Memory Card Class and Sizes (Jackets)

[CrazeUK]

Hey all.

I have some understanding of memory cards and Class's.
i.e. the class of the card identifies the speed:

Class = Speed
Class 2 = 2 MB/s
Class 4 = 4 MB/s
Class 6 = 6 MB/s
Class 10 = 10 MB/s

What i dont understand is the 100x number that comes after the information?

So one how much difference will there be in speed between a class 4 and a class 10 if i shoot in jpg or raw?

How does the speed affect the cam?

Also if i had a micro SD card in a SD card jacket would this affect the performance.

 

[NikkiA]

Hey all.

I have some understanding of memory cards and Class's.
i.e. the class of the card identifies the speed:

Class = Speed
Class 2 = 2 MB/s
Class 4 = 4 MB/s
Class 6 = 6 MB/s
Class 10 = 10 MB/s

What i dont understand is the 100x number that comes after the information?

So one how much difference will there be in speed between a class 4 and a class 10 if i shoot in jpg or raw?

How does the speed affect the cam?

Also if i had a micro SD card in a SD card jacket would this affect the performance.

the '100x' speed is a rating using the old CDROM speed guide, ie, 1x is 150KB/s. Thus a 100x card would be 15MB/s which obviously can't be expressed using the 'class' rating system, since class 10 is the highest they go to.

As for how it affects the camera, well, your camera will shoot images to an internal buffer, which is then written to the memory card. When you've taken a certain number of images, the buffer will be full and the camera will need to wait for enough space freed before being able to take more pictures.

Depending on the frame rate of the camera, the internal buffer size, the card interface, and the card write speed, determines how many images you can shoot, for how long continuously, and how long it will take before you can take photos again.

There aren't any cards, of any format, that are yet faster than the internal buffer, and the frame rate of a given camera, thus even the latest 'pro' cameras will have a limit to how many images can be taken before the buffer is full.

However, older cameras have slower card interfaces, so often in those cases, there is a point where buying a faster card doesn't reduce the time for the buffer to empty once that frame limit has been hit.

As for SD vs micro SD, if you have two cards that are the same speed, then there will be no difference, the microSD->SD adapter jacket is just adapting the physical form and the contacts to the SD format, the underlying card interface is the same.

That said, microSD cards tend to be a lower performance : price ratio, so a given budget is more likely to buy a faster/bigger SD card than microSD card.

 

[CrazeUK]

Nikkia, thanks for the well structured response.
That explains it, although what would be the case of a Class 6 Card with 100x, shouldnt that be a class 10?

The only reason i was looking at the Micro SD, was because they are more versatile for me than SD (they fit more of my devices).

The other thing i forgot to include was the make of the card, i have found 32GB SD Class 10's for £<£20, but then seen the same card in a branded model for £40

 

[terryt]

Some card manufacturers use the read speed as the "x" speed to make it sound faster so you need to be careful. Also, the class is not equal to the write speed, it's the minimum sustained write speed, a decent class 4 could actually be faster than a crappy class 10.

 

[hunnymonster]

Nikkia, thanks for the well structured response.
That explains it, although what would be the case of a Class 6 Card with 100x, shouldnt that be a class 10?

As I understand it there is only an official SecureDigital Association definition as far as Class 6... but since the progression from Class 2 > Class 4 > Class 6 is obvious, some manufacturers have made the extension to Class 8 (rare) and Class 10 and beyond...