Performance of CF cards and calculations

[frank_dzambic]

Ok, I just picked up a used 1Ds on Ebay, and I need to buy a Compact

Flash card for it.

 

The specs on these things have to be the most cryptic and

contradictory of anything I've ever seen.

 

The first problem is that I can't find any figures on the write speed

of the 1Ds in MB/s. I've seen that it will shoot 3.3 fps, but no

mention of the MB/s. However, after checking Roger Galbraiths' site,

it appears that there is a difference in write speeds between cards

(using the 1Ds) ranging from 2.074MB/s to 1.875MB/s in the top ten,

going from fastest to slowest. To me, this translates into write

times of approximately 33 minutes vs 36 minutes to write and fill a

4Gb card. Or, a difference of 2 secs per file based on a 35MB RAW

file. So, in my opinion, the difference is negligible, especially

since it's extremely unlikely if not impossible to fill an entire 4Gb

card up in one long continuous burst. Yet Roger Galbraiths conclusion

(whose opinion and testing I respect) is that in the 1Ds "what you

have is a digital SLR that will benefit from all the speed a

CompactFlash card can offer."

 

Looking at portable storage, specifically the Super DigiBin since it

appears to be the fastest thing out there right now, the specs on it

appear to be 2.6MB/sec transfer speed from the card to the SDG. It

appears to me, based on that, that it doesn't matter how fast of a CF

card I get, the limiting factor by far will be the SDG (or whatever

digital wallet you're using). Especially in light of the fact that

the Sandisk website states that all their Extreme and Ultra cards

write/read at a minimum 9MBsec/10MBsec, with the new Extreme III

rated at 20MB/sec (which appears to be by far the fastest thing out

there). So again, it appears that there's absolutely no advantage in

buying a faster card. It won't transfer the data to the SDG any

faster thereby saving on the battery consumption, and the SDG is

absolutely the limiting factor. For the record, I'm looking at a

digital wallet since I don't think I'll find it practical to lug

around a laptop in the field to take advantage of USB 2.0 transfer speeds.

 

Lastly, I checked the specs on a Lexar card reader at B&H. It has USB

2.0, and claims "USB 2.0 is 480 Mb/sec, 40 times faster than USB 1.1."

Simple math tells me then that USB 1.1 is 12Mb/sec. A little more

math then tells me that those numbers equate to 60MB/sec vs 1.5MB/sec.

So, now it appears that, using USB 1.1, it would take 45.5 minutes to

read the entire contents of a 4Gb card, with the USB 1.1 interface

being the limiting factor here since the cards themselves are capable

of much higher transfer speeds than that. Using the USB 2.0

interface, it would only take a little over a minute to read that same

4GB card, if the card was capable of such a high transfer rate.

However, going with the Sandisk specs of 10MB/sec and 20MB/sec (for

the new Extreme III), the transfer times would be almost 7 minutes,

and 3.5 minutes respectively.

 

So, to summarize, it seems that the only time it pays to have an

extremely fast card is if you're transferring files to a computer with

a USB 2.0 interface. Then the difference in transfer times can be

rather dramatic, but the card will ultimately be the limiting factor,

no matter how fast the card is, as none of them come close to to the

maximum transfer rate of USB 2.0 .

 

Bottom line, I should look for the best value in size, not speed.

 

Any thoughts, or comments would be appreciated since it's entirely

possible I've made mistakes here, or overlooked something. This will

be my first dSLR, and first CF card as well.

 

And please note, I'm not a pixel-peeping armchair photographer. I

chose the 1Ds based on image quality, but I'm choosing the supporting

hardware based on specs and real-world performance.

[bobatkins]

The only real practical benefit of faster CF cards is in terms of frame rate once you've filled the camera buffer. If you never fill the buffer, it really doesn't matter much. If you do then faster cards give you a faster frame rate if the camera can use them - and the 1Ds can.

 

Tranfer speeds to a computer are of little concern to me personally. Whether it takes 10 minutes or 20 minutes doesn't matter if I'm not sitting there waiting for it to finish. I just do something else (eat lunch, watch TV, sleep etc.) while the download proceeds at its own pace.

[peter_foiles2]

Go to www.robgalbraith.com, they maintain a database of performance for different brands and models of CF cards in different dSLRs. A card that is fast in a Canon may not be fast in a Nikon and vice versa. This will give you some real world data to base your decision on.

[beauh44]

Hi Frank, Bob's right - if you're a studio photographer or doing landscapes and macros, you can get buy without the fastest cards just fine. If, on the other hand, you're shooting sports or anything rapid-fire, then it helps to have a speedy card. You will get somewhat faster transfers to your PC with the faster cards if that's important for you.

 

(Why doesn't someone make a card reader that'll hold 4 cards and copy each, in turn to your hard disk, unattended? They could make it look like a little toaster!) ;-)

 

With regards to the super digi-bin, there are those who say that these devices days are numbered because the bottom has fallen out of the CF card market. In other words, it's getting close to the point where it may make sense to simply buy lots of CF card memory. Now backup is another issue! Good luck!

[basscheffers]

Beau, I think that's correct for JPEG shooters. For those showing a little appreciation for their images and don't want to waste too much time in Photoshop afterwards, ie: people who shoot RAW, the economics aren't quite there yet.

 

Frank, I don't know the SDG, but looking at those specs, the CompactDrive is faster. (3.5MB/sec with my 40/45x cards) Interestinlgy, it's also one of the cheapest you can get now and has incredible battery life.

[zhi_da_zhong]

<blockquote><em>

The only real practical benefit of faster CF cards is in terms of frame rate once you've

filled the camera buffer. If you never fill the buffer, it really doesn't matter much.

</em></blockquote>

<p>There's a bit of subtlety here, actually. It's true that card speed doesn't affect

frame rate before the buffer is full, but it

does affect when -- if ever -- you'll reach that point. Let me illustrate this with an

example. Suppose you want to shoot continuously at 0.5 fps with a D70 in raw mode.

Let's say the files are 6MB each. With a 3MB/s or faster card, the camera will always

have enough time to empty the

buffer before the next shot, and the buffer will never be full (until the card itself is full,

of course). Now if you use a 2MB/s card, the buffer will be full after 12 shots. Cameras

with bigger buffers allow you to shoot longer and/or use slower cards -- perhaps

long enough that you'll never reach the limit in practice, but the principle is the same:

a faster card will extend the useful time period of the buffer. How fast a card needs to

be depends on your particular situation.

</p>

[frank_dzambic]

Thanks for the input guys. I guess I should have specified I'm mainly shooting landscpapes, not sports or action photography. So, it appears my original assumption was correct then. (At least for me) the only advantage to getting an ultra fast CF card would be faster transfer times to the computer. I agree with Bob on that one--it's just not important. I can find something to do while that's going on.

 

Beau, if the bottom has fallen out of the CF market, I'd hate to see how much they cost earlier in the year. I haven't been pricing them as I haven't needed them up until now, but I'm finding them surprisingly expensive. I guess I just haven't started thinking of that CF card as an endless roll of film with processing included yet. As far as digital wallets days being numbered, I'm a little skeptical of that claim. That Super DigiBin I mentioned was as low as $329.95 for an 80GB model. I don't even want to think what 80GB of CF cards would cost. Of course, I would need a lot of storage capacity on a very long hike, or overnight hike, or a long road trip (since I don't have a laptop yet) shooting RAW.

 

Bas, thanks for the heads up on the CompactDrive. I'll look into that as well. The numbers you supplied are certainly faster than the SDG.

 

 

Thanks again all.