Thanks, Igor, for that erudite explanation.

I'll try an Ultra Plus. No point in going higher than that.

Alan C

-----Original Message----- From: Igor PDML-StR
Sent: 16 May, 2018 5:20 AM
To: PDML@pdml.net
Subject: Re: SD Card Question



Alan,

I was looking at this question at some point (I am still using K-5
iiS). Let me share a few thoughts.

First, you should be aware that different categories/lines of SanDisk
cards change their parameters over time. I.e. Extreme today is different
from Extreme 4 years ago. You are probably aware of that, but I thought
I'd mention this just in case.

Second, yes, you've already figured out, K5 can benefit from the speed of
just below 30 Mbps. But, when the card is rated at 30 Mbps, that is only
for the specific type of writing (large blocks, sequential, ...)
For smaller block sizes and some other conditions, - the speed goes down
drastically.
A good tool for checking that is CrystalDiskMark.
Here is an example of its test output (For *some* SanDisk Extreme Pro, -
maybe not the latest, - that doesn't matteR):
https://www.tweaktown.com/reviews/5400/sandisk-extreme-pro-sdhc-and-microsdhc-memory-card-review/index.html
I am referring to this image:
https://imagescdn.tweaktown.com/content/5/4/5400_10_sandisk_extreme_pro_sdhc_and_microsdhc_memory_card_review.jpg

You can see that 512K write speed is only a small portion of the "Seq"
test. (I was expecting about a half, - I suspect something might be wrong
here, but anyway... this is just what I quickly googled as an example.)

My point is that under some conditions, you might even benefit from a card
that is yet faster than 30 Mbps, because of the slower type of operations.

My best card for K-5 iiS is Samsung Pro (SDXC, I, Class 10, U1)
https://www.amazon.com/dp/B00IVPU6BY/
(I believe it is discontinued now.)

While nominally, with the *up-to* 80 Mb/s write speed, it seems like an
overkill, it seems to me that the card a step below sometimes creates a
bottleneck, especially with video recording.

An additional consideration: You can also benefit from the card's speed in
the card reader. If you have a USB-3 card reader (with the proper bus), -
you can copy the files from it much faster.

HTH,

Igor



Alan C Tue, 15 May 2018 11:28:51 -0700 wrote:

Thanks, PJ

That seems to settle it. The K5 bus allows a write speed of 25Mb/s so an
Extreme Plus (30Mb/s) would do better than the Ultra (10Mb/s) which I
have. Only the newer models like the K3 & K1 can take advantage of Extreme
Pro cards.


Alan C

-----Original Message----- From: P. J. Alling

Sent: 15 May, 2018 7:49 PM
To: pdml@pdml.net
Subject: Re: SD Card Question

This article seems to indicate a higher bus speed for K3 and a few more
recent aps-c models, but other testing seems to show it closer to my
original reply.

https://www.pentaxforums.com/articles/photo-articles/comprehensive-sd-card-guide.html


On 5/15/2018 9:10 AM, Alan C wrote:

    ScanDisk Extreme SD Cards are rated faster than Ultra SD Cards but
would the a K5 be able to take advantage of the higher write speed?


    The K5 files are considerably larger than the K7 files so a usable
higher write speed would be quite helpful.


    Alan C

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