July 18, 2011
Welcome aboard photo enthusiasts. It’s interesting to note that articles I write for The Triton get circulated through other Internet outlets, and I’ve received responses from people who may not be doing much sailing, but who are involved in photography.
In response the May issue discussing memory cards, I got this feedback from Robert Shullich of Brooklyn, N.Y. (slightly edited for space):
“Many of the issues you raise may be true as a single-shot photographer. And maybe these high capacities have made photographers lazy to shoot 1,000s of pictures in the hope that there is just one good shot in there. Actually, I can take 1,000s and still have 100 percent junk.
“Anyway, these capacities are more in line with video. For example, I just got a 8GB Flip HD camera. These cameras use built-in memory and are formatted FAT32.“With a FAT32 file system, the largest file size is 4GB. Although the camera boasts a two-hour HD recording time, I recorded an hour and it took 4GB in size, which means to shoot two hours would create two files.
“The point is that for long HD video recording, the current file systems and current media sizes are no longer adequate. And since many single-shot cameras also now have capability for video as well, SDXC cards are being used in them.
“And a 48GB SDXC card is almost the size of a dual layer Blue Ray disc. When these cards, which cost almost $200, come down in price, who knows, maybe Blue Ray will die?
“I am not a photographer. I do have a camera for taking family pictures and pictures at functions, etc. I just set them to automatic and hope the camera does the work.
“My interest, and why I locked into your post, was the exFAT tag, as I am in computers and involved with studying digital forensics. I have presented exFAT at various computer conferences as the file system is new, and used in desktop and server systems besides consumer electronics.
“For a single-shot camera, the speed issue is how fast can you take the next picture. I have experiences with different digital cameras that after I take a picture, I have to wait while the camera writes to the memory card. The camera is a computer and the memory card is basically the disk drive.
“In a digital camera, you are limited by the CCD that converts the image to digital, and any compression algorithms (such as JPEG, or MPEG for video) that have to run, and the speed to write the data to the card. What you don’t think of is that the memory card, since it has a file system on it, also has overhead for storing the file.
“This overhead may include keeping track of used and unused blocks, maps of where the blocks are, and the order of the blocks. This file system overhead can slow down the allocation and write speed of the card as well.
“So exFAT tries to address these issues in two ways. One is the reduction of file system overhead by the redesign of how the file system is organized. (I won’t go into the technical details.)
“The other part is I/O bus speed, with an increase of writing the bits of information much faster. SDXC cards have two speeds, UHS-1 and UHS-2. The max for UHS-1 is 104MB/S, that is mega-bytes per second, which is more than 800 mega-bits per second.
“A USB 2 channel has a maximum of 480 mega-bits per second. A firewire 1 is 400 mega-bits per second and a firewire 2 is 800 mega-bits per second, just to give you perspective. The UHS-2, at a maximum of 300 mega-bytes (2.4 giga-bits) per second, is really fast.
“But you are seeing class 10 to class 30 cards, with 30 mega-bits per second, and the cards are rated for a slower write speed and a faster read speed.“So although Lexar announced a 128GB SDXC card, it will be a while before you see a 2TB SDXC card,. And it will be long before you see 300MB/s speeds.
“But the speed is seen more for video than still. Although it may be annoying to have to wait between still shots for the image to be written to the card, delays during video shooting won’t be tolerated.”
I’d like to thank Robert for his insights for a better understanding of technical considerations and advances in camera memory cards.
In the next issue I will give voice to Jan Boles, who responded to the same article, but replied to the non-technical issue of increased capacity memory cards regarding quantity vs. quality. His thoughts heighten aesthetic aspirations, but for now I’ll take permission to go ashore.
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