Fun with filters

We fit protective filters to all our lenses which can accommodate them. Some people prefer to use them, especially on expensive hired equipment, so hopefully they'll be happy. Some people prefer not to, and that's fine. The most common reason for people not wanting to use protective filters is their concerns about what it does for image quality. So we thought we'd do some experiments.

First off, here's our man Richie with his test setup. From left to right:

• Nikon D700 camera
• Nikon AF-S 80-400mm f/4.5-5.6 G ED VR lens
• 34 (yes, THIRTY-FOUR) protective filters.

Here's a close-up of the test rig. As you can see these are all decent quality Hoya Pro 1 Digital filters, not your cheap rubbish. You're looking at about £1000-worth of filters on the end of that lens.

Here's another view of the test set-up. You can see that the front filter isn't exactly in optimal condition. It's got a huge crack and it's covered with dust and fingerprints and other crap. And ALL 34 OF THEM are rejects too: cracked, chipped, scratched, indelibly marked, that sort of thing. You wouldn't want to put one of these on your lens - and we wouldn't want you to - let alone 34 of them.

This is a test shot taken at f=80mm, without any filters. We'll use this to check what effect the filters have.

And this is a test shot taken at f=400mm, without any filters.

Here's what we got when we used all 34 damaged filters at full zoom of 400mm. Hmm. The contrast and sharpness aren't quite what they were. Still, there's no sign of the cracks and scratches in all the filters.

And this was an attempt to clean up the image. We've massively boosted the contrast, clarity, saturation etc. It's much better than the straight-out-of-the-camera shot, but it's still not brilliant. Still, we think it's surprisingly good bearing in mind what was on the front of the lens!

Here's what we got using all 34 filters with the lens set to its minimum zoom of 80mm. The vignetting is a little extreme, isn't it? That's because the lens is effectively looking down a long tunnel created by the filters. At 400mm, the field of view is narrow enough that the tunnel walls don't affect the picture; but at 80mm they do.

And finally this was an attempt to salvage the best image we could from the second image. Again it's not brilliant, but again all that crap in front of the lens hasn't done as much damage as you might think.

So what have we learned?

Well, probably not much that's of practical value in the real world.

We've learned that scratched, cracks and other crap on your filter don't necessarily show up on your image. Sure, you can degrade the image in terms of contrast and sharpness by attaching a really crappy piece of glass to the front of your lens; but the defects in the glass don't show up directly.

We've also learned how to make photos look just like they're on Instagram, using just a DSLR, a £2000 lens and £1000 worth of filters.

What about if we'd only used one filter?

Some people might be wondering what difference it would make to the image if we only used one good filter, instead of 34 bad ones.  The answer is that in most situations a good filter will have no noticeable effect on your image quality.

In the real world, we can only think of about three situations where using a *good* filter is going to noticeably degrade your image:

1. If you're shooting into the sun, a filter can make the lens flare worse.
2. With some telephoto lenses - especially image stabilized ones, we suspect - a filter can make the bokeh (out of focus background) look more harsh.
3. Filters can cause 'ghosting' if you have lots of bright points of light in the image, as in astrophotography or night-time city photography.

Field testing the new Canon EF 200-400mm f/4 L IS USM Extender 1.4x - Part 2

Part 1 of the weekend's field testing of the Canon EF 200-400mm f/4 L IS USM Extender 1.4x involved a village cricket match.  There are other interesting things happening in fields around Maidenhead during the summer though, so on Sunday it was off to the sheepdog trials at Hambleden, part of the annual Henley Show.

My specific goals were to investigate some aspects of the lens which weren't really issues at the cricket match: the ergonomics of the lens on a monopod; how it handles in situations where you want to zoom frequently and rapidly; and the AF speed on moving targets.

Sheepdog trials photography practicalities

Here is an overview of the course from the spectators' viewing area.  It's HUGE - about 400m long (left to right in the photo) and 250m wide.  Much bigger than the fields used for any ball sports, even polo.  Clearly the action at the far end of the field is going to require a very long lens indeed. 

Camera phone panoramic photo

For those who haven't seen "One Man And His Dog" on TV, here's a quick overview of what happens.  The shepherd stands at his station on the right. The dog runs from there down the far side of the course ("the outrun") and sneaks up behind the sheep on the left, aiming to get them moving ("the lift") with the minimum of fuss. The dog brings the sheep back to the shepherd ("the fetch"), ideally in a straight line, passing through the pair of gates on the way. The dog then rounds the shepherd and takes the sheep out to one side of the course, across the course through two more sets of gates ("the drive"), and back to the shepherd. Then the dog has to temporarily separate two sheep from the flock of five ("the shed") before the dog and shepherd take them to the pen where they are corralled ("the pen").

(Or rather that's what ought to happen.  On TV, where the competitors are amongst the best in the country, it usually does.  In a local event like this, things are much more unpredictable!)

Obviously a lot of the action happens a long way away.  Using Google Maps I estimated that the sheep release point was about 300m from me, and the shepherd's station about 150m.  With those sorts of distances to contend with, even 400mm x 1.4 = 560mm focal length isn't going to be enough reach; if I were doing this seriously I'd probably use the Canon EF 800mm f/5.6 L IS USM.  But during the "drive" phase, the dog and sheep would be coming more or less straight towards me - probably quite quickly and erratically - before turning to go through the first pair of drive gates, so hopefully that would present some interesting opportunities.

Results

As before, all images below are straight out of the camera - no processing, and no cropping.

I have to say that the lens is an absolute joy to use on a monopod.  It's perfectly balanced.  The zoom action is very light and fast.  Holding the lens with my left hand on the zoom ring, so that I could easily change the framing of the picture, was very easy indeed.  For example, frames [7] and [8] below were taken less than two seconds apart.  In that time the dog dashed towards me, stopped, turned, and started moving again; I went from maximum zoom to nearly minimum zoom, re-framed, re-acquired focus, and took the shot.  It was surprisingly easy.

One aspect of the lens which is very easy to overlook is that, when you're using the built-in Extender to increase your zoom range, the lens is no longer a fixed-aperture zoom.  It's effectively a sort of 200-560mm f/4-5.6 zoom.  This means that you have to be wary when using manual exposure.  For example, with constant strong sunlight under clear blue skies, I could just dial in something like 1/2500th at f/4 and leave the camera set like that all day.  That would avoid any metering issues with white-ish sheep and black-and-white dogs.  But as soon as you switch in the Extender, 1/2500th at f/4 becomes 1/2500th at f/5.6 and everything is under-exposed by 1 stop.  Of course there are workarounds: use f/5.6 all day, or tweak the shutter speed or EC whenever you use the Extender switch, or use aperture priority and deal with any vagaries of metering.  I chose the latter approach.  As you'll see from the images below, there's a natural tendency for images of black dogs to be a bit over-exposed, but it's easily dealt with.

The AF didn't struggle to keep up at all.  As with all of Canon's big white lenses, it seems to be essentially instantaneous.  Of course, an air show or motorsport event would tax it a bit more, but I'm confident that it would cope quite easily.  A border collie running flat out is faster than most things you'll see in the sports and wildlife arena, so it's obvious there won't be any problems there.  I sometimes had difficulty maintaining the focus lock on a running dog, but that's because I was using my trusty old 40D rather than a camera with a more capable AF system.  The difficulty was tracking the target as it moved from one AF point to another, and that's the camera' s job, not the lens's.

Overall, I'm very impressed.  I certainly couldn't justify £12,000 on a lens for personal use, but if I were a serious wildlife photographer I would definitely be putting it on my Christmas list and trying to persuade Santa that I'd been a good boy.  Or I'd be hiring it as and when needed from the UK's #1 lens hire business.

[1] f = 290mm, 1/2000th at f/4

[2] f=560mm, 1/1000th at f/5.6

 [3] f = 361mm, 1/800th at f/5.6

 [4] f = 560mm, 1/800th at f/5.6

[5] f = 560mm, 1/1000th at f/5.6

[6] f = 200mm, 1/3200th at f/4

[7] f = 560mm, 1/1250th at f/5.6

[8] f = 297mm, 1/1250th at f/5.6

[9] f = 200mm, 1/3200th at f/4

 [10] f = 250mm, 1/3200th at f/4

[11] f = 400mm, 1/2500th at f/4

[12] f = 560mm, 1/500th at f/5.6

Field testing the new Canon EF 200-400mm f/4 L IS USM Extender 1.4x - Part 1

The new Canon EF 200-400mm f/4 L IS USM Extender 1.4x has generated a huge amount of interest, not least with its 5-figure price tag. Can it really be that good? I thought it would be a good idea to field test it, to find out. Fortunately there are lots of fields around Maidenhead.

First up was some village cricket. I didn't have tickets for the test match, but this was almost as good. Pinkneys Green 1st XI vs Wraysbury 2nd XI in Division 2 of the Morrant Chiltern Cricket League.

And during the tea interval I shot down two bandits as they were lining up their strafing runs on the pavillion.

First impressions of the lens

If you're spending £12,000 on a lens you expect it to be good, and physically at least the Canon 200-400 doesn't disappoint.  It's reassuringly solid.  In an ideal world I think I would have hoped for it to be a bit lighter than the 500mm f/4, whereas it tips the scales slightly heavier; but still, it's good to know that if necessary I could probably beat off a wild animal without damaging it.

All the controls are where you'd expect them to be, if you've ever used a big white lens before, and (of course) they all work perfectly.  The manual focus ring and the zoom are very smooth.  The zoom isn't anywhere near as heavy as I expected it to be, when you think how much glass is being moved around inside.  The tripod mount makes an excellent carry handle, and the supplied padded shoulder strap is very comfortable.

The unique feature of this lens is of course the built-in extender, and the switch for this is a joy to use.  It's perfectly weighted and you can feel the extender softly but silently dropping into place.  I was tempted to switch it in and out more than strictly necessary, just for the fun of it.  But the user manual warns that you need to be careful to ensure the camera and lens aren't doing anything (shutter button half depressed, autofocus, image stabilization, continuous focus, live view, movie mode, etc.) before throwing the switch.  So you need to exercise a modicum of self-restraint, or at least pay attention to what you're doing.

Cricket photography practicalities

At a village cricket match, unlike a test match, you can sit where you like.  But since there aren't grandstands, you can't enjoy an elevated viewpoint and you can't watch from directly behind the bowler.  So choosing where to sit is non-trivial.  Most of the action you'll want to photograph takes place at the wicket at the far end of the ground, where the players are facing you rather than having their backs to you.  I tried to find a position where I had the sun more-or-less behind me, a clean background - this can be very important in village cricket - and some shade under the big trees around the boundary of the ground.  (It was 31°C in the shade on Saturday.)  This turned out to be between deep extra cover and long off, assuming there's a right-handed batsman at the far end.  With the help of Google Maps I've calculated that I was about 70m from the far wicket and 50m from the near one.

At that sort of range, with a big telephoto, you don't get much depth of field.  DOFMaster says that at 400-560mm focal length, f/4-f/5.6, 50-70m range, I should expect the zone of acceptable sharpness to be about 1-2m in front of and behind the subject.  Obviously that means that only one player on the pitch is going to be in sharp focus.

When your subject is the batsman, focussing is easy.  Configure the camera for back-button focussing, acquire focus as the batsman takes guard, job done.  He won't move more than 1-2m whilst he's making the stroke, so he'll still be in focus.

If you want to shoot the bowler, it's not quite so straightforward, though the lens has a nifty feature to help you.  It's the focus preset.  When a new bowler came on to bowl at the far end, I used his first one or two deliveries to focus on him just as he released the ball.  When I was satisfied I had a good focus, I used the focus preset to store this.  Then I could do whatever I liked with the lens, and whenever I wanted to get a shot of the bowler I just nudged the focus preset ring and it was set up to capture him.

Results

I haven't done any processing whatsoever to these photos.  That wasn't the point of the exercise.  They are exactly as they came out of the camera.  But more importantly, I haven't cropped any of them either.  That gives you a good feel what what the action looks like at various focal lengths.

It turned out that 200-560mm was a very suitable focal length range for capturing the action.  Typically, 200-300mm gave a good view of the scene with a few players involved; 400-560mm was great for close-ups of individual players.  I was using a Canon 40D with a 1.6x crop factor, though. With a full-frame camera (e.g. 5D-series), I wouldn't have been able to get good close-ups of individual players without [a] using another 1.4x Extender or [b] cropping my images a bit.

 f = 200mm

f = 280mm

f = 320mm

f = 320mm

f = 370mm

f = 420mm

f = 420mm

f = 490mm

f = 560mm

f = 560mm

What about optical quality?  I hear you ask.  Well, there's really nothing much to report.  You'd expect a lens like this to be excellent, and it is.  I see no trace of distortion or chromatic aberration.  The background blur is very pleasing.  And I have no complaints whatsoever about the sharpness.  The image below is a 100% crop, again with no processing whatsoever (i.e. unsharpened).  It's good enough for me.

The result

The visitors made 134 all out, and it looked like Pinkneys Green were going to chase down the target quite comfortably, but a middle-order collapse turned it into squeaky-bum time. They eventually scraped home with 2 wickets to spare on 135 for 8.

If you've done six impossible things before breakfast...

...you might feel like tackling the paperwork required to release an item which has been impounded by the UK Border Agency.

This is something of an occupational hazard at LensesForHire.  Whenever we send something to a customer in Jersey or Guernsey (which are not part of the UK, and not part of the EU), there's a chance that it will get held up at customs on the way back.  We're pretty good these days at getting equipment into Jersey and Guernsey without problems, and we try to get all the documentation in place so that it can come back in to the UK smoothly, but it's not guaranteed.  UKBA seem to be something of a law unto themselves.

And that's where the fun starts.  To get an incoming consignment released from UKBA, you have to fill in a C88A form which they very helpfully send you.  This is what it looks like:

Terrifying, isn't it?  There are 58 boxes to be completed, some of which have multiple sections.  There's an official notice on the HMRC web site which purports to tell you how to fill the form in, but it only mentions 28 of the boxes, and it refers you to various other official documents which are not conveniently available online.

The first time we had to complete one of these, it was a Kafkaesque nightmare.  It took about 10 hours of online research, 8 telephone calls to the HMRC helpline, and 6 attempts to complete the form before it was accepted.  Now we've kept a copy of the form which was finally accepted, so we use that as a template, and - unless the rules have changed, which they do from time to time - it's all reasonably straightforward.

But still, it's totally impenetrable.  It reminds me of a time back in the 90s when a friend worked for a small software company which got taken over by Microsoft, and he was offered a job in Seattle.  This was before Starbucks had taken over the world, but the coffee shop culture was thriving in Seattle, and he found out very quickly that ordering a coffee in Seattle was completely unlike the UK, where the choice was basically black or white, and how many sugars.  He was amazed that a work colleague could ask for a "double tall 2% wet cappuccino", and the person behind the counter would give him a cup of very nice coffee in return.  So he learned the mantra, even though he didn't really understand what any of the terms meant.

And it's just like that here.  What on earth does this mean?

Or this?

Or this?

I have no idea whatsoever.  It's complete voodoo.  But it works.  I've learned that if I write these things on the form, I will (probably!) receive a lens in the post in a couple of days time, and that's good enough for me.

Right, now I'm just off to prove Goldbach's conjecture.

Alphabetti spaghetti - Part 2, Nikon lenses

Ever wondered what all those different letters and abbreviations in the name of your lens actually mean? Well, here's our easy guide to the lens manufacturers' terminology. Part 1 covered Canon lenses, and in part 2 we look at Nikon lenses.

AF - Denotes that the lens uses Nikon's first-generation autofocus system, invented in 1986. It requires an autofocus motor in the camera, and uses a mechanical coupling between the camera and the lens.
(Not all DSLRs have autofocus motors built into them - it's omitted as a cost-saving measure in the smaller/cheaper DSLRs - so AF lenses will not autofocus on every camera. Cameras which have built-in autofocus motors can be identified by the mechanical coupling at about 7 o'clock on the lens mount.  Cameras without this can still use AF lenses, but in manual focus mode only.)

AF-S - Denotes that the lens uses Nikon's second-generation autofocus system. It uses an autofocus motor built into the lens to offer fast and silent autofocus. Every Nikon DSLR supports AF-S.
(This system was introduced in 1996. That sounds to me pretty much like an admission that, in retrospect, their first-generation autofocus was a bet on the wrong technology.)

D - Indicates that the electronics in the lens tells the camera the distance at which it's focussed, which in some situations allows the camera to make better decisions regarding exposure.
(All AF lenses introduced since about 1992 have been D-type, and are sometimes written AF-D.  All AF-S lenses and all G lenses incorporate the distance functionality, but they don't brag about it.)

DC - Nikon's totally unique, patented, Defocus Control. It's only available on a couple of specialised lenses, and it allows photographers to control the bokeh (the quality of the out of focus areas) in their images. It's a subtle effect - it is not the same as 'soft focus' - but it can be great for portraits.

DX - Denotes that the lens is designed especially for cameras with 'crop' sensors, which are conveniently designated by Nikon as 'DX' cameras.
(The key thing about DX lenses is that they don't project an image circle large enough to fill a 'full frame' sensor. DSLRs with full-frame sensors - see 'FX' below - detect when a DX lens is fitted to them an they can automatically crop the image, but putting a DX lens on an FX cameras is like buying a Porsche for the school run.)

ED - Stands for Extra-low Dispersion, and it refers to a type of glass which Nikon invented back in the 1970s. ED glass provides better correction of chromatic aberrations than "lesser" glass.
(Originally ED glass was only used in Nikon's high-end lenses, particularly telephotos. But over time it's filtered down into even their kit lens - the AF-S DX 18-55mm f/3.5-5.6 G ED II - so these days it's pretty useless as an indicator of quality of the lens.)

F - Nikon's standard SLR/DSLR lens mount, which was introduced in 1959, is known as the F mount.
(Until recently you didn't have to worry about this. All Nikon interchangeable lenses were F mount, so it went without saying - it's not written on the lens, or its box, or the camera, or anywhere. And then they introduced the 1 mount for their mirrorless cameras...)

FX - This is actually a designation for cameras, not lenses. It denotes that a camera has a 'full frame' sensor, the same size as a frame of 35mm film (i.e. 36mm x 24mm).
(You might think that lenses which are designed for FX sensors would be called FX, but you'd be wrong. They're not called anything. The reason is that Nikon lenses from the 70's, 80's and 90's were designed for film cameras, so they work on FX sensors, but that was long before Nikon ever coined the FX/DX terminology. So a lens is DX if it says DX, and it's FX if it doesn't say DX.)

G - G-type lenses don't have rings around them to allow you to control the aperture manually.
(All DSLRs support G-type lenses, but some film SLRs don't.)

IF - Internal Focussing. It means that when the lens is focussed (either automatically or manually), all the moving parts are internal. The lens barrel doesn't extend or rotate.
(IF is handy for two reasons. It means you can use filters such as grads and polarisers easily, because they don't rotate when you focus. And it means the lens isn't shifting huge volumes of air around, so hopefully it will be less prone to dust incursion. Unfortunately Nikon have given up being consistent about whether to metion that a lens is IF, so these days you can't tell without doing some research. For example the AF-S 70-200mm f/2.8 G IF-ED VR is clearly IF, but the AF-S 70-200mm f/2.8 G ED VR II is also IF.)

N - Nano Crystal Coat. This is an anti-reflective coating, applied to some of the optical elements of a lens, which reduces internal reflections, ghost and flare.
(Lenses with Nano coating can be identified by a stylised 'N' within in a gold hexagon on the nameplate of the lens. Its not part of the name of the lens, so you need to do some research if you want to figure out whether or not a particular lens has it.)

PC-E - This denotes a perspective control (a.k.a. tilt-shift) lens. Tilt movements alter the angle of the plane of focus relative to the sensor plane, which makes broad depth-of-field possible even at larger apertures. Shift movements slide the optical axis of the lens along the sensor plane, enabling photographers to correct or alter perspective. All Nikon PC-E lenses are manual-focus only.

SWM - This stands for Silent Wave Motor and it's a description of the technology which is used in AF-S lenses.
(You'll see this written on lenses, and in Nikon's marketing blurb, but - unlike virtually all of the other terms here - it's not part of the name of the lens. It doesn't have to be: SWM is completely synonymous with AF-S.)

VR - Vibration Reduction. This is a technology incorporated into some lenses (mainly telephoto lenses) to cancel out the effects of hand-held camera shake. It allows you to shoot with slower shutter speeds without suffering from image blurring caused by camera shake.
(The first implementations of VR offered up to 2 stops of shutter speed improvement: for example, if you could shoot at 1/500th without suffering from camera shake without VR, then the VR system would let you shoot at 1/125th. Newer systems offer up to 4 or even in some lenses 5 stops of improvement, so you could shoot at 1/15th instead of 1/500th! Unfortunately there's no way to tell just from looking at the lens how good the VR is. You have to do a bit of research.)

VR II - Some people think this denotes Nikon's 2nd-generation (i.e. improved) VR system, but it ain't necessarily so.
(True, some lenses have been updated to receive more effective VR systems, and sometimes that's reflected in their names. For example the only differences between the AF-S 200-400mm f/4 G IF-ED VR and the AF-S 200-400mm f/4 G ED VR II are that the latter has an improved VR system - plus incidentally it has Nano coating and it still has IF. But on the other hand the AF-S 70-200mm f/2.8 G ED VR II is a completely different lens from the AF-S 70-200mm f/2.8 G IF-ED VR, so in that case the 'II' seems to apply to the lens rather than the VR. And finally the new AF-S 70-200mm f/4 G ED VR has probably the best VR system Nikon have ever made, but it's just 'VR' rather than 'VR II' or even 'VR III'. Confusing, isn't it?)

Alphabetti spaghetti - Part 1, Canon lenses

Ever wondered what all those different letters and abbreviations in the name of your lens actually mean?  Well, here's our easy guide to the lens manufacturers' terminology.  Part 1 covers Canon lenses, and part 2 will look at Nikon lenses


EF - Denotes the EF mount system used by all Canon SLRs since 1987.  An EF lens will fit and work perfectly on every Canon DSLR, and on every Canon film SLR manufactured since 1987.  EF lenses can be identified by a red alignment spot on the rear edge of the barrel.

(EF stands for 'Electro Focus'. In the 1960s and 1970s, Canon - like every other SLR manufacturer - had a lens mount which was purely mechanical. Functionality like aperture setting and stopping down was achieved via a series of mechanical linkages between the lens and the camera.  In the early 1980s Canon realised that the future was going to be electronic, and, rather than retro-fit electronic functionality onto their existing lens mount design, they opted for an entirely new design for the EOS range of cameras. It must have been a pretty brave decision, because in one fell swoop they made their entire product line obsolete and they alienated their entire customer base. Fortunately their engineers got the design right in pretty much every respect!)

EF-S - Denotes a variant of the EF mount which is designed for DSLRs with 'crop' sensors.  An EF-S lens will not fit any 1-series or 5-series DSLR, and will not fit a film SLR.  EF-S lenses can be identified by a white alignment square on the rear edge of the barrel.

(The S in EF-S used to stand for Short, as in Short Back Focus, because EF-S lenses generally have their rear elements placed closed to the sensor than EF lenses.  However, at some point Canon realised that it is possible to design lenses for crop sensor DSLRs without requiring a short back focus, so they changed their mind about what the S stands for. It's oficially now S for Small, as in Small Image Circle. That's quite appropriate because the key thing about EF-S lenses is that they don't project an image circle large enough to fill a 'full frame' sensor.)

L - Canon's L series denotes their range of professional lenses. The L probably stands for Luxury, but it's hard to be entirely sure.  L lenses can be identified by a red ring around the barrel, and they incorporate a host of technologies to improve the image quality and ergonomics, typically including:

• fancy glass to minimise optical aberrations
• ring USM for fast, silent focussing
• internal focussing elements, so the lens doesn't extend when focussing
• full-time manual focus available even when in autofocus mode
• non-rotating front elements to facilitate use of filters
• good build quality
• weather sealing 

(Note that no EF-S lenses have the L designation.  Since the L denotes a professional lens, Canon seems to reserve this for lenses which can fit their flagship professional DSLRs.)

IS - Image Stablilisation. This is a technology incorporated into some lenses (mainly telephoto lenses) to cancel out the effects of hand-held camera shake. It allows you to shoot with slower shutter speeds without suffering from image blurring caused by camera shake.

(The first implementations of IS offered up to 2 stops of shutter speed improvement: for example, if you could shoot at 1/500th without suffering from camera shake without IS, then the IS system would let you shoot at 1/125th. Newer systems offer up to 4 or even in some lenses 5 stops of improvement, so you could shoot at 1/15th instead of 1/500th! Unfortunately there's no way to tell just from looking at the lens how good the IS is. You have to do a bit of research.) 

USM - Ultra Sonic Motor. This is a technology incorporated into many Canon lenses to provide very fast and silent autofocus.

(There are actually two flavours of USM. Ring USM is the better variety and is used on Canon's better lenses, including the L-series professional lenses.  Micro USM is a cheaper version which they've developed to further their aim of getting USM into their entire lens range. You can't tell by looking at the lens which type of USM it uses, but both varieties are much, much better than non-USM focussing.)

DO - Diffractive Optics. This is a technology developed by Canon whereby some of the optical elements in a lens incorporate precision diffraction gratings. The end result is to allow telephoto lenses to be shorter and lighter. DO lenses can be identified by a green ring around the barrel.

(It looks like DO might be something of a technological dead-end. Canon only make two DO lenses, the 70-300mm DO and the 400mm f/4 DO. Something about the technology means that DO lenses just don't seem to deliver as much contrast as regular lenses, and this shows up as an apparent loss of sharpness. It's quite easily correctable in post-processing, but it must put some people off. Having said that, Canon are continuing to file patents for more DO lenses, so maybe we'll see more in the future. Time will tell, I guess.)

TS-E - This denotes a tilt-shift lens. Tilt movements alter the angle of the plane of focus relative to the sensor plane, which makes broad depth-of-field possible even at larger apertures. Shift movements slide the optical axis of the lens along the sensor plane, enabling photographers to correct or alter perspective. Some Canon TS-E lenses are L lenses but they are all manual-focus only.

MP-E - Denotes a lens dedicated to macro photography. Most macro lenses can be used for non-macro subjects (e.g. portraits), so they don't carry this designation. There is only one MP-E lens, and it can't be used for anything other than macro photography. And it's bonkers.

I think I deserve a discount because.....

An occupational hazard of running a business like LensesForHire is that people are always asking us for discounts. Maybe I'm just a bit naive, but I've never really understood why that is. I mean, you don't ask Tesco whether they'll do you a discount, do you?  (Or maybe you do.  But I bet they've never said yes.)

Anyway, I thought it would be fun to compile a list of all the reasons people have put forward as to why they think they deserve a discount. I'll try to keep this updated as and when new ones crop up!

So - I think I deserve a discount because ...

• ... because I'm a first-time customer.
• ... because I'm a repeat customer.

(Well, that's 100% of the population covered already, before we go any further!)

• ... because I'm a student.
• ... because I'm a pensioner.
• ... because I'm unemployed. 
• ... because I plan to hire tons of stuff from you in future, honest.
• ... because I'm a professional photographer.
• ... because I'm a member of the armed forces.
• ... because I'll put a link to LensesForHire on my web site.
• ... because I'm a member of a camera club.
• ... because I'm doing a charity event.
• ... because I'm doing a product review.
• ... because I can't afford the full price.
• ... because I'll recommend you to all my friends.

Have I missed any?

For what it's worth, I think that offering discounts to one segment of the population just means that they're being subsidised by the rest of the population.  To my mind, it's fairer all round if we just try to keep our prices as low as we reasonably can for everyone.  So that's what we try to do.