Why don't they have a shuffling mode for dual card cameras?

To my knowledge there is only 3 types:

1 Shoot until fill, then switch
2 Shoot the same thing to both cards so you have a copy
3 Shoot one file type to one and one to the other

Why is there no option to shoot the first image to card 1, second to card 2, third to card 1 etc.? Let's assume you lose a card in all 3 of the current types of writing options assuming you have two full cards.

1. You lose half of your pictures in a big chunk (i.e. first half of day or second half of day)
2. You are fine but you are limited to half as much space (as it is mirror if you have two 32 gig cards you can only shoot 32 gigs of photos)
3. You potentially lose all of your raw files. JPGs lost probably won't matter.

If you alternate cards and lose a card you can still potentially have every photo. For example in a wedding, if you lost a card, you would still have a story from the whole day on the second card. Sure you might not have a specific shot of the bride getting ready, but you will have some because the 4 shots you took of the bride tying her dress got divided up to two cards. Whereas if you were filling both cards and you lost one you would lose the first part of your day.

It also serves to maximize your memory. If you shoot two 32 gig cards you essentially have 64 gigs of photos. If you lose one of them, instead of taking a chunk out of your story, it kind of "thins" the photos from throughout the whole shoot.

seems like a good application for something like Magic Lantern...

But with the falling cost of flash memory, its not unreasonable to have 2x64gb cards in a camera.. considering to have dual slots you spent >1000 US and the cards would run you around 200.

That said, I think its a good idea, though the memory controller may not be so happy depending on the architecture of the circuitry behind it.

I would rather just shoot RAW to both cards to have a complete back up. Memory cards aren't that expensive that it's cost prohibitive to purchase two very large (or multiple) cards. I guess if one was in a bind for memory space though, your suggestion would be useful.

Personally I want dual cards with staggered write and delayed backup.

That is, when shooting large bursts of photos at one time it will switch between which card it is writing the 'next' photo to during continuous shooting. So for a burst of photos half will be on Card A, and Half on B (assuming they're equal speed cards, a mismatch in speeds could see A freeing up for another photo to be written to it before B does.)

Then after the buffer is empty and no additional photos are being taken the camera will look at a list and start copying the files over to each card one at a time. if it gets powered off mid transfer then that photo gets 'flagged' on boot and the camera attempts an integrity check.


So you get the advantage of clearing the buffer as fast as possible, and reasonable file redundancy.

I see low application which is why this isn't available. Basically I suspect that people who need a backup need a real backup. If you shoot a wedding for pay, losing every other shot is better than losing the first half of the day, but it still isn't acceptable so what's the point? Especially when you can just put two big cards in the camera and have a full backup.

JeffreyG wrote in post #17188443
I see low application which is why this isn't available. Basically I suspect that people who need a backup need a real backup. If you shoot a wedding for pay, losing every other shot is better than losing the first half of the day, but it still isn't acceptable so what's the point? Especially when you can just put two big cards in the camera and have a full backup.

Writing every other photo to a card also means you can essentially double your card write speed, and clear your buffer faster. In my view it has just as much use as "Write to Card A till full, then use Card B", but spreads the data more evenly over the multiple cards.

While not a 'full' backup, it is still a far safer position than "Fill A then B" write option.

JeffreyG wrote in post #17188443
I see low application which is why this isn't available. Basically I suspect that people who need a backup need a real backup. If you shoot a wedding for pay, losing every other shot is better than losing the first half of the day, but it still isn't acceptable so what's the point? Especially when you can just put two big cards in the camera and have a full backup.

It would also help for travel photographers who could use the extra card space and don't want to lose an entire chunk of their trip if one card goes down. If you go to Spain and England you could potentially lose shots of an entire country.

benji25 wrote in post #17188543
It would also help for travel photographers who could use the extra card space and don't want to lose an entire chunk of their trip if one card goes down. If you go to Spain and England you could potentially lose shots of an entire country.

OK, I'll admit the usefulness may be higher than I first thought. I'm not totally sure this would improve buffer clearing because I don't know that writing to both cards would really improve what the processor is doing. Maybe it helps, maybe not.

Like somebody else said, probably a ML software bit first.

Luckless wrote in post #17188451
Writing every other photo to a card also means you can essentially double your card write speed, and clear your buffer faster.

Er, no.

Imagine you're filling buckets from a hose. It takes the same time to fill 2 buckets if you do them one-by-one or you switch every few seconds.

As for insurance against losing images - this happens so rarely that it's not worth the hassle. I've been using CF cards for 16 years. Apart from losing a whole card I've never lost an image.

benji25 wrote in post #17188040
To my knowledge there is only 3 types:

1 Shoot until fill, then switch
2 Shoot the same thing to both cards so you have a copy
3 Shoot one file type to one and one to the other

Why is there no option to shoot the first image to card 1, second to card 2, third to card 1 etc.? Let's assume you lose a card in all 3 of the current types of writing options assuming you have two full cards.

1. You lose half of your pictures in a big chunk (i.e. first half of day or second half of day)
2. You are fine but you are limited to half as much space (as it is mirror if you have two 32 gig cards you can only shoot 32 gigs of photos)
3. You potentially lose all of your raw files. JPGs lost probably won't matter.

If you alternate cards and lose a card you can still potentially have every photo. For example in a wedding, if you lost a card, you would still have a story from the whole day on the second card. Sure you might not have a specific shot of the bride getting ready, but you will have some because the 4 shots you took of the bride tying her dress got divided up to two cards. Whereas if you were filling both cards and you lost one you would lose the first part of your day.

It also serves to maximize your memory. If you shoot two 32 gig cards you essentially have 64 gigs of photos. If you lose one of them, instead of taking a chunk out of your story, it kind of "thins" the photos from throughout the whole shoot.

#2 just seems perfect to me. 2x 64GB cards, space not really an issue.

Just buy two big cards and shoot the same on both. If you run our of space have more cards available. Cards are cheap and small. I'd rather have a complete backup than risk losing half my shots as you would with your suggestion when shooting a wedding... that isn't a backup... it is stupidity when you have two slots available.

benji25 wrote in post #17188040
Why is there no option to shoot the first image to card 1, second to card 2, third to card 1 etc.?

I just don't see the point of it.

hollis_f wrote in post #17189501
Er, no.

Imagine you're filling buckets from a hose. It takes the same time to fill 2 buckets if you do them one-by-one or you switch every few seconds.

As for insurance against losing images - this happens so rarely that it's not worth the hassle. I've been using CF cards for 16 years. Apart from losing a whole card I've never lost an image.

That is only true if you're filling buckets with water from a hose and only have one hose. If you're writing data to cards then things are very different.

Flash memory is Slooooow, while volatile memories use for things like the camera buffer are exceptionally fast to read and write from. This is why you can take a bunch of photos really fast for awhile and then have it slow way down as it slowly writes to the card. However while CF cards might share a data bus they are completely independent devices, and that data bus can be easily made to exceed that of the CF cards. You can easily write two different files to two different drives at the same time, and therefore use less time over all.

It is far more like using two smaller hoses connected to a much larger hose, and then filling two buckets at the same time. You can only put water in so fast to a given bucket, but you have more than enough water in the pipes to fill more than one bucket at a time.

However my degree is in computer sciences, so I've actually done stuff like this with real hardware, and have no need to imagine it with buckets of water.


And as for insurance, fires happen so rarely... No one in my family has lost a home to fire in over 150 years, so why should any of us bother paying for insurance? Clearly it will never happen, and if it does it will obviously be on a home that isn't remotely important to us...

I think it's a very good idea.

hollis_f wrote in post #17189501
As for insurance against losing images - this happens so rarely that it's not worth the hassle. I've been using CF cards for 16 years. Apart from losing a whole card I've never lost an image.

That is almost more reason for it. Since they fail so rarely why have a complete backup? This way you maximize space and still have some recoverability when they fail once every 16 years.