Embracing Chaos

DSLR cameras make very little sense today.  Modern imaging technology is rapidly turning them into dinosaurs.  The forces keeping them alive are a combination of a physical legacy in hunks of glass, and aspirational marketing.  I’ll explain, but first, what’s a DSLR and why don’t they make sense?

Background on SLRs and DSLRs

(If you what “f-stop” means, feel free to skip ahead to the next section.)

SLR stands for Single Lens Reflex.  Practically speaking it refers to a camera where you can change the lens.  You look through the same lens that actually takes the picture, letting you put any lens from an ultra-wide angle fisheye to a telescope-length zoom lens.  You can also put filters on the front like star filters or color shifters or polarizers.  Imagine a classic 35mm camera — like what a P.I. would carry to snap pictures of your wife having an affair — that’s an SLR.

SLR’s require a mirror that physically moves to divert the light into one of two places — your eye, or the film / CCD. The mirror was important when the only technology for capturing images was chemical film.  But nowadays we have various electronic devices like CCDs that digitize an image.  DSLR cameras use a CCD to get many of the benefits of digital imaging, but still have the same physical form factor as an old chemical-film SLR.  They can use the old lenses, which is one of their big appeals.  But so many things about these cameras just don’t make sense.

The problems with DSLR cameras

First there’s the noise. The sound of the mirror slapping against its stops as it switches positions is very recognizable. We used to accept sounds like that as a necessary part of taking
pictures.  Today it just annoys me.  Especially when I’m at a small
event and some photographer is there making loud clicking noises all
the time while I’m trying to enjoy whatever it is they’re digitizing
with their dinocam.  In 99% of all use cases, it’s totally unnecessary.  CCDs can continuously capture images and display them on a screen, creating a digital light path that doesn’t require loud expensive mechanical assemblies.  These displays aren’t as good as what a human eye can pick out, so this doesn’t work all the time.  But if you don’t need interchangeable lenses, then the camera can have a second optical path just for the eye, which doesn’t need to be as good.

One argument against a separate optical viewfinder is that youc can’t put filters in front of the lens.  This is very true, but filters are also obsolete.  With few exceptions, everything that a physical filter does can be done later in photoshop with more control and accuracy.  Color tinting, sparkle, gradients, soft, mist, etc — these all used to be rendered in physical glass out of necessity.  Polarizing filters are probably the most important exception to this — since CCD’s don’t record a light’s polarization state, it can’t be adjusted later.  But for the most part, filters aren’t necessary anymore, meaning you don’t need the whole single-lens thing.

But what about interchangeable lenses?  Isn’t it useful to have the same camera body and be able to change lenses?  (I hear you cry.)  Yes, sorta.  There are definitely situations where one lens won’t be able to do everything you want.  But those situations are getting rarer and rarer.  And in the few exception cases, I’ll argue that interchangeable lenses aren’t the right solution.  The reason these cases are getting less and less common is that zoom lenses are getting better.  When SLR cameras first came on the scene zoom lenses basically didn’t exist because they sucked when they did.  You needed a different lens for each amount of magnification you wanted, so people had lots of lenses.  But with computers to help us design the lenses, and vastly improved manufacturing processes, zoom lenses are getting better all the time.  Nowadays a lens with a huge 10x zoom can even win accolades from camera snobs.  And lenses as versatile as 26x cover every situation most of us would ever want, and at a quality we’ll be thrilled with.  So for almost all situations, a single zoom lens is good enough today.

What about the situations where that’s not quite good enough?  Where you need that 14mm fisheye that captures people standing immediately to the left or right side of the lens?  Or that 8000mm super- long telephoto telescope?  It turns out in either of these challenging cases, getting the lens to fit the standard SLR form factor becomes the hardest part.

Why SLR’s cripple even the extreme lens cases

With ultra-wide fisheye lenses, the problem is the space reserved for that stupid mirror.  In this case, the focal length is very short, so as a
lens designer, you’d naturally want the focal plane to be very close to
the glass.  (Like about 14mm.)  But the place where the lens attaches to the camera body necessarily needs to be a certain distance away from the imaging plane.  That distance was determined by the size of the mirror, which was determined by the size of your chemical film — 35mm, which is more than you’d really want for a 14mm lens.  Even on today’s 2009 DSLR cameras, that distance is exactly the same as it was a generation ago in order to ensure backwards compatibility with old lenses.  The literal tons of carefully polished glass represent a very real barrier to improvement since people have invested lots of money in them.

So if you really want a camera that’s good at taking super-wide angle pictures, you don’t want your lens to have to be that far away from the imaging plane.  You’re better off with a specially built camera.  The lens will be simpler, cheaper and higher quality.  But super-wide starts to look funny, no matter what.  Funny meaning
distorted, because if your eye is more than a couple of inches away
from the reproduced super-wide image, then it won’t look right.  And it’s not super useful to capture 360 degrees in one shot — you can shoot a dozen pictures and stitch them together later in software, and it’ll look more natural.  This is all why people don’t pay a lot of attention to how super-wide lenses get anymore.

On the super-telephoto side of things, the SLR legacy is even worse.  To get a super-long telephoto lens you need lots of big glass.  This gets expensive quickly simply because it’s a large mass of carefully manufactured stuff.  The amount of glass you need for a lens is proportional to the cube of the length of your imaging plane, which for legacy chemical-film is 35mm. But CCD’s just don’t need to be that big.  On almost every DSLR they’re only about 20mm across, and on high-quality non-SLR cameras are as typically about 6mm across.  So that size legacy means you would need literally 200x  the almost 40x the amount of physical glass to make a good telephoto lens for an SLR vs a non-SLR camera.  This ridiculous discrepency is just going to get worse.

CCD’s are silicon devices, so they share manufacturing improves along with CPU’s and follows a Moore’s law-like improvement curve for performance.  A key way they improve is in pixel density, but also by simply getting smaller.  As they get smaller, high-quality zoom lenses get smaller and cheaper too.  But only if the lenses are specifically designed for the new smaller CCD’s.  With an SLR system they can’t be — the size must be fixed in order to maintain backwards compatibility.  So while sensor technology improves at Moore’s law speed, lenses for non-SLR cameras improve as well, but SLR lenses do not.  Expensive zoom lenses for modern cameras just don’t need to be that big or expensive — It’s like having to build a cell-phone big enough to hold floppy disks.

To illustrate this point, consider the popular Canon SX10IS camera which does not feature interchangeable lenses.  It features a zoom lens that goes from pretty wide (28mm equivalent) to really very far zoom (560mm equivalent).  Because its CCD is only 6mm across, it can do all this for under $400 and weigh in under a pound for the whole camera.  For comparison, a comparable SLR lens weighs in at over 11lbs and costs upwards of $7,000, just for the lens.  No doubt this lens can take better pictures than the tiny Canon, but a smaller lens built for a modern CCD could take pictures that are every bit as good for a fraction the price.

I would be remiss if I didn’t mention the noise floor on these sensors.  When the scene is dark, you need more light to get a good image.  A bigger hunk of glass captures more light.  This all makes intuitive sense and is mostly accurate.  CCD sensors can take more accurate pictures in low light when they are bigger.  But the limits here are electronic noise, which is also improving.  At some point we’ll hit some other barrier like the thermal noise in the sensor, although a piezo cooler could work around that.  Ultimately there’s the the quantization of photons, but if you’re taking pictures in a scene that dark, you probably can’t see what you’re pointing at anyway.  My point is that while there are advantages in low light for larger glass and sensors, technology is erroding away at those too.  We’re seeing ISO equivalents of 6400 as fairly common in cameras these days, with an economic competitive pressure to improve that.

In summary, the problems with the SLR format are that it ties its owner to a physical legacy that denies them the advantages of advancing technology.  There are cases where specialized lenses are still important.  But those cases are dwindling.  Personally, I’m going to be happier carrying around a full featured small camera that can transform itself into whatever I want without needing interchangable parts than a bag full of bits that were standardized before email.

This entry was posted on Sunday, March 1st, 2009 at 12:01 PM and is filed under Analysis, Gadgets, Geek, Travel. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.