For a professional photographer, digital image files are inventory and potential revenue. For an amateur image files may be memories and demonstrations of skill. In either case they are valuable and most likely irreplaceable.
So I'd like to begin this blog by talking about preserving digital image files.
Image File Formats
First, it is important to understand the image file formats. Cameras generally capture in either JPG (j-peg) or RAW format.
JPG is an image format designed for the web that allows different compression levels that allow image data to be lost. The more compression, the more loss. In addition, the camera creates the JPG from image sensor data. In the process the camera applies a white balance, sharpens the image, performs noise reduction and possibly other operations to produce a nice looking JPG file. The image is permanently altered in the process and the original sensor data cannot be recovered.
RAW format is manufacturer dependent because it stores the exact information captured in the image sensor. No processing has been done to the image and so this format has the maximum potential to recover image quality and to enhance the image later. The downside is that the file size is much larger than JPG, filling up the memory card, disk or other storage much faster. It also takes the camera longer to write the image to the card, possibly slowing down rate at which the camera can take images.
Adobe has introduced a generic RAW format called digital negative (DNG). This format encapsulates the original image (RAW or even JPG) and converts the raw data to an adobe standard. The idea is that if the manufacturer goes out of business or changes their RAW format in the future the original files may not be readable by programs in the distant future. But the more standardized DNG files will always be readable.
If your camera supports RAW format, I recommend using it. When shooting raw it is important to invest in higher speed memory cards so that the camera isn't slowed down.
Later, I will discuss other image formats used in editting images.
Memory Cards
The type of memory card you use is mostly dependent on your camera. I will list some memory card types and information about each.
Compact Flash (CF) cards are nearly universally supported by all the DSLR cameras. The CF cards are the fastest available and should be your first choice if your camera supports it. Sizes range from 2GB to 16GB. But more important is speed. Not all of these cards are alike and there are significant speed differences. And of course, the faster the card the more it will cost. But if you are shooting sports at 5 frames per second you will need the faster cards or your camera will suddenly slow down or stop to wait for the recording to complete.
My current recommendation is the SanDisk Extreme IV series. It is amazingly fast. In the SanDisk series the next fastest CF cards are Extreme III and Ultra II. In that order. The other brand I trust is the Lexar cards. The Pro series are similar to the Extreme series in the SanDisk line.
SD, SDHC, and micro-SD cards are all members of the same technology family. These cards offer sizes from 1GB to 32GB. And speeds of cards can be as different as CF cards. SanDisk makes Extreme and Ultra versions of the SD cards.
Other less common card types include xD (Olympus) and memory-stick (Sony). I don't have experience with memory sticks, but I do with xD. xD tends to be very slow. The fastest cards are labelled type M+. But if you have an alternative, use that.
The number one principle is that you want to select a reliable brand that is as fast as your camera (or faster). If the card fails between the camera and the computer the images are lost forever. That interval when the card contains the only copy of the images is the one area you cannot protect from loss by using good storage practices.
In the next article, I will talk about what to do once the images are on a card.
What I Use
My DSLRs can take both a CF and an xD card at the same time. I always shoot RAW format.
I keep a 2GB xD card in each most of the time, just in case I need them. Both are made by Olympus.
Nearly everything is stored on two CF cards from SanDisk - 4GB Extreme IV cards. I can shoot at 5 fps with the E-3 in RAW format using these cards without waiting for the writes to complete.
I also have a collection of older cards - SanDisk Ultra II and Lexar Ultimate 80x. But I only use these when I have to.
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