One point of failure vs many?
 

Three situations:

-- Shooting the entire day on one 64gb card
-- Shooting it on two 32gb cards
-- Shooting it on four 16gb cards

Which is best? Or are they all equally good/bad?

In the case of just one card, if you have card failure, the consequences are catastrophic. But in the case of four cards, presumably you've now quadrupled your risk of card failure, all else being equal.

Re: One point of failure vs many?
 

Hey Adrian

You are obviously shooting with more than one camera but really, if you have 4 cards fail as opposed to one then you are buying bad cards surely?? I simply use a card that will give me enough space for the amount of footage I'm likely to be recording ... my main cam that does the ceremony and speeches has a 32GB card (in case speeches go on and on (I had 10 of the buggers on Friday's wedding!!) but my other two cams do fine on a 16GB card.

You obviously don't want to change cards mid event either!!

Chris

Re: One point of failure vs many?
 

Which is best? Dual-Slot recording, or recording to a card and an external source.
In your case, if you have the discipline to not lose things, I would say 4-16gb cards, under the assumption that if one of them fails, you still have 3/4th of your footage.

If the odds of one card failing, are 1:1,000 (made up number), the odds of 2 cards failing are 1:1 million, and the odds of all four failing exceed the capacity of my calculator.
BUT... Once you have one card fail, the odds of another failing are 1:1000, so its still best to have dual recording

Re: One point of failure vs many?
 

Yeah, dual card recording is obviously best. But, Vince, I've got a feeling you've done the wrong equation.

If the chance of a card failing is 1/1000, and if you use four cards, then the chance that at least one will fail is 1/250, isn't it? So the likelihood that something will fail increases the more cards you use rather than decreases.

(Disclaimer: last time I did any sort of probability thinking was longer ago than I'd care to remember. So I might be completely wrong!)

Re: One point of failure vs many?
 

As I read the OP, he had 1 camera, so
As I recall, you need to be careful if they are independent of each other. Look at 4 sets of dice, and assume rolling a "1" means failure. If you roll dice#1, the odds of getting a "1" is 1:6. If you then roll dice #2, the odds of getting a "1" is still 1:6, etc.

Now, lets roll 2 dice at once. The odds of getting "1" and "1" is 1:36 (two failed cards)

Re: One point of failure vs many?
 

I think the best way to deal with potential card failure is to have some sort of backup system (if possible). If your camera has a clean HDMI out then an Atomos Ninja Star or Ninja 2 will offer higher quality ProRes or DNxHD codec while also allowing the camera's internal recording to serve as a backup. The higher bitrate 4:2:2 codec will help a LOT when color grading and this way you've got a backup to give you peace of mind. If your camera doesn't have a clean HDMI output then I would say go with a good brand of digital media like Sandisk. I've read about many people saving a few dollars on brands that are less expensive and then they regretted it when they lost footage.

I'm a big fan of using a backup/safety shot as well. I bought a Canon G20 which I just place on a tripod near the back of the ceremony, set auto iris and auto focus, and then hit record. I usually pick a fairly wide shot that I can cut to when our manned cameras don't have a good shot, but it also acts as a backup in case our B Camera (Canon 70D) has an issue. The 70D does not have a clean HDMI out and only can record to a single SDHC card so if the 70D had a card issue then we could still get away with the G20 as our second shot instead of just having our A Camera to work with.

Our A Camera (C100) has dual SDHC slots so it simultaneously records to both cards so that I always have a back up. This is the main camera with the groom's audio going to it so it's more important than the 70D in many ways. I don't think there's any way to guarantee you won't lose data, but I think that there are measures that can be taken to make it much less likely.

Re: One point of failure vs many?
 

For ceremony and speeches I have two much cheaper video cameras on light stands rolling continuously on wide angles. This way a B&G can't complain that I never provided their wedding. This is vital in my book.

Even if my card on my Sony A7S failed, the B&G still have their vows and speeches. So I wouldn't get my ass sued quite so badly...

But yea, I regularly see togs backing up cards over the meal. Myself however, I go home that night, set the back down, and copy the cards to the hard drives whenever I get a chance.

...I feel I should take some more care... perhaps take the laptop and start backing up at downtime on the day.

As for the probability question. If one card failing is 1 in a 1000, the probability of any of your four cards failing is 1 in 1000. The probability of all four failing is very very slight. I get the natural logic that the more you have, the higher the risk of incident - but I'm not sure if it is true...

Re: One point of failure vs many?
 

Using different smaller cards throughout the day instead of one big card is an equal risk, if any of those cards would fail you won't be able to provide the client a finished product, maybe the client told you their church is THE most important part of the day so you change cards before the ceremony and when that card dies...There goes your backup strategy.

The safest way is still recording to 2 cards simultaneously, in that way you don't need to swap out cards and use 2 big cards that will cover you all day, the risc that both cards would die at the exact same moment is like winning the lottery.

Re: One point of failure vs many?
 

Re probability question, I had a think over dinner and dimly recalled this: to work out the probability of at least one failure, that's 1 - (probability of no failure). Does that seem right? In this case: 1 - (999/1000) to the power of 4.

I think some people are suggesting that, given a number of dice throws, the chance that at least one of those is a 6 is always 1/6. But surely that's incorrect? What if you have a million throws? Still only 1/6 chance that at least one is a 6?

Re: One point of failure vs many?
 

More cards increases your points of failure. However, it reduces your loss should a card fail.

A Single card with everything is just suicide. If that card fails... you loose EVERYTHING. We shoot dual slot and a single card for all and then change cards in slot B. In a worst case scenario we only loose whatever is stored on that one card and as we change between each major part of the day we loose just one part of the day (but have multiple cameras anyway).

If you shoot single card and you are lucky enough to get a card which NEVER fails then top stuff. You save money, you make capture easier. But the thing with cards is... you don't know if you have that magic card. Its a lottery.

My advice is break the day up into many smaller cards. Each card we buy gets a full test before we use it by recording non stop until its full. Format and go again. We did this with our last batch of cards and found the 64GB cards were faulty and would crap out when half way full. Luckily we have dual slot but what if that was my only source?

You also have to remember. As careful as you are the camera itself can cause damage or they can get stolen. By breaking it onto smaller cards again you only loose whats not in the camera.

Re: One point of failure vs many?
 

Unless they steal your car with all your gear and cards :) I think we all know shooting to one card is always a risk, I have been doing so for the past 3 years. The problem is I use up to 5 camera's throughout the weddingday, often in a multicam setup and supplying every camera with a external recorder is a very expensive upgrade, not to mention the hassle of dual starting camera and recorder on each camera and the extra size it would add to each camera.
I have been thinking though about getting a atomos recorder for one camera but mainly to use it when I shoot for companies, then I only use one camera but for weddings it's a too expensive upgrade path.
Like I said, even if you swap out several small cards throughout the day, if one card from you main cam dies you still we be able to deliver but your client won"t be happy at all if that one card contained critical footage.

Re: One point of failure vs many?
 

Still 1 in 6 as previous throws do not influence the outcome of subsequent throws. The dice doesn't know that it's throw 1,000,001 & that 6 hasn't come up in a long time.

Re: One point of failure vs many?
 

Yep, sure! That's the "gambler's fallacy" -- "I've had a lot of blacks in a row, so there's a higher chance that the next spin will be red." Previous outcomes don't influence the next spin of the wheel.

But asking about the next throw is a different question, isn't it? I mean, different to asking, "Given a random sample size of a million throws, what is the probability that at least one of those is a 6?" Surely the probability here is higher than 1/6?

Re: One point of failure vs many?
 

You need o balance the equation that the more cards you use the higher the chance that one is going to fail but the fewer cards you use the more critical it is if one does actually fail.

No DSLRs or CSCs have the option of dual card recording so with multiple cameras we always preferred to have one card in each camera & use it all day. Swapping cards leads to the possibility of loss. At least you know that the card is in the camera (until the camera gets lost:-).

If you only shooting with a couple of cameras then an Atomos recorder on each would be worthwhile as transfer & logging after the shoot would be easier too as the cards could be ignored & just regarded as backups in case the recorder failed.

Re: One point of failure vs many?
 

The trouble with these sort of threads is that you can get paranoid about everything. What happens if you have twin card cameras for everything, or change cards several times during the day, then your car fails between the church and the reception, or on the way to the church. Does anybody have a spare car and driver available in case of such a failure? What do you do if your main camera has two cards, but the camera itself fails in the middle of the ceremony?

I have been filming weddings for 30 years and have never lost a wedding yet through tape or card failure. It may happen one day, but I check recordings periodically during the day to make sure everything is normal. If a card failed at some point during the day, it is quite likely that data would be recoverable as it is should only be corrupted from the file that it failed on. I also carry spare cards so that of a card fails, I can immediately change it, losing only a few moments.

I use more than one camera for the main parts of the day, so I won't be losing any sleep over failure. I also have a clause in my contract that says that I cannot be responsible for events beyond my control and I think that sudden card failure would be such an event.

Roger

Re: One point of failure vs many?
 

A little off-topic but taking up Roger's point about camera failure - during the ceremony/speeches I have a CX730 slung around my neck so I can lock off my camera and get some cutaways, but it would also come into play if my main camera went down.

Pete

Re: One point of failure vs many?
 

Adrian, the correct probability is always the same. If a card fails one out of 1000 times, that will stay true.

Then, the chance that two of your cards will fail at the same time is 1/1000X1000, or 1 in 1,000,000.

Back to the original question, I like to use 32GB cards, and we switch them out as we move between the 3 main parts of the day: before, during, and after the ceremony. With 3 cameras of coverage, if one card failed, we're not completely and utterly screwed.

Re: One point of failure vs many?
 

Roger, now I'm tempted to have a backup vehicle at all times in case my car dies!

Re: One point of failure vs many?
 

Hi Mike, Didn't mean to scare you :-)

Roger

Re: One point of failure vs many?
 

Hey Robert, let me have one more go at persuading you, because this question bugs me! And if this attempt fails, I promise I'll stop annoying everyone and won’t say another word about probability (but will be happy to read anyone’s correction to my half-remembered maths).

I flip a coin twice. What are the possible combinations?

HH
HT
TT
TH

And they’re all equally likely, right?

Question 1: What is the chance that I flip no heads at all? Well, there’s only one combination out of four that has no heads. So the probability is 1/4, right?

Question 2: What is the chance that I flip at least one head? Well, you could work it out by counting how many combinations out of four contain at least one head (ie, three). Or you could say the probability is:

1 - (chance of no heads)
= 1 - 1/4
= 3/4

I then flip the coin a third time.

HHH
HHT
HTH
HTT
TTT
THT
TTH
THH

Question 3: What is the chance that you've got at least one head over the course of the previous three flips?

By similar reasoning, it’s 7/8 (I'm hoping you'll agree). 7/8 is larger than 3/4, so the upshot is that the more you flip, the higher the chance that you’ll have flipped at least one head. (Or: the more memory cards you use, the higher the chance that at least one will be faulty.)

I then flip the coin one more time.

Question 4: What is the chance that it’s a head?

Well, possible outcomes are:

H
T

and the number of combinations that contain a head is one.

So the chance is 1/2. All the previous flips don’t affect the next flip.

Incidentally, if one really wanted to think like a robot, it's actually possible to go a step further beyond probability and apply "decision theory". To cut a long story short, I think the four-card choice vs the one-card choice, on decision theory, is the rational choice. Won't bore everyone with the explanation.

Re: One point of failure vs many?
 

Correct, though there is always the regression to the mean. If you flip you start flipping your coin, maybe you start with 8 'heads' in a row, which is statistically unlikely, but possible. The longer you flip the coin, the more likely it will regress back to the mean, or 50% heads and tails. Of course, every individual toss is still a 50% chance of heads or tails.
-----------
Our problem, of course, is that we're talking about our gear. We have no idea what the actual failure rate is for our memory cards, and the longer we use them, the higher that failure rate likely is. It doesn't mean its likely to fail, though, from a math point of view.

From a practical point of view, none of us take that chance, though. I'm sure we'd all say that, the day you're not prepared is the day something will break or fail for you.

We just all have to balance convenience to safety. I like 32GB cards and start fresh for the ceremony, then new cards once its over, etc. That's not really my safety measure. Running 3 cameras is (and I'll move to 4 soon). This protects me both from equipment failure, and from bad situations, like obstructed views. Same reason most of us use more than one audio recording method.

Re: One point of failure vs many?
 

Hey Adrian

OK so the bottom line is that you need a backup for everything ...spare car, spare clothes, spare cameras, batteries, tripods, lights, and the list just goes on and on.

I think this really comes down to being practical surely?? Carry spare cards and batteries with you but don't become obsessive about failing gear ... The likelihood of it happening is very remote so rather enjoy filming your weddings and let the gear look after itself

Chris

Re: One point of failure vs many?
 

Dice don't have any mean time between failure...

Because electronics DO, there should always be a clause in the contract/retainer limiting exposure to the original amount paid (for a full catastrophe, or loss/theft), or a part thereof, should there be an "equipment malfunction".

While any piece of electronics CAN fail, generally if it works initially (burn in or a few usage cycles), it will work for quite some time if not subject to abuse (liqiud, impact, crushing). This is presuming that you're not buying fakes/knockoffs or substandard quality products.

It's quite likely that decent quality cards will become unusable due to a requirement for larger file sizes or faster speeds before they "wear out" due to read/write cycles... my 8G cards are still working just fine, but when shooting XAVCS, 64 and 128G are the rule...

Re: One point of failure vs many?
 

Dave is absolutely right, rather than failing, cards etc tend to become obsolete as the technology progresses.

Another point is that card failure is more likely to be as a result of mishandling or placing somewhere where there is a high electro/magnetic risk. If a card is working fine in my camera at the start of the day, it is unlikely to suddenly fail. There is a remote chance of failure on removal by damage to the contacts, so the footage could be downloaded before removal to prevent that possibility.

I also like to make sure that the performance requirement of the camera doesn't exceed the performance of the card, to avoid glitches and lockups etc.

Roger

Re: One point of failure vs many?
 

And I'd point out that there have been "found" cards that were lost by their owners when the cam went overboard or down a crevasse or into a mudslide... and the images were recoverable.

Generally speaking, short of destruction, or an EMP, cards tend to be fairly reliable - some manufacturers do list use cycles or such that can give you some idea of "potential" failure rates, and I really suspect if a card is "good" through a couple write/read cycles, it's probably good for more than most of us will ever shoot before it's obsolete and no longer big enough or fast enough to hold our files...

Re: One point of failure vs many?
 

This kind of thing has always been a concern and now that I'm charging much more than I did years ago... the thought of a failure is always at the front of my mind when setting up.

This is why I shoot all wedding ceremonies with 4 or 5 cameras and individual audio recorders with wireless and wired mics going to my main cam and DR40.

As far as cards go, that's what I love about the Sony NX5. I get an instant backup to the FMU128 in real time.