picture – and then you move the camera lens to adjust the position of the subject. This trick works with focus and exposure values, and is extremely useful.
Exposure values
Exposure is about getting the right amount of light onto the camera film/chip to give a perfect picture. People’s faces will not be too bright or too light. Some cameras claim to detect faces and measure their correct exposure, more than any other part of the picture.
Correct exposure results from a combination of shutter speed and aperture settings.
· Slow shutter / small aperture
· Fast shutter / large aperture
· Medium shutter / medium aperture.
Exposure is measured, and then the shutter speed and aperture are calculated and set to give a perfectly exposed picture – not too light or dark.
The camera measures the light values at various places in the viewfinder and sets shutter/aperture values appropriately. You need to know where these areas of the viewfinder are, so that you can ensure the important parts of the picture are correctly measured and exposed [ eg. Faces of people].
Usually, with most cameras, you can hold the shutter button down lightly so that the exposure values are measured in one part of the scene, and then move the camera lens to point at the general scene. Press the shutter button further to take the picture.
Some cameras have ‘spot’ readings – an exposure reading at one specific spot in the centre of the lens. Some cameras have average readings, either taking various spot values and averaging them, or just taking a general/average value for the whole screen.
Bracketting – is the taking of several pictures at different exposure values to ensure that one of the pictures will be perfect. Typically bracketing takes 3 pictures – one too bright, one correct, and one too dark [called stops - +/-].
Zooming – digital cameras have 2 kinds of zoom. The first is based on optical zooming – the lenses move in and out to bring the action closer. The second is a kind of cheat – it’s called digital zooming and often starts when the optical zoom ends. It’s an electronic/digital zooming into the image on the chip. It loses quality [dependent on the quality of the chip].
Flash – flash is used to enhance dark picture environments.
Fill-in flash is used when it may not be strictly necessary but will fill in some of the shadows – that’s why it’s sometimes used on sunny days.
Red-eye is the result of flash bouncing back off the blood vessels in the rear of the eye. Clever flash gives several flashes – the first makes the iris constrict, so that the second [main] flash does not result in red-eye.
Auto flash – by default the flash comes on when the camera thinks it necessary.
Get your students to take these photos to see the effect of these settings on your camera. Take a notebook and try to record the camera settings for each picture. Print or view each of the photos to see the effects.
My advice is that you set the camera on a tripod wherever possible so that when comparing sets of photos [with differing exposure settings] you are eliminating other variables in your composition. If you are trying to concentrate on studying technical variables and their effect on photos, don’t worry about trying to take ‘pretty’ or nicely composed pictures.
Focus and depth of field:
· any view where most of the distant scene is in focus, eg. landscape
· a view where a nearby object [person?] is in focus in the centre of the picture but the main background is out of focus. Use lens fully zoomed [telephoto].
· a view where a nearby object [person?] is in focus at the edge of the picture but the main background is out of focus. Use lens fully zoomed.
· as 2&3 above – but with the lens zoomed in [ie. Wide angle].
· Depth of field – set up a scene where some objects in the field of view are at different distances from the lens [something close-up, middle distance and at infinity]. Take pictures with different stages of zooming. Take pictures at varying exposure values [especially aperture – small, medium, wide]. It may help to make a note of any settings when you take these pictures. You may have to use manual settings to control the aperture. Some cameras record these settings when they take the picture.
· Macro – take various pictures of a small flower bud using the macro function. This is often the tulip icon. You may have to focus by moving the camera towards/away from the subject until it looks sharp. Investigate how close you can get without the macro, on wide angle. Then zoom out/full and see how far away you need to be to get a sharp picture.
Exposure:
· take an ordinary scene where everything is at the correct exposure [as measured by your camera automatically]
· take a picture with bracketed exposure – minus 1 stop, plus one stop. Some advanced cameras have a button which automatically makes the camera take 3 pictures. With a simpler camera, if you have a manual control you may be able to take a darker and lighter version of your picture.
· take a picture of a person with a dark face/dark clothing standing in front of a light background. Don’t be too close to the person as we want a big light background. With a simple camera, just take a picture with auto exposure. Depending on the exposure system on your camera you might also be able to concentrate the exposure calculation on just the person, rather than an average of the whole frame.
· take a picture of a person with a light face/light clothing standing in front of a dark background. Don’t be too close to the person as we want a big dark background. With a simple camera, just take a picture with auto exposure. Depending on the exposure system on your camera you might also be able to concentrate the exposure calculation on just the person, rather than an average of the whole frame.
Programmes:
· Aperture priority – take a picture when it’s getting a little dark, or indoors – without using the flash. Take one hand-held, and one on a tripod. You may want to try these pictures with different ISO settings to see the differences.
· Shutter priority – take a picture of a moving object crossing your path. Take one with the camera stationary, and another with the camera tracking the moving object. You may want to try these pictures with different ISO settings to see the differences.
· Manual settings – put your camera on a tripod and try a photo in near dark conditions [in bright moonlight, or bright lights of the city]. Set the manual exposure to a 15 second exposure [most family cameras can do this]. Some cameras have further time settings [it used to be the B button] and you may then need a cable release.
99% of all ordinary photos can successfully be taken on Automatic settings. Camera technology has developed sufficiently for the electronic part of the camera to calculate the best setting, so why do we need other controls?
- If I want to take a photo with the foreground and background both in focus [ie great depth of field] the Automatic setting will not know thisis what I want. I will have to use Aperture preference to select a small aperture [ie great depth of field].
- If I want to take a photo of a horse rider jumping over a fence, I will have to use Shutter preferences to select a fast shutter speed as the Automatic setting will not know this is what I want.
The pragmatic way of taking photos, noting their exposure details and then assessing the results, is the tried and tested way of learning how to take better pictures in the future.
Every camera works on the same principles but you have to tune in to the idiosyncrasies of each individual camera.
Of course, you may get technically perfect photos but they are still rubbish – that’s all about composition, colour, subject matter etc!
