Are all SD cards more or less equal, given storage volume?
Oh god no! Not even close.
There are some very important things to know about memory cards before you
go and buy one, but unfortunately these things can be hard to find out from
the memory manufacturers.
One of the things I do at my job is image recovery for customers whose
memory cards have become unreadable for whatever reason. I get about six or
seven image recovery requests per week, and I've noticed some trends:
-- The majority of memory cards that come to me with problems are those
cheapass SanDisk cards that are sold just about everywhere (especially at
places like Costco and Wal*Mart). Note: this group does not include Ultra
or Extreme cards.
-- The next largest group of cards to come to me are "no name" memory
cards. "No name" refers to cards from a brand no one (in my lab, anyway)
has heard of or cards with no brand at all. Many of these cards come from
online retailers who package them with a camera to sweeten the deal, or from
the customer having to purchase more memory from a tourist trap while
travelling.
-- The smallest group consists of "professional" cards. In the last couple
weeks, I've seen two SanDisk Ultra IIs, one SanDisk Extreme, and one Lexar
Professional (which is the brand I use, and which I actually rarely see come
to me with problems).
What separates these groups?
Memory manufacturers generally have three tiers of quality, and they affect
the speed and reliability of the memory in each tier.
Tier 3: This is the cheap stuff. Cheapass SanDisk cards fall in this
category, as well as most other cheapass memory you find (this includes
cheapass memory you can buy for your computer and whatnot). If you were to
open a tier 3 memory card, you would see more than one piece of flash
memory. If, for example, you bought a 512mb card and opened it up, you
would most likely see four pieces of 128mb flash memory inside. These
modules are cheaper to produce, and so the manufacturers produce them en
masse and combine them into larger capacity cards. More memory modules
means higher chances of getting defective memory, as well as slower transfer
rates, but lower prices. Consumers buy this stuff because they think
they're getting a good deal, but in fact they're playing roulette with their
data.
Tier 2: This stuff is usually produced from a couple memory modules, but not
as many as Tier 3 cards. The modules have higher capacities (in some cases
there is only one piece of memory in tier 2 cards) and are usually produced
under tighter quality controls. These cards are faster than tier 3 cards,
but not always as fast as Tier 1 (though they can be very fast).
Tier 1: This is the high-end stuff. You generally get what you pay for with
tier 1 cards. They are made from a single memory module, and are generally
very fast (depending on the technology available at the time they were
designed, of course). They are produced under the tightest quality
controls, and are often tested at the factory before being shipped. Lexar
Professional, SanDisk Extreme, and SanDisk Ultra cards fall under this
category, but in my experience with so many bad cards, the Lexar
Professional cards seem to be the most reliable (though admittedly not
always as fast as the SanDisk cards)
So, after learning all this, it has become my opinion that, when buying
memory, one should spend the extra money and get professional-quality stuff.
You really do get what you pay for.
John Celio
P.S.: I do not claim to be an expert on this topic, nor do I have numbers to
back any of this up. These are my observations along with industry
information I have been trained on by my employer. Take it as you will.
P.P.S:
Barry A. Rice, Ph.D.
Invasive Species Specialist
Invasive Species Initiative
The Nature Conservancy
V: 530-754-8891
http://tncweeds.ucdavis.edu
You work at UCD? That's where I went to school for my BA. Are you coming
to the NorCal PDML meet next month?
--
http://www.neovenator.com
AIM: Neopifex
"Hey, I'm an artist. I can do whatever I want and pretend I'm making a
statement."
