I am looking at new memory cards, what would be the best one to get?

SanDisk 32GB Ultra 30MB/s SD Card (SDHC) - Class 10 @ £17.99 SanDisk 64GB Ultra SD Card (SDXC) - Class 10 @ 47.99 SanDisk 32GB Extreme SD Card (SDHC) 45MB/s - Class 10 @£26.96

I know that the higher write speeds are better, but would it be best to go for a couple of the £17.99 32GB cards?

  • 1
    Which size card to buy seems like a very personal choice. Some people prefer the convenience of not having to switch cards as often. Others prefer to spread the risk by having smaller cards so that if the card dies, they don't lose all of their photos. As for which speed, you might want to take a look at: photo.stackexchange.com/questions/325/…
    – forsvarir
    Jul 16, 2012 at 9:41
  • I guess it should be write speeds and not read speeds. Jul 16, 2012 at 9:43
  • @BartArondson lol yeah sorry facepalm
    – thatuxguy
    Jul 16, 2012 at 10:23
  • Personally I'd go for the £17.99 cards.
    – Diamond
    Jul 16, 2012 at 11:34
  • This is not really a helping answer, although the asker already has marked your answer... Could you maybe clarify why you would go for the £17.99 cards? Jul 16, 2012 at 12:41

2 Answers 2


Do not buy a single large card - or even larger than necessary cards.
Risk of data loss is minimised by using more smaller cards.
If you shoot RAW and if D3100 RAW files are around 20 MB (adjust to suit actual) you'll get about 50 photos/GB ~= 400 / 8GB
800 / 16 GB
1600 / 32 GB
3200 / 64 GB

JPG will give substantially more.
In almost any setting, having to change card every 400 photos is not a major imposition.
With say 4 x 8MB cards and swapping cards 'every now and then' and using all 4 cards, you will lose about 1/4 of the photos taken since copying if a card fails.
With 1 x 32 GB or 1 x 64 GB you will lose 100% WHEN the card fails.

If you have at least 2 x 16 GB you can transfer files from one while using the other.
Similarly with 4 x 8 GB.
This could be portable hard drive with peer to peer module, netbook, tablet etc.
Nowadays some smart phones will probably allow you to use a USB card reader to backup a card to the phone's 32 GB t-Flash. The phone's memory can be slower and so cheaper per GB.

Re card speed: In most cases a 10 MB/s Class 10 from a reputable manufacturer will suffice. With 20 MB RAW files a 10 MB/s card will take 2s to write and a 45 MB/s card about 0.5s. This is if those are genuine write speeds and if the camera can support 45 MB/s. Clone cards with fake labels and cards labelled for read rather than write speeds may cause bad surprises.

If you really must shoot RAW and must have > 1 frame/s then the 45 MB/s card may help. Camera buffer size and design will set max shots before buffer stutter starts.
IF the camera allows unlimited RAW shots if there is buffer room then
Buffer fill time is ABOUT

  • (Buffer size in MB) / (Camera data rate - card write rate)

    = (Buffer size in MB) / (File_size x frames_per_second - Card_write_rate)

    eg if camera produces 4 x RAW at 20 MB each per second.
    If buffer is 64 MB
    If write rate is 45 MB/s
    Fill time is ~= 64 MB / (80-45) = 64/35 or under 2 seconds.
    Buffer size is crucial in situations where camera rate exceeds card write rate.

More normally - say you write 10 MB files, use a 10 MB/s card, shoot 4 frames/s and have a 64 MB buffer (as above)
Fill time = 64/(10 x 4 - 10) = 64/30 = slightly over 2 seconds.

But get files size down to 5 MB and things may change
Fill time = 64 / (5 x 4 - 10) = 6.4 seconds.

  • Excellent info! So the £17 ScanDisk ones would be fine, and if i save in JPEG i'll get more photos and roughly the same quality as RAW?
    – thatuxguy
    Jul 16, 2012 at 14:24
  • @thatuxguy: For RAW vs JPEG, you might want to look at photo.stackexchange.com/questions/2627/…
    – forsvarir
    Jul 16, 2012 at 14:40
  • @thatuxguy - I made no comment about the relative merits of JPG and RAW - just re the effects of buffer size, write rate, file size and frame rate. You need to decide what the camera can do with the best card then use my simple formula to see if the result is acceptable. The RAW/JPG link that forsvarir provides is very worthwhole. Jul 16, 2012 at 16:04
  • Great read thanks :) Think i will stick to RAW and use smaller cards to save loosing all images. :) Thanks for all your help
    – thatuxguy
    Jul 16, 2012 at 16:24
  • Russell, as an evolving photographer, I am so thankful that you took the time to share such knowledge. You have made purchasing cards a breeze for me and gave me so much more insight into how best to make use of them. I love the suggestion of using smaller cards. You are so right, I used to buy larger cards figuring to have more space, but due to their ability to go bad easily, I found the loss of data to be devastating. By dispersing your data over multiple cards, you minimize the amount of loss and free yourself to be able to use one while downloading from another. Excellent point.
    – user13658
    Nov 22, 2012 at 9:42

Another thing that one may want to take into consideration is:

Should problems arise and should you contact Nikon (guess it goes for every brand), one of the first questions they´ll ask is if you are using a supported SD card. If you don´t, then the narrow-minded business respons will be to buy a supported SD card and if the problems still exist contact support again...

I´ve been using Kingston for most of my memory needs, but Nikon does not officially support and therefore does not test their camera´s with Kingston cards. Which must be due to a business reason rather than a technical one, because usually Kingston outperforms SanDisk when it comes to writing speed. For most people speed may not be that important, but when you´re into sports, concerts and such, well... it is :-)

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