xd card speed

Archived from groups: rec.photo.digital (More info?)

On 24 Jul 2005 07:54:46 -0700, calicoharbor@aol.com wrote:

> I have been trying to understand the ratings on digital camera cards.
> They give the write speed and the read speed, which I understand, but
> what determines the speed rating.

Essentially, testing the card in the fastest card reader and
seeing what it's speeds are for sustained read and write operations
using large files. When used in a camera, PDA, or MP3 player, the
device's limitations will often prevent the card from reaching its
maximum rated speeds.


> I was looking at the xd-picture card 128 mb the ratings are specified
> as:
>
> speed rating: 130x
> write speed: 3MB/s
> read speed: 5MB/s

That's about right for the write and read speeds, since my 1GB xD
card is rated at 3.5 MB/s & 5 MB/s. But I don't know where they got
the 130x figure. The basic rate used to calculate that is 150kb/s.
So a 4x card is 600kb/s, a 40x card is 6MB/s and so on. So using
its fastest rated speed (5MB/s for read operations), the card should
probably be labeled as a 33x or 34x card. A true 130x card would
indicate a throughput of nearly 20GB/s, whereas most (not all)
cameras never reach 2 GB/s speeds. So it's unlikely that you'll
want or need a faster card unless you have a USB 2.0 high speed card
reader that will let you copy files faster than 2 GB/s to your
computer, or until faster cameras that use xD cards are produced.

Archived from groups: rec.photo.digital (More info?)

Thank you for responding with such great detail. I now have a better
understanding what is meant by that rating.

I have a fuji finepix s3100. It appears to me that the fastest xd
cards available are the 3mb/s - 5mb/, would that be correct? I had
read that the quality of the photo would be determined by the quality
of the card you purchase. The faster it writes, the less likely it
will blur in low light. I have seen sd cards get as high as 20mb/s,
but have not found any xd cards go that fast. Thanks again for your
time and effort, it is greatly appreciated, Linda

Archived from groups: rec.photo.digital (More info?)

On 24 Jul 2005 12:55:45 -0700, calicoharbor@aol.com wrote:

> I have a fuji finepix s3100. It appears to me that the fastest xd
> cards available are the 3mb/s - 5mb/, would that be correct? I had
> read that the quality of the photo would be determined by the quality
> of the card you purchase. The faster it writes, the less likely it
> will blur in low light. I have seen sd cards get as high as 20mb/s,
> but have not found any xd cards go that fast. Thanks again for your
> time and effort, it is greatly appreciated, Linda

And BTW, you missed my point about card vs. camera speed. If you
could get an xD card that reads and writes at (up to) 30MB/sec, that
would only be its maximum in suitable devices. You camera does not
have the ability to write as fast as 3MB/sec no matter what current
or future card you use, so don't worry about the speed of any xD
cards unless you get another camera, possibly 2 to 3 years from now.
Then, the P&S cameras may be able to write faster then 3MB/second.

Archived from groups: rec.photo.digital (More info?)

Duly noted. I get it. No camera as of this date and time can write
faster than 1-1.5MB/s. Any card over 3MB/s would be of no use to a
camera of this date and time. The write speed has nothing to do with
quality.

At the risk of sounding like a complete idiot, do I dare ask how the
camera catches the picture? Where does it hold the picture as it is
being written on the card? Doesn't it make a little sense that if
the image was written faster on the card that it would cut down on
images blurring in a low light setting? Sort of like 35mm film that
had different speed of film, like 200asa or 400asa. I am not a huge
camera person, and I admit I don't know what I am talking about half
the time. I just pick up little bits and pieces of information and I
am just trying to figure it all out. I truly appreciate your help,
Lind

Archived from groups: rec.photo.digital (More info?)

On 24 Jul 2005 18:45:26 -0700, calicoharbor@aol.com wrote:

> Duly noted. I get it. No camera as of this date and time can write
> faster than 1-1.5MB/s. Any card over 3MB/s would be of no use to a
> camera of this date and time. The write speed has nothing to do with
> quality.

There are several cameras that can write faster than 1.5MB/s. But
not your camera, and of those that do, probably all or most of them
are DSLRs. Some cameras benefit from cards faster than 8MB/s.


> At the risk of sounding like a complete idiot, do I dare ask how the
> camera catches the picture? Where does it hold the picture as it is
> being written on the card? Doesn't it make a little sense that if
> the image was written faster on the card that it would cut down on
> images blurring in a low light setting? Sort of like 35mm film that
> had different speed of film, like 200asa or 400asa. I am not a huge
> camera person, and I admit I don't know what I am talking about half
> the time. I just pick up little bits and pieces of information and I
> am just trying to figure it all out. I truly appreciate your help,

The image is captured by the sensor, which is in the same location
that film would be in if it was a film camera. It doesn't make
sense that writing faster to the card would reduce blurring, because
no writing can occur until long after the shutter closes. The
shutter stays open long enough to collect sufficient light. If it's
very dim, it has to stay open longer to collect enough light
(photons) to record a decent image. If you handhold the camera,
there will always be some blur, but if the shutter speed is fast
enough you won't notice it. The longer it stays open, the greater
the amount of blur. Once the shutter closes, whatever blur exists
is already captured by the sensor. Then the camera starts
processing and copying the image to the card. If the camera was so
slow that it took 30 minutes to copy the image to the card, it
wouldn't add a bit of blur to the image, other than the amount that
it always intentionally adds. (don't ask, it's a normal part of the
camera's processing of the images, and is too small to easily see)

Archived from groups: rec.photo.digital (More info?)

I had no idea that the image is captured on a sensor. I can clearly
understand why the speed of the card is not relevant. I've only been
around people who talk about cameras and learn bits of stuff from time
to time. I am strictly a point click person and would never be able to
use a DSLR. I guess I got a hold of some bad information, that seemed
to make sense to me, but it is clearly out of the ball field. Thanks
for taking the time and painting a perfect picture for me!

Best Regards,
Linda