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06-22-2009, 01:08 PM   #1
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SDHC Review and Questions

This review of SDHC cards is interesting - 13 SDHC Memory Cards Reviewed : SD Memory Cards for Professionals - Review Tom's Hardware

Does anyone know if the K20D benefits from faster cards? I don't do continuous shooting for sports or the like, but I do use autobracketing for HDR and would like to reduce the write times if possible. I currently have a cheap a-data class 6 card.

06-22-2009, 01:15 PM   #2
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AFAIK, an SD card that matches the unscientifically measured write speed of around 10Mb/sec is the least you should have if continuous shooting is important to you. I 'calculated' the K10D/K20D at that rate by measuring how long it took to write an image onto the card against the file size.

Funny enough some class 6 cards have write speeds of 6Mb/sec (slower than the K20D's max) and some cards, also classified as class 6 (like the SanDisk Extreme III, which I'm glad to have) have blistering write speeds of around 20Mb/sec. Given also the reliability of these Extreme IIIs, I wouldn't hesitate to recommend them - over 2 years using them quite often and never a hitch.
06-22-2009, 01:35 PM   #3
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QuoteOriginally posted by jfsavage Quote
This review of SDHC cards is interesting - 13 SDHC Memory Cards Reviewed : SD Memory Cards for Professionals - Review Tom's Hardware

Does anyone know if the K20D benefits from faster cards? I don't do continuous shooting for sports or the like, but I do use autobracketing for HDR and would like to reduce the write times if possible. I currently have a cheap a-data class 6 card.
I also got the Sandisk Extreme III 8GB SDHC card and have been very happy with it. I shoot single and continuous. My decision was based on the size of the file which is RAW in my case not knowing the write speed of the K20D. These files are about 20MB.
06-22-2009, 03:23 PM   #4
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QuoteOriginally posted by jfsavage Quote
Does anyone know if the K20D benefits from faster cards? I don't do continuous shooting for sports or the like, but I do use autobracketing for HDR and would like to reduce the write times if possible. I currently have a cheap a-data class 6 card.
I have a range of SDHC cards for my K20D from 8gb 30MB/sec Sandisk to 4gb Class 6 Transcend. I have yet to feel a difference although I would like to think the 30MB/sec card can empty the buffer faster. I read an article recently whereby the Sandisk Extreme allowed some DSLR, Sony I think, to go from 4.8 to 5.0 fps. They didnt say as compared to what (a floppy disk?, Class 2).

Google for SDHC benchmark utility and d/l something to check read/write speed on your card for the typical pic size you use. Its important to use your typical file size as you will see the speed changes with file size. I found that the WRITE speed was very close between the cheap Transcend and expensive Sandisk. I will have to update this msg later when I have access to the numbers. The READ spead is only great when its time to unload so no help for you.

UPDATE - rather than attach a big set of graphs I'll just include one number for 3 cards I have handy: 5 MB File Size Read and Writes so its different numbers than raw transfer. Each test run twice to make sure answers stayed about the same. Utility used was Flash Memory Toolkit ver. 1.20. I have no explanation for the weird discrepancies.

Sandisk 8GB 30MB/sec measures 12.2MB/s write 18.7MB/s read
Sandisk 8GB 20MB/sec measures 10.8MB/s write 19.1MB/s read
Kingston 4GB 133x measures 15.5MB/s write 19.2MB/s read

You noticed that too?? My cheapest card is the fastest one, at least at 5MB files but it also was at larger files. Due to it being only a 4GB card or not? Beats me. Like I said, I don't notice the difference when using any card. When using the High-Speed mode of 120-some frames in 5 seconds it still takes a day to dump the buffer regardless of which SDHC card.


Last edited by imtheguy; 06-22-2009 at 06:53 PM.
06-22-2009, 04:48 PM   #5
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Read this:
https://www.pentaxforums.com/forums/camera-studio-accessories/58895-sd-sdhc-c...x-cameras.html
06-22-2009, 06:00 PM   #6
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Just to mention, 20MB/s is not the same as 20Mb/s. 20Mb/s equals 2.5MB/s (Mega-bits vs Mega-Bytes). File size is most often expressed in Bytes, while transfer rate is typically in bits (eight bits in a Byte). I'm just sayin.

Last edited by Duck Dodgers; 06-22-2009 at 06:15 PM.
06-22-2009, 06:24 PM   #7
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QuoteOriginally posted by Duck Dodgers Quote
Just to mention, 20MB/s is not the same as 20Mb/s. 20Mb/s equals 2.5MB/s (Mega-bits vs Mega-Bytes). File size is most often expressed in Bytes, while transfer rate is typically in bits (eight bits in a Byte). I'm just sayin.
Hello Mike - Who are you educating?
06-23-2009, 05:20 PM   #8
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Many thanks for the info!

06-25-2009, 11:36 PM   #9
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QuoteOriginally posted by imtheguy Quote
Hello Mike - Who are you educating?
I think he is refering to ASH. anyways, I'm just not certain as how to writing speed would affect the frame shooting speed of the K7 or the number of pictures written to the memory card under burst mode.

let's say a 5fps shooting speed with a max file size of 10 MB per file and an SDHC card with a write speed of 30 MB/s. that would mean that the K-7 would have 2 files (20 MB) that lagged behind and hasn't been written yet on the memory card. is this the reason that we experience subsequent slow-downs during burst mode, then regain it's speed again at a particular interval of writing?
06-26-2009, 06:51 PM   #10
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QuoteOriginally posted by Pentaxor Quote
I think he is refering to ASH. anyways, I'm just not certain as how to writing speed would affect the frame shooting speed of the K7 or the number of pictures written to the memory card under burst mode.

let's say a 5fps shooting speed with a max file size of 10 MB per file and an SDHC card with a write speed of 30 MB/s. that would mean that the K-7 would have 2 files (20 MB) that lagged behind and hasn't been written yet on the memory card. is this the reason that we experience subsequent slow-downs during burst mode, then regain it's speed again at a particular interval of writing?
You've got it. Take a more realistic file size into account, such as 15 Mb, and work the numbers. You will see that even the K10 can fill a buffer pretty quickly.
06-27-2009, 11:44 AM   #11
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My interest is in 5 shot bursts for autobracketting and how long between taking the 5 shots and viewing, or taking the 5 and being ready for the next 5.
06-27-2009, 06:01 PM   #12
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QuoteOriginally posted by jfsavage Quote
My interest is in 5 shot bursts for autobracketting and how long between taking the 5 shots and viewing, or taking the 5 and being ready for the next 5.
I think that would depend on the read speed of the card when viewing and write speed for getting ready for the next shot. so you might need a card with a 30MB/s read/write speed class 6 or 10. it doesn't matter what brand. I'll go for the cheaper ones.
06-27-2009, 07:03 PM   #13
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QuoteOriginally posted by Pentaxor Quote
it doesn't matter what brand. I'll go for the cheaper ones.
Not always true - I bought a cheapo PhotoFast 8GB Class 6 'Dual Channel' SDHC in my K200D and it just wont work, despite numerous and varied attemptts to get it to do so. Several Sandisk's and Lexmark's work fine.
06-27-2009, 07:45 PM   #14
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QuoteOriginally posted by rawr Quote
Not always true - I bought a cheapo PhotoFast 8GB Class 6 'Dual Channel' SDHC in my K200D and it just wont work, despite numerous and varied attemptts to get it to do so. Several Sandisk's and Lexmark's work fine.
those are more like compatibility issues. some sandisks used on other dslr systems don't work either. and sandisk as you know, aint cheap.

as for me, I'm perfectly happy with my ADATA 2x16gb class 6 sdhc cards. bought both for only 65 bucks.
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