Thursday, September 13, 2012

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.

Friday, June 22, 2012

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.

Monday, April 23, 2012

Which fisheye lens?

One of the most common questions we get from customers relates to the differences between all these different types of fisheye lenses.  We actually stock four different types of fisheye.  For Canon users they are:
  • Canon 15mm f/2.8 fisheye 
  • Sigma 10mm f/2.8 fisheye
  • Sigma 8mm f/3.5 circular fisheye
  • Sigma 4.5mm f/2.8 circular fisheye
and there's a similar range for Nikon users.

So what do they all do?

Well, the first thing to understand is that ALL fisheyes produce an image which is completely circular, and 180 degrees across - a complete hemisphere.  Like this:

Underscar, Lake District, March 2012 © Stewart Robertson 

The ONLY difference between the different fisheyes is the size of that circular image.  The longer the focal length of the fisheye lens, the larger the image.  Here's an illustration of the images produced by the four fisheyes  listed above, to scale - 15mm on the left, 4.5mm on the right:

But when we look at how big the sensor in the camera is, compared to these circles, then that's where things start to get really interesting.  In the images below, which are still to scale:
  • the red rectangle is the size of a full-frame sensor (1Ds series, 5D series - FX for Nikon users);
  • the green rectangle is the size of an APS-C crop sensor (7D, xxD / xxxD / xxxxD series - DX for Nikon users).

We can see that:
  • The 15mm fisheye is designed for full-frame sensors.  It fills the frame with an image which measures 180° across the diagonal, which is why this type of lens is sometimes called a rectangular fisheye or a diagonal fisheye.
  • The 10mm fisheye is a diagonal fisheye designed for crop sensors.
  • The 8mm fisheye is designed for full-frame sensors.  It creates a completely circular images which just fits into the frame, which is why this type of lens is sometimes called a circular fisheye.
  • The 4.5mm fisheye is a circular fisheye designed for crop sensors.
(Incidentally this shows why Canon introduced their 8-15mm zoom fisheye in 2011.  Clearly it's designed for full-frame sensors.  But it's not immediately obvious why you would want to use any focal lengths between 8mm and 15mm!)

In most cases you can mount a lens on a camera for which it's not designed.  For example you can mount a 15mm fisheye on a crop-sensor camera, or you can mount a 10mm fisheye on a full-frame camera.  But there's really not much point, because the effects you can achieve don't work particularly well if the size of the image circle isn't matched to the sensor.

Here's what you get using each of the different fisheyes on a full-frame camera.

And here's what you get using each of the different fisheyes on a crop-sensor camera.

Hope that all makes sense.  If anybody out there has any questions, do please drop us a line!

Monday, March 05, 2012

How big a lens do I need?

At LensesForHire we often get people asking for advice regarding what kind of focal length they will need.  This crops up with all sorts of applications - for example wildlife (e.g. on safari), birds, sport, motorsport, and theatre.

There are two straightforward ways to look at this, depending on whether you prefer a theoretical approach or a practical one.

The theoretical approach

If you can estimate how big your subject will be, and how far away it will be, then there's a relatively simple formula which can be used, and it gives quite good results in a lot of common situations.

The basic equation is:

Here are a couple of examples.  In each case let's assume I'm using my Canon 40D, which has an APS-C sensor measuring 22.2 x 14.8mm.

Let's suppose I want to photograph a giraffe, like this:


The big giraffe is about 4m tall, say, and I'd expect to be able to get within about 25m of it.  The sensor dimension which matters here is the 22.2mm because I'm shooting the giraffe in portrait orientation - the height of the giraffe aligns with the long dimension of the sensor.

So the focal length I need is ..... 22.2 x ( 25 / 4 ) x 0.75 = 104mm.

Or suppose I want to photograph the moon, like this:

The moon is 3,474km in diameter and its average distance from us is about 380,000km. This time the sensor dimension which matters is 14.8mm because I want to fit the diameter of the moon into the short dimension of the sensor.

So the focal length I need is ..... 14.8 x ( 380,000 / 3,474 ) x 0.75 = 1,214mm.

The formula is a pretty good approximation if you're shooting distant objects with a telephoto lens.  But don't try using it for close-ups or wide angles, because the approximation isn't reliable in those domains.

(By the way, the experts amongst you will have spotted that the factor of 0.75 in the equation is an arbitrary one to help give you a decent composition - you don't want your giraffe / moon to completely fill the frame, and this factor is there to give your subject bit of room to breathe in the frame.)

We find that even a "relatively simple formula" can faze some people.  And not everybody knows what size their sensor is.  So instead of doing all this maths, why not just take some pictures?

The other day we had an enquiry from a client who needed to shoot some people at an awards ceremony.  She'd be a little way from the stage - probably about 10 metres, give or take - but she wasn't quite sure how far.  And she wanted to know what sort of range of composition she would have available to her with a 70-200mm or 70-300mm lens.

Fortunately the LensesForHire office is quite long, and our colleague Richie would rather stand around mugging for the camera than doing real work, so I did some experiments.  I put a 70-300mm L lens on an APS-C Canon (a 350D as it turned out), I shot using all the focal lengths which are marked on the lens (70, 100, 135, 200 and 300mm), and I shot from ranges of approximately 15m, 10m and 5m.

Here are the results.  If you're going to be in a situation where you have to photograph people, you might what to take this along as a handy cut-out-and-keep guide illustrating what effects you'll get with different lenses.

Wednesday, February 08, 2012

Photography at the London 2012 Olympics, part 2

In my recent post "Photography at the London 2012 Olympics" I mentioned that spectators will be able to take photographic equipment into the Olympics venues as long as it fits into a bag measuring 30 x 20 x 20cm.  LOCOG have confirmed to me that the reasoning behind this is that a bag of that size will fit under your seat.

However, 30 x 20 x 20cm is one of the standard size boxes we use at LensesForHire for packing lenses.  So we've done some experiments to see how much gear we could fit into one of these boxes.

Our first thought was that a 300mm f/2.8 should fit.  The Canon one is officially 252mm long, and a bit longer with lens caps and lens hood, but we expected it would fit and we hoped there would be a bit of space to spare.  And we were pleasantly surprised.

Here we have:
(back row, left to right))
Canon EF 300mm f/2.8 L IS USM
Canon EF 24-105mm f/4 L IS USM
Canon EF 16-35mm f/2.8 L II USM

(front row, left to right))
Canon EF Extender 2x II
Canon EF Extender 1.4x II
Canon EOS 5D

and it all fits into the box quite comfortably.  In the following picture, the 300mm f/2.8 is at the bottom of the box (you can see its black leatherette lens cap, which we removed for the first photo), and the 16-35mm f/2.8 is standing upright in the back right corner under the Extender.

Now you might think that the 300mm f/2.8 is taking the mickey, just a bit.  It complies with the letter of the regulations, but arguably not with the spirit of the regulations.  (Andy Hooper told us that the regulations were intended to allow telephoto lenses up to roughly a 300mm f/4.)  And furthermore the London 2012 ticketing conditions  prohibit any behaviour which disrupts another spectator's comfort or enjoyment of the sport, and it might be argued that sitting next to someone waving a 300mm f/2.8 around would be a bit disruptive.  So we had another go to see what else we could pack into the same 30 x 20 x 20cm box.

Here we have:
(back row, left to right))
Canon EF 70-200mm f/2.8 L IS II USM
Canon EF 24-105mm f/4 L IS USM
Canon EF 100-400mm f/4.5-5.6 L IS USM

(middle row, left to right))
Canon EF 50mm f/1.2 L USM
Canon EF Extender 1.4x II
Canon EF Extender 2x II
Sigma 10mm f/2.8 EX DC HSM fisheye

(front row, left to right))
Canon EOS 40D
Canon EOS 5D

And again it all fits into the box very comfortably.  In the following picture, the 100-400mm and the 70-200mm f/2.8 are lying down in the bottom of the box at the right hand end, and the second camera body is standing upright at the right-hand end of the box, underneath the fisheye.

We could have got more into the box if we'd really tried to optimise it, but we thought two cameras, five lenses and two Extenders ought to be enough for most people!

So how much equipment will you be taking?

Wednesday, February 01, 2012

Photography at the London 2012 Olympics

Well here we are in February already, which means there are less than 6 months to go before the start of the London 2012 Olympics.  That's a significant milestone because at LensesForHire we accept bookings up to 6 months in advance, if you're hiring for a week or longer.

So the big question is, what kind of camera equipment will you be allowed to take into an Olympics venue?

It's been a bit confusing.  LOCOG's official ticketing conditions have about 7,000 words of dense legalese setting out what you must and may not do, and if you wade through them you'll find that the prohibited items include "large photographic equipment (including tripods)" (Clause 19.2.3) and the prohibited behaviours include "flash photography" (Clause 19.3.2).  But it doesn't define "large".

Back in March/April 2011 Amateur Photographer generated some controversy when it reported that even some compact cameras might be banned.   That prompted LOCOG to rush out a policy statement saying that DSLRs and high-zoom compact cameras would be allowed.

But there's still been no official definition of "large" photographic equipment.  Until now.

Last night I went to see Andy Hooper, chief sports photographer at the Daily Mail, talk at an event organised by Maidenhead Camera Club and the Sport In Focus 2012 project.  His talk was called "Capture The Moment".  That's also the title of his book, which is a practical guide to sports photography at the London Olympics.

Buried away on page 278 of the book, it says:
You are allowed to take camera phones, compact cameras and DSLRs into Olympic and Paralympic venues as long as the equipment fits into a bag no bigger than 30 x 20 x 20cm. .... Tripods and flash photography are not permitted within the venues.
Wow. 30 x 20 x 20cm? That's surprisingly big.

I made a point of asking Mr Hooper whether this really was official LOCOG policy.  His answer was that yes, these dimensions came from LOCOG. The book is an official London 2012 publication and these are the official guidelines.  The intention is to allow DSLRs with lenses up to about a 300mm f/4.  (Having said that, he also opined that LOCOG perhaps hadn't thought through the exact specification very thoroughly.)

So there you have it: you're OK as long as your equipment fits into a bag which is 30 x 20 x 20cm.  (Incidentally you don't have to have a bag which is that size; the requirement is just that your equipment would fit into such a bag, if you had one.)

Coincidentally, 30 x 20 x 20cm is one of the standard box sizes we use at LensesForHire.  We're going to have some fun over the next couple of days working out how much we can pack into one.

Personally, if I were planning to take a telephoto lens into an Olympic venue, I'd make sure I had a copy of Andy Hooper's book with me, open to page 278.  It's actually a very good book for anyone who's interested in photographing sports, and it's available for £14.99 from the LOCOG shop or somewhat cheaper from Amazon.

Monday, January 30, 2012

Welcome to the LensesForHire blog

Hi everybody.  For those who don't know me, I'm Stewart Robertson.  I'm the owner of Lenses For Hire Ltd. and I'll be using this blog to babble on about stuff that might be of interest to our customers and photographers more generally.

This is me in the office.

The artwork on the wall is a canvas by Paul Goldstein, who leads photographic trips for Exodus.  Paul is passionate about tiger conservation and we've helped raise a lot of money for his conservation projects.  We'll be doing more of that in the future too, so don't be surprised to see the odd hint that you can donate to his campaign!

So why is the picture of a polar bear instead of a tiger?  Well, that's a long story, but if you're interested I'll get round to it some day.