Thursday, March 04, 2010

Digital Photography and Memory Cards

What an age we live in. If you step back and look at the progress made in photography in the past 15 years, it's amazing, isn't it?

Apple and Kodak were among the first in digital photography with their first consumer digital cameras, the Apple QuickTake 100 in 1993, and the Kodak DC40. Both had less than half a megapixel resolution. My dad used to carry around a clunky digital camera that could record images on a 3.5" floppy disk.

A decade and a half later, it is embarrassing to have a CELLPHONE with that kind of resolution. A quick browse of FutureShop or other web sites shows that 10 megapixel pocket cameras sell for $99.

Storage has improved with the improvements in digital camera technology. I remember paying about $100 for a 64MB Sony Memory Stick back in 2002 for my video camera. Now you can get a 16 GB Memory Stick PRO
for half the price... 512 times the memory in 8 years. Secure Digital (SD) cards are the most common technology and you can find 4GB SD cards for $15 or less.

One thing you MUST keep in mind is that you get what you pay for, as always. These el-cheapo memory cards may have that storage, but they are not very fast. To give you an example, I purchased a pair of Kodak 4GB SD cards at the Wal-Mart photo studio a month or so ago for $25 or so. These "made in Korea" cards are fine for storage, but they are not fast cards.

SD cards are often rated as a number followed by an X. For example, "16x". This page does a great job explaining what it means. It boils down to a multiple of 150 KB/s, so a 16x card can handle 2.4 megabytes/s.

My Canon S3 is rated at about 1.5 frames per second continuous shooting. A decent SD card can keep up with that. However, these Kodak cards cannot. I typically shoot passenger trains on continuous shooting so I can record every car number. I noticed it on Tuesday when I was shooting the Hudson Bay that I kept seeing "BUSY" on the screen when I was blasting away. Basically the camera kept having to wait for the card to finish.

You can see it on this BNSF video. It looks like it is snowing, but it is not. That is digital noise, caused by the card not being able to store the video fast enough.

Let's do the math. Each full resolution JPEG coming out of my camera is about 2.7M in size, on average. Shooting at 1.5 frames per second, that is just over 4 megabytes/second. This would require about a 27x card. These el-cheapo Kodaks are clearly no more than 16x speed and cannot keep up.

Needless to say, these Kodak SD cards are going to be used in the Wii or other low speed applications, and I'll go back to my older, faster card. It's only 2 GB but it is fast enough for my camera.

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