SD vs xD camera/memory cards

Hi Fred,I have some camera questions for you.

Based on your outstanding road report from your cross country adventure and the great pictures you shared, I investigated and then purchased a Fuji Finepix S700 camera. (I got a great price for it at Amazon, and all the good reviews there helped me make up my mind.) While I'm waiting for it to be delivered, I was curious if it made a difference which type of memory card I got for this camera. I wasn't able to find any basic information describing the difference between the two type of cards (SD &xD) that the S700 accepts, and the only real difference I've been able to determine is price and a slight difference in capacity. I'd be grateful for any light you can shed on this subject.

You also mentioned that you use the Gimp for post-processing of your pictures. Do you still use the Gimp, and how satisfied are you with it? How steep is the learning curve if I'm coming from another image program (Pain Shop Pro 7)? I ask because now that SP3 is out for XP, I'm preparing to do what I call a Nuke & Pave to give myself a clean system to image now that XP is getting long in the tooth and I'm planning on using as much free and open source software as I can when I reload the system.

Take care,Lonnie

Functionally, the two kinds of cards are all but identical. They're both forms of electrically-rewritable "flash" memory that retains data even when powered off.

SD get its name from "secure digital." It's called "secure" because, unlike the RAM in PCs, the data in an SD card is retained at power-down. This is an obsolete use of the word "secure," so don't be misled: SD cards have no intrinsic encryption other features to make the data safe from snooping. Physically, an SD card contains a memory chip and some controller circuitry.

xD is "eXtreme Digital," another obsolete phrase. It was "extreme" when it first appeared ("look! no film!") but there's nothing extreme about it now. An xD card is basically just a memory chip in compact packaging; the camera (or other device) supplies the controller circuitry.

In short, both cards do the same thing.

xD is a semi-proprietary format (created by Olympus and Fujifilm), with the card's engineering internals shielded by patent laws and other measures. Its big advantage, when it came out, was its very small size--- roughly half that of typical SD card, and much smaller than Sony's "memory sticks" of yore.

It's proprietary, so part of the original marketing plan by Olympus and Fujifilm was to lock consumers into buying brand-specific memory for their cameras. Olympus went a little further and built a special "panorama" mode into some of its cameras, and then wrote code so that that mode is only enabled when an Olympus card is in the slot. There's nothing about the card that's special--- the camera's doing all the panorama work. Olympus just fixed it so the feature is only enabled when their special brand of card is used; a way to get people to buy their cards.

SD isn't proprietary, so there are a million different vendors competing for business. Although SD cards are actually more complicated than xD ones, they're often sold for less due to economies of scale. Bargain-oriented vendors also operate in this space, sometimes selling SD cards at near-giveaway prices.

There are also several variants of SD technology, including half-sized SD cards that are just as small as xD.

Many cameras and other devices actually can accept either type of memory. For example, even though my Fujifilm S700 is from Fujifilm, one of the originators of the xD format, the camera will happily eat either xD or SD cards, no problem. Likewise, my Acer laptop's built-in card reader also accepts both card types, no problem.

Which card to pick? Well, you first have to see if your hardware requires only one type of card. If it does, you're locked into that type. But again, it's becoming rare for this to occur.

Beyond that, speed matters. Faster memory may let your camera cycle faster between shots, and may improve memory-intensive tasks such as continuous shooting or large-format/high-frame-rate movie-making. Generally, faster is better, especially if you plan to keep the card for a long time; future cameras will likely need faster memory than today's. On the other hand, if you sell or pass on your cards with your older cameras, then it makes no sense to pay for memory speed your current camera can't utilize.

Speed specs overlap and vary enormously, but in general, SD can be faster than xD.

If you were designing a space mission or something equally exotic, the small power consumption differences might matter (xD, with less circuitry, is slightly more power-efficient than SD) But these differences are completely invisible in normal use, swamped by much larger variables such as flash/no-flash, camera temperature, etc.

Reliability also matters. The rock-bottom, third-tier and no-name brands are demonstrably less reliable than the bigger names. They only flash card failure I've ever had was in a cheapo SD card I got at an absurdly low price. Turned out it was priced that way for a reason!

Capacity matters. Flash memory normally uses old-style FAT or FAT32 hard-drive addressing (this is one of the reasons a card appears as a "removable drive" in your system). The software in your camera controls this; and thus sets software limits on card/drive capacity. A FAT-based file system limits you to 2GB usable memory because the software literally can't count high enough to access larger address spaces. If your camera uses old-style FAT, it may not even recognize a memory card larger than 2GB.

Newer cameras tend to use FAT32, which effectively removes the 2GB volume limit. It retains another limit, though, in that file sizes must be less than 4GB. This is rarely a practical limitation in normal use. (I've never run into it.)

Generally larger capacity cards are more convenient to use--- less swapping, more continuous shooting. On the other hand, the larger the card, the greater the temptation to let the card fill up without emptying it. With several smaller cards, you lose some convenience, but can help ensure that a single problem--- loss or malfunction of the camera, for example--- won't cause you to lose all your pictures.

I use a mix of cards now. My older, slower and lower-capacity cards get moved down the food chain to less-demanding uses, such as digital picture frames. The newer, faster, high-capacity cards go in my newest, best camera.

I generally keep a 2GB card in the camera at all times, just because it's available. (Why not?) On that month-long road-trip, I carried 3 cameras and a total of 8 GB in memory cards, but that was extreme because it was a once-in-a-lifetime trip, and I didn't want to miss shots.

If I had to buy camera memory today, I'd search for cards from the more-recognized brands; filtering for those that are larger (1 or 2 GB); and faster (look for a mention of "hi-speed" or some such in the advertising propaganda). Then I'd buy whatever's cheapest from among those that made the cut.

Simple as that!

Hoped that helped. More:
http://en.wikipedia.org/wiki/Secure_Digital_card
http://en.wikipedia.org/wiki/XD-Picture_Card
http://en.wikipedia.org/wiki/File_Allocation_Table

(This is getting long; I'll answer the GIMP questions in a later post.)