I’ve decided to talk about Exposure Time and Aperture in the same lesson because it is a strong relation between them, which I’ll explain later. First I will discuss about each of them to help you understand them better.
EXPOSURE TIME: The Exposure Time is the period of time in which the sensor will be exposed to light. This is done in the moment push the button to take the picture. A mechanism inside the camera will open for the precise amount of time that has been manually set or automatically calculated by the camera. The exposer time on a digital camera can vary in a wide range. For example, on my Canon 450D DSLR the exposure time interval is from 1/4000 to 30. That means that I can expose the sensor from the tiny amount of time that is 1/4000 of a second up to 30 seconds. This is set accordingly to light conditions where the picture is taken.
APERTURE: This is a little more complicated to understand than exposer time, but I’ll try to explain it as simple as I can. The aperture is a characteristic of lenses and it is usually specified on these as a value like 1:3.5-5.6 (on lenses with zoom capability) or 1:1.8 (on lenses with no zoom). To make an analogy with the human eye, aperture is similar to the pupil. It gives us the ability to set the amount of light that enters through the lens by closing or opening a mechanism similar to the eye pupil. A smaller number means a wider opening so more light will come in. The numbers specified on lenses means the maximum opening of the aperture that can be achieved. For example a value like 1:3.5-5.6 (or f/3.5-f/5.6) on some zoom lenses means that we can get a maximum aperture opening of 1:3.5 (or f/3.5) on no zoom and a 1:5.6 (or f/5.6) one on maximum zoom.
Another very important aspect about aperture is the Depth Of Field (or DOF). Depth of field is a term which refers to the areas of the photograph both in front and behind the main focus point which remain “sharp” (in focus). Depth of field is affected by the aperture. A larger aperture (smaller f-number, e.g. f/2) has a shallow depth of field. Anything behind or in front of the main focus point (the main point that you want to be sharp) will appear blurred. A smaller aperture (larger f-number, e.g. f/11) has a greater depth of field. Objects within a certain range behind or in front of the main focus point will also appear sharp. Here is an example:
The relationship between aperture and exposure time is that a smaller aperture will result in less light that will enter through lenses, so a longer exposure time will be required and vice versa. So you can achieve the same luminosity in a picture using different aperture/exposure time combination. The main reason for playing with these two is again the DOF (Depth of Field). There are many situations when you want a shallow DOF (so a blurred background), like in portraits, macros, etc, and there are situations when you’ll prefer a greater DOF, for example in landscape photography. To master this two in combination will require time and a lot of exercises, but I assure you that it worth the effort.
So now you have your digital camera in your hands and you are about to take the first shots. Most beginners in this situation will put the camera into full auto mode, or into one of the auto mode presets. In this lesson we will talk about these modes so you can know their advantages and their limits.
AUTOMATIC MODE: Auto mode tells your camera to make all the adjustments to take the best shot that it can. Some cameras lets you make your own settings for flash or red eye reduction. This mode will give you nice results in many usual shooting conditions, however you need to know that you’re not telling your camera any extra information about the type of shot you’re taking so it will guess what you want. As a result some of the following modes might be more appropriate to select as they give your camera a few more hints without you needing to do anything more.
PORTRAIT MODE: When you switch to portrait mode your camera will automatically help to keep your background out of focus. Portrait mode works best when you’re photographing a single subject so get in close enough to your subject or use the zoom function so that your photographing the head and shoulders of them. Also if you’re shooting into the sun it will be a good ideea to trigger your flash to add a little light onto their face.
MACRO MODE: Macro mode lets you move closer into your subject to take a close up picture. It’s great for shootinginsects, flowers or other small objects. Different digital cameras will have macro modes with different capabilities that includes different focussing distances, usually between 2-10cm for point and shoot cameras. When you use macro mode you’ll notice that focussing is more difficult as at short distances the depth of field is very narrow. Keep your camera and the object you’re photographing parallel or else you’ll find that a lot of it will be out of focus. A tripod is very useful in macro shots as the depth of field is so narrow that even moving towards or away from your subject slightly can make your subject out of focus.
LANDSCAPE MODE: This mode is almost the exact opposite of portrait mode in that it sets the camera up to make sure as much of the scene you’re photographing will be in focus as possible. It’s ideal for capturing shots of wide scenes, particularly those witch points of interest are at different distances from the camera. Your camera might also select a slower shutter speed in this mode so you might want to consider a tripod or other method of ensuring your camera is still.
NIGHT MODE: This is a fun mode to play around with and can create some interesting shots. Night mode is for shooting in low light situations and sets your camera to use a longer shutter speed to help capture details of the background but it also fires off a flash to illuminate the foreground (and subject). If you use this mode you should use a tripod or your background will be blurred – however it’s also fun to take shots with this handheld to purposely blur your backgrounds – especially when there is a situation with lights behind your subject as it can give a fun and experimental look.
These are the most important fully automatic modes. Different digital cameras can have more additionall modes but they are not so commonly used. In the next lesson we will talk about shutter speed and aperture so we can talk later about the semi automatic modes.
Batteries are another very important aspect that you will have to take into consideration. Some digital cameras (mainly the DSLRs) come with their own rechargeable batteries, so the only thing you can do after you get your camera is to see if this one is enough for you and if not, you can buy another one (or more), so you can change them in case you need to. If the camera doesn’t come with it’s own rechargeable battery then in most cases it will be compatible with standard AA ones. Choosing which one to buy can be a discouraging job since there are so many models on the market today. This can be very much simplified if you take into consideration this two aspects:
1. Number of mAh (milliampere-hour): This is a characteristic of rechargeable batteries that tell us how much current can they give. The bigger the value is, the longer the batteries will resist until you will have to recharge them again. Common good values today rise from 2500 mAh up.
2. Recharging device: The main thing that is important about these devices is the speed of recharging. It is not as important as batteries capacity, but sometimes can matter a lot. Basically there are two categories: normal rechargers and fast rechargers. With the first ones you can recharge your batteries within approximately 12 hours, sometimes more, which is a considerable time that can be very important in some situations. The second ones, on the other hand, can recharge your batteries in about 3 hours, some models even faster. The fast recharging is also a recomanded way to do it.
I hope these informations will make the job of choosing the right rechargeable batteries a lot easier for you.
Choosing a memory card is actually an easy task. All you have to do is to follow a few easy steps:
1. Memory card type: To find out what type of memory card does your camera support, all you have to do is to look into camera specifications. Nowadays there are a lot of memory card types (SD, CF, MMC, etc) and manufacturers have their own reason of choosing one type or another. From the user point of view this in not actually very important.
2. Memory card capacity: Here, bigger is better. The last thing you want to happen to you is to find yourself in front of a very interesting subject and not being able to shoot because you have remained out of space on your memory card. It is also wise to consider buying two or more memory cards so you can change them if you need. There is a wide range of capacities going up to 32 GB. All you have to do is thing on your needs and choose what is best for you. The number of pictures that you can “squeeze” on your card depends on the number of megapixels that your camera have and the quality of picture that you have set on your camera (it is always recommended to shoot at the best quality the camera is capable of, even if lower quality means more pictures on the same memory card capacity). To give you an example, with a 12 megapixels camera, at the best picture quality, I can shoot approximately 650 pictures on a 4 GB memory card.
3. Memory card speed: In my opinion this is the most important aspect. There are a lot of cameras, especially DSLRs, which offer a function called “burst mode”. In this mode, several images can be captured with one press on the shutter. These images are taken as fast as the camera can, but if the memory card speed is slow the rate the pictures are taken will be slow down. Another time when you will greatly appreciate the speed of memory card is when you download your pictures from the camera to PC. If you have a high capacity memory card this time can be pretty long on slow cards.
Digital cameras have an ISO rating indicating their level of sensitivity to light. The normal setting for most cameras is ISO 100, although some go as low as ISO 50. The sensitivities can be increased to 200, 400, 800, or even 3,200. High-end digital SLRs also allow some intermediary values. When increasing the sensitivity, the output of the sensor is amplified, so less light is needed. Unfortunately the undesired noise is also amplified. This creates more grainy pictures, just like in conventional photography, but because of different reasons. It is like you will turn up the volume of a radio with bad reception. This will not only amplify the desired transmission but also the undesired noises. Lately a lot of improvements has been done in sensor technology to reduce the noise level at higher ISOs, especially on higher-end cameras.
Here is an example of how ISO level influence the final image:
So your question may be: why should I use higher ISO level if it adds so much noise in the picture? The answer is very simple. A photography with some noise in it is preferred to a blurry one. When you press the button to take the picture, a mechanism in the camera opens and expose the sensor to light for an amount of time (it is called exposure time). The lower the light level is, the greater the exposure time will be. If you are taking the picture from your hand, a longer exposure (how long? this will discuss in further lessons) will result in a blurry picture because of the uncontrollable shake of hands or movement of subject. In this case, if you can’t control the level of light, the only thing you can do is to increase the sensibility of the sensor (higher ISO level) which will require less light for the picture so a lower exposure time.
In conclusion, the different ISO levels makes the cameras more versatile, allowing us to use them in different light conditions, but with the disadvantage of adding some noise into the final picture.
