Bạn đã chọn lấy máy ảnh DSLR hoàn toàn mới của mình Bạn rất vui mừng (Chúng tôi cũng vui mừng cho bạn). Nhưng sự vui mừng đó sớm chuyển thành nỗi kinh hoàng khi các nút bấm và màn hình chỉ kèm các hình ảnh tượng hình. Chúng có nghĩa là gì? “ƒ/”? Tôi phải chia “ƒ” cho điều gì?/ Đừng lo lắng, chúng tôi sẽ cho bạn biết. Đây là một khoá học cấp tốc để tìm hiểu kiến thức cơ bản về máy ảnh DSLR mới của bạn.
Thành thật xin lỗi, nhưng nội dung này chỉ có sẵn bằng tiếng Anh. View a machine-translated version
To really get the most out of your DSLR (Digital Single Lens Reflex, in case you were wondering what it stood for) we recommend you start by understanding the three ways you can control how light enters and affects your images. These are Shutter Speed, F-Stop/Aperture, and ISO. Learning these three will allow you to shoot effectively on manual. They may seem intimidating and complicated at first, but trust us, they’re pretty simple once you fully understand them. Learning this will allow you to grasp about 80% of how your camera works and, in the process, get some amazing shots! Let's begin by first defining each and we will explain how to use them in practice later.
Shutter speed is how long your camera’s shutter remains open after you press the shutter button. This is also defined by how long your camera’s sensor is exposed to light and how motion is captured in your image. It’s probably the easiest value to change, therefore it is often the first value photographers will adjust to get the exposure of an image right.
The F-stop (ƒ/) is how wide the opening of the lens’ aperture is. The aperture is what controls how the lens lets light in. In technical terms the f-stop value is the ratio between the diameter of the aperture opening and the focal length of the lens. All you need to know now is that a smaller number equals a larger aperture opening. The larger the opening, the more light that is let in; thus the brighter the image will be. The reverse is also true: smaller opening equals darker image. The aperture also controls your lens’ depth of field, which is basically how blurry your image’s background will be, but we will explain this later.
ISO is the sensitivity of your camera’s sensor to light. The higher the number, the more sensitive your sensor will be to light and thus, the brighter the image. Be aware: when your sensor is more sensitive it becomes less accurate, creating a noisier/grainier image. ISO can typically range from 50–32,000 depending on the camera, with some models going even beyond that.
Each of these work together to control how much light your camera’s sensor is exposed to and thus, how exposed (bright) your image will be. This is most often referred to as the “Light Triangle”.
As stated above, the first concept to understand about shooting with a DSLR camera is the balance between Shutter Speed, Aperture, and ISO. This is most often referred to as the "Light Triangle" or the "Exposure Triangle". It means that in order to capture a well-lit image in the manner you desire, there needs to be a give and take between these three.
In practice, the goal is to balance each of these values so that you get a good overall exposure. This is achieved by pointing your light meter's dial to 0. A negative dial means your photo will be underexposed and a positive dial means overexposed. The light meter can either be found in your viewfinder or on your camera's display.
A way to calculate the give and take between Shutter, Aperture and ISO is through their exposure stops. Shutter, Aperture and ISO all have scales with values where each step represents an exposure stop. Each stop on the scale lets in twice as much light as the previous value.
For example, an aperture of ƒ/2.8 lets in twice as much light as an aperture of ƒ/2. This is a lot easier to remember for shutter speed and ISO since the numbers literally double or halve with every step, e.g. changing the ISO from 100 to 200 doubles the light exposure. Because aperture values are based on the diameter, but the exposure is based on the area which is proportional to the square of the diameter, the ƒ-stop numbers double every other value, i.e. 32 - 16 - 8 - 4 - 2 and 22 - 11 - 5.6 - 2.8 - 1.4.
The convenient thing about each of these stops is that they're equivalent. No matter your values, moving one stop up or down on either ISO, shutter speed, or aperture will add or remove an equal amount of light — either by removing half the light or adding twice as much light.
Be aware, however, that most DSLRs these days have half, third or even quarter stops for some of the values. For example your shutter speed might have extra half and third stops, but your ISO might only have full stops. We only mention this so that you don't panic if you see extra stop points as options on your DSLR. Just make sure your movements are equivalent and if all else fails, you can rely on the light meter to determine how correct your exposure will be.
When I was taught first how to use a DSLR, I was required to memorize each of the equivalent stops. While it’s useful to understand the system behind it all, it’s more or less a hold over from the days of film where each shot mattered more and getting the exposure right on the first try was more important. Now with digital you have instant feedback on how your image looks and can more easily correct what your exposure needs to be.
Let's start with Aperture. Stylistically, aperture affects your image's depth of field (which in simple terms is how in focus or blurry your background will be). The larger your aperture opening (represented by a smaller number), the shorter the depth of field of your image will be (how much of your image is in focus; or in even simpler terms, how blurry the background will be).
The reason you might want a large aperture opening (again, represented by a smaller number) would be for a portrait where you want to blur the background so that all the focus will be on the person. A large aperture opening (again, represented by a smaller number) will give you a shorter depth of field and thus a heavy focus on the subject and a blurred background. This also means that the amount of light being let in will be high, so to counteract your image being overexposed, you would either quicken the shutter speed or lower the ISO (sensor sensitivity).
On the flip side of this, the reason you might want a smaller aperture opening would be for a landscape photograph where you need both the foreground and the background in focus. A smaller aperture opening will give you a larger depth of field and thus more of your scene will remain in focus. This also means that the amount of light let in will be small, therefore to counteract your image being underexposed, you would either have a longer shutter speed or a higher ISO (sensor sensitivity).
Now let's say you're photographing a moving object and you'll need a fast shutter speed to freeze it in place. A shutter at that speed doesn't let in a lot of light, so you might have to either have to raise the ISO or the Aperture to correctly light the shot. Sports photographers will generally use a higher ISO (sensor sensitivity) so they can both capture the movements of the players without motion blur and get a wide enough depth of field to keep the action in focus.
Alternatively, you might want to capture motion blur. If you've ever wondered how the pictures of light bands of traffic are captured, it's with a long exposure, i.e. a very slow shutter speed.
1/60th is generally the limit of how long you can hold your camera still with your hands. Anything lower will result in unintentional shaking from your hands and body. This is the point below where you'll need to use a tripod.
ISO (sensor sensitivity) is arguably the least influential of the three. Whereas shutter speed and aperture have stylistic reasons for changing them, changing your ISO (sensor sensitivity) is only done when you don't have any room to change the other two values. And increasing your ISO only has negative effects on the quality of your images, as a higher ISO sensitivity also leads to more graininess and noise in the image. You want the ISO as low as possible to avoid this, but sometimes you have to sacrifice graininess to bring in more light (caveat: there could be times where you want a grainy or noisy image if you like the effect and/or for the sake of artistry).
Once you understand how Shutter Speed, Aperture and ISO work together, you can understand their role in each of the cameras shooting modes. For the majority of DSLRs, you can change the mode you shoot in on a dial placed either behind your shutter button, or on the opposite side. The modes are usually laid out in a similar order to the figure below:
The two most important modes on your DSLR are M (manual) and Auto. The others we will spell out, but it's not likely that you'll end up using them. Very few professional photographers will ever use any other mode than Manual.
M (Manual): This mode gives you full control over each of the camera's exposure settings. This is the mode you will find most professional photographers on. Your DSLR will have buttons or spinners that will allow you to manually change shutter speed, aperture and ISO.
A good way to approach shooting on manual as a beginner is to first set your ISO. Examine your shooting conditions and choose an ISO based on how much light you have available, e.g. if you're outside on a sunny day, you would use a lower ISO and if you're shooting inside, you would choose a higher value.
Then set your aperture based on what you're trying to photograph: e.g. if you're photographing a person, you can set a lower f-stop (which means a larger aperture) or if you're shooting a landscape, choose a high f-stop (which means a smaller aperture).
Finally, check the exposure on the light meter, set your shutter speed accordingly and adjust the other two if needed. This process will change the more advanced you get; for example, if wanted to capture motion you'd set the shutter speed first then adjust the other settings from there, but this is a good way to start.
Auto: This mode will adjust every setting for you. Depending on how intelligent your camera is, it will either use a type of scene detection or decide based on how much light is available for what it believes will look best. The camera will automatically choose the shutter speed, aperture size opening, and ISO. It will always give you a properly exposed image, but it won't always give you the specific look you want for your scene (e.g. too blurry of a background, or bad shutter speed for the conditions).
Macro (Flower): This is an auto mode made for close-up subjects (usually very small subjects), therefore the camera will choose settings that will add extra focus to the foreground. The aperture setting directly affects this, as a larger aperture creates a bigger contrast in focus between the subject and its background. The success of these types of images may depend on your lens, as there are macro lenses specific to this style.
Portrait (Person): This mode is similar to macro as the subject (foreground) takes precedence over the background. Your camera will generally strive to have the smallest f-stop as possible (the widest aperture opening possible) to have a nice blurry background. Your camera might also have facial recognition capabilities to better aim the focus and either take multiple shots to make sure the subject's eyes are open or detect when their eyes are open. This mode may also include features such as skin softening and automatic red eye removal.
Night Portrait (Person with star): This will operate similar to portrait mode, but will also account for the low light situations of shooting at night. It will strive to have a small f-stop (a wide aperture opening), but also use a slower shutter speed to let in more light; which is why it's recommended to use a tripod with this mode. It will also use a flash when it detects there's not enough light available without one.
Landscape (Mountain): This mode again uses aperture but for the opposite effect as portrait. This mode will use the largest f-stop number possible to shrink the aperture for a wide focal plane (meaning the foreground and background will both be in focus). You will most likely get the best result taking landscapes on a tripod.
Action (Moving Figure): This final auto mode adjusts the ISO and the shutter speed for a clear, well-lit shot for fast-moving objects. It will set a very fast shutter speed and, depending on the conditions, a higher ISO or larger aperture to let in more light.
A/Av (Aperture Priority): This mode sets all settings for you aside from Aperture. So if you adjust the aperture setting it will automatically change shutter speed or ISO to compensate to get a proper exposure.
S/Tv (Shutter Priority): This mode sets all settings for you aside from Shutter Speed. So if you adjust the shutter speed it will automatically change aperture or ISO to compensate to get a proper exposure.
P (Program): This mode is a bit of a hybrid of the former two, similar to a semi-automatic mode. On most DSLRs, it will allow you to change the Shutter Speed and f-stop (aperture opening) in tandem, or in a way that makes sure your image is still properly exposed. So if you choose a slower shutter speed, the camera will make your aperture opening smaller to let in less light so it's properly exposed and vice versa. This is opposed to manual where changing one value won't affect the others. On this mode, you should also be able to adjust the exposure value, which on the little dial means you could tell the camera to either overexpose or underexpose the image.
White balance, in a nutshell, is making sure objects that are white in real life look white in your photos. Different sources of light produce light with different color temperatures, but most of the time we don’t notice since our brains adjust automatically based on surrounding information (sometimes our brains guess wrong and this is why the blue/gold dress ignited so much controversy). Color temperature is measured in Kelvin (K) and will affect how warm or cool your images will look. Surprisingly, lower temperatures represent warmer colors and higher temperatures represent cooler colors.
Your DSLR camera will have an Auto White Balance setting, several lighting condition-specific settings (e.g. Daylight 5200K, Fluorescent 4000K, or Tungsten 3200K) and a custom white balance setting. The purpose of White Balance is to ensure that your image's whites and grays look white and gray and not blue or orange.
You can usually leave your camera on Auto White Balance. The reason you would switch to a different setting is if auto wasn't producing a correct or consistent result, but this is rarely an issue.
Before you start shooting, you should be aware of what image file type your camera is saving your images as. Most DSLRs will give you the option to either choose JPEG or RAW file type or both. RAW files are the raw image data from the sensor, meaning nothing has been changed or altered to decrease image size; thus RAW image files take up a lot of memory, but will be the highest quality available. JPEG files are compressed and optimized to take up a smaller amount of space.
If you look at the JPEG below, you can see a larger grid made up of 8x8 pixels. This is the compression in action. Instead of saving the values for each pixel, JPEG instead creates each 8x8 square by overlaying different pixel patterns. These patterns have been carefully chosen so that some of them are more visually important than others, enabling the JPEG encoder to use more storage space for the more important patterns. As you lower the quality setting of a JPEG, less and less information is retained, making the image more and more "blocky".
The other image file options on your DSLR will allow you to choose the JPEG image size and how much it is compressed. On most Canon cameras, the L, M, and S refer to the image size (how many pixels it has) and the curved or stepped block next to it refers to how compressed the image will be, with curved being less compressed and the stepped being more compressed.
If you're planning on editing your photo online through Clipping Magic, you should shoot on the highest quality JPEG setting. This will give you the best results. Shooting in RAW is only suited for editing in a special program like Photoshop or Lightroom. Otherwise, since RAW files take up a lot more space and need to be eventually converted to JPEG to be used online, there isn't much of a point to using them.
When it comes to transferring your images to your computer, we suggest using one of two methods: either tethering the camera to the computer (using a long USB Mini-B to USB cord) so each image is imported separately in real time, or by removing the SD card and inserting it directly into your computer to import your library. We suggest these methods as opposed to importing the entire library via the tethering cord as this method runs the risk of corruption during importing.
Sử dụng chế độ thủ công của máy ảnh DSLR cần có sự am hiểu sự trao đổi giữa Shutter Speed (Tốc Độ Màn Trập), Aperture (Khẩu Độ)/F-stop và ISO (độ nhạy sáng). Nếu bạn không muốn tìm hiểu tất cả các điều đó, chỉ cần chụp ảnh ở chế độ Tự Động và đảm bảo rằng bạn đã thiết lập cân bằng sáng thành Tự Động và đầu ra hình ảnh là JPEG chất lượng cao nhất.
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