Recommeded memory speed for supercompact?

On 08 Jun 2007, GT wrote:

"Richard Polhill" wrote in
message . ..
GT wrote:
"Richard Polhill" wrote in
message .. .
GT wrote:
"Richard Polhill" wrote in
message . ..
Joey wrote:
If I get a modern super-compact digital camera such as a
mid-range Canon IXUS (US: Canon Powershot) for general use
then ...

... what minimum speed of SD memory should I get to avoid
delays?

I see "x133" mentioned a lot on memory adverts. Is x133
fast, slow, just right for the sort of camera I am thing of?

I would probably get 1GB or 2 GB from this sto
http://www.jacobsdigital.co.uk/index...uery=sd+memory

I don't believe the fact that it's a supercompact is relevant.

The question is whether the camera can use it at all, but if
it's recent there should be no reason why not.
The speed rating of the memory is its maximum speed, so if the
camera can't go that fast, then the memory will run at less
than top speed, so don't worry about compatability due to
speed.

Compatability due to size of memory card may be an issue though
- see Richard's last line below

Realistically, you'll probably find no speed difference
between a 40x and 133x card. If you buy based on the size and
price rather than speed you'll typically end up with a fast
(say, 133x) card anyway.
Not true. It depends on what the camera is capable of - fast
frame shooting will benefit greatly from faster memory, but I
don't know how many frames per second this camera can do.
Not if the camera cannot write at 133x, and AFAIK most can't.

133x is around 20MB/s write speed.

Surely the limiting factor in the transfer from camera buffer to
storage RAM will be the RAM speed - I would be very disappointed
in a new camera if the buses couldn't handle something faster
than 20MB/s. I would expect the theoretical bus speed to be many
times that - maybe even 50 times faster than that!!

You would expect the bus to be faster than 20MB/s and it probably
is. This just means the bus isn't the bottleneck. You'll be hard
pushed to find a digicam that can write as fast as 10MB/s. Expect
around 5MB/s.

You need to consider what the camera can achieve, not what the
performance of an individual component (bus, card, etc.) is.

But the camera is made up of these components and the performance
of the camera WILL be as slow as the slowest component. Basically,
there is the image processor, the bus and the flash storage. The
image processor can internally process the image much faster than a
flash card can read/write it. And the bus can handle data transfer
at rates many times faster than any flash card.

The camera has to interpret the data from the sensor and convert
it to JPEG and write it to the filesystem, all of which imposes
processing overhead. Unless the bus is the bottleneck the speed of
it is irrelevant. Same with the card; if the card is at least 66x
(that is 9.9MB/s) then it isn't going to be the bottleneck.

My EOS can take 3 frames per second until the buffer is full. In
8Mpixels, high JPEG mode, it shoots about 14 shots until it has to
sit and wait for the memory card to catch up - you can watch the
access light to see this. In RAW mode, this delay is more obvious.
So the image processor and bus are not the bottlenecks - the card
is!

I 'expect' that a compact digital camera will be slightly slower at
processing images, but it is still a dedicated chip and will
process images much faster than any memory card can transfer them.

I don't think it matters how long the image processor takes to deal
with the photo - it will be significantly less time than it takes
the card to store it away - why else have Sandisk been working on
faster and faster cards - the Extreme IV is with us now. I don't
know figures, but it can probably save 30+MB/s, but will still be
the bottleneck !!



So based on the exchange here between Richard and GT, the answer to the
OP (me) is that the memory should be reasonably fast but is not likely
to have to be as much as x133 and something like x66 would most likely
do.

Did I get that about right?

GT wrote:
"Richard Polhill" wrote in message
. ..
GT wrote:
"Richard Polhill" wrote in message
.. .
GT wrote:
"Richard Polhill" wrote in message
. ..
Joey wrote:
If I get a modern super-compact digital camera such as a mid-range
Canon IXUS (US: Canon Powershot) for general use then ...

... what minimum speed of SD memory should I get to avoid delays?

I see "x133" mentioned a lot on memory adverts. Is x133 fast, slow,
just right for the sort of camera I am thing of?

I would probably get 1GB or 2 GB from this sto
http://www.jacobsdigital.co.uk/index...uery=sd+memory

I don't believe the fact that it's a supercompact is relevant.

The question is whether the camera can use it at all, but if it's
recent there should be no reason why not.
The speed rating of the memory is its maximum speed, so if the camera
can't go that fast, then the memory will run at less than top speed, so
don't worry about compatability due to speed.

Compatability due to size of memory card may be an issue though - see
Richard's last line below

Realistically, you'll probably find no speed difference between a 40x
and 133x card. If you buy based on the size and price rather than
speed you'll typically end up with a fast (say, 133x) card anyway.
Not true. It depends on what the camera is capable of - fast frame
shooting will benefit greatly from faster memory, but I don't know how
many frames per second this camera can do.
Not if the camera cannot write at 133x, and AFAIK most can't.
133x is around 20MB/s write speed.

Surely the limiting factor in the transfer from camera buffer to storage
RAM will be the RAM speed - I would be very disappointed in a new camera
if the buses couldn't handle something faster than 20MB/s. I would expect
the theoretical bus speed to be many times that - maybe even 50 times
faster than that!!
You would expect the bus to be faster than 20MB/s and it probably is. This
just means the bus isn't the bottleneck. You'll be hard pushed to find a
digicam that can write as fast as 10MB/s. Expect around 5MB/s.

You need to consider what the camera can achieve, not what the performance
of an individual component (bus, card, etc.) is.

But the camera is made up of these components and the performance of the
camera WILL be as slow as the slowest component. Basically, there is the
image processor, the bus and the flash storage. The image processor can
internally process the image much faster than a flash card can read/write
it. And the bus can handle data transfer at rates many times faster than any
flash card.

The camera has to interpret the data from the sensor and convert it to
JPEG and write it to the filesystem, all of which imposes processing
overhead. Unless the bus is the bottleneck the speed of it is irrelevant.
Same with the card; if the card is at least 66x (that is 9.9MB/s) then it
isn't going to be the bottleneck.

My EOS can take 3 frames per second until the buffer is full. In 8Mpixels,
high JPEG mode, it shoots about 14 shots until it has to sit and wait for
the memory card to catch up - you can watch the access light to see this. In
RAW mode, this delay is more obvious. So the image processor and bus are not
the bottlenecks - the card is!

Doesn't matter. In tests the EOS 350D only writes images at between 4 and 6
MB/s. http://www.robgalbraith.com/bins/mul...?cid=6007-7699

Doesn't matter if the card and bus can do 20MB/s, the camera still doesn't.


I 'expect' that a compact digital camera will be slightly slower at
processing images, but it is still a dedicated chip and will process images
much faster than any memory card can transfer them.

I don't think it matters how long the image processor takes to deal with the
photo - it will be significantly less time than it takes the card to store
it away - why else have Sandisk been working on faster and faster cards -
the Extreme IV is with us now. I don't know figures, but it can probably
save 30+MB/s, but will still be the bottleneck !!



Err Sandisk are generating big numbers because big numbers sell. Besides,
faster is *better*, it's just not guaranteed that anything can use the extra
speed yet.

Joey wrote:
On 08 Jun 2007, GT wrote:

"Richard Polhill" wrote in
message . ..
GT wrote:
"Richard Polhill" wrote in
message .. .
GT wrote:
"Richard Polhill" wrote in
message . ..
Joey wrote:
If I get a modern super-compact digital camera such as a
mid-range Canon IXUS (US: Canon Powershot) for general use
then ...

... what minimum speed of SD memory should I get to avoid
delays?

I see "x133" mentioned a lot on memory adverts. Is x133
fast, slow, just right for the sort of camera I am thing of?

I would probably get 1GB or 2 GB from this sto
http://www.jacobsdigital.co.uk/index...uery=sd+memory

I don't believe the fact that it's a supercompact is relevant.

The question is whether the camera can use it at all, but if
it's recent there should be no reason why not.
The speed rating of the memory is its maximum speed, so if the
camera can't go that fast, then the memory will run at less
than top speed, so don't worry about compatability due to
speed.

Compatability due to size of memory card may be an issue though
- see Richard's last line below

Realistically, you'll probably find no speed difference
between a 40x and 133x card. If you buy based on the size and
price rather than speed you'll typically end up with a fast
(say, 133x) card anyway.
Not true. It depends on what the camera is capable of - fast
frame shooting will benefit greatly from faster memory, but I
don't know how many frames per second this camera can do.
Not if the camera cannot write at 133x, and AFAIK most can't.
133x is around 20MB/s write speed.

Surely the limiting factor in the transfer from camera buffer to
storage RAM will be the RAM speed - I would be very disappointed
in a new camera if the buses couldn't handle something faster
than 20MB/s. I would expect the theoretical bus speed to be many
times that - maybe even 50 times faster than that!!
You would expect the bus to be faster than 20MB/s and it probably
is. This just means the bus isn't the bottleneck. You'll be hard
pushed to find a digicam that can write as fast as 10MB/s. Expect
around 5MB/s.

You need to consider what the camera can achieve, not what the
performance of an individual component (bus, card, etc.) is.
But the camera is made up of these components and the performance
of the camera WILL be as slow as the slowest component. Basically,
there is the image processor, the bus and the flash storage. The
image processor can internally process the image much faster than a
flash card can read/write it. And the bus can handle data transfer
at rates many times faster than any flash card.

The camera has to interpret the data from the sensor and convert
it to JPEG and write it to the filesystem, all of which imposes
processing overhead. Unless the bus is the bottleneck the speed of
it is irrelevant. Same with the card; if the card is at least 66x
(that is 9.9MB/s) then it isn't going to be the bottleneck.
My EOS can take 3 frames per second until the buffer is full. In
8Mpixels, high JPEG mode, it shoots about 14 shots until it has to
sit and wait for the memory card to catch up - you can watch the
access light to see this. In RAW mode, this delay is more obvious.
So the image processor and bus are not the bottlenecks - the card
is!

I 'expect' that a compact digital camera will be slightly slower at
processing images, but it is still a dedicated chip and will
process images much faster than any memory card can transfer them.

I don't think it matters how long the image processor takes to deal
with the photo - it will be significantly less time than it takes
the card to store it away - why else have Sandisk been working on
faster and faster cards - the Extreme IV is with us now. I don't
know figures, but it can probably save 30+MB/s, but will still be
the bottleneck !!



So based on the exchange here between Richard and GT, the answer to the
OP (me) is that the memory should be reasonably fast but is not likely
to have to be as much as x133 and something like x66 would most likely
do.

Did I get that about right?

Err yeah about that. To be honest you'll probably find the best deals are in
the 133x and 150x cards anyway so it is becoming moot. ;-)

On Fri, 08 Jun 2007 13:31:05 +0100, Joey
wrote:



So based on the exchange here between Richard and GT, the answer to the
OP (me) is that the memory should be reasonably fast but is not likely
to have to be as much as x133 and something like x66 would most likely
do.

Did I get that about right?


Mostly, but in general when you see a card with only one
speed rating like 133X, that is the read, not write speed.
You'd be interested in the write speed of course and that is
generally lower than read speed.

I would recommend a card with read speed higher than 66X
also because once you have a lot of pictures on it, a card
reader can transfer those to the PC faster and the card
would have a longer viable lifespan. Wherever you plan on
buying, it should not cost substantially more to get a card
with higher speed until you get to the premium grade cards,
and that might be the break-point which makes the best
value.

GT wrote:
"Joey" wrote in message
...
If I get a modern super-compact digital camera such as a mid-range Canon
IXUS (US: Canon Powershot) for general use then ...

... what minimum speed of SD memory should I get to avoid delays?

I see "x133" mentioned a lot on memory adverts. Is x133 fast, slow,
just right for the sort of camera I am thing of?

x133 is medium to fast. However, how many shots can the camera take in a
second? If you were looking at an SLR with 2 or more frames per second, then
memory speed starts to become an issue, but if the camera can only shoot 1
frame per second, then memory speed doesn't really matter.



Except most compacts can shoot video. When my 1GB card failed and I had
to use a 256MB, I couldn't shoot sustained video.

I guess any big, newer card should be fast though.

"Richard Polhill" wrote in message
.. .
GT wrote:
"Richard Polhill" wrote in message
. ..
GT wrote:
"Richard Polhill" wrote in message
.. .
GT wrote:
"Richard Polhill" wrote in
message . ..
Joey wrote:
If I get a modern super-compact digital camera such as a mid-range
Canon IXUS (US: Canon Powershot) for general use then ...

... what minimum speed of SD memory should I get to avoid delays?

I see "x133" mentioned a lot on memory adverts. Is x133 fast,
slow, just right for the sort of camera I am thing of?

I would probably get 1GB or 2 GB from this sto
http://www.jacobsdigital.co.uk/index...uery=sd+memory

I don't believe the fact that it's a supercompact is relevant.

The question is whether the camera can use it at all, but if it's
recent there should be no reason why not.
The speed rating of the memory is its maximum speed, so if the camera
can't go that fast, then the memory will run at less than top speed,
so don't worry about compatability due to speed.

Compatability due to size of memory card may be an issue though - see
Richard's last line below

Realistically, you'll probably find no speed difference between a
40x and 133x card. If you buy based on the size and price rather
than speed you'll typically end up with a fast (say, 133x) card
anyway.
Not true. It depends on what the camera is capable of - fast frame
shooting will benefit greatly from faster memory, but I don't know
how many frames per second this camera can do.
Not if the camera cannot write at 133x, and AFAIK most can't.
133x is around 20MB/s write speed.

Surely the limiting factor in the transfer from camera buffer to
storage RAM will be the RAM speed - I would be very disappointed in a
new camera if the buses couldn't handle something faster than 20MB/s. I
would expect the theoretical bus speed to be many times that - maybe
even 50 times faster than that!!
You would expect the bus to be faster than 20MB/s and it probably is.
This just means the bus isn't the bottleneck. You'll be hard pushed to
find a digicam that can write as fast as 10MB/s. Expect around 5MB/s.

You need to consider what the camera can achieve, not what the
performance of an individual component (bus, card, etc.) is.

But the camera is made up of these components and the performance of the
camera WILL be as slow as the slowest component. Basically, there is the
image processor, the bus and the flash storage. The image processor can
internally process the image much faster than a flash card can read/write
it. And the bus can handle data transfer at rates many times faster than
any flash card.

The camera has to interpret the data from the sensor and convert it to
JPEG and write it to the filesystem, all of which imposes processing
overhead. Unless the bus is the bottleneck the speed of it is
irrelevant. Same with the card; if the card is at least 66x (that is
9.9MB/s) then it isn't going to be the bottleneck.

My EOS can take 3 frames per second until the buffer is full. In
8Mpixels, high JPEG mode, it shoots about 14 shots until it has to sit
and wait for the memory card to catch up - you can watch the access light
to see this. In RAW mode, this delay is more obvious. So the image
processor and bus are not the bottlenecks - the card is!

Doesn't matter. In tests the EOS 350D only writes images at between 4 and
6 MB/s. http://www.robgalbraith.com/bins/mul...?cid=6007-7699

Very interesting - I was not aware of that!

So that suggests that there is another component causing the bottleneck -
the 'transfer chip' that sits at the business end of the flash transfer bus!

Doesn't matter if the card and bus can do 20MB/s, the camera still
doesn't.

Am I right in saying 6MB/s equates to around 40x?

GT wrote:
"Richard Polhill" wrote in message
.. .
GT wrote:
"Richard Polhill" wrote in message
. ..
GT wrote:
"Richard Polhill" wrote in message
.. .
GT wrote:
"Richard Polhill" wrote in
message . ..
Joey wrote:
If I get a modern super-compact digital camera such as a mid-range
Canon IXUS (US: Canon Powershot) for general use then ...

... what minimum speed of SD memory should I get to avoid delays?

I see "x133" mentioned a lot on memory adverts. Is x133 fast,
slow, just right for the sort of camera I am thing of?

I would probably get 1GB or 2 GB from this sto
http://www.jacobsdigital.co.uk/index...uery=sd+memory

I don't believe the fact that it's a supercompact is relevant.

The question is whether the camera can use it at all, but if it's
recent there should be no reason why not.
The speed rating of the memory is its maximum speed, so if the camera
can't go that fast, then the memory will run at less than top speed,
so don't worry about compatability due to speed.

Compatability due to size of memory card may be an issue though - see
Richard's last line below

Realistically, you'll probably find no speed difference between a
40x and 133x card. If you buy based on the size and price rather
than speed you'll typically end up with a fast (say, 133x) card
anyway.
Not true. It depends on what the camera is capable of - fast frame
shooting will benefit greatly from faster memory, but I don't know
how many frames per second this camera can do.
Not if the camera cannot write at 133x, and AFAIK most can't.
133x is around 20MB/s write speed.

Surely the limiting factor in the transfer from camera buffer to
storage RAM will be the RAM speed - I would be very disappointed in a
new camera if the buses couldn't handle something faster than 20MB/s. I
would expect the theoretical bus speed to be many times that - maybe
even 50 times faster than that!!
You would expect the bus to be faster than 20MB/s and it probably is.
This just means the bus isn't the bottleneck. You'll be hard pushed to
find a digicam that can write as fast as 10MB/s. Expect around 5MB/s.

You need to consider what the camera can achieve, not what the
performance of an individual component (bus, card, etc.) is.
But the camera is made up of these components and the performance of the
camera WILL be as slow as the slowest component. Basically, there is the
image processor, the bus and the flash storage. The image processor can
internally process the image much faster than a flash card can read/write
it. And the bus can handle data transfer at rates many times faster than
any flash card.

The camera has to interpret the data from the sensor and convert it to
JPEG and write it to the filesystem, all of which imposes processing
overhead. Unless the bus is the bottleneck the speed of it is
irrelevant. Same with the card; if the card is at least 66x (that is
9.9MB/s) then it isn't going to be the bottleneck.
My EOS can take 3 frames per second until the buffer is full. In
8Mpixels, high JPEG mode, it shoots about 14 shots until it has to sit
and wait for the memory card to catch up - you can watch the access light
to see this. In RAW mode, this delay is more obvious. So the image
processor and bus are not the bottlenecks - the card is!
Doesn't matter. In tests the EOS 350D only writes images at between 4 and
6 MB/s. http://www.robgalbraith.com/bins/mul...?cid=6007-7699

Very interesting - I was not aware of that!

So that suggests that there is another component causing the bottleneck -
the 'transfer chip' that sits at the business end of the flash transfer bus!

Yeah I kind of put it down to the processing on board, but it does seem rather
slow.


Doesn't matter if the card and bus can do 20MB/s, the camera still
doesn't.

Am I right in saying 6MB/s equates to around 40x?


Yes.

The multipliers are based on the standard CD-ROM transfer rate of 150kB/s.

GT wrote:

x133 is medium to fast. However, how many shots can the camera
take in a second?

The IXUS series are normally capable of producing slightly more that 2
images/second at the highest resolution, until the card runs full.
Assuming that an image is around 2-3 MB is size, a card capable of
writing 7MB/seconds seems to be enough.

As for movies, MJPEG (a common choice for small cameras) runs between 1
and 2 MB/sec. It makes me wonder just how slow my old non-movie-capable
SD-card really was.
--
Toke Eskildsen - http://ekot.dk/

On Fri, 8 Jun 2007 14:51:42 +0100, "GT"
wrote:


Doesn't matter. In tests the EOS 350D only writes images at between 4 and
6 MB/s. http://www.robgalbraith.com/bins/mul...?cid=6007-7699

Very interesting - I was not aware of that!

So that suggests that there is another component causing the bottleneck -
the 'transfer chip' that sits at the business end of the flash transfer bus!


True, but, speeding up processing is one of the clear
evolutionary points of newer cameras, that test was 2005.

Also, that was a Compact Flash card not SD which could make
a difference.



Doesn't matter if the card and bus can do 20MB/s, the camera still
doesn't.

Am I right in saying 6MB/s equates to around 40x?


yes, but it is really worth trying to think in terms of
slowest possible? C'mon, a 133X 2GB card with 15.5MB/s
write speed is a mere $23, versus ~ $15-20 or so for a lower
end card (the exception being that some really low end cards
are now practically free after rebate, but I've no idea
about the rebated products in the UK).

http://www.newegg.com/Product/Produc...82E16820233021

While the price may be higher in the UK, it's probably also
quite a bit higher because OP is thinking of buying it from
a camera store which tends to mean a price premium and often
older stock (slower stock) since they don't move product
nearly as fast as a larger 'eTailer.

On Fri, 08 Jun 2007 09:52:18 +0100, Joey wrote:

If I get a modern super-compact digital camera such as a mid-range Canon
IXUS (US: Canon Powershot) for general use then ...

... what minimum speed of SD memory should I get to avoid delays?

I see "x133" mentioned a lot on memory adverts. Is x133 fast, slow,
just right for the sort of camera I am thing of?

I would probably get 1GB or 2 GB from this sto
http://www.jacobsdigital.co.uk/index...uery=sd+memory

You might as well get the cheapest ones you can find - you'll never notice
the difference.