UDMA/RAW/EOS 50D question

[dikjenkins]

Bob please help me on this. These are my understandings: The 50D is UDMA compatible. I have a Max. Burst of 16 shots in succession when shooting in RAW. I'm looking at a new CF card that has a Read Speed of 80MB/sec, a Write Speed of 50MB/sec and a Speed Rating of 533X. If I always shoot in RAW what are my limiting factors in this marriage of CF and 50D?

The Max. Burst of 16 shots doesn't appear to be a limiting factor to me because I shoot air shows, athletic events and surfing where I never link more than 16 shots in succession. I always shoot in RAW, period. One of the Canon techs in their call center told me I was wasting my money buying a 533X, UDMA CF card.   

[jodaco]

UMDA will not help the maximum burst which depends on the memory buffer in the camera not the card. Where you will benefit is emptying this buffer to the card and, with a UMDA reader, offloading from the card to the computer. The camera begins writing to the card as soon as the first shot is taken. It will continue to take shots as fast a possible until the buffer is full. Then as memory becomes available again it will continue to shoot if the shutter remains pressed. So a faster card will increase the post-burst speed as well as how long it takes to completely clear the buffer to prepare for a new full burst.

Whether or not this is worth it is entirely up to you. I would think any action setting (like air shows and sports) increases the benefit of UDMA.

[Bob Atkins]

An ultra- fast UDMA card is probably not going to help too much, especially if you don't shoot long enough bursts to fill the buffer. It can speed downloads from a (UDMA compatible) card reader and it can clear the camera buffer slightly faster. It would likely make more difference to the number of JPEGs you can shoot, but that's already a pretty large number with the 50D.

There's no harm in buying the fastest possible UDMA memory card, except perhaps to your wallet! You may get very slighly more performance out of the fastest card you can buy, but probably not enough difference from a 300x card to make a large price difference worthwhile.

I'd look at something like the Lexar Pro 300x cards. They are UDMA compatible and will pretty much max out the perfiormance of the 50D.

If you want to really max out you could look at the Transcend 600x cards. Also UDMA, and they are about the same price per GB as the Lexars. I've used Transcend cards myself and they have all performed well (though I haven't tried their 600x cards yet). The Sandisk Extreme Pro cards are also 600x UDMA but they are about twice the price of the Transcend. I have used the 16GB Extreme Pro card and I can confirm that it's really fast!

[dikjenkins]

Thank you both for your input. I will look into the cards you've suggested Bob. I don't use a card reader. I was once a consumer of card readers but I'm very pleased with the transfer rate I get right out of the camera via USB to my computer's external hard drives. I must be shooting portions of a burst during the surfing and air show events because I'm forced to wait many times for the buffer to clear. That is the objection that I am wanting to remedy. If you track a surfer along a wave he will perform several nice moves during his ride. If he's good when he bails out he will become airborne and it is those times that I attempt to capture. So it's 4 or 5 shots, a two second pause, another short burst. As I pull the camera away from my face when it refuses to fire I see the red light on the back of the camera flashing regularly indicating it is saving data. I thought a 533X card would be just a bit more that double the cards I now use and that would do the trick. So if we can disregard the transfer rate during the uploading of images out of my camera to the computer/external drives because I'm quite happy with that then I'm understanding you as saying the faster card will not really benefit me in my concerns over rapid fire action shots with the 50D. As I mentioned, I never shoot in JPEG format, always in RAW.

Another observation: When I shoot panoramas I always bracket my shots. The 50D will allow but 3 shots in a bracket. I use Nodal Ninja panoramic head hardware to index my shots and prior to shooting a scene the overlap is established in the indexing head. As I move through the scene quickly  I'll notice that the buffer is constantly working and just barely clearing when I depress the shutter for the next group. I'm using RiData, 233X 8GB CF Cards..

I've just got to go back and discuss the card reader. I've had several card readers in my life and found that they were painfully slow. I'll shoot perhaps 1000 shots at an air show, come back to the motel and begin the upload process to the USB drives. I'd leave the motel for supper and upon returning it would still be working that task. Off to BestBuy one day to get the latest and greatest card reader and this tech asked me why would you use a card reader when a USB cable direct from camera to storage media is faster. I tried that method and it reduced my upload time by approximately 90%. That's not a typo.     

[Bob Atkins]

There are indeed some very, very slow card readers. However there are also some very, very fast ones, faster than camera transfers. The faster ones can easily be more than 10x faster then the slower ones.

For example the Lexar Professional ExpressCard™ CompactFlash® Reader can transfer data at up to 133 MB.s which corresponds to about 880x in CF card speed terms.

I use a high speed SanDisk card reader which runs more than 2x as fast as my 40D. For a comparison of transfer rates, see this article - http://www.bobatkins.com/photography/digital/sandisk_compact_flash_card_readers.html

[jodaco]

You should be getting more than 4 or 5 RAW in a burst on the 50D. I get more like 15 (I forget the actual spec). The frame rate is of course about 6 fps. Could it be that its AI Servo focusing that's slowing you down and not the memory card?

[dikjenkins]

Again, thanks for all your good advise and information. To Jobaco, yes I get about 16 images in burst before the buffer wants to empty its holdings. I was trying to describe by actions when shooting a surfing event when I said I shoot 4 or 5 shots in a burst depending on the surfer's moves. As for AIServo being any slower to focus, I've never had reason to consider that point as the focus is instantaneous with the f/2.8L, 300 prime. So what I'm gathering from this is that yes, I will realize improvement in the amount of time I must wait between a series of bursts by going to a faster UDMA card. I'll always be limited to a maximum of 16 images in burst with the 50D but the process time in the buffer will be something less.