Monday, February 28, 2011

Keeping in touch with home

As someone who spends a lot of time away from home, I've always been interested in keeping in touch with my family (sometimes they're not travelling with me). Today there are lots of options. I've explored most of them over the years, so here's an overview:


Mobile phones have been around for a while now, and when you're in range they're supremely convenient. Here in Australia it usually costs the same to call from one side of the continent to the other as to call next door, and the only issue has been whether you can get reception. Most country towns have cell towers, and major highways have coverage. But if you're off the beaten track they're of limited value.

Being able to call home every now and then to let them know you're OK is good for the people at both ends of the call.
But when travelling overseas this can get very expensive, as international roaming rates can be a bit nasty. SMS messages become more useful then, as it usually costs nothing extra for the people at home to send you a message (and nothing for you to receive it) and only a "slight" (e.g. 100%!) markup on the cost for you to send a message home. It's sometimes surprising how much value you can get out of 160 characters (but then many people have been getting used to the 140 characters of Twitter). Where possible I do use local SIMs (or special "roaming SIMs": I have one from RoamingSIM) to cut the costs, but even then you need to be careful: it'll probably cost a lot more than the normal calling rates you're used to at home.

Internet and Email

If you have internet access you can email, either from your laptop or today it's just as easy to do it from a smartphone. But you do need internet access! It was only 5 years ago I stopped using a dialup modem while travelling around Australia, as WiFi became more accessible. Then for a few years when on road trips it wasn't unusual for me to find the nearest WiFi-enabled McDonalds and from my laptop send and receive emails (and download recent podcasts, etc) before moving on. It was both faster and cheaper than using a modem.

Incidentally, I rarely pay for WiFi access. Either I find a free hotspot, or if I'm in Australia I instead simply use my iPhone's 3G/GPRS data (either stand-alone, or tethered to my laptop). Today my phone plan has a 2 GB/month allowance: plenty for me when away from home. Unfortunately the international data roaming charges are ridiculous, so by default I turn this off while overseas. Travelling overseas is pretty much the only time I've paid for WiFi access, and even that's rare: free access is becoming almost ubiquitous in many places.


If you've got WiFi it's just as easy to stay in touch from the other side of the globe as from the next state, and you're not limited to just email. Right now I'm keeping in touch with my wife and her sister who are travelling through Cambodia and Laos for several weeks while I'm at home in Australia, and we've been using a combination of SMS and Skype to communicate. SMS to attract the other's attention, and Skype to either talk or to text-chat (when the network's too congested for voice) for free. And they're just travelling with their iPhones. It's great to see and hear it all come together while hearing my wife's voice clearly, with her sitting in a Laotian cafe using the free WiFi, and I'm either at home at my desk or out and about using Skype over 3G. We used Skype in a similar way in 2009 while I was Artist in Residence aboard a Hurtigruten ship on the Norwegian coast for over a month, although often the satellite internet link on the ship wasn't up to the job of handling voice traffic.

When you're away from the networks...

But again, all of that needs some telecommunications infrastructure. There are many times I'm away from mobile phone or WiFi access, which by default means no voice calls, no SMS, and no email. But there are options available to fill the void.


I wrote about this in 2008, when I started using the first version of the SPOT Messenger. This device requires an annual subscription of a bit over $100, but uses an internal GPSr and the Globalstar satellite network to send messages and your location. After configuring your device via their website, the "OK" button sends a map URL and a customised (but static) text message to your specified list of email contacts. For a some time I've used this to send "I'm OK, and this is where I am" messages home, and these messages also update this website's Where's David? map.
The device also has a "HELP" button to send a different text message to a (possibly different) list of email addresses, and a "911" or "SOS" button to send emergency services to your location. I keep the SPOT in my camera bag so that even if I'm out of mobile phone reception and down a bush track by myself I have some chance of getting help in an emergency. I do try to send an OK message at least once a day too. This has provided a lot of peace of mind for my family. It's also configured to automatically add points to the "Where is David?" map on this website.

The original SPOT messenger has been replaced by a slightly smaller version, and now in 2011 SPOT are introducing the SPOT Connect, which uses Bluetooth to connect to your smartphone and allow you to send short (40-character) text messages typed in via a phone app and sent via the Globalstar network. This is a big advance on the basic SPOT functionality, although it is still one-way communication. There's no way for the people at home to send you a reply.

While you don't always want to be able to receive messages (after all, for many of us that is part of the allure of the remote outdoors experience!) there are times it's good to be able to have 2-way communication with your loved ones at home (e.g. when on very long trips).

The SPOT has been a great device for me, but only if I''m travelling somewhere that it covers. Despite being billed as a "worldwide" device, it doesn't cover ALL of the world. It sends simplex messages via the Globalstar satellite network:

It's OK for most of the populated world, but those dark grey areas are described as "reduced or no coverage". Not so useful for travel to places such as South Georgia, the Antarctic Peninsula, Madagascar, east and south Africa, India, or Svalbard.

Satellite phones

These allow us to have voice communications with home, and some provide SMS messaging. But each satellite network has its own pros and cons.
  • The Globalstar network supports voice calls, but the duplex coverage area is even smaller than for the simplex coverage used by SPOT. I've used a rented Globalstar phone in the middle of the Simpson Desert: where there's coverage they definitely work well, and that handset was also a GSM phone for cheaper calls when we were near a phone network (although that's not much of a selling point these days, as almost everyone has a GSM-capable phone anyway).
  • Thuraya is another network with cheaper handsets but smaller coverage areas.
  • Inmarsat even provides high-speed data connections across most of the globe (except the poles) but requires you to point the antenna at the appropriate geostationary satellite position.
  • Iridium is the only network with truly global coverage. Iridium ran into very public financial problems early on and some people assume the network disappeared, but it's still very much active and being maintained. Iridium does provide data connections, but only at 2.4 kilobits/sec (plus compression) and charged per-minute as a phone call.
All these satellite phone systems have one thing in common: they can be VERY expensive to use. If you need that sort of access, it's important to choose the best phone plan for you that isn't going to cost you thousands of dollars every year. It can be a complex choice. If you have a standard post-paid SIM from Telstra (an Australian phone provider) you can use this in an Iridium handset. It's very expensive, but it works and for a small number of calls might be the solution you're looking for.

On our November 2010 South Georgia/Antarctica expedition I used a friend's Iridium phone for a few phone calls to home (this was during a challenging time with a family friend having cancer) and being able to talk to my family every day or two was great. I've recently acquired an Iridium handset and a pre-paid SIM, which for my projected use was the most cost-effective solution. It will allow me to call home with voice calls (cheaper than the family calling me) and to send and receive SMS messages from anywhere on the globe (although a few governments don't like you to use satellite phones within their territories, they're not on my destination list at the moment). I'll even now be able to keep the Where's David? map updated when we're in Antarctica out of SPOT coverage (via an SMS gateway that allows me to send GPS coordinates as well as short blog posts).
However it is a relatively bulky device, and might not go everywhere with me in my camera bag.

Local communications

Telecommunications isn't just useful for talking to your home base: it has uses in communicating with other travellers. Away from phone networks, "walkie-talkies" are still useful today.

While on expeditions in the Australian outdoors, licence-free UHF CB radios allow us to stay in touch between 4WD vehicles or if we split up on foot. Various repeaters are situated around the country for long-distance calling, and the distress channel is monitored in many locations. The radios can be up to 5W in power (even small handheld units) although I've found 0.5W units to work well over a few kilometres. I often have one clipped to my jacket when working in the outback.
The UHF CB band is split into 40 channels, although some of them are reserved for special purposes. Note that in 2011 Australia and New Zealand are both moving to an 80-channel arrangement, which will cause the introduction of new radios (keep that in mind if you see bargain-basement sales of 40-channel radios).

However these UHF CB frequencies can only be used in Australia and New Zealand. In other locations other solutions are required (and other countries' radios can't be used in Australia). Check with the relevant governments for details!
For example in Europe and much of Africa the UHF PMR446 licence-free radios (0.5W max, 8 channels) are available, and in North America there seems to be a lot of confusion between the 14 licence-free UHF FRS channels and the 8 extra GMRS channels (which in the US require a licence, but not in Canada). Other systems are used around the world, but the Australian system is very convenient, with lots of available channels and with much higher power allowed than some other licence-free bands (useful in the outback).

On safari in Africa we sometimes use PMR446 radios to chat to other vehicles in our group, but even there it's sometimes easier just to call someone's mobile phone: GSM coverage keeps expanding the world over!

Today there are lots of communication options available (both to stay in touch with family/friends and for emergency situations). If you're heading out into the outdoors by yourself, think about the options! And even if you're looking for "alone-time", in many situations it's great to have emergency response plans in place.
Continue reading "Keeping in touch with home"...

Friday, February 25, 2011

CF card speeds: 7D and 5DmkII

Despite manufacturers often claiming amazing speeds for their flash memory cards, these are never achieved by cameras writing to them. Sometimes this is because the quoted number is the maximum read speed in an ExpressCard reader, but in any case each camera model has different card interfaces, different CPUs, and different firmware, and these can result in dramatically different speeds overall. Thus when selecting a memory card for use in your camera it's important to look at measurements in that camera model.

There are a few websites around with this data. A well-known one is Rob Galbraith's CF/SD database, with benchmarks of a large number of cards in different cameras. However it doesn't always have the camera model you're interested in, or the card model. For instance the EOS 7D isn't listed in the CF/SD database, although results for some recent cards can be found elsewhere on the site. Also Chuck Steenburgh reports some card speeds in Nikon bodies.

Primarily I'm looking at these CompactFlash cards in terms of how they work in my own EOS 7D and 5DmkII cameras. I shoot all my images as RAW files, so "JPEG speed" doesn't interest me.

From my point of view there are several requirements for the speed of a card:
  • Can it keep up with recording movies? At 1080p HD, my cameras generate either 5.5 MB/s or 6 MB/s (the difference between PAL and NTSC: 25 and 30 fps) of data. A card that can save files at 8 MB/s or faster provides a nice safety buffer. But don't believe the hype that you need a top-speed card for video on these cameras.
  • Burst rate for action shooting. These cameras have buffers that try to insulate you from the card's speed, but if the camera is busy saving files it can disrupt things like reviewing images. Usually this isn't an issue, but when it is it's very annoying. And if you're shooting action and manage to fill the buffer, it can feel like an eternity while waiting for room to reappear in the buffer. Obviously the buffer fills quickly if you simply hold down the shutter in continuous shooting, but I sometimes fill the buffer even when triggering each shot independently. A couple of frames here, a couple there, a few more, etc. It can add up quickly.

By the way, times that I am heavily exercising the 7D's buffer include things like shooting flying albatrosses on the Southern Ocean, or following the action of a kill on the Serengeti.

Southern Giant Petrel (A2_054408)

So I'm interested in the underlying write speed (in MB/s) as a start, but also how this impacts the overall shooting speed. Manufacturers like to advertise speeds, either in MB/s or "X" (where 1X is 150 kB/s: the transfer rate of the original CD-ROM drives). But as noted above, a 400X card (nominally 60 MB/s) is unlikely to actually achieve that speed in your camera. Rather than relying on the manufacturers' numbers, we need to test in each model.

The cameras

At 4 fps (well 3.8, but who's going to quibble?) this camera isn't a speedy action camera (it's AF isn't the best for this either) but it can still do a decent job of some action scenarios. The 14-bit RAW files are usually between 22 and 30 MB each (with 25 MB being a reasonable average for rough calculations) so it does help to have a decently-fast card.
In RAW mode the viewfinder indicates a buffer of 13 frames, although with a slow card I've seen it only actually produce 12 continuous frames, and with fast cards it gets up to 16 frames without pause (although the displayed maximum buffer is always 13). That's an additional second of shooting.

At 8 fps and with a great AF system, this camera makes an amazing sports camera.
The RAW files are a similar size to the 5DmkII's (20-29 MB, with 25 MB the average even at relatively high ISOs) but a fast card is even more important as the buffer can fill so quickly.
While the buffer indicator maxes out at 15 in RAW mode, with most cards it actually manages 16 (that's 2 seconds of solid shooting).
In low-speed (3 fps) mode it can manage 32 frames (almost 11 seconds) before the buffer fills.

The raw numbers

I've collected here what I've found to be the useful data for a number of cards. I've tested most of these myself, and for the same cards I've been getting numbers generally consistent with those reported by Rob Galbraith's site. Thus I've included their results for several other common cards to put them in context.
Because there're usually only small variations between cards of the same type but different size, I've merged the report for various card sizes unless there was a noticeable "outlier". Because of this and because of the inherent precision problems of using a stopwatch to measure the speed, I've rounded all the results to 2 significant digits. All these tests were done with manual focus engaged, at fairly low ISOs, and in quite bright conditions.

Lexar Professional 600X4554
SanDisk Extreme Pro (robgalbraith)4145
Transcend 600X3745
SanDisk Extreme3639
Lexar Professional 300X (robgalbraith)3135
SanDisk Extreme IV 45MB/s edition (robgalbraith)3134
SanDisk Extreme IV 4GB3034
SanDisk Extreme III 30MB/s edition2328
SanDisk Ultra2227
SanDisk Extreme III1516
Ridata 80X PRO II 2GB5.65.6
Silicon Power 45X 1GB5.35.3

The above links are to the appropriate product pages at B&H Photo (my usual source for such things) to make it easy to compare prices.

It's plain to see here that these cards do roughly keep their relative rankings between these two bodies. Sometimes a card will excel in one model but be a dog in another, but not here. However, these raw numbers don't tell the full story by themselves.

The Cards

The slowest cards in this list provide an illustration of the limits for video recording. At 5.3 MB/s the Silicon Power card was only able to record short video clips before the buffer filled, while at 5.6 MB/s the Ridata card could record PAL clips fine, but soon stuttered in NTSC mode. Note that the Ridata is advertised as an 80X card, which would be 12 MB/s. That's about the fastest I've been able to read files off it in a card reader, but the cameras are a long way behind when writing.

The older SanDisk Extreme III cards were fast for their day, but without UDMA they max out at around 16 MB/s in these cameras. I keep mine in my travelling kit as a spare of last resort.

The SanDisk Extreme III 30MB/s cards are noticeably faster. But while I'm more than happy to use these in my 5DmkII, I do prefer to put some of the faster cards in my 7D.

The SanDisk Ultra (not the older Ultra II cards: the "30MB/s" one) offers speed virtually identical to the older Extreme III 30MB/s, and it's a common assumption that these cards were simply re-badged (although with different environmental constraints: the Extreme series purports to be more rugged). As such these do offer a great budget card with decent performance. Note that the current 2 GB model is only described by SanDisk as a "15MB/s" device (I have not tested this model).

The SanDisk Extreme IV was one of the first UDMA cards in 2006, and still produces a respectable speed today. The later "45MB/s" version is essentially the same speed in these cameras, and is matched by the Lexar 300X cards.

The SanDisk Extreme cards introduced in 2009 are quite speedy, and the significant performance improvement with this in the 7D over the Extreme III 30MB/s cards prompted me in 2010 to look at fast cards in more detail. Having mainly been a SanDisk user for years, by default I was considering getting some Extreme Pro cards but thanks to the results listed by Rob Galbraith I decided to branch away from the SanDisk family and add a faster Lexar 600X card to my kit. Both manufacturers keep dropping their prices, and when I bought it the Lexar 600X was cheaper than the equivalent SanDisk Extreme Pro. As an experiment, at the same time I bought the much-cheaper Transcend 600X 8 GB.

That's pretty much given you the summary of my own card choices, but there is some more interesting detail to look at. The above numbers do translate into significant real-world differences in the speed of the cameras.

Both of these cameras have buffers which mean that the speed of the card won't affect all shooters, with files being written to the card in the background. The 5DmkII is listed as having a 13-shot buffer in RAW, and the 7D having 15 shots. Unlike some older cameras which would then effectively lock up while the buffer was flushed, these cameras keep working, with AF/metering/etc continuing if you press the shutter even if the buffer is full. But if you're shooting action sequences and often fill the buffer, you'll be interested in how quickly it empties (or rather how quickly it gets room for more shots). In fact a very fast card can flush the buffer so quickly it seems bigger!

Here are graphs of some audio recordings of the cameras shooting with various cards. First the EOS 5DmkII (trying to shoot at 3.9 fps) with SanDisk Extreme III (NOT the 30MB/s version), UltraExtreme, Transcend 600X, and Lexar 600X cards:

As you can see, the faster cards effectively increase the buffer size. Once the buffer fills, the camera slows down but keeps shooting at a fairly regular pace. The Extreme card performs very well here, and it just keeps improving with the faster cards. With the Lexar card, the 5DmkII can maintain 2 fps RAW shooting until the card fills.

Now for the EOS 7D (trying to shoot at 8 fps with the same cards):

The buffer size doesn't really change much, but when the buffer fills the behaviour becomes a bit erratic, with uneven pauses between bursts of frames (usually 2, but sometimes 1 or 4).  The longest gap I've measured with an Extreme III was 5.5 seconds before the camera would take another two shots. With action scenes unfolding in front of you while you wait, even one second can feel like an eternity!

The more-regular behaviour of the Extreme card is a lot more pleasant to use, and again it just keeps improving with the faster cards. With the Lexar card the 7D can maintain an average 2.75 fps RAW shooting until the card fills.

By the way, the EOS 7D also has a low-speed continuous mode (3 fps), and the Extreme III card can save 27 frames (9 seconds) before pausing. With the Extreme card this expands to almost 17 seconds, and I gave up testing after 30 seconds continuous shooting with the Lexar 600X. With the underlying 2.75 fps speed noted above it can't go on at 3 fps forever, but even so that's a lot of shots!

Gentoo Penguin, porpoising off our bow (A2_049933)
Card sizes

The size of card we should use is a common question, so I'll try to give you my take on it. Cards are extremely reliable these days, and in my workflow it's usually not long (less than a day) before I've copied all the files off a card and backed them up to multiple hard drives. So I'm not worried about "putting all my eggs in one basket" by using a large card. In fact one large card can be safer than many small ones, as when you're changing cards in the field they're at risk from things like rain, fumbling, dropping overboard or in the mud, etc. Incidentally, with SD cards I'd add "blowing away in the wind" to that list.

I remember years ago hearing people say they wouldn't use a card larger than 1 GB because that was too much data to have in one place. But today that size card seems tiny. It's useful to translate the gigabytes into a number of images for your camera. For example my EOS 5DmkII estimates that a 4 GB card will hold around 140 photos. For a regular outing photographing landscapes or macros, this is usually more than enough for me, but if I'm photographing action such as wildlife or airshows (or fast-changing landscapes from a moving ship) I can fill that very quickly! For me my busiest shooting times are when I'm in places like South Georgia or Antarctica, spending several hours at a time amongst wildlife and icebergs, and my busiest days can involve over 3000 photos! (Yes I do end up deleting quite a few of those later.) But for each outing from the ship I've found I'm unlikely to fill a 32 GB card.

If I had a very large and very fast card for each camera I'd be happy (as long as I had a spare card of some sort in my pocket for the eventuality of filling even that up). But the largest cards get very expensive, and if I compromise and get a cheaper slow one I'll just be frustrated in the field. Because of the changes over time, the "sweet spot" of price/performance keeps changing. But for now the largest cards I have are 16 GB. I only have two 16 GB cards, with the rest being smaller cards (the oldest is now a 4 GB Extreme III from 2006: back then at 6 MB/s it was one of the fastest cards for my EOS 30D).

I prefer to start off with my largest card in the camera, so that I've got a safety-buffer if I do fill it (rather than quickly filling small cards and then shooting for ages on a big card and getting stuck if it runs out). So even though my 4 GB SanDisk Extreme IV is faster than my 8 GB and 16 GB Extreme III 30 MB/s cards, it tends to get used last. In 2010 I had occasional frustration because my fastest card for the 7D was an 8 GB Extreme, with a big drop in performance to the Extreme III 30MB/s cards.

Today on action shoots I tend to start off with a 16 GB Lexar 600X in the 7D, with 8 GB Transcend 600X and SanDisk Extreme cards as backups. A 16 GB SanDisk Extreme III 30MB/s starts off in the 5DmkII, with an 8 GB Extreme III 30MB/s as backup, and an assortment of 4 GB cards (Extreme IV, Ultra, Extreme III) as last-chance spares (or for temporary loan to workshop participants).
Of course I can use any card in either camera, but I do try to keep the fastest cards for the 7D.

Gento Penguin calling (A2_007618)


While I'm not always shooting intensive action, I'm conscious that future cameras are likely to only increase the bandwidth demands on my cards. I remember when the Ridata 2 GB card was faster than my cameras! The top-speed cards are obviously more expensive, but today I regard the SanDisk Ultra as the absolute minimum I'd purchase, preferring something like the SanDisk Extreme (or faster).
While the Ultra is likely to become a limiting factor in some future camera, I currently have no replacement camera in mind and cards just keep getting cheaper. Mind you I do feel I've got enough cards for now, and the only thing likely to drive me to purchase more is when I eventually do start using a camera with even larger files. At which point I'll be stuck with the same old problem of what to do with my smaller and slower cards...

We each have to make our own compromises when choosing cards for ourselves. Hopefully this article will help some EOS users make those choices. Some will go for cards that are "fast enough for now" while others will try to make decisions for the future. Whatever you do, remember to check the current prices as well as the technical results before you choose.
Continue reading "CF card speeds: 7D and 5DmkII"...