The DSLR: A proof that photographers are clueless
As a hobbyist photographer owning a DSLR camera, I’ve been asking myself every now and then why there is a moving mirror inside my camera. You know, the one that gives the camera its name (SLR stands for Single-Lens Reflex camera). I mean, I understand why they put the mirror in film cameras, but not why it’s still there in digital cameras.
After all, the whole point of SLR was to present the frame precisely as it will be captured on film through the real lens, as opposed to having a separate viewfinder. This way, the photographer can adjust the focus and sees the image change for real, and also how zoom affects the frame. In short, the mirror’s job was to send the actual image up to the viewfinder.
And then came the digital sensor. All of the sudden, every cheap point-and-shoot camera shows the wannabe-photographer the image exactly as it’s going to be captured on an LCD screen.
So here comes the question: Why is this old-fashioned mirror still there in professional cameras? Why aren’t camera manufacturers putting a small but high-end LCD screen inside the viewfinder, as they do with these semi-DSLR cameras (except for a small niche of cameras)? The use and feel would be exactly the same, only you’re watching a rendered image instead of a direct optical link.
It’s not like somebody does the focus manually, and needs to see “a sharp image” in the viewfinder (except for a few who install those split prisms). Let’s face it, focusing manually based upon the sharpness in the viewfinder alone is a recipe for a blurry result.
Let’s see how an LCD-viewfinder on high-end cameras change things:
- Reliability and durability: It’s well-known that mechanical parts, and moving mechanical parts in particular, are the weakest link in any electronic device. With the mirror removed, it’s possible to design a significantly more reliable camera with no moving parts in the camera body.
- Dust on sensor: The mirror moves and creates dust which accumulates on the sensor’s surface. Without the mirror, it would be possible to install a protective glass window so that the sensor would reside in an isolated environment.
- Focus: Today’s DSLR cameras have these special focus points, which are essentially small image sensors feeding an image processor, which in turn determines how sharp the image is. In an LCD-viewfinder arrangement, the real sensor would be exposed all the time, so there wouldn’t be any need for special focus sensors, and focusing could be done on any spot (as opposed to a limited number of points).
- Price: An LCD screen is cheaper than the optics, motor, mirror and focus sensors necessary to maintain the SLR arrangement.
- The critical moment: With an LCD viewfinder you don’t loose touch at the moment of shooting. On the contrary, the camera may even show you a quick snapshot of the captured image, which is very helpful when using external flashes (did all of them fire?) or when the subject is moving quickly.
- Night photography: When shooting at night (long exposure or with flash), it’s pretty common that one sees nothing in the viewfinder. With an LCD viewfinder this doesn’t happen, as we know from cheaper cameras: The camera responds to the low light with a longer exposure time and/or amplification, resulting in a low-quality image in the viewfinder, but good enough to work with.
- Vibration during shooting: In some cases, the small vibrations caused by the mirror’s motion may have an adverse effect on the image’s quality.
- Overhead photography: Sometimes there’s no choice but to shoot with the camera away from you. Journalists raising their camera over a crowd, for example. The irony is that some semi-DSLR cameras have an adjustable LCD screen, so you can point the screen towards yourself allowing precise aiming and focusing even when the camera is above your head. DSLR cameras, on the other hand, may sometimes support a live view on the LCD screen, but it’s clearly not intended for serious shooting. And an adjustable LCD screen is not something one could think about, even though journalists would surely find it useful.
So all in all, there are several substantial advantages to removing this mirror and putting an LCD screen in the viewfinder instead. Apparently, there is no disadvantage in doing this. So why isn’t this the mainstream trend?
I suppose the answer lies in this post’s title. Camera manufacturers know their market. “SLR” stands for quality and professionalism, regardless of being an obsolete technology. It’s mixed with high-end optics, the ability to control the shooting parameters and switching lenses. And the fact that it makes the camera more expensive and harder to reach for amateurs is not necessarily a disadvantage.
Reader Comments
This is certainly a well written argument. I never really thought about this before – and obviously, nobody else has too, or this prototype would be out on the market. It only makes sense actually. I have been doing something like this without even thinking about it and it’s really nice ! I bought a BigEye from LightCraft – and use it on the back of the camera’s LCD screen as a viewfinder. It’s easy to set exposure (even in manual mode) and really easy to focus because of the magnification of the detachable finder. You can even zoom in for x10 for a fine focus and then zoom back. Obviously, in the live mode, you cannot do high speed action photography, but it is great for most still subjects. Nice angle and great story !
The reasons why the SLR is still the standard for quality photography are the same as they have always been. When you look through the viewfinder you are seeing the scene exactly as it will appear to the camera in all the glory with which the human eye is capable of rendering it. Since you’ve broken your argument into several points, I’ll respond point-by-point.
It is well known that electronic parts are more reliable than mechanical parts.
—
This one is just pure hogwash. I have an old film SLR which is 100% mechanical, it was built in the 1970s and works as well now as it did the day it was made. Every 100% electronic camera I’ve ever had, has had a lifetime of 5 years max, then they break… invariably the electronic components are the parts that break.
Without the need for a mirror the sensor could be encased in protective glass
—
The more glass you put in front of the sensor the less light gets through to the sensor and the more the possibility of focal aberrations. The best solution is to leave the sensor uncovered and just clean it when it gets dirty.
You wouldn’t need special focus points
—
You may have a point on this one, but this is what one would expect. Compact cameras are simpler and don’t need as many parts and are therefore cheaper, but they don’t give as good quality all-round.
Price of LCD screens
—
Again, correct but LCD screens give a much poorer quality image than the human eye (with the assistance of all those motors and optics) so you’re only getting what you pay for.
The critical moment
—
I don’t quite get what you mean by ‘lose touch’, unless you’re referring to the fact that in an SLR, when the mirror’s up you can’t see through the view-finder, but why would you want to? If you’re having to adjust lighting mid-exposure then you’ve already got the lighting wrong and will have to try again. Perhaps you think that SLRs with a sensor that is always powered up and ready to record as soon as the shutter is pressed are somehow slower than compact camera sensors, but if this is the case you’re even more wrong.
Night photography
—
You have a point with this one too, but would you want to sacrifice all the advantages of using an SLR just so it is easier to compose night-time shots? You could just let your eyes adjust to the dark so you can see through the viewfinder well enough to compose the shot, or you could use a torch.
Vibration during shooting
—
You can use mirror-lock to prevent this. The mirror flips up a couple of seconds before the photo is taken.
Holding the photo above your head
—
If you have to hold the camera above your head to shoot then you’re gonna struggle to product perfect results, even with an LCD screen pointing downwards it is difficult to compose the image and the image is going to be a bit shakier. It’s also probably a bit of a crush if you’ve got a crowd around you, so this is where a compact camera would be better anyway. Doesn’t mean you should forgo the SLR because occasionally you will need to do this.
The biggest reason why you wouldn’t want to replace the image you see through the SLR’s viewfinder with one on an LCD screen on the back is quality. You simply cannot produce consistently excellent results with only an LCD screen to look at, you have to see it with your own eyes. You may not often need to manually focus any more but you need to use your eyes to determine that you are focussing on the exact point you need to. Your eyes also have a much higher dynamic range than any LCD screen allowing you to see the full range of the image. Most importantly your eyes see everything almost instantaneously, if you were trying to photograph a moving object and looking at an LCD screen you’d have difficulty with the significant lag between what is on the screen and what is actually in front of the camera.
Eli,
I may not be an electrical engineer, but I do know that when my gadgets fail (in 3-5 years of ordinary use), it is usually the electronics that go first and the mechanics keep chugging along.
When and if you design electronics do you design for them to last 10+ years? I doubt it due to the fact of the rapid pace of development.
As the previous poster stated, there is not a mechanism better or faster than the human eye. The eye sees the full dynamic range of colors, light, shade and depth. The eye can make instanst adjustments whereas electronics will have a lag.
I do take issue of your inaccurate statement that the movement of the mirror “makes” dust. The mirror does not make dust, the movement of the mirror “moves” the dust that is already there. As long as photographers continue to expose the interiors of the camera by changing lenses, there will always be dust to contend with.
I don’t intend to turn this into a discussion board, but I’ll address the claims repeated:
First and foremost, I don’t argue with the superiority of the human eye. But if the photographer wants to know what the image is going to look like, an LCD image of what the camera is about to capture is more reliable than the direct view. In other words, the optical reality is not relevant, but the way the camera is about to distort it. As for lagging of the LCD image — that doesn’t exist where engineers have bothered to eliminate it (e.g. endoscopy cameras and LCD screens).
For example, if the wrong white balance has been picked, the LCD image will show the mistake as it’s about to be made.
As for the reliability of electronics vs. mechanics; I can’t argue with your personal experiences, but the common knowledge is that electronics has a by far better reliability than its mechanical counterparts. That’s one of the reasons carburetors were exchanged for fuel injectors in cars, and pneumatics replaced by fly-by-wire on airplanes. It’s also commonly known that when electronics fails, it’s almost always some mechanical issue: A jammed fan, bad contacts etc.
If equipment has become short-lived lately, it’s more a question of their intended lifespan and how they’re manufactured.
Having said that, the electronics vs. mechanics argument is irrelevant anyhow, because my original claim was that eliminating a moving part will make the camera more reliable.
As for the mirror producing dust, I took that from the camera’s user manual, but who knows, maybe it’s wrong. Either way, if the sensor would be behind a glass (how many glasses are there in a lens, so we’ll worry about putting another one?) the internal camera cavity could be cleaned safely and easily from any dust entered during lens switches. You can’t clean the sensor directly.
I hope this clarified my view.
Eli, some things that may interest you.
DSLR cameras are still quite profitable, but the manufacturers of MILCs are starting to eat into Canon and Nikon’s market share for the intermediate range: http://www.bloomberg.com/news/2011-09-07/canon-clinging-to-mirrors-means-opportunity-for-sony-cameras.html
Recently, Nikon has been rumored to launch a mirrorless camera: http://www.the-digital-picture.com/News/News-Post.aspx?News=1204&Title=Nikon-Mirrorless-Interchangeable-Lens-Digital-Cameras-Coming
It’s a good bet MILC will become more common, I think it’s inevitable that Canon, Nikon, and other manufacturers will develop mirrorless cameras. I believe, primarily, they will become popular with the range of beginner / intermediate cameras that are a step above typical point-and-shoots, and with those wanting a powerful camera that can specialize in videography since things like articulated screens and electronic viewfinders would be desirable for that application.
However, I believe serious hobbyists and professionals will continue to use and purchase traditional DSLRs over new mirrorless counterparts. There’s no guarantee that new models of MILCs will use the same typical full-frame and APS-C sized sensors, which will be important to anyone conscious of image quality, especially in low-light photography. There’s also the question of whether a new series of cameras would be compatible with the current generation of lens mounts, and those photographers already invested in high quality lenses will summarily balk at throwing out their functional high-quality glass simply for a new mirrorless mount. And even if both those conditions were met, those shooting sports and any sort of fast moving action would still likely opt for a DSLR. DSLRs use phased-based autofocus which is faster and more accurate than the contrast-based AF utilized by point-and-shoot / mirrorless cameras.
D-SLR’s have no less useful as SLR’s. If they weren’t useful then we wouldn’t be using them.
Pros:
- Your vision is significantly better than a camera’s live view. It’s instant. You’re seeing the scene as efficiently as possible.
- The mirror allows for the use of phase detect auto focus and other technologies which make focusing almost instantaneous.
- The optical viewfinder keeps the sensor switched off when you’re waiting to take a shot (framing or just carrying the camera), which both keeps it cool (temperature can effect it’s noise performance), and also keeps it from draining the battery all day.
- Mechanical shutters are very durable. As stated, many SLR cameras that are more than 30 years old are still functioning exceptionally.
- Live View is a relatively slow way of using a D-SLR. Contrast based auto focus is many times slower than phase detect auto focus.
These statements are based upon today’s paradigms in designing cameras, which is aimed towards the products we all know. So of course there’s a slow response on live view and maybe the sensor gets warm when running live. And since professional photographers use the viewfinder when shooting, there’s no point in investing efforts on making the sensor-based focus quick nor energy efficient. This can all change, once the paradigm changes.
While phase detection autofocus is superior in the sense that it tells the camera which way to turn the focus, it also does stupid things, as it depends on a very narrow region, and can accidentally focus on something very small and irrelevant. With a sensor-based focus, the autofocus can do what we really expect it to do: Make a certain visible region as sharp as possible.
Leave it to the engineers to design sensors, LCDs and signal processors that will do the job well. The thing is that there’s no demand for that today.
Not really sure your right in all modern DSLR I reckon some have no mirror they are just keeping the name because it defines the category.
As an electrical guy, you say stupid things like:
“It’s well-known that mechanical parts, and moving mechanical parts in particular, are the weakest link in any electronic device.”
If you take an old analog SLR, you will have troubles with broken electrical parts, obsolete ICs, etc.
If you take a very old analog SLR, you will have no
problem with a fully mechanical shetter, telemeter, etc.
In automotive, this is the same: for decades,
guys like you are hyping about “steer by wire” gadgets
but the steering systems are still mechanical,
for safety.
There is a lot of nostalgia around old cameras. Anyhow, my experience with fixing electrical parts is that its their mechanics that failed (contacts and electromechanical parts) rather than the silicon. But this seems to be a matter of faith.
As for automotive, Volkswagen introduced the electrical power steering wheel in its latest models, which shows what a safety-oriented company thinks about electronics. After all, if the electronics goes crazy, the steering wheel can take all the way to the left or right in the middle of a highway. And still.
All motors for the last decade are based upon electronic control rather than the carburetor, which improved their reliability by far. And modern airplanes are completely controlled by computers and electronics.