KNOW YOUR CAMERA
Usually located on top of the camera you will find a dial that has a variety of letters and pictures on it each of the letters and pictures represents an exposure mode, some of these modes will be fully automatic as with the modes indicated by pictures, these pictures are fairly straight forward e.g. the face is for portrait, hills are for landscapes, others will let you set, or require you to set different things for the correct exposure e.g.shutter speed.
Below is a list of the most common dial setting depending on your camera will have more settings but read up on these settings and which ones are suitable for HDR photography:
AUTO : Set point and shoot the camera controlls everything. Anybody who can see through the viewfinder can easily take a photo. Not suitable for HDR photography as the exposure will adjust both shutter speed and Aperture to suit the light.
P : Program mode basicly fully automatic very limited control over some settings good if you are after the camera to do the exposure settings but may want to adjusts inbuild flash or the ISO setting. not suitable for HDR photography camera controls the settings.
M : This mode allows you full control over all settings, you have to set all of the exposure setting to reach a correct exposure. Can be used for HDR photography but you have to set each exposure.
AV or A : Aperture priority this settings allows you to fix the aperture to a specific value and the camera meter will alter the shutter speed to suit. For HDR photography this is the setting you will use.
TV or S : Shutter priority this setting allows you to set a fixed shutter speed and the cameras meter will alter the aperture to suit. Mostly used for action photos so you can freeze the action. Not used for HDR photography as the Aperture is varied.
B : Bulb allows you to open the shutter for as long as you want, when using this setting use a suitable remote trigger device and you will need to set the aperture manually. Used for doing long exposures such as capturing star trails Can be used for HDR photography but requires you to manually reset the shutter speeds.
To give you some idea of how each stage of a DSLR camera works to capture an image read the following.
With a DSLR camera when you look through the viewfinder and a system of mirrors lets you see through the lens allowing you to see the same view as the camera's sensor which captures the finished image.
Following is a basic description of what occurs in a DSLR camera to take a picture. The first thing to do is select what exposure settings you are going to use for the photo, be that one of the automatic settings or the manual settings. the next is to compose the shot while looking through the view finder, when your happy with the image press the shutter release button, the main mirror moves up (meaning you cannot see through the veiwfinder) exposing the sensor, which caputures the picture and saves it to the cameras memory card, when the exposure is completed the main mirror drops down and you can see through the lens again.
In order for a photo to be correctly exposed three things need to be calculated to achieve the correct exposure for a picture these are the shutter speed, F stop and ISO, the following are basic details of what each of these settings do.
Shutter speeds (Varied for HDR photography )refer to the amount of time the shutter is open for, they are written in seconds for long exposures, or fractions of a second for faster exposures. Depending on your subject and the availible light you will alter the shutter speed (TV) to suit.
If you want to freeze the action you use a fast shutter speed such as 1/1000sec or faster.
If you want to create a blur effects such as water running a slow shutter speed is required such as 5 second or slower.
With HDR photography shutter speed is varied as you will use a fixed aperture and the exposure is bracketed either side of the correct exposure.
A basic rule to keep in mind for shutter speeds is if you lens has a focal length of say 50mm don't use a speeds less than 1/50th sec when hand holding the camera, at less than this speed shake from your hands can and will cause blur in your shots so using the above example when the shutter speed goes below the 1/50th use a support or a tripod.
F stop (Fixed for HDR photography) also called the APERTURE it is written as follows f/5.6, the aperture is an iris (opening) in the lens, this iris opens and closed to allow more or less light to pass through to the sensor. The easiest way to think of it is like a tap the more you open it the more water (light) flows through the opening. The actual figure f/5.6 is derived from dividing the size of the iris opening by the focal length of the lens.
The smaller the number say f/2.8 the bigger the opening and the more light that passes through the lens to the sensor, allowing you to shoot in lower light with suitable shutter speeds. In bright daylight an aperture of f/22 may be required to shoot with the same shutter speed to get the shot correctly exposed.
On the front ring of your lens you will see printed details for your lens such as the focal length and the maximum aperture with fixed focal length lenses this will be for example f/2.8, for a zoom lens it may be f/3.5-f/5.6 this is due to the varied focal length of the lens altering the aperture depending on the focal length being used.
Each f/stop is a doubling or halving of the light coming through the lens, going from f/5.6 to f/4.5 doubles the amount of light passing through the lens, or going from f/5.6 to f/8 halves the amount light passing through the lens.
The other thing the aperture controls is what is called the depth of field, this refers to the amount of the photo that will be in focus, the bigger the apertue the narrowed the area of focus e.g. at f/2.8 possible a subject at 3m distance may have 0.5m of usable focused area, which is perfect for portrait work, but not for landscape and HDR photography.
An aperture to f/22 on the same subject will give a usable focus area from 1m in front of the camera to infinity. Ideal for landscape and HDR photography.
Selecting an aperture that suits you're subject is important to the effect you want to create, if you are shooting portraits then an aperture of f/2.8 will give you a narrow depth of field where the face is in focus and the background blurred, if you are shooting a HDR photography of a landscape then you would want the largest depth of field as possible so you would use an aperture around the centre of you're lens range say f/11, this should give you a picture which is in focus from a couple of metres to infinity with the best detail.
ISO/ASA refers to the light sensitivity of the medium used to capture an image, today we use a sensor previosly it was film.
For HDR Photography the ISO setting has no effect other than for the finished quality.
When you got a roll of film you noted the ISO/ASA rating of the film and set your camera dial to this so the meter would calculate your exposure correctly, once set you couldnt change this setting for the role of film, so usually you would pre select the film type to suit the type of shot you where taking.
The higher the ISO/ASA number the more sensitive the film was to light.
The lower the ISO rating less sensitive the film was to light.
A low ISO give a fine quality to the finished shot and the better the colours, so a film with an ISO of 50 gave you fine detail, meaning the light sensitive surface on the film when developed came out with a fine crystal structure, that when printed gave fine detail and colour.
A higher ISO was more sensitive to light meaning you could shoot in less light, but the trade off was that the grain in the film would be larger and more noticeable in prints and colour and tonal range would be more limited.
Today with digital cameras we can adjust the ISO at any time so as you are out taking shots and go from the daylight to indoors you can change the ISO to suit, for bright sunlight you use a low ISO of say 100, when you walk into a building and find that the light doesn't allow you to use a suitable shutter speed for handholding the camera and using a flash or tripod is not an option due to restrictions in the building or a flash would be ineffective, so you increase the ISO to 1600 increasing the sensors light sensitivity and now you will find that your shutter speed has increased, the down side of using a high ISO is the you will get noise in your shot this is spots on your shot, you can remove large amounts of these spots with software but your shot will still not be as detailed as using a low ISO and a tripod.