CF cards vs. SD cards?

Question

fhotoace provided this gem of information in an answer to another question:

"CF memory cards (the ones that are used in the pro cameras) have a 120,000 format cycle. That means that if you were to format your card every day, it would last only 57 years. "

Do you know about the format cycle on SD cards? Can you list some reasons why the highest level of cameras are using CF cards instead of switching to SD? Or - why are virtually all P&S cards using SD cards now? Personally, I kind of like the feel of CF cards, but I can see how those delicate pins deep inside the camera might become damaged...

(Yes, I see a CF vs. SD question from 5 months ago, but I was really curious about the format cycle...)

Answer 1

There are only 3 manufacturers of memory chips in the world. So no matter what the brand of your memory or your card is, it comes from one of those. All three tend to use pretty well the same designs for their chips, memory is a very simple concept that doesn't offer a lot of leeway in terms of different designs. All three produce virtually identical quality too, digital devices are unforgiving, the memory must work at all times so there is no choice but to manufacture to that specification.

In terms of longevity, the actual chip in your computer or your card theoretically can last forever. What destroys it usually is being manhandled, being subjected to an unreasonable voltage, or being allowed to get too hot. If none of those events happens the chip will last practically forever. Well, at least you'll be able to will it to your grandchildren and they'll still be able to use it.

However there's more to it than just the chip. First of all the chip has to be connected to the outside world. So you've got very fine wires connecting it to the pins that connect to the outside world. That is a weak spot, if the card is flexed a lot, one of those little wires can break and the chip stops working as a result even though there's nothing wrong with it. Secondly, the pins themselves are vulnerable to coming loose or corroding (yes gold does corrode, just slowly and poorly). So if one of the external pins fails then, again, the chip no longer works.

The duty cycle of a memory card would be determined on the basis of it being removed and inserted a certain number of times and being written to and erased a certain number of times. These tests are also done in an environmental chamber in which the card is heated to it tolerances and cooled as well. (In my case it has to work to about 40C since I am sometimes in the tropics, and it has to operate for me to -35C when I'm out in a severe winter storm in winter). It's usually subjected to typical physical stresses too. I don't know how the data is intergrated but once integrated you end up with a duty cycle as you have discovered. Another term that's more common in that business is the MTBF - the mean time between failures, usually measured in hours. However in the case of memory cards they don't stay turned on for hours or days like in a computer so the duty cycle or format cycle makes more sense when measuring longevity.

I'm not surprised at the duty cycle of the CF card. While it may be pin based, it's incredibly robust in construction so removing and inserting it doesn't really cause anything to flex and thus the little wires from the chip are less likely to break. Add to this, it doesn't have a lock switch which would expose the inards to the outside world, instead it's completely sealed and air tight which further ensures that it's protected from abuse.

I don't know what the duty cycle is of SD cards however I'd suggest that it's a lot lower. Those cards can flex and contaminants can enter through the lock switch. Overall they're more delicate and as a result more likely to fail prematurely if you don't treat them gently.

As to the two cards becoming standards et al, the world needs standards, there have been too many different types of cards on the market. That's confusing for consumers and also potentially expensive as they go from one camera to another and find they have to once again buy new cards.

For the moment the emerging standard is the CF card and the SD card. I doubt very much that there will ever be one for a number of reasons. First of all the SD card was developed because consumers like to carry around cameras the size of a credit card. I won't comment about their taste in image quality as a result. In any case a CF card would occupy too much real estate within such a camera so a smaller footprint was needed. The SD card admirably fits that footprint. By contrast, professional equipment is always huge, so there's lots of space in it to accomodate a larger card. And if the physical container needs to be enlarged a little to accomodate a CF card it wouldn't matter because the professional camera is already so big a little more wouldn't be noticed anyway.

The second reason is capacity. The professional equipment is usually a higher resolution and as resolution continues to climb there will be ever more demand for larger and larger capacities in the cards. Large scale integration is great but it has its limits. As a result in time the SD card will hit a wall and will not longer be able to provide ever larger capacities. By contrast, the CF card is twice the physical size so there's lots of room for ever larger memory chips. This then meets the longer term needs of the professionals.

The third reason is durability. You can practically drive a truck over a CF card and it will survive. While I wouldn't recommend it, you can also drop your CF card into the lake and fish it out, dry it out, and chances are it will continue to work. That is not the case with the SD cards. They're a lot more delicate. As a result it's possible to easily damage an SD card and lose a days shooting whereas it's almost impossible to damage the CF card. Professionals demand that kind of reliability hence the CF card is alive and well.

Now you're right that the pins are an issue with CF cards and yet are they? These days these cards go into high end equipment that is build to incredible tolerances. Once the CF card is in the slot it's impossible to not mate accurately with the pins. And the pins are quite short (relatively speaking) so it's not easy to bend them. Additionally, each pin hole in the card was reamed slightly to better guide each pin into its hole even if it was slightly misaligned. The odds of a bent pin exist but they're almost zero.

By contast the SD card doesn't have that issue but in turn it can, and does, suffer from occasional corrosion on its external pins. It can also flex so you're always running the risk of eventually breaking one of the connecting wires. The lock switch leaves it vulnerable to outside contaminents including water. And it's inserted into devices that aren't build to professional tolerances so it can sometimes slip in not quite perfectly. I'd suggest that the SD card is a greater risk than the CF card.

I use both cards myself. I have a Canon P&S camera that uses that format and I'm generally happy with the cards but they also make me nervous. So I take special care when I handle them so that I don't lose a day's shoot. I have two Nikon SLRs, a D70s and a D200 both of which use CF cards. I love those cards and prefer them. I never hesitate to drop them into a sweaty pocket when one is full, I don't mind dropping them accidentally, and when I insert them into the camera I never really borther to think about the pins, the card always mates perfectly because the tolerances of the slot allow nothing else to happen. My preference will always be for the CF card especially at the moment. You can already get 16GB CF cards but you'll be hard pressed to find an SD card over 4GB at the moment. The SD cards wil catch up of course, eventually, but by the time they do the CF cards will likely be up to 32GB or more.

As a side bar, the CF card actually started its life as a hard drive about seven or eight years ago. At the time there was what was called "microdrive". The initial ones were about 500MB which was unprecedented at the time and shortly thereafter grew to 1GB. There was talk of producing a 2GB one as well but by then the memory cards started to grow in capacity. At the time all those pins were needed because you weren't just transferring data back and forth, you also needed to provide power for the drive and signals that controled what it was to do. When the microdrive then became solid state, that is, it got a memory chip installed in place of the hard drive, the pins were retained so that it could be used in all the cameras at the time that supported microdrive and so that if you owned a few microdrives, you could use them in future cameras too. So the physical shape and size of the CF card had initially been developed to contain a hard drive. That's also why the CF card has no lock switch. The hard drive was very delicate so the card had to be completely sealed to protect if from outside contaminants.

So that's a little about duty cycle and also why both cards have become the standards and why I feel both cards will survive.

I'm not sure if this answers all your questions but I hope it does.

Answer 2

No, CF cards do not have a 120,000 format cycle. The lifespan of ANY card depends on the brand and what components are used in the construction of a particular card. There are many numbers floating around regarding this, anywhere from 10,000 to 50,000 format cycles, none of which are anything other than guesses. This is the first time I've ever heard of 120,000 and I suspect it's just a manufacturer's marketing claim.

An SD card built with the same quality components as a comparable CF card shouldn't last any longer or shorter, the thing that most likely will kill one before another is little manufacturing defects between the two. Again, that's a manufacturing quality issue.

On to top-end dSLRs: one of the highest-end dSLRs available is the Canon 1D-series. They accept CF cards. Lo & behold, they also accept SD cards.

The newest entry-level cameras accept SD cards and this will likely become the norm for most higher-end cameras soon because SD cards now come in higher capacities. This really is the only reason why up until now, most dSLRs supported CF... for the larger capacity that CF *once* offered to the photographer.

Then there's the issue of minituarizing: manufacturers constantly look for ways to improve a camera yet make it smaller AND/OR add more features, knobs, dials, etc... by implementing the smaller SD card slots, there's possibilities for downsizing the physical size of the camera as well as for adding more controls where called for (primarily for the higher-end).

Anyways, in a nutshell, the CF vs. SD argument is for the most part moot, any disagreements usually come from those who've accumulated gigs and gigs of CF memory and whine and moan about having to buy SD cards for a new model that they're keen on obtaining ;)

Answer 3

You can recover deleted or formatted images from SD memory card with H-Data picture file recovery tool. You see, when you delete photos video files on a memory card, the file does not actually get erased, instead it is hidden from view and will be written over when new data arrives.

Answer 4

Good Grief!!!!!!!!!!!!!!!!!