FYI....I
FYI....I
Same here guys, Cheers!
I hope you guys realize that the 7D cuts it's frame rate in-half in dark light or with the lens cap on, and the MKIV does not.
If you're shooting with the lens cap on with the 7D then this will slow the frame rate down, therefore, it will take longer for the buffer to fill up, which will make the RAW shot burst data appear higher.
Aren't you really more concerned to see if the CF card can keep up with the maximum burst rate (when you see the busy signal) as opposed to 1/2 the burst rate?
Rich
Rich
One thing I wanted to find out, is if your in a situation where you have a target that you are continually shooting would the faster card help or is it just wasted speed.(lets say big foot just come out in front of you and has been there for 2 minutes, I would want every picture I could get)
The original idea was to find out how fast the camera would write to the card, and how many mbs it was writing. We were trying to find out if it worth spending the extra money on a 90mbs card. Unfortunately I don't think we have fully answered that, however it appears that both bodies will not write faster than the 60mbs. Maybe when John gets his, he will be able to compare both.
One thing I noticed is that the shorter the burst, the faster mbs it writes. So going for 20 seconds it is bottle necking in the camera somewhere. But the fastest rate I got was 56mbs.
But I did find it interesting that the bursts were 35-40 frames rather than the 26 published in the book.
As far as the lens cap goes, if that is the case there is no way to draw equal comparisons between the 7D and 1D IV if what you say is correct. Unless of course you have them set up side by side with equal light.
What puzzled me was why I was getting slower rates than Brant was on the 7D. I think the answer is I had the ISO on Auto on the first round of tests. Cap on it probably was shooting at 6400 and was just chocking down.
Rick
Side Note: I just sent an email to Hoodman and asked why their $400 32GB card wasn't keeping up with the 16GB card.
Originally Posted by HDNitehawk
The way I understand it, is that you want the card to write faster than the speed of the buffer, so this way you can clear the buffer faster to keep on shooting.
Lets say we take Canon's conservative numbers, in that the 7D can shoot 15 RAW shots in a burst. At 20MB each shot that would be 300MB of data that we have to get out of the buffer quickly so that we may shoot another burst. So, if the card can be written to at 30MB/sec then it would take 10 seconds to clear the buffer, however lets say it only takes 3 seconds to fill it. So, you will start to see a backlog. That's why it's good not to hold your finger on the shutter continuously, because you wouldn't want Bigfoot to come out while you're getting a busy signal. Now keep in mind that you don't have to clear the entire buffer before you may resume shooting, you only have to clear some space for more shots.
Now, if we have the 60MB/s card then we can clear the 300MB of data in our buffer in 5 seconds.
With the 90MB/s card the hope was that our 300MB of data would be cleared out of the buffer in 3.3 seconds. Now, were talkin'. However, if the data from everyones testing is correct, then this test seems to demonstrate that even though the "cards can be written to" at faster speeds, the camera can only "write to the card" at approx 40MB/s for the 7D and 50MB/s for the 1D MKIV.
So, if the testing above is accurate, then there doesn't seem to be any advantage of the 90MB/s over the 60MB/s.
By the way, I hadn't noticed any difference between these two cards in actually shooting, but I never tested them.
So, to answer your question it does appear that the faster 60MB/sec card (as compared to the 30MB/sec card) does help with the 7D, and perhaps the 90MB/s card will help when we get some faster bodies from canon.
Digic V here we come!
Can you say "Hello to My Litlle Friend" the 1D X?
Rich
Yep, all of my tests were conducted with the cap off. The "test" where Rick and I had similar set ups, I was shooting at a white piece of paper that was lit by a desk lamp. My burst rates have been consistent at 22-24 frames in ~3 seconds and then it slows down. With the setting we had agreed to, the exposure was still something less than -3EV. In those tests, I had ~40-43 MB/s write rates. Previously I seen ~48 MB/s, but I am wondering if the ~5-8 MB/s difference is just error in my calcs or tests. Anyway, I should get my 32 GB 90 MB/s card in soon, so I'll see if it is an improvement with the 7D.
Rich
Just when I think I have all the answers I want, a few more pop up.
With the 32mb card I did the 3 second burst, which gave about 26 shots. It cleared in 7.5 to 8 seconds. It wrote at 51KBs compared to the 38KBs test for 20 seconds.
I didn't test the 16mb card in this scenario, so I thought I would give it a go. Here are the results:
- 4 tests for the average
- 3 second burst
- 430mb on the card
- 26 average pics
- 6.7 seconds to recover from the initial start
- 64MBs
So then I decided to try for 1 second
- About 4 tests and it was very hard and not as accurate
- 159 mb on the card
- 9 pics
- 3.1 to recover fully
- 51MBs
So with the 16mb card recovering from a full burst, it was writing 64mbs. This is the only instance so far over the 60mbs number. So 4MBs advantage, that would be a .41 second advantage over being limited to 60MBs.
Maybe on the next Jack Links Beef Jerky commercial I will set up and practice on Sasquatch and see if the .41 second is going to matter.
Congrats, on breaking the 60MB/s barrier!
I
Ok, I just received my new Sandisk Extreme Pro 32 GB 90 MB/s card. And it is the slowest of my three cards.
Test results for the card using the same settings as before:
3 sec test: Shots=23, File size= 418 MB, Write Time = 23 seconds for a write rate = 18 MB/s
20 sec test: Shots = 42, File size 731 MB, Write Time = 45 seconds for a write rate = 16 MB/s
For comparison, my Sandisk Extreme 8 GB, 60 MB/s card was giving write rates under identical conditions of 40 MB/s last week. I tested again today and I got:
20 sec test: Shots = 66; File Size = 1.21 GB; Write Time = 31 secs for a write rate = 39 MB/s
With my Sandisk Extreme III 4 GB, 30 MB/s card I just got:
20 sec test: Shots = 48; File Size = 915 MB; Write Time = 38 seconds for a write rate = 24 MB/s
So, by far, my best performing card on my 7D is the 8 GB, 60 MB/s Sandisk Extreme.
I'm am interested to see what others find.
Thanks,
Brant
Edit:
I wanted to put my results into a Table:
[img]/resized-image.ashx/__size/800x0/__key/CommunityServer-Discussions-Components-Files/24/0488.CF-Card-Write-Rate.jpg[/img]
It is interesting, but the efficiency "Percent of Rated Speed" is nearly linear (R2 = 0.989) with the card size when comparing the 20 second test results. I tend to not get too excited about 3 data points, but if someone has a 16 GB card, it should clock in at ~50% (ok....51.6% according to the formula) of it's rated speed, if this is linear and holds at all.
Brant
I found several blogs and articles on the net, and the consensus is that then maximumwrite speed of the 7D is 48mbs to 53mbs.
Since your 8mb card is 60MBs, what your seeing is what I saw when comparing the 16mb vs the 32mb card.
Since my 16GB card was faster than the 32GB card, could it be that the camera does write slower as the card gets larger? It is starting to appear that way.
Rick
Rick,
That is what I am beginning to think. I had expected the 90 MB/s card to come in similar to the 60 MB/s card, expecting the limitation was the camera and not the card. But that doesn
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