Back to Basics
Part 1 – Taking your camera off auto
The aim of these workshops is to enable you to produce digital data that will allow you to get good quality A3 size prints. If you can do this then any projected digital images will also be of good quality.
1. The camera
There are three common types of digital camera; compact, bridge and DLSR. They differ in two major ways. The first is sensor size (not to be confused with pixel number) and the second is in operation.
Most compact and bridge cameras have a very small sensor (about 7mm x 5mm) and DLSRs have bigger sensors (about 22mm x 15mm for “crop sensor” cameras and 36mm x 24mm for “full frame” cameras) In general, bigger sensors give better quality although it is the actual pixel size that is important.
The major effect of small sensor size is seen at higher sensor sensitivity settings (the ISO setting, we will look at this later) where the picture will show more digital noise, less detail and poorer colours.
Pixel number is the most common selling point for cameras. This is not actually very important for pixel number above about 8Mp (8 million pixels).
Questions – How big is your sensor? How many pixels?
The operation of compact, bridge and DSLR cameras are fundamentally different. The major differences are how you hold the camera and how you see what you are photographing.
Most compact cameras do not have an optical viewfinder. Therefore you have to look at the screen on the back of the camera to see what you are photographing. Generally this means holding the camera at arms length. This can lead to several problems. Firstly, it is almost impossible to hold the camera steady, especially at longer lens zoom settings and in low light when a slower shutter speed will be set. Secondly you will not be able to see the screen very well outdoors in daylight. Thirdly, seeing the screen is difficult for anyone wearing glasses. Camera settings can help reduce these problems and we will look at those later on.
Bridge cameras have electronic viewfinders. These are improving, but at present give a fairly poor view of your intended photograph (they can be noisy, low resolution, burn out in highlights, have low refresh rates). They cannot really be used to check focus.
DLSR cameras have optical viewfinders that give a view through the lens you are using. They do not always show the exact framing but usually show above 95% view. Viewfinders on full frame cameras tend to be brighter although the more modern crop sensor cameras also have excellent viewfinders. There is usually a host of information displayed in the viewfinder giving details of the camera settings. DLSR cameras also allow you to change lenses. The lenses tend to be of better optical quality than on bridge or compact cameras. The downside is that they can be heavy and cumbersome to carry around. Most of the problems associated with bridge or compact camera lenses ( vignetting, distortion, chromatic aberration) can be corrected in post-processing. This will be covered in Part 3.
Questions – How do you hold your camera? Can you see what you are photographing?
2. Camera Settings
There are two main settings to consider; RAW vs jpeg and in-camera processing.
The sensor collects light passing through the lens and the in-camera processor converts this to digital information that makes up a picture we can see. You can control how much processing the camera does. Why would you want to do this?
Most compact cameras are set up to give the “best-looking” results straight from the camera. This is so they can be viewed on a computer, sent on via e-mail or printed out immediately. There is no problem with this if that is all you want to do. However, our aim is to produce good quality A3 prints and in-camera processing can throw away a lot of useful digital information.
You can switch off all in-camera processing by using a RAW setting. Very few compact cameras have this setting, but most bridge and all DLSR cameras do. The problem with RAW information is that it has to be post-processed to produce a picture (covered in Part 3). The advantage of RAW is that more digital information can be retained and used.
It is quite possible to produce good quality A3 prints using jpeg settings. Jpeg settings are a clever way of reducing the size of a digital picture file without reducing the viewing quality. The advantage is that more pictures can be fitted onto the camera memory card and into computer memory for storage. The downside is that you can be throwing away quality and since computer memory is less expensive than it was, it is perhaps better to try to retain quality over space.
Most cameras will have a range of jpeg settings. There are two variables, jpeg quality and jpeg size. They are all about the balance between quality and space. For our aim of producing good quality A3 prints you will want to set the jpeg settings to the largest size and highest quality. This is usually called something like “Large Superfine”. The digital files will still be much smaller than RAW files.
Questions – Can you use RAW? How do you change your jpeg settings?
Let’s consider the other in-camera processing. This section does not concern RAW files, because these are not processed in-camera.
You will access these settings through your camera menu. The first thing to note is that the range of settings may vary depending on what mode your camera is in. The modes are usually set by a dial on top of the camera and will have settings like P, Tv, Av and M etc. We will cover these later. In-camera processing may allow you to change colours, contrast and sharpness. I suggest that you set these to change as little as possible, but note that you will then have to do more post-processing in the computer to get optimum results.
On the Canon G10, you can only change the in-camera colour settings. The camera still carries out in-camera sharpening, tone curve adjustments and noise reduction, but you have no control over those. This doesn’t mean that results are poor, just that you have to use the manufacturer’s idea of optimum settings.
Questions – How do you change in-camera processing? What settings can you change?
The other setting that is commonly available is the overall colour setting, usually called white balance. This will also affect RAW files, but for these, the settings can be changed easily and accurately in post-processing. Think about the white balance as though you are putting a coloured filter in front of the lens. What you are doing is trying to tell the camera what white should look like in you final photo. You can set Auto White Balance and the camera will work out what it thinks is white. For most cases this is fine, but if you have a strong overall colour in your picture that you wish to appear in your final photo (such as an orange glow at sunrise or sunset), then Auto White Balance will not work, because it will try to neutralise the overall colour shift. There are other White Balance settings. These settings will just apply the “colour filter” that you want to apply and will not try to second guess the colours. The different white balance settings are just like different “colour filters” so a cloudy setting will apply more yellow to try to get bluish shadows back to white.
Why is white balance important? You cannot post-process to remove overall colour shifts on jpegs accurately. You will get some crossover between the three colour channels (this is usually a small effect). Occasionally you can use a white balance setting to unsaturate a particular colour in order to retain more detail. Say you are photographing a bright blue flower and the blue channel is saturated then you will lose detail in the blue petals. You can drop the overall exposure, but this may make the picture dark or you can choose a white balance that will reduce the blue (maybe the cloudy setting or maybe use a custom white balance setting). You will need to be able to see the colour channel histograms to gauge the setting.
Questions – How do you change white balance? What do you want to set it to?
3. Picture Settings
Now let’s get around to actually taking pictures! In our aim to produce good quality A3 prints, there are two technical aspects that you must get right. The first of these is exposure and the second is sharpness. Picture content and style is something we cover in Part 2.
To get exposure correct, you must consider shutter speed, lens aperture and ISO setting. You can get the same exposure with different combinations of these. To increase exposure you can set a lower aperture, a slower shutter speed or a higher ISO. So why don’t you set the lowest aperture, the lowest shutter speed and the highest ISO for all photos? Obviously there are consequences with your choice.
The aperture controls both the amount of light passing through the lens and also the amount of your picture that is in sharp focus. The lower the aperture, the less there is in focus. This is not so much of a problem with small sensor cameras but, conversely, small sensors make it difficult to use differential focus where you want to have one part of your picture in focus and other parts out of focus.
The shutter speed controls how long the sensor collects data for. This limits the amount of movement you can see in your picture. You may want to show movement (e.g. when panning motorcycles), but generally you will want to eliminate movement and you will need to set a fast shutter speed. This will remove both subject movement (e.g. flowers blowing in the wind) and camera shake, which is caused by not holding the camera still enough. Camera shake is a major cause of quality loss in compact cameras. Some cameras have special settings (e.g. image stabilisation) to help you take photos at slower shutter speeds, but I suggest that you cannot rely on them.
The ISO setting changes the sensitivity of the sensor. Unfortunately, the sensor collects both the digital information that you want and also produces digital noise, which you don’t. Both of these increase with higher ISO settings. To get the best quality you will need to set the lowest ISO setting. In practice, modern DSLR cameras will obtain excellent, noise free quality up to 1600ISO. Compact cameras are limited to 100ISO for reasonable quality.
Question – How do you know what aperture, shutter speed and ISO your camera is set to?
So you can use different combinations of aperture, shutter speed and ISO to get the same amount of digital data, but this doesn’t mean that the exposure is correct. A correct exposure will have details in the highlights, details in the shadows and a smooth tonal range between. To get the correct exposure with film cameras, you had to build up lots of experience, know your film and maybe bracket exposures. This is still valuable advice today, apart from the bit about film of course! However, we have extra help with digital cameras in the form of the histogram. This shows the range of brightness you are trying to photograph. It will show if the general exposure is correct and will also show whether you have details in the highlights and details in the shadows. However, histograms are notoriously difficult to see on the camera screen in daylight, but I can’t emphasise enough how important the histogram is, until you have built up experience of your camera.
The histogram will show a correct exposure when the peak is somewhere around the middle and the left and right tails are contained within the max and min exposure range. Sometimes, even indoors, it is difficult to spot burnt out highlights. In is possible to set some cameras to show these clipped highlights on the screen (by flashing).
Question – how do you see your histogram?
So what do you do if the histogram is not ideal? If the histogram is too far right or too far left then you need to change the exposure. If the highlights are burnt out you need to decide if you need to drop the exposure (a few specular highlights may be unavoidable). If the shadows are blocked up, then you can increase the exposure unless this means that the highlights will then burn out. In that case you will have to resort to other methods to increase exposure in the shadows (e.g. fill-in flash, graduated filters).
So what do you do if the histogram shows that the exposure is not ideal. This is where we first have to talk about camera modes. These are the settings called A, P, Tv, Av and M, usually on a dial on the top of the camera. These modes control the combination of aperture, shutter speed and ISO. The camera has a built in light meter and will know how much light to let through to the sensor. Knowing how to use the light meter in you camera will be covered in part 2. If you set the mode to A (auto) then the camera will set aperture, shutter speed and ISO. If you set the camera to P (program), Tv (shutter priority) or Av (aperture priority), the camera will set the combination of aperture and shutter speed. As the light varies, the P mode will change both aperture and shutter speed to keep the correct exposure, the Av and Tv modes will change the shutter speed only or the aperture only respectively. The M (manual) mode allows you to choose both the aperture and shutter speed, but if you choose the wrong combination, then the exposure will be wrong.
Question – How do you know what aperture, shutter speed and ISO you are using?
The camera modes will allow you to control the combination of aperture, shutter speed and ISO but, so far, you have not changed the exposure. This is where exposure compensation comes in. There should be a setting which allows you to offset the exposure from the camera light meter value. If the histogram shows that the exposure is too high, then you can dial in some negative exposure compensation and retake the photo.
Question – How do I set exposure compensation?
Now let’s move away from exposure and talk about focussing. All cameras will have an auto-focus system built in and, if you have a compact camera or a bridge camera, then you will generally have to rely on the auto-focus being correct. These auto-focus systems have become more and more sophisticated recently (e.g. with face detect), but you must understand what rules the system uses so that you will recognise when it may struggle. The most common problem is taking a picture with the main close up subject off-centre and the camera focussing on the background instead. To avoid this, most cameras allow you to point at your main subject, half press the shutter (to lock the focus) and then recompose your picture before pressing the shutter fully.
Question – Can I use focus lock?
With DSLRs, the viewfinder is usually clear enough to allow you to see what is in focus or not. The view through the aperture is at the lowest aperture setting and so to see the real effect, you must press the pre-view button. This may make the viewfinder too dark to see clearly and is probably of limited value. The modern auto-focus systems are also getting more complicated by allowing you to choose the focus point or by choosing focus following on a moving subject. These settings will be covered in Part 2.
This ends Part 1 where we have covered the basic camera controls. Part 2 will cover picture taking in more detail, both getting the exposure and focus as you want them and also covering some aspects of composition. Part 3 will cover post-processing in the computer.