That all kind of came into focus a few weeks ago when we were getting ready to evacuate from Hurricane Irene. I realised that the hypothetical total loss was now a real (if remote) possibility – a flood or structural damage could take out the wedding photos, all of our vacation and family pictures, our entire music collection (all 2000 discs) and much more. My best effort at the time was this:

I pulled the backup drives out of the server, put them in waterproof bags, and didn’t let them out of my sight for 3 days. It worked, but not really a practical solution!

So since then I’ve been working on realizing a long time plan of having reliable, up-to-date offsite as well as onsite backup for everything I care about. I needed a solution that would at minimum take the data from the server and put it somewhere safe away from the house – and of course cost is always a concern. I was looking initially at Amazon S3, which is a service that provides essentially unlimited cloud storage and charges a pretty reasonable amount per GB. A number of commercial online backup providers use S3 behind the scenes so I figured it would be even cheaper going straight to the source. It was, but not by much – I was still looking at a bill of at least $100 a month for the amount of data I wanted to store.On top of that you need to pretty much roll your own software as S3 is just a big place to put stuff, not a full backup system.

I then came across a company called CrashPlan. They specialize in backup solutions for large enterprises but also offer a pretty neat solution for home users. You download and install their software on each machine in your house, and it backs up your data to any one of a number of locations. You can pay a subscription fee to backup to their data center, or (and this is the cool bit) you can backup to other computers for free. That ability extends beyond your home network – so you and a friend can get together to swap backup space. You backup to her machine and she backs up to yours, all in realtime over the internet. It’s a really nice solution, and what’s more they support Windows, Mac and Linux which, I found, was pretty unusual. All the backups are encrypted so there is minimal risk of anyone being able to access your data.

So far I’ve setup CrashPlan on 3 machines, and am backing up all the data to two locations – locally to our server like before, and remotely to CrashPlan HQ. The former is of course much faster and will provide quick access to any data lost, the latter is the emergency failsafe. As well as easy backup the software also lets you restore old versions of files, so if you accidentally mess something up you can go back to a version from yesterday, last week or even last year. As a final bonus I’ve been able to switch off my old homemade backup scripts, which saves me a lot of hassle!

As I mentioned the software is free, and you can optionally pay a subscription for access to their servers. I have the family plan which gets unlimited data storage from up to 10 machines for around $120 a year – which is a great price if you have more than 100GB or so to backup. If you have less than that then some of the other services like Carbonite may end up cheaper. Personally, I’m expecting to be using a couple of TB by the time I’m done, but obviously the upload time for all that is quite considerable!

So I’m not affiliated with CrashPlan in anyway, I didn’t get anything for writing this, I just thought it was a pretty neat solution and very reasonably priced – so as a customer I’m now interested in them doing well   If anyone I know is reading this and is interested in backing up to my machines just drop me a line!

Lens Types & Cost

After reading the last post on lenses you may be wondering why lenses cost such radically different amounts, even while the length is the same. As an extreme example, Canon currently make 4 different 50mm lenses:

• EF 50mm f/1.8 II Autofocus Lens ($100)
• EF 50mm f/2.5 Compact Macro Autofocus Lens ($300)
• EF 50mm f/1.4 USM Autofocus Lens ($400)
• EF 50mm f/1.2L USM Autofocus Lens ($1500)

The prices are approximate, but you get the idea. A 50mm prime could cost anything between $100 and $1500! So let’s take a look at what’s going on here. There are a few differences in the names of these lenses, so lets break one down – starting with the cheapest.

• EF – means it fits a Canon EF mount
• 50mm – the length
• f/1.8 – the maximum aperture (or speed) – more on this later!
• II – this is the second revision of this model
• Autofocus – capable of automatically focusing, almost all modern lenses have this

Now if we compare to the next one, the speed is different (f/2.5 vs f/1.8) and it’s a “compact macro” (we’ll discuss macro later but it’s basically a specialty type of lens for taking close up photos of very small things). Comparing to the third lens, the speed is different again, and now we have “USM”. This stands for “Ultrasonic Motor” and it’s a Canon term for a particular type of motor used in the autofocus mechanism (the Nikon equivalent is SWM). A lens with USM will focus faster and more quietly than one without. Finally, onto the crazy expensive one. Notice the speed has changed again and now we have an “L” after it. The L is significant – it marks the lens as being from Canon’s professional series – these have a red ring painted on the end so you can tell them apart easily. The L series lenses have better build quality, better internal design and generally give much better images – as well as being much more expensive, larger and heavier.

Aperture/Speed

Although there were a few differences between those four 50mm lenses, the most significant is probably the varying speed (or maximum aperture). The aperture is simply a hole in the lens that the light goes through before it hits the sensor. Most lenses can adjust the size of this hole, to allow more or less light to pass through, and the number quoted is a measure of how large the hole can be on this particular lens.

Before talking about why a larger aperture is both good and expensive, let’s touch on shutter speed. When you press the button to take a photo, the camera allows light to hit the sensor so the image can be recorded. In an SLR this is done with a physical curtain called the shutter, normally it’s closed, when you want to take a photo it’s briefly opened. In order for the image to be of the correct brightness we need to carefully control how long the shutter is open for – too long and the photo will be too light, too short and it’ll be too dark. Obviously in dark conditions we will need to open the shutter for longer than in very bright daylight to get the right amount of light onto the sensor. So varying the amount of time the shutter is open for (the “shutter speed”) is one way we can compensate for the lighting conditions. But there’s a problem with using shutter speed on it’s own – movement. If the shutter is open for too long then any movement (either the subject moving or the camera itself moving) will cause the picture to be blurred. This isn’t an issue in nice bright daylight, but indoors or in dark conditions then it can become hard to open the shutter for long enough to get a well-lit photo without it being blurred.

This is where the aperture comes in. If more light can get through the lens (i.e. a larger aperture), you can have the shutter open for less time and the same amount of light will hit the sensor in total. This means that a larger aperture allows for a faster shutter speed to be used with the same end result. It should now be obvious why a lens with a large maximum aperture is useful – it allows for faster shutter speeds which reduces the likelihood of blurring, particularly in tough lighting conditions. As for why it’s more expensive, making the aperture larger greatly complicates the design of the lens if you want to avoid distortion. You need more glass, more gears and a more complex design.

Finally let’s talk about the actual measurements used for aperture. What does “f/1.8″ mean compared to “f/1.4″? Put very simply, the smaller the number the larger the aperture, so the $1500 f/1.2 is larger than the $100 f/1.8 (you’d hope so, given the price!).

How much larger? Well that gets (a lot) more complicated. The f-number is a scale made up of values (called “stops”) derived from a geometric series. Whe you move from one stop to the next you double (or halve) the amount of light hitting the lens (and thus, halve or double the required shutter speed). Most DSLR cameras allow for adjustment of the aperture to one-third stop values, so moving three steps (one stop) will double or halve the shutter speed.

We can tell from the table that f/1.2 is a full stop faster than f/1.8, so the expensive lens will let in twice as much light as the cheaper one, allowing for shutter speed that’s twice as fast to be used. This is a very significant difference, and it’s why a lens with a larger aperture is called “faster” – it allows for a faster shutter to be used.

In the image above, we see the results of taking the exact same shot 4 times with different settings. First, in the top left, we have the properly lit shot according to the camera’s exposure meter, which gave us an aperture of f/4 and a shutter speed of 1/250th of a second. In the bottom right we see an equivalent shot using f/10 and a shutter of 1/50th of a second. f/10 is almost 3 full stops smaller than f/4, and so the corresponding shutter speed is significantly slower. The top right shows what happens if we use too long a shutter speed – 1/50 is far too slow for an aperture of f/4 so too much light is allowed in and the image is too bright. The bottom left shows too short a shutter speed – the aperture of f/10 is too small when used with the shutter of 1/250 – not enough light means a dark photo.

Note: There are other effects of changing the aperture (most significantly depth of field), but more on those later.

Macro

As previously mentioned, a Macro lens is one specifically designed to allow you to take photos of very small things (flowers, insects, etc). This is usually achieved by allowing the lens to focus on subjects very close to the camera – as all telephoto lenses have some degree of magnification this close-up view will magnify the subject producing the desired effect. The design changes needed to achieve this will cause a Macro lens to cost more than an equivalent non-Macro, as can be seen with the comparison of 50mm lenses above. The Macro at f/2.5 is more expensive than the f/1.8 which is significantly faster.

Image Stabilization

One of the reasons for wanting a lens with a large aperture is to increase shutter speed and so decrease blur caused by movement of the camera. Another way to do this is to use image stabilization which is a system that detects and compensates for the movement of the camera. This can be a nice alternative to sheer lens speed, as it’s typically cheaper and works reasonably well. In the Nikon system IS is referred to as VR (Vibration Reduction). The really important caveat is that IS/VR is useless when the subject is moving, it only compensates for movement of the camera itself. So if you want to get a nice clear shot of that speeding F1 car you’ll still need a fast lens.

That’s it for the lens primer, check back for more photo tips soon!

On the left you see the sensor, represented by the yellow box. You can see that the image projected onto it by the lens is a little larger than the sensor – this is quite normal. Whatever does hit the sensor becomes your final image, shown on the right. Now imagine the sensor is smaller – the lens is exactly the same, so the projected image is the same, but less of it will hit the sensor. The final image is also the same size (we’re assuming that both sensors have the same resolution – the same megapixel count). End result? The final image looks like it’s taken with a longer lens, it’s been magnified. The crop factor is a measure of how much smaller the sensor is, and thus how much longer the lens appears to be. It’s called the crop factor because it has the effect of cropping (trimming) the image.

Hopefully that makes things a little clearer, if you have any questions feel free to leave them in the comments!

Compatibility

One of the first criteria, pretty obviously, is that the lens has to work with your camera. In general, if you own a Canon camera you buy Canon lenses, Nikon for Nikon, and so on. There are, of course, exceptions. There are third party manufacturers such as Sigma and Tamron who make lenses for multiple camera types (usually referred to as “mounts” – the physical design of the connection between the lens and the camera). These third party lenses are typically of decent quality and considerably cheaper than their first-party cousins, but beware that there have been incidences of compatibility issues in the past, as neither Canon nor Nikon officially publish or license their specifications. So there’s a small risk there, and you’ll also find far fewer reviews of the third party lenses so they’re more of an unknown quantity. But if you’re on a budget, they may well be worth considering.

Secondly, even within a given manufacturer there are differences. For example, current Canon cameras use either the “EF” (film and pro level DSLRs) or “EF-S” (consumer level DSLRs) mount. They’re similar, but not identical – an EF lens will fit in either type of camera, but an EF-S lens can only be used in an EF-S camera. Nikon also have a consumer level DSLR format, called DX. Things are a little different here – a DX lens will fit fine on any of their current cameras but might give less than ideal results if the camera isn’t aware of the lens type. There are no physical incompatibilities between current Nikon gear though, so you are a little safer! In general make sure you know the type of camera you have and if in doubt ask the seller or read online reviews.

Focal Length

The key differentiating factor between lenses is the focal length, or just “length”. It’s a number usually measured in millimeters, and it translates to how much the lens magnifies the scene. A “long” lens, with a high focal length, is good for taking shots of things a long way away, you can think of it like a telescope. A “wide” lens, with a low focal length, is good for landscapes as it allows you to get a whole mountain or building into the shot. Lenses are broken down into categories based on their focal length – I’ve listed the most common below.

The Normal group is probably the most important. Most portraits, family photos, weddings, and even many outdoor shots are taken with a lens around 35-50mm. The reason for this is that this length gives you a magnification and perspective similar to that of the human eye, so the photos look more natural to our brains. The perspective point is important, but a little complex to explain here. Basically, taking a shot from a long distance with a telephoto lens doesn’t give the same result as getting close to the subject and using a normal lens – the latter will usually look better, but is often hard to do!

The example below shows the same shot taken at 85mm (telephoto), 35mm (normal) and 17mm (wideangle).

Crop Factor

Update: I’ve posted a (hopefully) clearer explanation of Crop Factor here.

So we’ve figured out that a 35mm lens is “normal”, anything “wider” or “shorter” than that is wideangle, and anything longer than about 60mm is usually considered telephoto. This seems too simple, so inevitably there’s a catch! It’s called the “Crop Factor”, and it applies to many commonly used DSLRs. It all comes back to sensor size, as discussed in part 3. This way of categorizing lenses came about when SLRs were film based, and most used a film frame that was 35mm in size (diagonally). That’s why a 35mm lens is considered “normal” – the image it produces is the same size as the film. A 70mm lens would be magnified twice as much, and a 140mm twice as much again. Now some DSLRs use a 35mm sensor – these are called “full frame” cameras and typically cost at least $2000. If you have one of these the crop factor is irrelevant, your 35mm lens is normal and everything is simple. For the rest of us, our cameras probably use a smaller sensor, typically APS-C sized. That means that a 35mm lens is no longer normal – it’s bigger than the sensor and so has some magnification. The crop factor for an APS-C camera is 1.6x, which means that to get the “effective” length of a lens when used on that camera you need to multiply it by 1.6.

This means that my 35mm lens, when used on my Canon 7D with a crop factor of 1.6x, is actually equivalent to a 56mm lens on a full frame camera. Why does this matter? Well it matters when we’re at the extremes. A big problem is wideangle lenses with APS-C cameras. Typically 16mm is considered pretty wide, but put that on a 1.6x crop camera and now it’s a 26mm – not really very wide at all. To counter this I have to buy a 10mm lens (equivalent to 16mm with the crop factor) – and 10mm costs a lot more than 16mm!

At the other end it’s an advantage however – my 300mm telephoto is actually equivalent to a 480mm! That’s a huge difference, and means that users of APS-C cameras looking to take wildlife and sports shots can actually buy shorter lenses than their full frame owning friends. Shorter lenses are smaller, lighter, and cheaper.

All in all you need to be aware of the crop factor of your camera when buying lenses, if you read a guide or book suggesting good lengths for certain shots or techniques, remember to apply the appropriate crop factor before buying that lens.

Zoom vs Prime

So far we’ve talked about lenses with a single focal length, for example 35mm. These are called “prime” lenses, and whilst back in the day that’s all you had, these days lenses with adjustable focal lengths are more popular. These are called zoom lenses. To clarify (because it’s a common misconception) – “zoom” doesn’t mean the same the same thing as telephoto – it just means variable length. In fact, that 10mm wideangle lens I mentioned earlier is actually a 10-24mm zoom. Very far from a telephoto (there’s no way you could use it to magnify a distant subject!) but it’s adjustable, so it’s a zoom. Getting out of the habit of using “zoom” to mean long length (as in “zoomed in”) will help a great deal when lens shopping!

Zoom lenses are obviously very convenient. Rather than carry around a whole bunch of different length lenses you could (theoretically) just have one zoom which covers 16mm-600mm and call it a day. The problem is that this is a compromise. A zoom lens is much more complex than a simple prime – there are many more moving pieces involved. That makes them larger, heavier, and more expensive than equivalent primes. What’s more, the image quality is always going to be worse than a similarly priced prime, and they’ll also be slower (see later for a discussion of lens “speed” and why it matters).

I started off, like most people, with a mid range zoom lens covering kind-of-wide to kind-of-telephoto (a Canon EF-S 17-85mm). It’s a great lens, and I still use it a lot. If you only have space in the bag for one lens then something like that is ideal, you’re likely to be able to cover most situations which come up. However, once I got my hands on a 50mm prime I’ve been using that wherever possible. Although the zoom does 50mm just fine, the pictures which come out of the prime are so much nicer, plus it’s smaller and lighter. My recommendation is really to do the same. Start off with a decent quality zoom covering roughly 16-100mm or thereabouts, and over time you’ll understand which primes might be worth investing in. I think a 50mm or 35mm prime should probably end up in everyone’s bag if they’re serious about taking shots of people.

Of course, if you’re taking pictures of animals who don’t appreciate you getting too close to them, you need a long telephoto, and these are almost all zooms these days. Not to worry, they’re very suitable for wildlife shooting – you don’t need to go looking for a 400mm prime!

To Be Continued…

That’s all for now – tune in next time for more lens talk – we’ll cover speed and aperture (“f-stops”) as well as features such as image stabilization, macro and auto/manual focus.

All Canon DSLRs have a model number starting with 1, 2, 3 or 4 digits and ending in D. For example you have the 5D, the 60D and the 600D. Here’s how to tell what you’re looking at:

• The fewer digits, the higher end the camera is. So a 1000D is basic, 500D is entry level, 50D is mid range and 5D is pro.
• Except for the single-digit numbers, higher is newer. So the 40D replaced (and is better than) the 30D, which previously replaced the 20D.
• For the single digit numbers, lower is better. The 5D is awesome, the 1D is the ultimate. Newer models in this range get suffixes, e.g. the 5D mkII.

I believe Nikon use a similar scheme (although I’m not a Nikon expert) but they put the D at the beginning!

Now just to confuse us, Canon sometimes use different names for their entry level cameras in different regions. For example, you may hear about a Canon “Rebel” – this is the brand name sometimes used to refer to the 3 and 4-digit entry level models in the US (in Asia they’re “Kiss”!). But they’re the same camera, and most people I know use the  standard number to avoid confusion. Here’s the current cross reference guide in order of newness:

• 600D = Rebel T3i = Kiss X5
• 1100D = Rebel T3 = Kiss X50
• 550D = Rebel T2i = Kiss X4
• 500D = Rebel T1i = Kiss X3
• 1000D = Rebel XS = Kiss F

You’ll see the name “EOS” floating around as well – that’s the overall name Canon use to refer to their whole DSLR and lens system.