This is the third in a series of articles dealing with the subject of digital photography of scale models. This article will cover some of the technical aspects that need to be understood in order to achieve the best results.
Photography is a subject that is very technical in nature. There is a vast amount of highly specialised equipment available and potentially many factors to take into account in getting the perfect photograph. Entire books have been written about the technical side of photography with chapters about filters, lighting, lenses etc.
Fortunately, for the vast majority of modellers the subject can be simplified. If you are trying to win an international photography competition then you are reading the wrong article. However, if you are a modeller who is simply trying to get reasonably good photographs of your work then there are just a few technical matters that you need to be aware of and these are described below.
If you wish to find out about other technical terms related to photography then a good place to start is the Glossary provided by the Digital Photography Review website .
1. White Balance
White balance concerns trying to capture the true colour of objects in photography. To understand white balance it is necessary to know why objects look the colour that they do and what is meant by an object’s ‘true’ colour.
What is white light?
For all practical purposes, all natural light comes from our sun. Even moonlight is simply sunlight reflected. The light that we see with the human eye is called the visible part of the electromagnetic spectrum and it is a mixture of all the colours of the rainbow.
Normally all the colours in the visible part of the spectrum are mixed together to give us normal sunlight which is known as white light. When you see a rainbow you are witnessing sunlight passing through rain drops and being split up into it’s different colours – red, orange, yellow, green, blue, indigo and violet.
White light can also be split into it’s component colours by passing it through a prism – a piece of glass or transparent plastic cut in a specific shape. Sometimes when white light passes through glass or water you may see a similar effect, at least in part.
The important thing to remember from all this is that sunlight is actually a mixture of different colours that only appears white when they are all mixed together.
Why do things look the colour they do?
Why does grass look green, why does coal look black? The human eye sees light reflected from objects. When sunlight (white light) falls on any object some of that light is absorbed and some of it is reflected depending on the surface of the object. Grass looks green because it absorbs all the colours of the rainbow except for green which it reflects back into your eye. An object that looks white is absorbing very little of the visible spectrum and is reflecting all of the colours. An object that is black is absorbing almost all of the colours, so very little light is reflected back into the eye. Thus white objects appear brighter than black objects because they are refecting a greater proportion of the light that falls on them.
It is worth noting that in nature very few objects are truly black since almost all objects will reflect some light. You may think of a rubber car tyre as black, but if you put something that is really black against a tyre and you will find that it is really dark grey.
Colour changes with the type of light
Having established that objects appear different colours depending on the light they reflect, it is easy to understand that if the colour of the light changes, then the reflected colour from objects will also change.
Most artificial light is is a different colour to sunlight, so objects viewed in artificial light will appear to be a different colour.
The colour of light is measured in units of Kelvin. The lower the value, the more the light tends towards orange. The higher the value the more the light tends towards blue. Sunlight is about 5500K, whereas a fluorescent bulb is only about 4200k and a traditional filament/incandescent light bulb is only about 3000K. Therefore, it can be seen that most artificial lights will cast an orange/yellow light and thus the colours of objects viewed under artificial light will tend towards yellow and orange.
The situation is even more complicated because even daylight can vary. For example clouds will filter out certain wavelengths of light so objects will appear slightly different colours on a cloudy day. A cloudy day will have a colour temperature of about 7000 Kelvin and will give objects a blue tinge.
Most good cameras will have an automatic white balance adjustment. This attempts to adjust the colours depending on the type of light and sometimes it works quite well. Of course the camera will not know whether the light is produced by sunlight, artificial light, or if the sky is cloudy, so sometimes the automatic white balance adjustment will not work well and some objects may not appear to be their true colour in photographs. You will be able to see the colour of objects in your photograph by using the LCD screen. If the colours look correct then you need to take no further action, but if the colours are not right – normally with a yellow/orange tinge to them, then you will have to over-ride the automatic white balance function.
Most good cameras will allow the user to over-ride the automatic white balance setting and choose a setting manually to match the type of light. The camera will probably have settings labelled something like ‘Cloudy day’; ‘Fluorescent Light’, ‘Incandescent light’ etc. Do not take too much notice of these labels. Simply work through each of the settings and look at the effect on the colours on the camera’s LCD screen and select the setting that give the most accurate colours.
It is possible to adjust the white balance after taking the photograph by using image editing software on a computer, but generally it is best to get it right when taking the photograph.
Important facts about white balance:
- Objects appear different colours in different types of light;
- If objects do not appear their true colours on the camera’s LCD screen, then change the ‘White Balance’ setting on your camera until the colours look right.
The aperture of a camera is the hole that lets in the light. Just like the human eye, the size of a camera’s aperture can be changed to let in more or less light. Letting in just the right amount of light is important to avoid the photograph being over-exposed, or under-exposed. However, the aperture is not the only factor here as shutter speed and sensitivity will also affect the amount of exposure. The aperture also affects the Depth of Field.
The aperture of a camera is measured as a fraction of the focal length of the lens. These numbers are generally known as ‘f-stop’ numbers and confusingly the lower the ‘f’ number the wider the aperture and the more light is let in.
A camera’s aperture cannot be made wider or smaller in a continuous motion, but in a series of distinct steps. Each step halves or doubles the amount of light that is let in. A typical digital camera will have a widest aperture of f/2.8 and a smallest aperture of f/8.
Most cameras will automatically adjust the aperture, shutter speed and other factors to get the best picture. However, when taking photos of scale models it may be necessary to over-ride the automatic settings and reduce the size of the aperture (increase the f stop) in order to improve the depth of field. This is why it is very useful to have an ‘Aperture Priority’ setting on your camera to manually reduce the aperture size below what the camera would automatically set.
Important Facts About Aperture
- The wider the aperture the more light is let in and the lower the f-stop number.
- A smaller aperture requires a slower shutter speed (bad) but gives a bigger depth of field (good)
3. Depth Of Field
Depth of Field (DoF) is not something that generally concerns many amateur photographers, but it is a critical factor when taking pictures of scale models.
It is normal to think of a photograph as being either in focus (sharp) or out of focus (blurred), but the situation is not so simple. In any photograph, only one exact distance from the camera will be precisely in focus. This distance is known as the ‘focus point’. Everything in front and behind the focus point will be out of focus and the further away from the focus point it is, then the more it will be out of focus.
Fortunately, an object can be a little bit out of focus (blurred) without it being noticable. The DoF is the distance before and after the focal point where the focus is acceptable i.e. where the picture appears reasonably sharp.
Factors affecting the DoF are:
- aperture – larger aperture equals smaller DoF
- distance to subject – shorter distance equals smaller DoF
- focal length of lens – longer focal length equals smaller DoF
- sensor format and size
When taking a normal photograph the DoF is not an issue. For example, when taking a picture of distant mountains the DoF will be huge and almost everything in the photo will appear to be in focus. If you put your finger right in front of the lens it will be badly out of focus, but everything else from a couple of meters to infinity will be good and sharp. This is because DoF increases with the distance to the subject. In other words, when taking pictures of distant objects the DoF will be large and almost everything will appear in focus.
Unfortunately, when taking pictures of close objects the DoF becomes increasingly small and only a small part of the subject will be in focus. This is a particular concern when taking pictures of scale models because the subject may only be a few centimeters from the camera so the DoF will be very small indeed.
Example photos showing the effects of depth of field
How Depth Of Field Affects Model Photography
The following example will illustrate the effect. Let us say that you wish to take a photo of a warship, which has a long thin shape. When taking a photo from the side (profile) the DoF will not be a problem. In order to get the entire length of the ship in frame you will need to keep some distance between the camera and the ship so the DoF will be fairly good. Furthermore, because the ship is side on the entire ship is a similar distance from the camera and so will all be in focus. The diagram on the right illustrates this.
However, if you want to take a picture from the front of the ship then DoF becomes a big problem. The front of the ship will be very close to the camera, but the rear of the ship will be much farther away. If you focus on the front then most of the rest of the ship will be out of focus with the rear being very blurred. If you focus on the centre of the ship then both the front and rear will be out of focus. You will find it almost impossible to get more than a small section of the ship in focus. Again the diagram on the right illustrates the problem.
At this point it is worth noting that it is not always desirable to have everything in a photograph in focus. For example, portrait photographers sometimes deliberately reduce the DoF so that the person in the photograph is in focus, but the background is blurred. The human eye will naturally be drawn to the part of the photograph that is in focus. When taking photos of scale models you can emphasise a particular part of the model by making sure that the critical part is in perfect focus whilst the rest of the model is slightly blurred. However, most of the time we will want as much of the photo in focus as possible, so normally every effort is made to maximise the DoF.
How to maximise the Depth of Field
1. Move the camera as far away from the subject as possible. If your camera has a high resolution, say, 8 million pixels or more, then you may be able to take a photo of your model with the model taking up only a small part of the photo, but crop the excess away by editing the photo later. A camera with a 9 million pixel resolution will produce photos that are 3456 by 2592 pixels, but for posting on the internet you will probably only need photos that are 1024 x 768 pixels so you can afford to cut away or crop quite a lot of the photo.
2. Reduce the size of the aperture. Over-ride the automatic aperture setting of your camera and choose the ‘Aperture Priority’ mode, then reduce the aperture to as small as possible (F8 on many digital cameras). The disadvantage with this is that less light will enter the camera so the shutter speed will need to be reduced to let in more light (your camera will probably do this automatically). With a slow shutter speed any camera shake will be apparent which is why it is necessary to use the camera on a tripod and set it off with either a remote control or by using the timer facility. Be aware that increasing the amount of light falling on your model can also compensate for a small aperture.
It is worth noting that aperture settings are very different between digital and traditional ‘film’ cameras. Traditional cameras may have apertures that can be reduced to f/20 or higher, but most digital cameras only allow the aperture to be reduced to f/8. However, due to other factors, an aperture of f/8 on a digital camera will give the same DoF as a much higher setting on a traditional camera.
There is a very useful calculator on the Internet that shows the effect of changing the aperture and subject distance with particular cameras and this can be found at www.dofmaster.com .
4. File Formats
Digital picture files can be created in a mind boggling number of formats. Each of these formats has different characteristics. For example, some file formats produce larger file sizes, but may be higher quality.
The most commonly used format is the JPEG format and most digital cameras will automatically save files in this format. Images in this format will have a file name that ends in ‘.jpg’ or ‘.jpeg’. This format is good for keeping file sizes from getting very large so is very popular when images are being transferred from one place to another such as being sent in emails or downloaded from the internet. The JPEG format does have one big disadvantage in that every time a JPEG image is saved the data is re-compressed and some data will be lost.
There are two ways to avoid data loss. One is to reduce the number of times that you save JPEG images. In other words do not keep opening them up and then saving them to new locations. Additionally, when saving a JPEG image there is normally an ‘options’ button that will allow you to choose the trade off between file size and quality. Choose maximum quality to minimise data loss.
Alternatively, some cameras will allow you to save photgraphs in different formats. .RAW, .TIFF and .PNG will all produce good quality images without data loss. However, they will also produce much larger file sizes. Therefore, you will fit a smaller number of images on your camera’s memory card and sending images over the internet will take longer. Even if your camera will not support these other file formats you will probably get the chance to convert the files from JPEGs to one of the other better quality formats on your computer.
In summary, JPEGs are fine for most purposes, which is why they are so commonly used, but try to avoid re-saving them and choose a low compression rate when you do. If quality is paramount (such as when sending a photo for publication in a magazine) then try to use one of the formats that does not compress the files.
Armed with knowledge about these few technical matters you will be able to take better photographs of your models. However, enough of the theory – time now to move on to the forth article that deals with the set up and taking of model photographs.