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Thread: SD Memory Card Class 10

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    SD Memory Card Class 10

    I have got a 30gb sd card in my Sony a77 and this is a much quicker camera to my old Sony a390.
    This card was in the old camera and it is now in the new camera.
    Doing some research I found that there are a lot faster cards out there today.
    So I began to wonder if I should get a faster card to go with the faster camera.
    I am looking at a 95gb card and I was wondering what are the thoughts here about this.
    Or am I just wasting my time with the new purchase of a card that is faster.

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    Are you sure you're not confusing the speeds with capacities? Do you mean 30 mb/sec and 95 mb/sec? Cards usually come in 8, 16, 32, 64, 128, and 256Gb capacities.
    Last edited by Warbler; 03-01-2015 at 10:45pm.

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    Administrator ricktas's Avatar
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    Agree with Warbler, think you have card speed and card capacity confused.

    Card speed is very variable. Yes a camera that can read/write faster helps, but things like your card reader in your computer can be slower than the card's max speed and then you reach the bottleneck at the card reader point. Faster cards are good for devices that can use that faster throughput, things like video benefit from faster cards, or high speed shooting (10fps) etc. For general photography, speed is not so much an issue.
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    95Mb/s SD cards aren't all that expensive nowadays, so you may benefit from getting one for the A77.

    I guess it depends on a few things too tho.

    1. price. Is the price for a speedy card acceptable.
    2. do you need another card too? It's always handy to have access to more storage capacity then less capacity of course.
    3. do you regularly shoot a high frame rates to make full use of the card's speed advantage?

    If you tend to shoot predominantly landscapes and take your time about it, then the speedier card is a waste of money!
    If you sometimes shoot birds in flight, or kids running around playing, then you may see an advantage.

    I just checked(and assuming your A77 is the new model, and hence the vII and not the first model) and it appears that the A77II is capable of capturing 28raw frames in succession within it's buffer.
    This is quite a lot of frames .. except maybe for a professional sports shooter! .. and it's rare to capture this many frames all in the one shooting situation.

    This buffer capacity is independent of card speed. So even if you had an ancient 1mb/s SD card .. the camera will still be able to capture those 28 raw frames per second.
    (the buffer is an internal memory capacity)

    Where the difference in card speed will be noticed is how quickly the buffer empties out after a series of consecutive frames. A faster card will allow the buffer to empty more quickly, hence allowing the camera to capture more images in quick succession again(sooner).

    So in effect there's a balance to take into account.
    So as an example, if you shoot a lot of faced paced situations and you need to shoot (say) 8 frames quickly, which is easily done with the A77II as it can shoot at 12fps! ... but then you need to quickly shoot a similar frame count in quick succession again(eg, within 1 sec) and you're doing this regularly for 5 or 10 seconds with barely a sec or two between successive shoots .. then the faster card will make a considerable difference.

    Something you can do at home to determine if the faster card may be worth your while is very simple to do.

    * With the current card you have, set it to 12fps shooting(continuous high speed mode) find an average scene with a bit of colour(more colour a scene = higher Mb count in the files) and shoot at high speed until the buffer fills up(where the camera slows from the machine gun sound of 12fps, to a slow clack clack of about 1fps.

    * As soon as you hear that slow down, stop shooting! Buffer is full.
    From here, what you need to notice is how long the buffer takes to clear it's files onto the SD card. This is usually indicated by a light of some type on the camera body which will stay on or maybe blink as the buffer writes to the card. This light indicates that files are being written to the card and so not to remove the card until it's gone out.
    You need to know the time from when you stopped shooting to the time the light goes out. This is the buffer clear time.

    * other things you need to know are how large(on average) are the files you just shot. eg. they may be 25 or 35Mb's each.(raw) or if you shot in jpg mode they may be 12Mb's or whatever.
    remember just an average is good enough for this test.

    * If each file is about 30mb and you shot 20 images, then you have 600Mb's of capacity for the camera's buffer. If it takes 60sec to clear the buffer, then the camera's data bandwidth system only allows for about 10Mb/s to the card.
    Going by what we assume of your card's ability, it appears that the card's speed is about 30Mb/s. You may never see this full speed ability, but you should see about 10-15Mb/s on the average SD card for write times.

    If you can't get between 10-15Mb's card write speed, you either have a cheapo brand SD card, or the camera is not capable of writing any faster than this.
    If your card brand is cheapo, then it may be worth the money on a faster card ... 99.9% likely that you will see an improvement. Not in shooting speeds tho .. just how quickly the camera clears it's buffer for the next shooting session!
    If your card brand is a well known brand(eg. Sandisk/Lexar/Toshiba/Whatever!), then the chances are that if you can't get good speed(clearance rates) with this card, the faster card is a semi waste of money.

    Note that it may only be a semi waste of money, because even if the card doesn't work very quickly in the camera, there is a good chance that it will work much quicker on your computer!
    What you need tho is USB3 and a fast USB3 card reader. If you have, or plan to update to these faster devices, and you shoot quite a lot of frames per shooting event, the time saved in downloading the cards' contents to your computer is quite noticeable with the right setup.

    I have a D800, and while it doesn't shoot very quickly, it's major hurdle is the size of the raw files. 75Mb each minimum.
    This in itself is not a problem, but having slow cards and card reader subsystem for the computer made it painfully slow to transfer the images to the PC.
    Each file may have taken about 5sec or so to transfer. Having (say) 100 images on the card .. more likely 200 .. took an eternity to transfer to the PC.
    So I ended up getting a faster card as well as a new USB3 card reader.
    With the new card and new reader each file now takes less than 1 sec to transfer to the PC.

    It hasn't made the camera 'noticeably' faster in a major way. That is on first impression the camera still shoots at 4fps and shoots about 20 shots in a long burst. In that the card hasn't made any difference.
    But what the card has done, is that it clears the massive buffer much quicker than with the slower cards I had to use previously.
    As I rarely shoot more than about 3fps for a quick 3 shot capture .. I barely notice this speed improvement on the camera. I've only done it for testing and I know it's quicker.
    Where I justify the expense is that it's so much quicker to transfer large amounts of files off the card. I sometimes shoot over 300 or 400 images in a single shoot, and this makes it worth the expense.
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    I have got a class 10 Sandisk 32GB and 30MB/s card now in my camera.
    Taking shots in quick succession is what I am on about here, I have found a card that has all the above but is a class 10 and 95MB/s card.
    And not for too much money and is also a Sandisk card.

    Knowing about the capacity isn't the issue here and I actually do know what I am on about.
    I have got a 16 GB class 4 card as my backup card but I would like to get this new card as my main card
    making the current card as my backup card.

    The test run I done was good the day I got the new camera and it handle it okay, but I am yet to do a fully serious test on it.
    This will happen when I get the chance to do so but from looking on Youtube the card I am on about will just prove to be what I want.
    In this would become my main card to use all the time.
    I hope this clears it up a little.

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    Administrator ricktas's Avatar
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    I have got a 30gb sd card in my Sony a77
    I am looking at a 95gb card and I was wondering what are the thoughts here about this.
    Knowing about the capacity isn't the issue here and I actually do know what I am on about.
    We worked out what you were on about, but your comments (quoted here) are what had everyone confused and unsure if you did know what you were on about. You do not have a 30gb card or a 95gb card, you have cards with read speeds of 30Mbps and 95Mbs as you originally stated, which triggered the confusion of those replying.

    Yes a faster card will allow faster read/write times. Note that the quoted speed is generally the READ speed, not the write speed of any given card. But there are numerous things that will not allow a card to read/write at its maximum speed. Including but not limited to, hardware in the camera--actual read/write speed the camera can do, camera buffer -- how much memory the camera has that it hold the photos in before they are written to the memory card, and more. The read/write speeds of a card are based on all other factors being able to meet those speeds, also, before the max can be achieved.
    Last edited by ricktas; 04-01-2015 at 3:03pm.

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    Sorry about the confusion over that then.
    I see what you mean now as the card I have is a 32 GB card and I am looking at the same capacity card just a way to transfer it to the card quicker.
    So I looked around and found that there are cards out there much quicker that I have got now.
    I was even amazed to find cards that are triple this speed but this is where you are throwing money into a pit I think.
    I really don't think I would ever need card as fast as some out there.
    Over time you will work out that at times I may not be so good with wording things as some here.

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    I remember a test that was done for the Sony Alpha (unfortunately didn't bookmark the test and can't find it now), can't remember the model but it was probably the a77 (big during that time), buying a 95mb/s card, compared to the regular class 10 (30mb/s) will yield little results on the a77.

    On the a77ii, it's a little more evident, but on the a77, you'll only get a slight improvement.

    The problem is, Sony's cameras are just simply slow. The speeds you see are the maximum possible, but that will come down to the device utilising it. The extra speed only helps Sony's camera not feel too congested when running, but Sony just doesn't quite utilise it.

    If you have the money and it's not a huge price difference, you can go for the faster card, especially if you plan on shooting video in the new XAVC S format (don't know if Sony updated the a77 to support it or not though) as you'll need to make sure the card is SDXC (SDHD doesn't support the new video format). It is still a slight improvement (newer technology, more efficient, more head room to work a little faster), but the real difference is when copying files to your computer (specially if you run USB3.0)

    But all in all, if you're not doing anything majorly huge like sports photography where you really want that buffer to clean out the quicker the better, then class 10 will still last you.

    Either way, if possible, request a test run.
    David Tran

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    To this point in time I really have no interest in using the video part.
    I may later on down the track but right now as it stands, no not what I am after.
    The card I have mentioned is not going to throw anyone broke and this is why I looked at this one in particular.
    So I might go hunting for that for what you mentioned so I can be a little more informed.
    Thanks for your thoughts on this.

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    Basically a card can read/write to its maximum read/write speeds in a perfect situation only

    Things that can affect this;

    1. Hardware in the camera might not be able to read/write at the same speeds the card can. You might have a 95Mbps card, but the camera it is in has hardware that maxes out at 50mbps., so that is the best you will get with that card..in that camera.

    2. Computer, transferring files to the computer is affected by the card read speed, the speed of the card reader itself. USB speed (USB 2 is slower than USB3) so you might hit the max USB transfer speed rather than the card speed. Connection point to computer motherboard, and even the Hard drive the files are going onto. Along with whatever else your computer is doing at the time (virus check?). All these things affect read/write performance.

    3. The camera buffer. Cameras have a memory buffer. When we take 5 shots on one go on high speed, these files cannot all be transferred to teh card as fast as the camera can take them. Remember cameras can do 10-15 shots per second. Your camera has a memory buffer and all the photos are put in that buffer and written to the card in sequential order, until the buffer is emptied and the images are on the memory card. That buffer in your camera, like all memory is finite. The more photos you take, the more the buffer fills. Once it gets full, your camera will refuse to take photos until the buffer can purge the files to the memory card. This can slow down everything.

    So a faster memory card can be invaluable, but it is not so valuable that it ensures all photo copying issues will go away. There are so many things involved from the clicking of the shutter through to getting the photos onto your computer, and any one of these things can affect speed of transfer, anywhere along the way. Card Speeds are a theoretical maximum, mostly cards do not run at the max speed all the time, or even most of the time.

    Yes a card that is 95mbps will generally copy/store/save files faster than one that has a max of 30mbps, but it is not that simple. To many other factors (as above) affect the real world speed you will get. And that speed will change all the time too.

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    Startup/Shutdown

    Power on to first shot ~0.8 second Time it takes to turn on and capture a shot.

    Shutdown ~1.0 second How long it takes camera to turn off before you can remove the memory card.

    Buffer clearing time 7 seconds after 19 large/extra fine JPEGs* Worst case buffer clearing time. -
    12 seconds after 15 RAW files* - This is the delay after a set of shots
    13 seconds after 13 RAW+ L/EF JPEG files* before you can remove the card.

    Startup and shutdown times are a bit slower than typical SLRs, but much improved over older firmware versions. (These results were measured using v1.06 firmware.) Buffer clearing times were reasonable given the size of files and buffer when using a very fast card. (We used a fast "up to 94MB/s" UHS-I compliant Sony SDHC card.)

    This is the info I found on my camera about buffering.

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    A royal pain in the bum! arthurking83's Avatar
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    The info about buffer clearing times you've posted seems to be from an external source .. ie. not yours.

    While it's partially relevant, it may not be fully so.

    Reason is, in the buffer clearance times quoted(eg. 12sec after 15 raw files* .. etc) do they say how large the raw files were, on average?

    eg. if you test the speed of the camera's bandwidth, and you do so with a lens cap on, the image is all black. ie. not much data info in it. maybe it's 15Mb .. maybe a bit more, or a bit less.
    if you took a well exposed image of a very colourful scene, because of the colour info present in the image, the raw files could be significantly larger.
    The larger file size impacts the camera's bandwidth system in two ways.

    1. it puts more pressure on the camera's CPU to process that raw info into 'data' which includes post processing of the picture style set in camera, and it has to generate some jpg preview files contained within the raw file too. This obviously slows down the camera in a small way.

    2. if your files are smaller or larger than any test sites raw files, then you can't compare directly if a faster card will help.
    It can offer a guide + some expected leeway(say 10-20% at worst case).

    All you can do is try a similar test yourself to see what comparative performance you do get with what you currently have.

    So for example, just take a quick round of consecutive images set to high speed shooting mode.
    Shoot a similar number of exposures .. doesn't really matter if you have more or less by one or two. But if you want to keep it as accurate as possible(without knowing the files sizes of the other test shots) .. then set the camera up to only max out at 15 exposures(most cameras have this ability in continuous high speed mode).

    Once you have your 15 raw files shot, time the speed at which the buffer clear light goes out.

    If you get something like 30 sec or more .. then you know that your 30Mb/s card is slow to the point where it may pay you to update your current card.
    If you get a time more like 15 or 20 sec to clear the buffer, then I would seriously question if the card is worth any expense!
    (of course this doesn't take into account any need for more storage space tho .. this is totally up to you).

    So, without knowing who or how the testing(above) was done .. lets assume an average file size of 25Mb for each raw file.
    These sorts of tests are best done in raw mode only .. not jpg, or raw + jpg .. just raw .. as it gives you a way to reasonably assess the performance in simple number terms as well.

    So if each raw file of those 15 raws were 25Mb .. then the total amount of data in the buffer may have been 375Mb
    if it took 12 sec to clear the buffer, then the write speed of either the card or the camera's maximum ability to write to the card is 31.25 Mb/s (375Mb/12s).
    That's actually not too bad .. but as you can see .. nothing like the 95Mb/s rated speed that the card claims to be.

    AGAIN!! these numbers are all hypotheticals based in assumptions .. the numbers could be higher .. they could be lower. Without knowing the data in the test it's impossible to know.

    Like I said .. all you can do is to a rough comparison to see how much slower your card is in your camera .. and take it from there.

    As already said .. for Video a faster card is a must if you don't want choppy video processing video takes up massive bandwidth nothing like still shots can generate!
    The buffer fills almost immediately in video mode, so in reality is basically rendered useless after the first few seconds. from there on, it's basically straight to the card .. and this is where fast write speeds are required.

    For stills mode(which you seem to be predominantly interested) .. unless you're continuously filling the buffer ... a faster card may still not be of any benefit.

    eg. if your buffer can take 15 raw files and you shoot a maximum of 6 frames in one second and tend to wait a bit till the next round of machine gun fire .. even if this wait is only 1-2sec, the buffer is clearing all this time, so where you just shot 6 frames(and then wait a sec or two) .. it may then only have 2 or 3 frames remaining to clear.
    If you shoot another 6 frames in one sec again .. then you still have more than enough capacity to shoot another burst of 6 or 7 frames immediately.
    These are a lot of images, and unless you're doing something fast paced .. it's very rare to shoot like this.

    remember .. you shoot images they go into -> [BUFFER]. from there they get written to the -> [card]
    Unless you're constantly maxing out the [BUFFER], the faster card is a waste(unless you're also into video!)

    if you can get a 64Gig or 128Gig 30Mb/s card for the same or less money .. then the capacity advantage may be a better value for money solution.

    PS: Sony claims a buffer full rate of 28 raw files for the A7II. Where are those test figures from, and are they of an A7II?
    Most tests will tend to take the camera to it's maximum potential.
    It seems a bit weird that the numbers in the test you posted are only 15 raw files.
    While we don't expect manufacturers to be absolutely spot on with their numbers, in the years I've been interested in camera gear .. I can't ever say I've seen a manufacturer claim off by close to half the amount tested in real world situation. They're usually off by one or 2. rarely more than that.

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