canon - What to consider when choosing a memory card?

I have a Canon 20D and was looking to buy a memory card. Turns out there are lots of options that vary in price. This got me wondering, what should I be looking out for when buying a memory card.

Based on some research that I've done, I have some points:

1. 
   

   What is the maximum memory size your camera supports ?

   
   
   
   
   • From what I can tell, the 20D supports up to 8GB (could not find it in the manual), so anything over that would be a waste. Although I did find some posts where users claim they can use a larger card, as long as they dont format it using the camera. Can anyone speak to that? Personally I might just stick with the limit set by the camera.
   
   
   
   


2. 
   
   

   Read/Write Speed?

   
   
   
   
   • I am still trying to figure this one out. I saw this post on speeds that sheds some light. Essentially the write speed of the card should be higher than that of the camera, which makes sense. However how do I figure out the write speed of my camera? Does anyone know what the write speed of a Canon 20d is?
   
   
   
   


3. 
   

   What brand to buy?

   
   
   
   
   • I currently have a SanDisk Extreme 512MB card. That is why I started looking for the same card with a higher capacity. A Kingston or Transcend is approx. $15 while a SanDisk is over $30...
   
   
   
   
   


4. 
   

   Extreme temperatures?

   
   
   
   
   • Not sure how important this is, but I do live where the temperature can go pretty low below 0F. That doesn't mean I will necessarily be doing photography outside in that temperature. What kind of problems do people run in to with low temp?
   
   
   
   

Are there any other things that I should be looking at?

Answer

The Canon 20D topped out at around 6 MB/sec when Rob Galbraith tested many of the cards currently available back in 2006 or so. Considering that the 30D improved to almost 7 MB/sec using many of the same cards, I would say anything over 6 MB/sec is overkill for the 20D. The slowest cards on the market today are faster than that, unless they are unsold older stock.

As far as reliability goes, I've never had a problem with any card from SanDisK, Transcend, or Lexar. My newer cards are all the Transcend brand. I've used them heavily for years. I follow a couple of simple rules: NEVER insert or remove a CF card in a device that is powered on. SD cards and USB drives are designed to be hot swappable if "ejected" properly before removal. The design standards for CF includes no such provision. Also, rather than "erasing all images" from a card, I format the card in the camera in which it will be used.

The design standard for all CF cards is a lot more tolerant of extreme temperatures than other types of flash memory such as SD cards. SanDisk touts the durability of their cards when used in extreme temperatures and at high altitudes. My own experience shooting in sub-freezing weather is that it is a non-issue with any of the cards I own.

In cold environments battery life will be your primary concern. Take at least two and keep one warm with the body heat inside your clothes while you shoot with the other. You can swap them and warm the cold one back up and it will 'recover' some of the energy it lost as it was cooled.