Two memory card slots

1 month 4 weeks ago #680669 by Alfonso Camil
Good morning.   Perhaps you can shed some light on this question I have.   I was reading a camera review last week where it stated it wasn't good that the camera didn't have two memory card slots.  That's it, nothing else stated on the subject.  Why is this so important?  Is that based on you can take even more photos because of the added space?


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1 month 4 weeks ago #680671 by garyrhook
There are other threads here on PT on this subject.

The primary reasoning behind two is backup. You can have your camera write images to both cards, in parallel. Therefore, so the logic goes, if one card turns out to be bad, you have another.

Professionals rely upon this as just an additional safety net.

You can also write RAW files to one card, and JPGs to another (at least on Nikon), and I've used this on vacation when all I had for editing/posting was an iPad, and it worked well, The RAW files were fine when I got home.

And there's overflow: moving from one card to the next when full. But given the size of cards now, I don't see the point. A 128MB card in my D850 can hold a few thousand images, far more than I now shoot in a day.

Plenty of professionals shot pleny of events (weddings included) with cameras with only one slot.
Cards rarely go bad on you. At least, good quality cards (Sandisk, Lexar, Samsung). I've used and discarded off-brands, but no longer.
Most folks aren't going to need redundancy.

So, while nice, it's not required by everyone.


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1 month 4 weeks ago #680672 by Shadowfixer1
It's based on having the images recorded on the second card as well as the first. If one card fails, the images are on the card that didn't fail. If you shoot things that can't be done over, it will save you. The least important is probably being able to store more photos. Some people record raw to one card and jpg to the second. Some record stills on one and movies to the other. There are various reasons but the instant backup is the most important one. 

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1 month 4 weeks ago #680673 by Alfonso Camil
Oh, I see now.  But if the camera is writing twice, does that use up double resources in the camera?  


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1 month 4 weeks ago #680675 by garyrhook

Alfonso Camil wrote: Oh, I see now.  But if the camera is writing twice, does that use up double resources in the camera?  


What resources might that be?

Other than the slight amount of electricity required, no.


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1 month 4 weeks ago #680676 by Nikon Shooter
I would be happy to have only one card in the camera
but my shots are as safe as the cards are… I couldn't go
for risking to lose the work nor the client.

Light is free… capturing it is not!
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1 month 4 weeks ago #680679 by Alfonso Camil
No, like buffer or processor power. 


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1 month 4 weeks ago #680680 by 7Wishes

garyrhook wrote:

Alfonso Camil wrote: Oh, I see now.  But if the camera is writing twice, does that use up double resources in the camera?  


What resources might that be?

Other than the slight amount of electricity required, no.


Read write speeds are slower and are only as fast as the slowest card in camera. Shooting RAW to both cards would take at least twice as long to write to. The camera buffer fills quicker and takes longer to clear. The battery drains quicker. 


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1 month 4 weeks ago #680682 by Nikon Shooter
Yes, processing power since one file in the buffer
is copied — read BU — on the second card.

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1 month 3 weeks ago #680691 by garyrhook

7Wishes wrote: Read write speeds are slower and are only as fast as the slowest card in camera. Shooting RAW to both cards would take at least twice as long to write to. The camera buffer fills quicker and takes longer to clear. The battery drains quicker. 


I'm not entirely sure that that is true for every camera. My Nikons seem to be gated by the slowest card, yes, but the writes happen in parallel. It's not one card then the other (again, on my Nikon).

So saying that read-write speeds are slower is, first off, not relevant. Write speeds are the issue, and no, it doesn't take twice as long. The buffer fills as fast as the buffer fills, which is nothing to do with the cards. The speed at which the buffer is emptied depends upon the cards.

I've never seen any measurable impact on battery life when using both slots (which I do all the time). YMMV.


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1 month 3 weeks ago #680694 by 7Wishes

garyrhook wrote:

7Wishes wrote: Read write speeds are slower and are only as fast as the slowest card in camera. Shooting RAW to both cards would take at least twice as long to write to. The camera buffer fills quicker and takes longer to clear. The battery drains quicker. 


The buffer fills as fast as the buffer fills, which is nothing to do with the cards.

 YMMV.


if this is the case, why the need for ever faster cards. For instance why does the new canon 1DX III have dual CFexpress card slots. I'll point you in the direction of a recent video at Fro Knows Photo comparing the buffer between the 1DX III and the Sony A9 II (from 35.16m), you'll notice how slow it is to clear the buffer and continue you shooting. 


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1 month 3 weeks ago #680702 by garyrhook

7Wishes wrote: if this is the case, why the need for ever faster cards. For instance why does the new canon 1DX III have dual CFexpress card slots. I'll point you in the direction of a recent video at Fro Knows Photo comparing the buffer between the 1DX III and the Sony A9 II (from 35.16m), you'll notice how slow it is to clear the buffer and continue you shooting. 


The faster the device can write to the card, the faster the buffer is cleared. Having faster media helps, but there's also a constraint in the hardware, which faster media cannot overcome. Have you considered the possibility that the hardware in those two cameras is different?

Then: what does that have to do with this discussion? We're talking about the behavior of two cards in a single body, and nothing you've stated here seems relevant to that specific issue.

Also: Fro is a buffoon, and I care not not whit for anything he has to say. Worse than the Northrups.


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1 month 3 weeks ago #680792 by Pettigrew
Speaking of two cards and write speeds, any camera have double CFExpress card slots?

Canon EOS 7D SLR | XT W/18-55 Kit Lens | Canon 50mm 1.8 | Tamron 17-50mm 2.8 | Canon 28-105mm | Canon 75-300mm | Canon 100mm 2.8 Macro | Canon 100-400
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1 month 3 weeks ago #680797 by Nikon Shooter
Not that I am aware of!

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1 month 3 weeks ago #680813 by 7Wishes

Pettigrew wrote: Speaking of two cards and write speeds, any camera have double CFExpress card slots?


Canon EOS 1DX III and the Nikon D6


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