steve_stoneblossom Loc: Rhode Island, USA

I was just window shopping online for SD cards, contemplating upgrading my cards for my Nikon D7100 from 45mbps to 95mbps. I noticed that SanDisk now has cards rated as high as 280mbps read and 250mbps write.

While I am aware that faster cards are able to empty camera buffers quicker, is there a point where the card speed will exceed the camera's ability to transfer from the buffer to the card?

Additionally, the description goes on to say that they have a minimum sustained write speed of 30mbps. How is this "minimum sustained speed" relevant, and is the "mss" of other cards available for comparison?

Dngallagher Loc: Wilmington De.

Pretty much anything above 104 MB/s is exceeding the top speed of most current DSLR's. Many current DLSR's are UHS-1 compliant, meaning 104 MB/s is the speed limit.... anything higher and you are into UHS-2 speeds - requires additional connection pins for the higher data rates for the card.

http://www.integralmemory.com/faq/what-uhs-1

When they provide a minimum speed, all that says it it will write AT LEAST that fast... like a class 10 rating - to me worthless, a minimum speed of 10 MBs is slow as far as I am concerned, and being the MINIMUM they guarantee, I am interested in the fastest & sustained (real world) write speeds, not a crappy minimum of 10 MBs.

FYIW- I use a Samsung Pro 32 GB card as my main card in my D7100, 80 MB/s write speed, it greatly speeds up writing from my buffer. I shoot 14 bit raw files only and the difference in speed IS very noticeable ;)

Good info here on real world speed tests - various cards and various cameras...

http://www.cameramemoryspeed.com/

steve_stoneblossom Loc: Rhode Island, USA

Thank you. I will check the link shortly.

Isn't the Samsung card to which you refer also class 10?

Dngallagher Loc: Wilmington De.

CLASS, only refers to a MINIMUM speed rating - so most cards today are all class 10 - just because they are faster then 10 MB/s.... to me the class rating is not very important....because it only states a minimum speed that is very slow today.

Now if they continued to a class 20, 30, 40, 50, 60,70,80,90 & 100 then it would be a good rating, but it stops at 10, so every card that is at least 10 MB/s is a class 10 card.

steve_stoneblossom Loc: Rhode Island, USA

OK, thanks again.

OddJobber Loc: Portland, OR

Yup. I have class 10 cards rated at 35MB/S and class10 cards rated at 95MB/S.

steve_stoneblossom Loc: Rhode Island, USA

Which is why I wondered if this "minimum sustained write speed" is a commonly disclosed spec for SD or CF cards. Seems this spec would be more pertinent than the max speed.

Dngallagher Loc: Wilmington De.

I guess it all depends on how it is arrived at - for me what matters is now many raw shots can I get in a burst, I test myself with a 30 second burst - Now, in actual shooting will I ever shoot for 30 seconds? Probably not, but it gives me a good idea of the real write speed I am getting.

When switching over to JPG and getting the ability to get a no stop burst for 30 seconds (the 100 max count for a burst stopped the camera from going further), I was amazed.

Pecos Loc: trundlebus

UHS Speed Class 3 (U3) provides at least 30MB/s sustained write. The U1 rating provides 10MB/s.

For CompactFlash there are Video Perfomrance Guarantee (VPG) 20 and 65 for 20MB/s and 65MB/s minimum write speeds.

These ratings are useful to determine if a card is suitable for video recording that requires a certain bitrate. In this application the card either works or it doesn't (if it can't sustain the bitrate), so the ratings are useful.

In continuous shooting photography you might want to know a maximum continuous write speed. The camera buffer will hold several shots and the write speed of the card is one factor that determines how quickly it can empty the buffer. The camera is often a limiting factor as well. Unfortunately not many cards are labeled with a maximum speed. The labels are almost always a read speed, not a write speed.

Newer cards may have a U3 rating on the label, but there are many fast Class 10/U1 cards that had labels designed before the U3 speed rating. So these minimum speed ratings (Class 10, U1, U3) aren't a good indicator of maximum speed capability.

steve_stoneblossom Loc: Rhode Island, USA

I, like you, shoot mostly 14 bit lossless raw. Usually not a problem for me with the 7100; when I am shooting bursts, they are seldom long bursts, so I take my 5 shots, pause, and shoot the next 5 shot burst.

The difference in buffer rate of raw vs jpeg has proven useful twice before. I had switched to jpeg for some simple snapshots to email and neglected to switch back. The next real shoot, I jumped as I began to shoot in CH and the camera did not slow down. Stopped and reset from jpeg to raw.

I need to do a better job of checking ALL my settings.

steve_stoneblossom Loc: Rhode Island, USA

I understand that in order to be designated as class 10, a card must be able to write at a minimum sustained speed of 10mbps. What I am asking is whether or not a class 10 card might have a minimum sustained speed higher than the required 10mbps, and if so, is this a commonly disclosed spec for card manufacturers?

Pecos Loc: trundlebus

A Class 10 card could be capable of much higher sustained write speed. There is no SD Class above Class 10, and the UHS Speed Class ratings are only U1 and U3.

Some manufacturers claim a maximum write speed for specific cards. Sometimes it is on the label or disclosed in marketing materials. A few with it on the label are Kingston 90R/80W, Transcend 95R/85W and 95R/60W, etc. Lexar often discloses a write speed on the back of their packaging and sometimes in marketing material. SanDisk Extreme/Plus/Pro cards usually have it in marketing materials (on their website). These speeds are generally only reached under very specific circumstances with benchmark program run on a computer. In actual use when separate files are being written such as in a camera these speeds will not be reached. But they are a starting point for comparison.

steve_stoneblossom Loc: Rhode Island, USA

So it would appear to me that while a class 10 card may read and/or write anywhere from 30 to 95 mbps, it is only guaranteed to write no slower than 10mbps, and there is no disclosure of whether or not the card(s) outperform the minimum or by how much they do so. Though the link provided by dngallagher did offer performance ratings for some cards used in some cameras.

Pecos Loc: trundlebus

Defining write speed is a tricky proposition. Speed can be affected by fragmentation, bad sector/error management, wear leveling among other factors. An SD card can be designed to meet a minimum sustained speed. It may be able to be faster, most of the time, but any of those factors could cause the speed to drop, if only temporarily, but still maintain a minimum level. The SD Class and UHS Speed Class designations take some of these factors into consideration to help assure a card will work for a given purpose (video that requires a specific bitrate) over the life of the card.

Maximum write speed claims generally do not use such criteria. They are typically benchmarks writing a large amount of data (random or otherwise) sequentially (can be 1GB or more at once, not seprate files). The speed may be averaged over the test sometimes with only a "best of" run reported.

Write speed can change based on type of data, writing separate files, state of card (new, empty, nearly full, fragmented, etc). Also one flash memory chip may be faster than another.

So maximum write speed is not the same type of measurement as a Speed Class. The card could be designed around providing some guaranteed speed in the same manner as the Speed Class, but that is more of a design criteria and "worst case" number rather than marketing material so it is not likely to be published.

steve_stoneblossom Loc: Rhode Island, USA

And now the $64 question...

Not being overly concerned about shooting in large bursts, would I be wasting money upgrading from my 45mbps (class 10) SD card to a 95mbps (class 10) card for my D7100?

And what about the 30mbps CF card I am using in my D700? I use the 700 at 14 bit uncompressed setting, at which buffer fills at about 15 shots which, again, is only a minor concern.