I'm cutting-and-pasting from a post of mine for reference.
I tested three SDXC cards for upload rates. At the last minute I added my fastest rated SDHC card.
1. Lexar Professional 133x 64GB, claimed 20 MB/s
2. Sandisk Ultra 64GB, claimed 20 MB/s
3. Transcend Ultra 64GB, claimed 25 MB/s
4. Sandisk Extreme Pro 8GB, claimed 45 MB/s (new 64GB claims 90 MB/s, not tested because I'm not spending $200 on a memory card (donations accepted)).
Procedure:
I set a K5 with FA 50mm f/1.4 to manual and pointed it at the same indoor-hopefully-constant-light-scene. I put the camera in high-speed mode, jpeg+raw, with the jpeg settings at 2MB and 4 star compression. I then held down the shutter button until I got bored.
First up: Time stamp of file.
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I used the time stamp on the file, which only reads to the second. With this amount of time it's a small error. I normalized all results to the timestamp of the first file.
Second up: File size.
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I actually took the first three cards on the same day with exactly the same settings. I screwed up on the second day with different exposure values. Oops. I don't think it has any real impact on the final results but if you'd like to disregard the results, have at it.
Third up, and perhaps most important: transfer rate.
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The regular sandisk does poorly. The lexar also doesn't really impress, even though it's the snazziest to look at. The Transcend does quite well but the Sandisk Extreme Pro barely nudges it.
Fourth up, and what's really the most important: relative cost.
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For reference - the cost on Amazon right now. I list the cost of the 64GB Sandisk Extreme Pro rather than the 8 GB, which is something like $40 right now.
All in all, on the K-5, you only benefit *very* slightly from SDXC. The Transcend 64 is (or was) far and away the best value in terms of size, transfer speed, and cost.
Last edited by ElJamoquio; 01-09-2013 at 09:56 PM.