I actually asked Nikon support essentially this same question but from a slightly different angle. I was considering getting an Eye-Fi card for the second slot and only saving basic JPEG to the card (so I can preview on my iPad), using the primary to save RAW. I was concerned about the speed differences effecting performance.

The response I got from Nikon was that the two slots operated completely independently of each other and writing lower res images to a slow card would not effect the performance of the other card. They recommended using the fastest Class 10 card available and implied that the camera can write faster than any card available today. I asked explicitly about the SanDisk Extreme SDHC Class 10 (30MB/s) 32GB card, and the reply indicated that it would support the card at full speed.

In the past few weeks I was working in porting a SD-Card driver for an embedded Linux device at work, and there are many factors you can blame when write speed is not what you want...

As mentioned before, the D7K does not need hyper speed cards :), the more faster cards will help you only in downloading the photos from your SD card.

There is another factor to take into account with SD cards, that is related to the SD card embedded controller, that may stop the write procedure in order to run some housekeeping procedures in balancing the usage of the card.. and this may hit you. The housekeeping may take almost a second, which may cause the write rate to drop below the requirements of the camera.

I think it does not matter whether the tester chose 15,25 or 50 images in his test procedure. The important part is that there was no difference in result whether using 30 MB/s, 45 MB/s or 95 MB/s rated cards. The limitation was the D7k's write speed.

Nikon have been rather pissy about inquiries about the write speed of the D7k since the very beginning. Their bad attitude about customers has done little to build brand loyalty or trust. They behaved like a bunch of knuckle heads and deserve to be treated as such.

The point of the linked article was that you get more 'bang for your buck' with a 30 or 45 MB/s rated card than with a 95 MB/s card. As the price drops the price premium for the 95 MB/s card will also so that you may be faced with a choice of buying cards that outperform your current camera so that they will be prepared for the next generation camera that has a better write speed.

The question no one seems to have any idea about at all is whether the write speed of the D7k is controlled by firmware (and hence capable of being uprated) or is hardware limited. My guess is that it is hardware limited, but I have no basis in fact for that other than my suspicion because of the poor way Nikon have treated customers about the entire affair.

Let's face it, 6 fps sound nice on paper, but is of limited utility when you can only do so (in RAW) for 10 exposures. After that the exposure rate drops to less than 2 fps until the buffer clears.

The 95 MB/s cards do not seem to be well distributed through the retail channels at this point. In a few months perhaps they will be and the prices will be more in line with the 45 MB/s cards.

Just to add more fun to this thread, I found at work, when using SD cards for recording images from a PillCam, that the write speed of a card is not the only parameter you need to look, also, the write speed may change as soon the card gets full, also it changes according to the age of the card (heavy used cards may take more time to write than brand new ones due to fragmentation or free clusters management.. (Every manufacturer does its NAND/NOR flash memory management differently, and not always published).

Oy...too much thinking going on 'round here.

http://en.wikipedia.org/wiki/Secure_Digital#Speed_Class_Rating

Class # x 1 MegaBYTE/sec (8 megaBITS/sec) = minimum sustained speed

:-)

I think the Sandisk class 6 cards are 24MB/sec, so it's more like 4MB/sec x the class number.

DaveO

As TaoTeJared commented at the beginning of this thread, it is enough to have a Class#6 card, faster cards will not speedup the camera processing/saving.. but it may speedup the download-to-your-computer speed. (e.g. using a faster card-reader for reading the SD card.)

About the class number and speed rating of SD (Secure Digital) cards can read here: http://en.wikipedia.org/wiki/Secure_Digital

Beware of the huge confusion between Mega bits per second or Mega Bytes per second, this changes the numbers by a factor of 8 (8bits=1Byte)

Hope it helps.

right now im using a platinum ii 100x 8gb card(it says 15mbs/s). so it would clear it faster? i read somewhere that cameras can only clear images at a certain speed no matter how fast the card. so would the extreme pro be wasted on the d3100?

Depending what your definition of "significantly" is and what you are using now, it would clear it faster.

how would the sandisk extreme pro be on the d3100? would if significantly reduce the time it takes to clear the buffer?

I have no personal experience with either, teeboy, but I have used slower cards and have experienced no problem with recording video the highest quality settings. One thing you can get from this thread is that even with the $20 16GB Transcend cards I bought myself for Christmas I get 9MB/s transfer speeds. The D7000's video will not be any higher than 3MB/s (24Mbps), so unless you need the card speed for stills or you need faster transfer to your computer it won't make any difference.

Welcome to the forum.

Has anyone tried the sandisk extreme pro? i'm thinking of getting the extreme pro or extreme memory card for the d7000. if there's not much difference at all especially in video recording in terms of speed then i'm better off w/ the extreme :)

jonnyapple said:
Do you think you'll get a D7000, then, Hearty?

I think I might. just need for the finances to come right a bit and its off to the shops! (Still not fully recovered from my long stretch of unemployment :-( ). I was hoping for the D5000 replacement to come out this week as I may go for that instead and wait for the D300S Replacement as well. I kinda like that level of camera.

... maybe I should just sell my S5Pro .. sigh its such a nice camera. Nah.. I will probably get the D7000 in a few weeks time. the prices have come down a lot now here in OZ land.

Do you think you'll get a D7000, then, Hearty?

I dont believe you! you and your magic symbols! we should just burn you at the stake! or get some virgins to dance in the moonlight naked!

I will have to do some tests myself when I get hold of one.

I think you checked out too early to see my bottom line, hearty, so your third conclusion isn't right. My fault for mistaking my audience (non-nerds), most likely—Drab is probably the only one who read it. ;-)

If you plug in the numbers, you get more than 11 frames before the buffer is full with the 10MB files and a fast card (it's the equation that starts N = above). For example, it works out to 18 or 19 before the buffer fills on 12-bit compressed with a 25MB/s card. Even my lowly 9MB/s card predicts almost 13 before the buffer fills at that file size. I actually get 14 at those settings before it slows down, so my model is too simple. The number of frames that fit in the buffer for each file size probably includes some wiggle room on how long it will take to process the files, and it's probably worst case so people are only pleasantly surprised.

A couple of notes that most people wouldn't be interested in (the kind of thing I'd write in the margins of a lab notebook):
-Once the buffer fills, it's possible to find the time to process and write each file by pressing the shutter button halfway and watching the remaining frames in the buffer tick back up to full (r00 to r11 or whatever).
-At 14-bit lossless compressed, the buffer clearing is not at a uniform rate. Two frames get freed up in quick succession and then there's a pause before the next set of two are freed up—I estimate about 0.5 s between the close frames and then 2 s between sets. This can be confirmed using the r00 number mentioned above, as well.

jonnyapple said:

Re: my user role, it's the mods' retribution on me because I used to close all my posts saying, "Yeah, baby!"

LOL! really? @ SportsPhotoGuy : I am sure you believe him! heh!

@ JA : Thanks for the math.. (I checked out early).. Thanks for doing the test though. I am surprised that both took 11 frames to fill the buffer. It probably shows that the buffer is used only for PURE RAW before any compression occurs. It also probably means that clearing out the buffer is a lower priority task ie the clear buffer function is not run unless you are no longer pressing the shutter OR if it is full so it clears the one space and fill it again in the next shot. so from this we can predict the following.
1) Once the buffer is full, it will take the same amount of time to flush the buffer after you stop pressing the shutter release.
2) using higher compression rates should allow for higher FPS rates after the buffer is filled.
3) since initially the buffer is not cleared while the buffer is filling up(ie no write to SD occurring). It would probably account for the curious 0.75 sec you needed to add/subtract to your results to get a uniform write rate.

I would say not the best implementation for buffer clearing but good to know. looks like the cpu /process is single tasking. wonder if its the same for the other nikon cameras. I think I heard somewhere that the high end cameras have multiple cpu's but I guess they need to upgrade the OS to be multi threading :-) heh! If they open sourced the thing we could hack android into it huh !

Cool! this was fun.

SportsPhotoGuy said:
My test results are described as "effective" rates - both in terms of frames per second and megabytes/second. Neither is intended as any sort of absolute measure, but a means of comparing cards under similar conditions.

The following is likely reflective of a difference in our backgrounds, rather than a treatise on right vs wrong:

IF one were to determine the buffer size of a camera (expanding on my thoughts above) AND one were to determine the native write speed of a camera (possibly two different speeds on the D7000 due to the differing buses between SD and UHS) one could model card performance and accurately predict how fast any given card would be on the camera based on a simple write test performed with a card on a computer.

This would eliminate the vast majority of variables, tighten up the error bars, and allow one test (the card-on-computer one) to answer the question for all modeled cameras.

OR:
One could walk down the street, catch a show, and drink a few beers.
;)

EDIT:

jonnyapple said:
Re: my user role, it's the mods' retribution on me because I used to close all my posts saying, "Yeah, baby!"

Took me about 30 minutes to catch that.
;)

Oh, I think your results are great, sportsphotoguy. And I wouldn't criticize you if you were 10% off in your results (prices fluctuate by more than 10% so write speed doesn't need to be known better than that, IMO). So thanks for doing the tests so that everyone including me can make more informed decisions when shopping for cards.

I think what threw paperman off is something that might confuse a lot of your readers—the "effective frame rate". That shouldn't even be included because it depends on how many shots you take. The write speed, which you also list, is the important number because it is not a (strong?) function of file type, frame rate, number of shots, or buffer size.

Re: my user role, it's the mods' retribution on me because I used to close all my posts saying, "Yeah, baby!"

Wow. Lots of discussion here!

My test results are described as "effective" rates - both in terms of frames per second and megabytes/second. Neither is intended as any sort of absolute measure, but a means of comparing cards under similar conditions.

There's really no such thing as a "standard" here. I probably never shoot 15, and only 15, frames in a row at top speed. I chose 15 because it is more than the buffer will hold at my selected settings (which are typical for many sports situations). It is not unusual for long bursts - or multiple shorter bursts fired in quick succession - to fill the buffer, so having an idea of how quickly the camera can clear the buffer to allow additional shots is paramount.

I'm actually measuring two different times here - the time to fire all 15 shots, and then the total time to write all of the shots to the card.

Ultimately, it's important to view the results in comparison to those of other cards, rather than as an absolute measure of what the camera or cards can do.

I guess that the bottle-neck is in the interface the camera has for writing the data to the SD card, therefore a faster card than that write-speed is not needed. and this is what I'm looking for :)

From other side, a faster card, has also a faster "read" speed, that is required when you download the photos to your computer (preferable with a good card reader and not via the camera)

And determining the buffer size would be best accomplished by shooting with the lowest jpg compression quality, smallest resolution, lens cap on, max shutter speed, minimum (largest number) aperture, lowest ISO, very slow SD card (of a known maximum write speed tested on a computer), all custom picture controls off.

This should give incredibly small jpegs (essentially uniformly black) which require very little CPU to compress, removing as many variables from the equation as possible except actual buffer size.

IF anyone cares. ;)

Hearty, if you're interested, I think I've worked out the total time you can shoot without filling the buffer. To start, you set the number of frames remaining in the buffer to zero:

-B - R*t + W*t/S = 0

Here, B is the buffer size in frames, R is the frame rate, W is the write speed in MB/s, and S is the image size in MB/frame. This equation is generally true for any camera, file type, and write speed.

Then, solving for t gives

t = -B/((W/S) - R)

If you prefer to know the number of consecutive shots that can be taken before the buffer fills, just multiply by the frame rate R

N = R*t = -B*R/((W/S) - R)

After the buffer fills, the frame rate is now limited by write speed and the equation isn't as useful anymore (well, it just says you can keep shooting at that rate for infinite time, which is true if you have a card with infinite capacity).

Rfull = W/S

Plugging in some numbers from the D7000 and my card: B=10f, W=9MB/s, S=15MB, R=6f/s I get...negative time: -1.9s. Brilliant. ;-) Does anyone see where I went wrong?
If I had a card with a 25MB/s write speed, the number would be 2.3s. Is it worth it? Probably to some people.

EDIT: I found it. How I interpreted B I needed a negative sign.

All right. Enough math—I'm off to have a swim.

Also, hearty, don't confuse write speed with file size. Remember that the D7000 can take 6 (or 7? I forget) frames per second so even with a file size of 10MB, that works out to one shot per second cleared from the buffer once the buffer fills.

Here are the results you wanted. The ones from above were taken in 14-bit lossless compressed—the highest raw quality settings on the D7000.

(the buffer was 11 shots for both of these)
14-bit compressed:
36 shots, 469MB, 54s, 8.7MB/s

12-bit compressed:
36 shots, 367MB, 42s, 8.7MB/s

heartyfisher said:for best value maybe a class 6 would be sufficient as if we can assume that it may have the same 40% performance above its rated MBPS

Unsafe conclusion.
Class 10 is the highest recognized non UHS speed class. Therefore 40% faster than 10 should be sold as 10s, while those 40% faster than 6 could be sold as 8s.