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.
When buying a digital camera one of the factors that you will be looking at is the power of the zoom function. People who are not very experienced in this field are starting to be a little mislead because manufacturers are often claiming a zoom function called digital zoom, or they add this zoom to the optical zoom so the total zoom to be greater. This is not so fair on the consumer as you will understand from this lesson.
Optical zoom is the real zoom. This function of a camera uses the lens to draw the image closer. When using optical zoom quality remains the same and the full resolution of the camera can be used on the zoomed image. The motion of the front lens moving outwards on a camera is the lens achieving a greater level of zoom.
Digital zoom is not a true form of a zoom function. The image doesn’t actually come any closer because the optics in the camera stay the same. The way the digital zoom works is the same as it does on your PC. The idea behind digital zoom is that it takes a portion of the image and expand that image to the full size of the image so the section you are looking at becomes bigger, not closer. The image does look closer because it has been expanded however all that has happened is that the image quality has been reduced.
Here is an example of optical and digital zoom:
So the digital zoom is the same as the zoom you can do on any software of digital image manipulation and it is also done with loss of quality. In conclusion the only zoom that is really important when you choose a digital camera is the optical zoom, the digital zoom if just for marketing purpose and in my opinion it’s useless.
To define optical zoom, first I’ll have to briefly explain you what is focal length (or focal distance). If you look on the lenses of any decent camera you’ll see written there something like this: 5.8 – 34.8mm (or any other pair of values like that). This is the focal length specification and it is a characteristic of the lenses. I will not enter into physical theory of lenses and stuff like that, the main thing you have to understand about focal length is that if you are at the same distance from the subject, with the same camera (it is important, because the sensor is part of equation), the smaller the focal length is the further the subject will appear in the final picture.
Here is an example:
- focal length 18mm:
- same distance from the object, but focal length 55mm:
As you can see, the bigger the focal length is, the larger the object will appear in the picture, but the angle of visibility will be smaller.
Now that you have an idea about focal length, lets talk about optical zoom. This specification of cameras will always be seen just on point and shoot digital cameras, but it’s also applicable on DSLRs lenses. You will find it as a value like 3X, 5X, 10X or something like that. These numbers are obtained by dividing the biggest focal length of the lenses to the smallest. For example, if you have a lens with focal length 18 – 55mm, the optical zoom will be 55 / 18 which is approximately equal with 3, so 3X. In other words the optical zoom is the number of times the subject will be magnified compared to the subject dimension at the minimum focal length of the lenses. So in the example above the object has been magnified 3 times.
In the next lesson we will talk about the difference between optical and digital zoom.
Now you have an idea about the differences between point and shoot digital cameras and DSLRs and you know which one is best for you. The next step is to actually buy the camera. In the next few lessons I will explain to you a couple of very important technical aspects that are essentials in choosing the right camera from the vast number of models that exists on the market today.
In every camera’s specifications you will find the number of megapixels that it has. But what is a megapixel? A megapixel means 1 million pixels. A pixel is a single point in a graphic image. All graphic images are made up of thousands of tiny points. If your camera is 5 megapixels, it means that any pictures it takes will consist of 5 million of these pixels (on its highest quality setting). Generally, 5 megapixels is enough to print good quality 8x10s. But just because one camera has a certain amount of megapixels doesn’t mean that it will take better pictures with one with a lower amount. There are many factors which affect this, including build quality, type of camera, etc.
If you’re just planning on printing small prints of your photos, or viewing your photos on a computer, you can do this with a lower number of megapixels. But if you want to print quality 8x10s, you will need a bigger number of them. For a quality print, you’d want to start with a photography which contains at least 240 DPI (or dots per inch), 300 DPI would be even better, but 240 is enough. So, for a 4×6 print at 200 DPI, we would need an image size of 960×1440 pixels or better. For a 5×7, we would need 1200×1680, and for an 8×10 we would need 1920×2400 or greater. Now, most 5 megapixel cameras produce an image of around 2592×1944, which when printed at 240dpi comes out to a 10.8″ x 8.1″ print. So, with a 5 megapixel camera you could print 8x10s but only is you are not cropping your image.
Why isn’t more megapixels always better? Camera companies keep increasing the number of megapixels and now even some point and shoot cameras have well over 10 megapixels. But does this mean that they will take pictures of better quality than older models with lower number of megapixels? The answer is no. By continuously increasing the number of megapixels which cameras can output, the camera companies are not paying as much attention to quality as they should. Just because you are cramming more pixels into a photo doesn’t mean that the pixels are sharp enough for there to be any discernible increase in image quality. So, while your pictures may be getting larger, they might not even be sharp enough to be printed at this larger size, merely because there was an increase in pixels, but not an increase in quality. In theory, more megapixels would mean a nicer photo, but in actuality it may just mean a terrible photo composed of more dots.
Once you get past 4 megapixels or so, the resolution stops mattering as much, and optical quality comes more into play. This is why a 8 megapixel DSLR camera will take better pictures than a 10 or 12 megapixel point and shoot digital. Another fact worth mentioning is that DSLRs have larger sensors than a typical point and shoot. These larger sensors produce much less noise than their point and shoot rivals, leading to a much cleaner shot.
