Instruction manual

Format a card only after transferring your photos to a hard drive or other

storage device and then checking them. Additionally, you should regularly format

your memory cards to help prevent them from becoming corrupted.

1.3.3 Media Card Corruption

To understand how media cards can lose data, you need to understand how

photos are written to media cards and how this information is organized and

stored on the cards. When you press the camera’s shutter release button the

shutter opens, light hits the sensor, and the computer in your camera places this

information in its memory buffer; the buffer is a volatile, temporary storage area

where the camera's computer can hold the information while it writes it to your

flash media. The camera continuously and automatically saves photo information

from the buffer to your media card; when the buffer is full the camera must write

some information in the buffer to the media card to free up space. The camera

will not let you take any more pictures until the buffer has written enough data to

the media to allow space for another photo in the memory. [Note: When you’re

shooting in continuous mode the D200 can record up to 100 photos, although the

frame rate will drop once the buffer has filled.]

This data is organized on the memory card like files on a computer hard drive;

your memory card has a File Allocation Table (FAT) that is like a table of contents

for your memory card. Most cards have two copies of this FAT, either of which

can be used by your computer. However, since most cameras can only use the

first copy this means that, if the first copy of the FAT gets corrupted, your camera

will not be able to find any information on the card. In addition to the FAT there is

also a master boot record that is used to set up the "geometry" of the card.

Following the master boot record is the root directory, which is the filing cabinet of

your card; this contains sub-directories where information or data is stored. Each

of these areas has pointers to where the data is kept. The majority of problems

with media cards stem from corruption in one or more of these areas of the

memory card.

A corrupted media card has damaged data that prevents it from performing

properly, and may even become unreadable. Since media card corruption often

results from human error, understanding the main causes can help prevent it from

occurring.

• Turning off a camera before a photo is completely written to the memory

card. Wait a few seconds to let the camera finish writing the information

from the buffer to the card; if your camera has a blinking activity light,

make sure it has stopped blinking. Only then should you shut off the

camera and remove the card.

• Removing the memory card from a camera while a photo is being written

to the card

• Removing the card from a memory card reader while files are still being

transferred to a computer

• Removing the card from a card reader while folders and files from the

card are open on a computer