Well now this is I’d never excepted. Since I ve started buying 8GB SDHC memory cards for my camera I hadn’t dreamed I would need 4GB cards. BUT don’t forget them ! You are gonna need them for your Canon SX20 IS camera ! yep that’s true. If you are waiting for the CHDK version for Canon SX20 IS which is still under beta you will need 4GB SDHC cards. Because you can’t use larger SDHC cards then 4GB with CHDK.
I realized this when I was trying to install CHDK for SX10 into one of my 8GB Verbatim class6 SDHC cards. You can use FAT16 partition only upto 4GB. So if you want to use CHDK for your Canon SX20 IS or Canon SX10 IS cameras then you are gonna need few class6 4GB SDHC memory cards. Make sure you are buying class6 cards because you need the highest speed you can get. I use 4GB and 2GB SDHC cards with my Canon SX10 IS camera for CHDK and things happen painfully slow when you take photos. Also if you want to take photos in RAW format then you won’t able to take more than 150-200 photos with 4GB SDHC card so better keep 3-4 class6 SDHC 4GB cards with you. They are cheaper than those 8GB or 16GB SDHC cards so it won’t be a big problem. Here’s are few 4GB Class6 SDHC card recommendations,
- Transcend 4 GB SDHC Class 6 Flash Memory Card
- $11.84
- SanDisk Extreme III 4GB Class 6 SDHC Card
- $27.39
- SanDisk Extreme III 4GB Class 10 SDHC Card
- $37.70
- Lexar 4GB 133x Class6 SDHC Memory Card
- $38.68
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is the second best HDHC card in SanDisk HDHC card list. it has a Minimum 20MB/ sec sequential read/write speeds and Extended temperature tested ( 13º F to 185º F ). Serious professional photographers who demand one of the fastest, most rugged, and most durable memory cards on the market should choose the SanDisk Extreme III SDHC card. Built to work under the most challenging conditions, with SanDisk Extreme III youll get more speed, better performance, and unmatched reliability.
( $27 )
( $12 )
( $45 )
( $10 )
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and 
is speed-rated at 60x, the equivalent of a minimum sustained write speed capability of 9MB per second. Lexar speed-rated cards are individually performance tested before they ship, ensuring quality and performance and providing a higher level of confidence, whether you’re capturing HD video of important events or snapping photos on vacation. The 
. Its expensive but faster than the Lexar 8 GB Platinum 2 60x HDHC card. There is a good new for American Amazon.com buyers because they can buy 
have greater data transfer speeds and capacity than SD memoney cards. They have redesign the card because digital cameras and digital video cameras these days have higher resolutions, which equate to larger file sizes and faster data transfer needs. So its better buy SDHC memory cards for your Canon Powershot SX20 IS camera.