CF card transfer speed. When does it matter?

[Kermit power]

Hi All,

I am looking at the price of Compact Flash cards. They seem to vary widely in price, mainly based on the transfer speed, which seems to be 30, 60 or 90MB/s.

Where does this transfer speed come in to play?

Assume I'm using it with a Canon 7D, would I ever experience issues using the cheaper 30MB/s cards in camera, or would it simply mean waiting a bit longer for the card to transfer the shots to my PC?

[Kermit power]

Anyone?

[mph999]

When you take pictures on continuous shooting.

If you knocking off 6 or 7 fps, you need the card to be quick enough so the camera can write the files, before the cameras buffer fills up.

Martin

[4Lmike]

Im not 100% sure here, so feel free to correct me if im wrong, but i think it might be to do with burst shots. On continuous shoot mode your camera might be able to take 6 photos a second for example, but it wont be able to achieve this if it cant be transferred to the memory card fast enough. i know my burst mode slows down after a while of continuous shooting.

ETA mph999 beat me to it

Edited by 4Lmike on Friday 10th December 19:41

[Olivero]

Firstly, the speed of a card is called the write speed. It is a measure of how quickly a card can record information.
The faster your card the faster you can take photos. It depends on your style/approach.

For typical everyday 'normal' use 30MB/s is fine. When you could really do with a much faster card is when shooting quickly or in bursts. For instance motor sports, paparazzi-style or fashion.
The other time you would want a fast card is for shooting video.

Please buy from a good company. There are lots of fakes out there, that often turn out to be duff.

This page will also give you some good pointers -

http://rocketnewyork.com/memorycards

[LongQ]

You need to look for Read speed and write speed.

Read will usually be faster than write, though they may be claimed as the same.

Read speed comes into its own mainly when downloading and then it depends on the device from which you are downloading.

I almost always take the cards out of the camera and use a reader (unless working 'tethered').

I just bought a new reader - at is 3 to 4 times faster (using USB2) then my older reader - which is quite a time difference when downloading (or uploading depending on your preferred teminology) a large capacity card that is full.

If you never shoot continuously or use a small capacity card or rarely fill a large capacity card or always shoot low res. jpg, then card performance probably does not matter at all.

ETA; If you shoot video check the max output the camera can deliver. A card with a write speed that matches or exceeds that rate per second will be fine. Mostly shooting rapid sequences of full resolutio RAW images will require a far higher record speed card (for optimum availability of the next shot slot) than does video.

Edited by LongQ on Friday 10th December 19:52

[tinman0]

Kermit power said:

Hi All,

I am looking at the price of Compact Flash cards. They seem to vary widely in price, mainly based on the transfer speed, which seems to be 30, 60 or 90MB/s.

Where does this transfer speed come in to play?

Assume I'm using it with a Canon 7D, would I ever experience issues using the cheaper 30MB/s cards in camera, or would it simply mean waiting a bit longer for the card to transfer the shots to my PC?

Check the speed of the bus on the 7D and match it to the card. If the 7D can transfer at 30MB/s then don't bother with a 90M card. And so forth. The manual should tell you what card it wants as a minimum.

[LongQ]

If you have the time to work through it and interpret the information for your specific purposes, this might be of interest.

http://www.robgalbraith.com/bins/multi_page.asp?ci...

[RobDickinson]

7D can writ to UDMA6 or 90mb sec cards.

Remember through raw shooting produces 200mb a sec so no card is fast enough to clear the buffer as fast as you can shoot.

A 90 vs 30 you will get aprox 2 shots extra a second once your having buffer issues (theoreticaly).

Also a faster card can help with downloads to the pc.

[Kermit power]

Thanks all. I very rarely anticipate filling the buffer (16 Raw shots or thereabouts), and I'm not bothered about transfer speed to the PC, so sounds like the 30MBs cards will be just fine.

[The_Jackal]

If I had a thousand pound camera I wouldn't think twice about buying the best card to put in it. Why put a slower card in it?
The difference is only £60 between a 60 and a 90 speed 16Gb Sandisk CF card.

[LongQ]

Kermit power said:

Thanks all. I very rarely anticipate filling the buffer (16 Raw shots or thereabouts), and I'm not bothered about transfer speed to the PC, so sounds like the 30MBs cards will be just fine.

60Mb, at a sensible price of course, is more likely to be future proof a little longer.

A 16Gb Sandisk Extreme (2010) works well with the 7D. At 20 to 25Mb per RAW file they fill up quite quickly though.

[Kermit power]

The_Jackal said:

If I had a thousand pound camera I wouldn't think twice about buying the best card to put in it. Why put a slower card in it?
The difference is only £60 between a 60 and a 90 speed 16Gb Sandisk CF card.

What a strange attitude. Why waste money I don't need to waste?

The only difference between a 60 and a 90MBs Sandisk CF card, apart from price, is the write speed, and it would appear that I'm not going to need to higher write speed. Given the size of the buffer on the 7D, I'd have to take 2+ seconds of continuous shots to fill the buffer. Given that I can't imagine any scenario when that's going to happen, why would I want to pay extra to cater for it?

The cost of the camera is, if anything, a contributory factor towards not spending the extra money. If it were cheaper, it would doubtless have a smaller buffer, thus increasing the need for card speed.

[RobDickinson]

I have a 350x Adata 16GB card.

I get 22-23 shots raw before the buffer chokes.

This is usualy beyond plenty, if your shooting sports and machine gun get the fastest card.

If your into shooting thousands of shots a day and need them downloaded quick, get a faster card.

[Kermit power]

RobDickinson said:

I have a 350x Adata 16GB card.

I get 22-23 shots raw before the buffer chokes.

This is usualy beyond plenty, if your shooting sports and machine gun get the fastest card.

If your into shooting thousands of shots a day and need them downloaded quick, get a faster card.

That's pretty much where my thinking has got to. The most I do on burst is something like a fish eagle coming into a pond in a falconry display, so to need more than the 7D's buffer would just mean I'm indulging my own poor photography skills if I can't time it better than that, and I'm only an enthusiastic amateur, so never have to worry about processing lots of shots to a deadline.

30MBs and a few quid saved it is, then!

[LongQ]

inkiboo said:

The_Jackal said:

If I had a thousand pound camera I wouldn't think twice about buying the best card to put in it. Why put a slower card in it?
The difference is only £60 between a 60 and a 90 speed 16Gb Sandisk CF card.

Why on earth would you buy a 16gb card? If you need 16gb, buy two 8gbs. Significantly cheaper and more flexible.

I still run my Sandisk Extreme IV 4gbs without any issue.

Mainly because you have less card changes to deal with on a busy shooting day. It's interesting how the card always goes from 100 file capacity to zero just when you are in the middle of shooting something interesting .... unless you change early and avoid filling the previous card ....


Edit to add: And pricing per Gb is usually about the same with bigger cards of the same manufacturer and spec. being, maybe, a tad cheaper per Gb UNLESS there are special offers on the go.

Edited by LongQ on Sunday 26th December 23:33