Photo Technical

Your camera is a computer, so optimize files, space and data – A67

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 they are very much involved in photography.  I like to give a voice, especially to those who take the time and interest to offer their experience and insight or otherwise would like to further the discussion.

Let me begin by giving voice Robert Shullich, in response the May issue discussing memory cards.  Due to space limitations for the column I had to edit his words somewhat…

“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 1,000’s of pictures in hope that there is just one good shot in there. Actually, I can take 1,000’s and still have 100% junk.

Anyway, these capacities are more in line with video. For example, I just got a 8GB Flip HD camera. These camera’s use builtin memory and are formatted FAT32.

With a FAT32 file system, the largest file size is 4GB. Although the camera boasts a 2 hr HD recording time, and I recorded an hour and it took 4GB in size, which means to shoot 2 hrs would create 2 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 and above 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 the 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 which converts the image to digital, and any compression algorithms (such as JPEG, or MPEG for video) which 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 2 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, which the max for UHS-1 is 104MB/S, that is mega-bytes per second, which is over 800 mega-bits per second. A USB 2 channel has a maximum of 480 mega-bits per second, and 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, as well as 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.”

Robert Shullich, CPP, CISA, CISM, CGEIT, CISSP, SSCP, GSEC, CIPP, CEH
Brooklyn NY 11202-6156

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 now I’ll take permission to go ashore.