Hi,
I'm trying to guesstimate what kind of continuous shooting speed I could get on my E-PM1 after the buffer fills up, when using various SD Cards that I don't have. Hopefully this will help me to decide whether or not I want to get a faster card, and if so which one. I'm posting my research here in the hope that some kind or curious person or persons might like to confirm or correct some of my numbers if they happen to have the cards in question, or their equivalents. If this info proves helpful to someone, so much the better. Also I find this kind of thing fun. I must be nuts

The resources I'm using for this are:
1) my own testing with my E-PM1 and Sandisk 8GB Class 4 card
2) dpreviews review of continuous shooting performance of the E-M5 an E-PM1
3) Giulio Scorios test on his blog of his E-M5 including the card I have and some that I'm interested in. Giulio didn't record his "buffer-full" shot rate but I think I can extrapolate it from his results by referring to and comparing with my and dpreviews numbers.
4) amazon.co.uk for pricing

I'm making a few assumptions, namely:
- E-M5 jpegs are 11MB
- E-M5 buffer takes 16 jpegs
- E-PM1 jpegs are 8MB
- E-PM1 buffer takes 9 jpegs


Same 4 cards as on Giulio's test minus the eye-fi.
Remember the main thing I'm looking for is a shots per second speed when the buffer is already full.
Numbers and maths follow from here, lets dive in!

Sandisk 8GB Class 4
My test:
10 shots in 15.99sec -> 0.63 shots/sec when buffer full on E-PM1
14.37 sec to clear buffer
Giulio:
Buffer cleared just under 56 seconds.
11MB/shot * 16 shots = 176MB / 56sec = 3.1MB/sec = 0.3 shot/sec on OMD, or 0.5 on PM1

So for this card our numbers are much the same, when allowing for timing inaccuracies and rounding errors and whatnot.
Price per speed for this works out at £4.48 / 3.1MB/sec = 1.40£/MB/sec


Sandisk Extreme 4GB 30MB/s
Giulio:
Buffer cleared just under 13 seconds.
11MB/shot * 16 shots = 176MB / 13sec = 13.5MB/sec = 1.2 shots/sec on OMD, or 1.6 on PM1
DPReview:
8MB/shot @ 1.6 shots/sec = 12.8MB/s = 1.1 shots/sec on OMD, or 1.6 on PM1

Again the two sources match up pretty well. Interestingly the buffer-full-shooting write speed is considerably less that the speed written on the card label, but greater that the 'class rating' speed (which is 10 for this card)
Price per speed £8.79 / 13MB/s = 0.67£/MB/sec


Sandisk Extreme Pro 16GB 45MB/s
Giulio:
Buffer cleared just under 17 seconds.
11MB/shot * 16 shots = 176MB / 17sec = 10.3MB/sec = 0.9 shots/sec on OMD, or 1.2 on PM1
I don't have other data to compare for this card so I'll have to take Giulios word for it, but he looks like a trustworthy bloke. As G noted, this card tested a bit slower than the smaller but slower-rated 4GB 30MB/s card.
Price per speed £14.40 / 10.3MB/s = 1.40£/MB/sec


Sandisk Extreme Pro 8GB 95MB/s
Mine - this one was really tested - not just guessing the numbers!
7.8MB/shot * 18 shots = 141MB / 10sec = 14.1MB/sec = 1.8 shots/sec on E-PM1


Sandisk Extreme Pro 16GB 95MB/s
Giulio:
Buffer cleared just under 10 seconds.
11MB/shot * 16 shots = 176MB / 10sec = 17MB/sec = 1.6 shots/sec on OMD, or 2.1 on PM1
Price per speed £32.30 / 17MB/s = 1.90£/MB/sec


Sandisk Extreme Pro 64GB 95MB/s
DPReview didn't post numbers for Large/SFine jpeg/11MB, so from the numbers they did post I guesstimate the E-M5 buffer full rate at 2.2shots/sec so:
11MB/shot * 16 shots = 176MB / 6sec = 29MB/sec = 2.4 shots/sec on OMD, or 3.6 on PM1
Price per speed £128.87 / 29MB/s = 4.44£/MB/sec

It looks like DPRs 64GB card is faster than Giulios 16GB one.
Also DPRs card can apparently write at pretty close to the PM1s continuous shooting speed of 5fps!


The price / performance sweet spot among these is owned by the Sandisk Extreme 4GB 30MB/s card, which for £8.79 should give a buffer-full shooting rate of 1.2 shots/sec on OMD, or 1.6shots/sec on PM1. Above this the law of diminishing returns starts to kick in.


What do you think? Is this kind of thing helpful? Does anyone have any corrections or extra info to add? Did anyone read all the way down this far?

cheers,
-J

Alright, I own an E-PM1, a few SD cards, and I am enough of a geek to appreciate this. Can you detail your testing procedure and math so I can duplicate it as exactly as possible?

The testing procedure is actually pretty simple.
Set the camera to the fastest continuous shutter speed (5) to minimise the effect of the camera writing to the card while filling up the buffer, and hold down the shutter. When the shooting speed slows down the buffer is full. Any time now start a stopwatch and count off ten shots. At the end of the ten shots stop the stopwatch. Then take your finger off the shutter button. Repeat several times and take the average time if you care about accuracy (I mostly didn't.)

now the maths.
10 shots divided by the number of seconds it took gives you a shots per second figure. In my first example above it took 15.99 (lets call it 16) sec so 10 / 16 = 0.63 shots/sec.

Assuming the shots are 8MB we can also get a MB/sec rate. The total amount written to the card during the test was 10 shots * 8MB each = 80MB total.
80MB / 16sec = 5MB/sec
That's actually pretty good for a class 4 card!


I'm finding it interesting that the MB/sec rating on the front of the card doesn't equal the write speed in continuous shooting, especially for the faster cards. They typically claim that the number on the front is the "sequential write speed" which I had thought would be exactly the thing that would be going on when shooting in burst mode. I have to assume that when it stops writing one file and starts on the next one that's when it stops being a "sequential" write.

I've noticed that over at amazon some kind soul has posted performance charts for many of the more popular cards, under the "customer images" for each card. I'll have to go see which of their stats matches up with my results. I'm guessing it's somewhere between "sequential" write and "random" write. Maybe sequential + random / 2?

-J

Nice work OP. I expect an in-camera test is the way to go. If anyone doesn't want to take the time to repeat the testing, Tom's Hardware has an extensive set of performance charts on SD cards.

__________________
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Thanks for the info. I'll try to run some tests later today and post results.

Personally I've been finding that for my largely non-sports photography, the speed benefits of cards beyond 20 MB/s just don't show up much in real shooting. The burst buffers don't seem to get any deeper in most cases, possibly due to limited write bandwidth in camera regardless of card speed?

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Good info here! Next time I test I'll do a full buffer test too.

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Sounds reasonable.

One less obvious benefit of faster cards in my experience has been startup speed for the camera. Switching from a generic 16GB SD to a Sandisk Extreme Pro cut the off-to-ready time for my E-PM1 from 3 seconds to around 1. A worthwhile gain in my case as I am forever turning the camera on and off (to save battery life).

DH

I recently switched from my Class 10 SD card to the Sandisk 95 MB/s UHS card for my E-M5.

I must say that it is really impressive how fast the buffer clears.

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Every now and then I like to shoot my 1 year old kid in burst mode and and hope maybe one or two of the shots come out ok. I'm finding two seconds worth of buffer just isn't enough for this. I already set the burst rate lower, now I get three seconds - still not really enough, especially compared to the likes on Canikon where you typically get 100+ shots worth of buffer (a friend has a D90).

So the point of this exercise is to see if it's possible to minimise the problem with lack of buffer size by getting a faster card. If I can shoot at 3fps for 3sec, then it reduces to 2fps until the card is full, that's not bad.
At the moment I get 0.5 fps and feel like I'm missing some shots. Babies move faster than that!

Giulio, please test the same cards on the PEN Mini! I'm also curious to see if PM1 and EM5 will write at same speed to same card.


-J