We've already seen that one of the main features that the camera manufacturers advertise is the pixel count in the sensor. But the primary feature we need in a DSLR camera for astrophotography is low noise. Most of the latest cameras from Canon and Nikon are very low noise, and they are all good for astrophotography. So what other features should we look for? The most useful for astrophotography is Live View. In a new camera, I consider this an essential feature. You will not believe how much Live View helps in focusing a camera for astrophotography. If you are going to buy a new camera, don't get one without Live View. The latest craze with DSLR cameras is video. New cameras can record 1080p or 720p high definition video with sound. This is great if you want to make movies, but not really that helpful for long-exposure deep-sky astrophotography. HD video can be very useful if you want to use your DSLR to try to do some high-resolution planetary work. I discuss how to do this in detail in my book A Guide to DSLR Planetary Imaging. Another feature on most new cameras is dust reduction. If tiny specks of dust get on the sensor, they will show up as spots or shadows of spots in your images. They are especially noticeable in blank areas, such as the clear sky. Different manufacturers implement dust reduction in subtly different ways, but they basically work the same way. They use a glass element in front of the sensor to protect it. This protective glass vibrates in an attempt to shake the dust off when the camera is turned on or off. Others charge the glass with an electrostatic charge that is supposed to repel the dust. Whether these methods work is open to debate, and the additional complexity just means something else can go wrong with the camera. However, most new cameras employ some type of dust reduction technology, so there's not much you can do about it. Other non-essential features for astrophotography are the framing rate and buffer size. The framing rate is the rate at which the camera can shoot consecutive frames in a sequence. The buffer size is memory space and it determines how many frames can be shot before the files need to be written to the memory card in the camera. These two features are mostly of concern to sports and wildlife photographers. For astrophotography, you will usually be shooting only one frame at a time every couple of minutes. New technology such as microlenses direct more light into small pixels. Better in-camera processors produce lower noise. Every new generation of DSLR cameras seem to have lower noise, which is great for astrophotography. The LCD display on the back of the camera is bigger, with more dots, in the latest cameras, and is now awesome in the 900K-dot LCD displays. The latest cameras by Nikon and Canon, such as the Nikon D5000 and Canon 60D and 600D, are now offering an articulated LCD screen. With an articulated screen, you can pivot and move it to a more comfortable viewing position when the scope is pointed overhead, and the camera back is pointed to the ground. Another thing to consider is the bulb setting. This setting allows exposures longer than 30 seconds. Inexplicably, Nikon cameras can't shoot bulb exposures with their remote-control software, while Canon cameras can. Both Nikon and Canon cameras can control bulb exposures with a remote release cord, although some Nikon cameras will only work with an infrared remote. High end cameras also use a proprietary remote-release plug which they can charge more for. Canon low-end cameras use a simple mini stereo plug for the remote release. You can even make one yourself very inexpensively. Most new cameras work in 14 bits of Bit Depth. Old cameras work in 12 bits. This has to do with the number of steps, or levels, of brightness that can be represented between black and white. 12 bit cameras have 4096 steps. 14 bit cameras have 16,384 steps. Without going into a long technical explanation, more is better in theory, but in the real world, you really won't see much difference between a 12-bit and a 14-bit camera. One thing to note with higher bit-depth cameras is that the amount of RAM memory and processing power needed in your computer will go up when you work in higher bit depths. A 15 megapixel camera's files open up to a 45 megabyte file in 8 bits for a JPEG, and 90 megabytes for a high bit-depth file. Other camera features are the type of autofocus system and number of autofocus points. Again, this is mostly of interest to daytime photographers since you won't be using autofocus too much for astrophotography. Most high-end cameras also use environmental sealing to better protect against dirt and moisture, but this is not of much concern for astrophotography. Consumer grade cameras are less expensive because they offer fewer features and use more plastic in their construction. This keeps the weight down and makes them very light. High-end cameras are more rugged because they are made out of more metal, but they are also significantly heavier. Lighter cameras are better for astrophotography with inexpensive mounts, and their plastic parts work just as well as metal ones. If you are going to use your camera professionally and will be banging it around, then you would need the durability of a higher-end model, but for astrophotography, a low-end model will do everything you need. Some high-end cameras also offer wireless control and file transfer. This gives the photographer the ability to control the camera wirelessly from a computer and to transmit files from the camera back to the computer wirelessly. You certainly don't need these features for astrophotography. Almost all DSLR cameras, including consumer level, prosumer, and professional, offer noise reduction. Long-exposure noise reduction is standard, and high-ISO noise reduction is also available on some models. Long exposure noise reduction can be useful for astrophotography, but since almost all cameras have this, it's not something you need to go out of your way to find on a potential purchase.
|
|||||
|
Back | Up | Next |
