SD card speeds?

[Terry Pinnell]

I want to buy some new SD cards, 2GB and maybe 4 GB. But the majority
of the supplier sites seem to show no data on speeds (50x, 150x, etc).
Does anyone know of a good reference source for that info please? Or a
supplier that *does* quote that?

 

[Marty Fremen]

I want to buy some new SD cards, 2GB and maybe 4 GB. But the majority
of the supplier sites seem to show no data on speeds (50x, 150x, etc).
Does anyone know of a good reference source for that info please? Or a
supplier that *does* quote that?

The 150x etc only seems to refer to read speed. For the all-important write
speed (important for cameras anyhow) you need to read some reviews, since
accurate figures rarely seem to be availale on suppliers' sites.
Furthermore, read speed seems to bear little relation to write speed, for
instance I bought a "MyMemory" own brand 133x SD card and its write speed
was only about 2-3 MB/sec, whereas other brand cards of that spec have
anything up to 20 MB/sec write speed. In practice, the MyMemory 133x speed
card turned out to be slower than my Sandisk 33x card.

Looking through my bookmarks, you might try
http://www.dcareview.com/tables.html

 

[Michael J. Mahon]

I want to buy some new SD cards, 2GB and maybe 4 GB. But the majority
of the supplier sites seem to show no data on speeds (50x, 150x, etc).
Does anyone know of a good reference source for that info please? Or a
supplier that *does* quote that?

A Google search on <sd card speeds> reveals:

http://www.gadgetspage.com/cameras/understanding-sd-flash-memory-card-speeds.html

Which contains further links to actual speed tests with particular
cameras.

A general rule is that if the card is slow, it won't advertise its
speed.

The manufacturers sites also have speed info, but I'd much rather
trust a third party test. Also, relatively few consumer devices
require high speed cards.

High speed cards are more expensive, since they use "single-level"
bit storage, or one storage cell per bit, as opposed to "multi-level"
storage, which currently stores two bits per cell (by storing four
discrete levels of charge per cell). Single-level storage requires
either more chips or bigger chips for the same amount of storage,
hence the higher cost.

From a practical point of view, the "sweet spot" cards of 1GB and
2GB can usually be found at speeds of 30x and up for under $10 per
gigabyte if you shop carefully. (There has been a glut of capacity
in the flash memory market for almost a year, now.)

-michael

"The wastebasket is our most important design
tool--and it's seriously underused."

 

[Terry Pinnell]

A Google search on <sd card speeds> reveals:

http://www.gadgetspage.com/cameras/understanding-sd-flash-memory-card-speeds.html

Which contains further links to actual speed tests with particular
cameras.

A general rule is that if the card is slow, it won't advertise its
speed.

The manufacturers sites also have speed info, but I'd much rather
trust a third party test. Also, relatively few consumer devices
require high speed cards.

High speed cards are more expensive, since they use "single-level"
bit storage, or one storage cell per bit, as opposed to "multi-level"
storage, which currently stores two bits per cell (by storing four
discrete levels of charge per cell). Single-level storage requires
either more chips or bigger chips for the same amount of storage,
hence the higher cost.

From a practical point of view, the "sweet spot" cards of 1GB and
2GB can usually be found at speeds of 30x and up for under $10 per
gigabyte if you shop carefully. (There has been a glut of capacity
in the flash memory market for almost a year, now.)

Thanks both, very helpful. I'll follow up those links.

 

[Bob]

The 150x etc only seems to refer to read speed. For the all-important
write
speed (important for cameras anyhow) you need to read some reviews, since
accurate figures rarely seem to be availale on suppliers' sites.
Furthermore, read speed seems to bear little relation to write speed, for
instance I bought a "MyMemory" own brand 133x SD card and its write speed
was only about 2-3 MB/sec, whereas other brand cards of that spec have
anything up to 20 MB/sec write speed. In practice, the MyMemory 133x speed
card turned out to be slower than my Sandisk 33x card.

Looking through my bookmarks, you might try
http://www.dcareview.com/tables.html

Excuse my ignorance. What is the importance of SD card speeds. Does it
affect the quality of photos or transferring shots to PC or something else?

 

[Michael J. Mahon]

Excuse my ignorance. What is the importance of SD card speeds. Does it
affect the quality of photos or transferring shots to PC or something else?

For some cameras, it can affect the time required to write a photo
to the card. If shooting multiple pictures, it can therefore affect
the picture taking rate.

Some video recording modes also require a minimum write speed to
keep up.

Frankly, the speed issue is very badly handled by both card and
camera manufacturers. The "x" notation is actually related back
to audio CD speeds, so you can see how out of sync with today's
requirements it is!

Card manufacturers should be required to spec sustained (large
file) read and write speeds in MB/sec, and camera manufacturers
should express their minimum requirements in the same units.

As with gasoline, if the speed limiter is your camera, then using
a faster card does not help--it just costs more.

-michael

"The wastebasket is our most important design
tool--and it's seriously underused."

 

[Bob]

A Google search on <sd card speeds> reveals:

http://www.gadgetspage.com/cameras/understanding-sd-flash-memory-card-speeds.html

Which contains further links to actual speed tests with particular
cameras.

A general rule is that if the card is slow, it won't advertise its
speed.

The manufacturers sites also have speed info, but I'd much rather
trust a third party test. Also, relatively few consumer devices
require high speed cards.

High speed cards are more expensive, since they use "single-level"
bit storage, or one storage cell per bit, as opposed to "multi-level"
storage, which currently stores two bits per cell (by storing four
discrete levels of charge per cell). Single-level storage requires
either more chips or bigger chips for the same amount of storage,
hence the higher cost.

From a practical point of view, the "sweet spot" cards of 1GB and
2GB can usually be found at speeds of 30x and up for under $10 per
gigabyte if you shop carefully. (There has been a glut of capacity
in the flash memory market for almost a year, now.)

Thank you Michael.

 

[Jürgen Exner]

Excuse my ignorance. What is the importance of SD card speeds. Does
it affect the quality of photos or transferring shots to PC or
something else?

No, yes, and yes
Long answer: It has nothing to do with quality of photos. And normally the
speed won't affect your normal photo shooting either.
However in cases where the camera needs to store a lot of information in a
very short time then a card with a faster write speed may be able to keep up
with the data stream while a slower card could become a bottle neck and slow
down the speed with which you can shoot photos. Typical scenario would be
shooting in quick succession e.g. in burst mode (up to 10 photos a second)
and maybe even using RAW (10MB+ per photo). That will quickly push any card
to its limits. Of course a faster write speed will only benefit you, if your
camera does support that faster speed, too.

A faster read speed will accelerate the download to your computer provided
your card reader knows how to utilize that faster card speed.

jue

 

[Bob]

No, yes, and yes
Long answer: It has nothing to do with quality of photos. And normally the
speed won't affect your normal photo shooting either.
However in cases where the camera needs to store a lot of information in a
very short time then a card with a faster write speed may be able to keep
up with the data stream while a slower card could become a bottle neck and
slow down the speed with which you can shoot photos. Typical scenario
would be shooting in quick succession e.g. in burst mode (up to 10 photos
a second) and maybe even using RAW (10MB+ per photo). That will quickly
push any card to its limits. Of course a faster write speed will only
benefit you, if your camera does support that faster speed, too.

A faster read speed will accelerate the download to your computer provided
your card reader knows how to utilize that faster card speed.

jue

Got it. Thanks.

 

[Marty Fremen]

For some cameras, it can affect the time required to write a photo
to the card. If shooting multiple pictures, it can therefore affect
the picture taking rate.

It's not just the picture taking rate but the picture-to-review delay - you
can't examine a picture at full resolution until it has finished writing to
the card. Having to wait a few seconds until you can verify that you got
the shot in the can (e.g. zooming the shot to check focus, or checking for
highlight saturation) is irritating and may even mean you lose the chance
to have a second go. In my case I'm writing an 18MB raw+jpeg so card speed
it critical, however even on point and shoots with 2MB jpegs I find the
shot-to-playback delay can be improved noticably with a faster card.
Getting the review delay down from say 2.5 secs to 1.5 sec may seem trivial
but subjectively at least it makes a difference to the picture taking
experience.