Canon 5DM3 Dual Card Slots

[Warbler]

Yes, when writing only to the CF card, speed is unaffected. Whenever you write to the SD card, things slow down markedly.

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In the table that Joost linked, I am using a Lexar 32gb 1000x Professional CF card and a Lexar 64gb 600x Professional SDHC card. I haven't timed it, but the figures in that table would be about right from what I've experienced, if I'm reading the right lines. The SD card is about 25% as fast as the CF card.

[wideangle]

Yes, when writing only to the CF card, speed is unaffected. Whenever you write to the SD card, things slow down markedly.

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In the table that Joost linked, I am using a Lexar 32gb 1000x Professional CF card and a Lexar 64gb 600x Professional SDHC card. I haven't timed it, but the figures in that table would be about right from what I've experienced, if I'm reading the right lines. The SD card is about 25% as fast as the CF card.

OK, thanks for that. I guess those shooting landscapes and architecture, aka still moving subjects and no need for large in camera buffer clearence then its not too bad.

[Warbler]

OK, thanks for that. I guess those shooting landscapes and architecture, aka still moving subjects and no need for large in camera buffer clearence then its not too bad.

No, it would be fine for that, but you'd still be wasting your money buying fast SD cards for the 5D3, no matter what you shoot.

[wideangle]

No, it would be fine for that, but you'd still be wasting your money buying fast SD cards for the 5D3, no matter what you shoot.

I guess a benift of a faster card would be the transfer speeds to a computer would be fast. Could be worth getting if say you have a 32GB card to take photos off.

[arthurking83]

I guess a benift of a faster card would be the transfer speeds to a computer would be fast. Could be worth getting if say you have a 32GB card to take photos off.

This is the only reason I got a reasonably fast card for my D800.
Writing to the card is pretty slow on the D800 too, but not slow as in the internal specs are simply slow .. the files are huge so it seems slow.
But once you have 32-ish Gig's of files .. even with a speedy USB3 reader and speedy card it's still feels slow when transferring everything .. again not because the hardware is slow .. it's just that on average the D800's files are 90-100Mb .. so it seems slow.

If I use the same cards in the D300, everything is transferred in a fraction of the time, D300 has 20-25ish Mb files, as opposed to 90-100Mb files.

Another benefit of getting a faster card, apart from quicker read rates, is that if at some point in the future you get a new camera with faster write speeds, you already have the card hardware for it to make use of that benefit.

I suppose it's a balance between how much you want to spend vs how quickly you want to get things going .. vs how much data you want to store .. etc, etc.