Our recent launch of Bickington Photography Club made me think of the initial frustration I had in photography i.e. lack of basic understanding of how best to use my camera and what all of the settings meant. So I thought I would write a quick blog on maybe how to best go about improving one’s photography and for use in our club meetings too.
You have to start with the basics. There is no quick way to get better, as the old saying say “you can’t run before you can walk”. I am writing a short talk about this for the club so I thought I would type it out here first to get some feed back.
Principles of a digital camera
The wiki definition of a DSLR is as follows: A single-lens reflex camera (SLR) typically uses a mirror and prism system (hence “reflex”, from the mirror’s reflection) that permits the photographer to view through the lens and see exactly what will be captured, contrary to viewfinder cameras where the image could be significantly different from what will be captured.
Most cameras you can buy on the market are essentially based on the same concept. You have a body which holds the sensor (this analogous to the film we used to fit) with a number of glass lenses (elements) on the front to guide the incoming light (photons) onto it. The sensor has multiple tiny sensors (analogous to pigment spots on film negatives) in it to capture photons of light. The bigger the sensor (large format>medium format>full frame>APS-C>micro full thirds>compact>phone camera) the more photons of light it can capture and thus is generally considered more sensitive to light.The light enters the lens and is focused on the back screen and sensor but a DLSR also allows the exact scene to be seen before capture as it is reflected off a mirror in front of the sensor. The light is reflected up into the pentaprism (of glass) and then exits out of the view finder. The view is interrupted when the shot is taken as the mirror flips up allowing the light to hit the sensor. Live view is a real-time view of the scene as the mirror is locked up and the scene is displayed on the LCD back screen of the camera. This can be very useful for portrait and landscape and still life especially with the fine focusing functions.
This information is gathered and processed. There are many different image file types but cameras are usually associated with either RAW files or jpegs. A RAW file is the raw data that the sensor captures and nothing is added or taken away. All cameras have the ability to shoot in jpeg. This is where the camera records the raw data and then processes it for you. The camera automatically helps to remove aberrations in the image causes by the lens and also changes the sharpness of the image, colour balance, contrast and saturation to name but a few. As you can see for a quick pic you want this speedy automation but for a lot of photographers, after a while, they want more control and hence shoot in RAW and then perform post (rather than in-camera) processing.
There are too many cameras to name all of the different ways it uses lenses, mirrors (and no mirrors) and technology to take a photo but essentially the light comes into the front of the lens and it directed through a series of lenses to make a good representation of the image onto the sensor. Prime lenses (fixed focal length) use a few glass elements to get this image where as a zoom lens has to use more in order to account for the differences in the directions the light beams take. Generally fixed focus lenses like these are often lighter, sharper and have a wider maximum aperture.
Sensor sizes and formats
In digital photography, the image sensor format is the shape and size of the image sensor. The image sensor format of a digital camera determines the angle of view of a particular lens when used with a particular camera body. Most digital SLR cameras tend to be smaller than the 24 mm × 36 mm image area of full-frame 35 mm cameras, and therefore lead to a narrower angle of view thus a full frame camera has the same angle of view as the 35mm film cameras they are based on.
Lenses produced for 35 mm film / full frame cameras (EF (Full Frame) vs EF-S (Crop) in the canon system for example) may mount well on the digital bodies of cropped sensors, but the larger image circle (projected on the back screen) of the 35 mm system lens allows unwanted light into the camera body, and the smaller size of the image sensor compared to 35 mm film format results in cropping of the image. This latter effect is known as field of view crop, it can however be advantageous for the longer focal lengths when buying lenses that also may eventually be used on a full frame body. The format size ratio (relative to the 35 mm film format) is known as the field of view crop factor, crop factor, lens factor, focal length conversion factor, focal length multiplier or lens multiplier (most people use crop factor). For more info http://en.wikipedia.org/wiki/Image_sensor_format. Here is an image below to help visualize it:
Exposure is basically how much light falls on the sensor and is detected. Thus if too much light hits the sensor then the image recorded will be deemed over-exposed – too little and it will be underexposed. Of course when elements of the image are very dark and light this can be desirable such as low-key portraits or especially with high-contrast monochrome work. When too much or too little light hit the sensor and either are 100% black or 100% white then this is called clipping. This is generally bad, especially with landscape photography, as there is no information in these areas apart from black or white. However when an image is slightly over exposed, especially when shooting in RAW, then more information can be present in the capture (which can be seen by a bigger file size) this is called shooting to the right. I’ll explain more about this later.
As you can see the exposure is related to the aperture (N) and exposure time (t) – please don’t memorize this but the basic rule of thumb is if you double the exposure time, half the aperture or double the ISO you will double the exposure and vice versa. To halve the exposure or amount of light recorded you can halve the ISO, exposure time or double the aperture size.
DoF and f-stop
Before it hits the sensor, along the way it passes through an iris (exactly the same principle as your eye). This allows us to control the amount of light coming through. It also has another effect. The narrower the aperture (the hole) the less light is let in but also this increases the amount of the scene/object will be in focus. The aperture settings are based on a formula and is called the f-stop. It is inversely proportional to the size of the aperture which can be confusing. Thus an aperture of f/2.8 is very wide and lets a lot of light onto the sensor but less of the scene will be in focus whereas at an aperture of f/22 the hole is very small but almost all of the scene will be in focus. This is called the Depth of Field or DoF. For further info : http://commons.wikimedia.org/wiki/Depth_of_field
One error that we all make when we start out especially in landscape photography is getting the aperture right for the scene we want to capture. One advantage of a DSLR camera is you have much more control of how you want to play with the light. With a compact you are confined to a narrow range of apertures and poor light sensitivity. Many people with a basic concept of photography will want to get everything in focus and then choose f/22 or higher. This is partly true but as in life every extreme has its problems. At these narrow apertures the light suffers from diffraction when passing through the iris. The light interferes with each other and then starts forming ripples if you like in the image and this dramatically reduces the sharpness of the image. This is worse with cheaper DSLRs and cameras as they have smaller sensors and magnify the problems compared with larger sensors. Thus it is rarely best to go above f/11 on say a cropped sensor camera especially for landscape photography.
At the opposite end, lenses can also perform badly, when it comes to image sharpness, when used wide open and some may even display vignetting / light fall off at the edges of the picture as not all of the light reaches the edges of the sensor and you get the dark halo in the periphery of the image.
Each type of lens will have what some photographers call a “sweet spot”. This is where the lens performs at its best – for many wide-angle landscape lenses this is f/8-f/11 where the DoF and sharpness and lens aberrations are at their optimum. Portrait and sports photographers for instance would want more light to enter the camera and have a shallower DoF to soften the image by allowing some of the scene to be out of focus. These out of focus areas causing soft circular blobs of light on pinpoint sources especially is called Bokeh and is generally considered desirable.
The focal length, for simplicity’s sake, is the distance between the rear lens element and the sensor. Thus if the lens is very close to the sensor the amount of the scene it can capture is very wide (wide-angle) – the further away it gets the narrower the field of view and it will then have a zooming effect. It’s the same way binoculars work. Obviously a prime lens is fixed and therefore can’t zoom in and out. A wide-angle lens effectively tries to get the beams of light from a wide area and focus it onto the sensor whereas a telephoto/zooming lens from a narrow area and thus it looks like it is close when it is far away. Thus a wide-angle lens has a focal length of say 24mm all the way to a fish eye lens of say 9mm. The opposite with a zoom / telephoto lens where they have a focal length of 100mm say to 1000mm for example.Buy using multiple elements inside the lens the focal length can be squashed into a short body instead of having something over 1 meter long ;). There is further complexity as the focal length is based on the 35mm film camera (or full frame DSLR) and this with smaller sensor cameras (crops etc) we then talk about equivalents (i.e. the same scene captured ont a smaller sensor compared with a larger sensor) but that is beyond the reach of this article). A good wiki article about optics for further reading: http://en.wikipedia.org/wiki/Lens_%28optics%29.
This is a complicated topic and it depends upon what type of shot you are wanting to take. A shallow depth of field if often desirable for studio / portrait work but landscape photographers mostly try to achieve a shot where all of the scene is acceptably in focus. The amount that is in focus is related to both the focal length and the aperture. A rule of thumb is the shorter the focal length and the narrower the aperture the more DoF you have at your disposal. But as above, very narrow apertures result in reduced sharpness due to diffraction and very short focal lengths result in objects looking very distant. So it is really dependent on your composition. Thus your lens selection is dependent on your composition first and foremost. Then where you focus to get the DoF you want is dependent on your focal length. In landscape photography f/11 is generally considered a good starting place with a reasonable DoF. In landscape photography one has to remember that we can’t always have every part of the scene in perfect focus so we have to decide which elements are the most important and so the other areas are acceptably in focus. This is usually the sky and distant landscape where detail is lost being so far away.
There are 3 main ways to focus in landscape photography. 1. Infinity Focusing. 2. “Third the way in” 3. Hyperfocal Focusing.
1. Infinity focusing. Is often employed in star photography. The lens is set on its infinity mark ∞ or one can MF or AF onto a distant star or moon if no infinity mark is available. The problem with this approach is that the foreground, if close enough, will be very soft. Some photographers will take a separate shot and blend these two to get the foreground in focus as well as the stars for example. Infinity focusing is OK if you are not including very close foreground but generally the latter 2 types are employed more frequently in landscape photography.
2. Third way in – Essentially this is a rough way of focusing – on most DLSRs you will find a grid overlay on live view. This allows you not just to help with composition (read rule of thirds) but also to aid in focusing. A relatively standard landscape shot taken on a camera at head height, level where the focus point is a third in from the bottom of the screen with have acceptable sharpness throughout the scene. But this is not the case when a shot is taken in portrait and is low to the ground or pointing down especially with a WA lens. The DoF is too narrow so one may have to increase the f/stop a little, focus stack (combine more than one image together) or use the hyperfocal distance to modify our composition.
3. Hyperfocal Distance: It is a distance beyond which all objects can be brought into an “acceptable” focus. There are two commonly used definitions of hyperfocal distance, leading to values that differ only slightly:
Definition 1: The hyperfocal distance is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp.
Definition 2: The hyperfocal distance is the distance beyond which all objects are acceptably sharp, for a lens focused at infinity.
They are pretty much the same but it’s easier I think to calculate the former – you can also download tables and mobile apps to calculate it for you like the one below (depends on why type of sensor you have and what focal length you are using) there is also a nice website you can generate it dynamically and print it out: http://www.cambridgeincolour.com/tutorials/hyperfocal-distance.htm
A note also with zoom lenses; obviously prime or fixed focal lengths lenses only lose focus when the camera or subject moves. However zoom lenses are different. There are 2 types parfocal and varifocal. With parfocal, when the focal length changes, the object still remains in focus, with varifocal lenses when the focal length changes, the subject needs to be refocused.
As you can see where to focus is a choice and often dependant on your composition (unless you spend a lot of money on a tilt-shift lens). As can be seen from the following link it is also a controversial subject and thus where to focus is a personal choice in what you are trying to achieve and like composing your image takes time and practice? http://www.northlight-images.co.uk/article_pages/hyperfocal_distance.html.
One feature of many DSLRs is the DoF preview button. This can be found on the body near to the lens attachment. When you press the button it will narrow the aperture to the present setting. This will allow you, especially using live view, to zoom into all aspects of the scene to be more precise on which parts of your image are acceptably or not acceptably focused. I find this immensely useful.
This was used initially with film cameras where the higher the ISO number the more light-sensitive the film was. In lower light conditions you can keep the shutter speed high and capture a sharp image. This is almost analogous in digital photography where you can set the sensitivity of the sensor to the same degree. But this comes at a price as with film. The higher the ISO the more noise (how grainy the image is). This is because it picks up more stray photons of different wavelengths and reduced the clarity and sharpness of the image. Sometimes grain/noise is wanted, but again, a balance is needed and depends on the scene. For landscape photography using a tripod to hold the camera steady helps in keeping the ISO down (ideally ISO 100) and this will give you the least noise and therefore the most sharp and clear image. Increasing the ISO if often needed without a tripod if capturing moving subjects as in wildlife photography where a sharp image without moment blur is more important than some noise – “A bit of noise is more preferable to a blurry image”.
Basically this is pretty simple. Whether the shutter (called a curtain which is exactly what it does) is mechanical or electronic it basically uncovers the sensor, like opening a pair of curtains, for a split second. It is calculated in a fraction of a second i.e. 1/5th or 1/100th etc. The longer the time it is open for the more light it lets in. The shutter is the easiest thing to change to allow more of less light in without affecting the image too much. However as with all things at extremes we have problems. Too fast a shutter and there might not be enough light, too long then we may get motion blur from a moving object or if hand-held, motion blur from camera movement. The former can be desirable i.e. long exposure photography. But when the camera is hand-held in low light the image will be blurry due to camera shake or motion blur of the scene. Thus for landscape photography of a non-moving or slowly moving scene it’s not much of an issue as most of the elements in the scene will be essentially a still life. The shutter is the one main variable we use to alter the exposure. A tripod is really essential for most aspects of landscape photography.
Shooting to the right
Basically a histogram whether in a graphics program like Photoshop or Lightroom or on your back LCD screen of your camera gives you a representation of the exposure of the darks, mid-tones and lights in your shot if it is set on RAW and a real representation if shot in jpeg (in RAW it has to convert it into a temporary jpeg first in-camera or be converted by the program you are first). Note: if your in-camera setting are set to anything other than neutral (sharpness, saturation etc) when shooting in RAW then the histogram will be based on these settings which will skew the histogram.
Basically it’s a graph and so all you need to know is that left represents darks, middle is mid-tones and right it highlights/lights. The height of the line represents how much of it is there and so the area of the graph underneath represents how much information is in the image.
The graph at the top is the Red (R), Green (G) and Blue (B) combined and the 3 below are the representations of how much of darks, mid-tones and highlights of each colour channel is in the capture. Now not wanting to go into it too much further you can see below you can see an image where the is a good distribution of darks, mid-tones and lights without clipping (i.e. big tall lines at either end of the graph).
As you can see the image below is over exposed. When shot in camera this is what we mean by shooting to the right – the whole curve is shifted towards the lights end of the curve. But as you can also see if you push this too far clipping can occur which is where there is a large spike at the end of the graph where there is pure white which means there is no information in this area apart from white and thus the more clipping you get often the smaller the file size. It’s often about getting a happy medium where you get more detail shooting to the right but making sure you don’t start to clip.
So that is about it regarding the basic principles of using your camera whether it is a DSLR or a compact. I hope to add onto these tutorials for the camera club in time.