A gray card is a special card of various dimensions. It is used in digital photography to set the white balance and for measuring the exposure. A gray card set might contain a white, gray and black cards.
In general, it’s better to use an 18% gray card, as a white card might be too bright for the digital camera sensor (sunny day, reflected bright light), which then can cause the camera sensor to record a false value.
To use a gray card to set the white balance, your camera must have the option of setting the white balance manually. Ensure that the gray card is in the same environment (amount of light, angle of reflectance) as your subject, then set the white balance with your digital camera, and lock it so that the camera remembers the setting. Remember that you will have to set it again (or use auto white balance) if you want to use your camera under other circumstances.
Metering is a photography term which roughly means “light measurement”. In many “point and shoot” digital cameras, and in all DSLRs, several metering modes let you control the exposure of your photos. While digital camera manufacturers name them differently, there are three main metering modes found in modern digital cameras.
Matrix Metering (Evaluative, Multi-Zone, Multi-Segment)
This mode is used in most digital cameras as the default metering mode. The camera divides the whole picture into several zones and measures the light intensity in each of them in order to find the best exposure for the whole picture. This mode is best used when the subject takes up a large part of the frame and when shooting panoramas.
This mode is also known as Center-Weighted Average Metering. When your digital camera is in this mode, it meters the entire frame, but gives greater weight to the center of the scene. Using this mode when your main subject is in the center of the frame emphasizes it, while keeping from isolating it from the surrounding areas.
Spot, or Partial, metering mode instructs the digital camera to optimize the exposure by measuring the light intensity only at a given spot in the center of the frame. In some digital cameras, this spot can be moved along with the af frame, allowing the photographer to meter the shot in any area of the picture.
RAW is not an abbreviation. It’s an image format that doesn’t use lossy compression. A RAW image holds the raw data that comes directly from the digital camera sensor. It preserves every single detail captured by the camera. Like the negatives in film cameras, RAW images need to be processed first. They then have to be saved in another image format, like TIFF or JPEG, in order to be viewed.
Unlike other image formats, RAW doesn’t have a defined standard. This means that if you have two different digital cameras with RAW capabilities,your post-processing software (like Photoshop) may be able to open a RAW photo from one camera, but may not be able to recognize the RAW image from the other, newer digital camera. That’s why post-processing software developers have to constantly update their programs to support newer digital cameras. In 2004, Adobe developed and started promoting the DNG (Digital Negative) format as a solution to this problem. You can read more about this on the Adobe DNG page.
Because RAW files require post-processing, which takes time, this format might be suitable only for professional photographers or serious amateurs who want to control every step of the image processing, like setting the white balance. Setting the latter when saving your photos in JPEG is not possible to do after you take the photo. This is one of the benefits you receive when saving your photos in the RAW format. It gives you more control.
Lenses have different focal lengths. Normal lenses have a focal length of about 50mm. They are known as normal because they “see” as a human eye does. A telephoto lens has a focal length of 70mm or more, and it is used to bring the subjects closer, or magnify them.
A telephoto lens with a 200mm focal length magnifies the subject four times as much as a normal, 50mm lens. 400mm telephoto lenses have a magnification of 8x compared to a 50mm lens, and 2x compared to a 200mm lens.
If you are planning on buying a telephoto lens, be sure you have a tripod. And if your digital SLR camera isn’t equipped with sensor shift stabilization (body based stabilization), try to find a lens with built-in image stabilization (lens shift stabilization) to counteract camera shake, which is amplified the longer the focal length of the lens.
Before explaining what macro photography is, let’s define the word “macro”, just to be clear. Macro means large, big.
Not every lens is capable of macro photography, but, in general, zoom lenses have this capability; the photographer only needs to turn this setting through a menu or dedicated button. And while some lenses cannot focus on a subject that is too close, other lenses allow shooting at a distance as small as 0 cm from the end of the lens.
Often perceived as having the same meaning, close-up and macro photography are actually different. The difference between the two is the size of the subject being photographed compared to the size of its projection on the camera’s sensor (or film). In simple terms, if the image on the sensor/film is the same size or bigger (1x or more magnification), then it’s called macro photography; if it’s smaller than the subject (less than 1x magnification), then it’s a close-up picture.
Let’s say we are taking a picture of a small button, which has a diameter of 5 mm. If its projection on the camera’s sensor/film has a 10 mm diameter, then we just got ourselves a macro photo. If the diameter of the image on the sensor/film equals 2 mm, it’s technically a close-up picture.
SD is an abbreviation of Secure Digital, a memory card format used in digital cameras and other electronics.
SD memory cards, based on the SD Specifications Version 1.01 and Version 1.10, have a capacity of 2 GB or less, although 4 GB non standards-compliant cards can be found. The 1.01 cards have a maximum transfer rate of 10 MB/s (66x, 1x=150 KB/s), whereas the 1.10 compliant ones are rated at 22.5 MB/s maximum (150x).
SDHC is short for Secure Digital High Capacity, which is based on the SD Specifications Version 2.00. The SDHC memory cards have capacities that can range from 4 to 32 GB, although theoretically they can reach 2 TB, or 2000 GB. SDHC cards also support transfer rates up to 150x.
As its name implies, an intervalometer is a device that performs a specific function at regular intervals. In digital cameras, an intervalometer makes it possible to automate the process of taking tens, hundreds and even thousands of pictures without us even touching the camera. It makes Time Lapse Photography a lot easier.
Time Lapse Photography is the process of taking several photos, then making some kind of movie by combining them. The subject of the photos might be a blooming flower, a building being constructed, or somebody’s face as it changes over time. Time lapse photography is certainly possible without an intervalometer, and it is even impractical at times, when you want to take one picture per day, for example. So don’t panic if your digital camera doesn’t have an intervalometer, because you can have fun with time lapse photography, intervalometer-free!
The CHDK firmware addon for Canon Powershot digital cameras (Digic II and Digic III) adds some advanced intervalometer capabilities, either with the firmware addon itself, or through an additional script.
OVF is short for Optical Viewfinder. An optical viewfinder is used in SLR and DSLR cameras. After entering through the lens, the light is reflected towards the viewfinder by a mirror inside the camera. See also EVF.
EVF stands for Electronic Viewfinder. An electronic viewfinder in a digital camera is a small display that gets the image directly from the camera sensor. An EVF is mostly used in non-DSLR compact digital cameras. See also OVF.
SLR stands for Single Lens Reflex film camera. DSLR (or dSLR, or digital SLR), is short for Digital Single Lens Reflex.
The term Single Lens Reflex means that the camera uses the same lens to direct light both to the sensor (or film) and to the viewfinder.