Mirror-less on the Wall

Magic mirrors that could show the future may exist only in fairy tales, but if they existed today, a question all DSLR users and serious photographers would like to ask is:

“Mirror, mirror on the wall, what is the future of the DSLR?”

The SLR camera which was the workhorse of many serious photographers and which ruled supreme for about half a century seems to be getting some competition from a new technology that does not use a mirror. We will see in this article how this new technology is different from DSLRs, what are its pros and cons compared to DSLRs, the present market scenario, future trends and some points that you should keep in mind if you want to invest your hard earned money in this technology.

The first step in acquiring knowledge is to use the right nomenclature. Unfortunately, the “mirror-less” cameras are being called by a number of names. Here is a list –

Interchangeable Lens Cameras (ILC)

Interchangeable Lens Compact Cameras (ILCC)

Compact System Camera (CSC)

Mirror-less Interchangeable Lens Cameras

Electronic Viewfinder Interchangeable Lens (EVIL) Camera

Digital Single Mirror-less (DSLM – used by Panasonic)

And so on! While all are correct, we will be using the name CSC as this is most popular.

First let us see how a CSC operates (Picture 1). Compared to the complexity of a DSLR, a CSC is very simple in construction. There is no mirror or prism and the light simply passes through the lens and falls on the sensor. There is no optical viewfinder. The image that is recorded by the sensor is shown on the LCD monitor on the back of the camera and this will serve as a viewfinder. If you don’t like holding camera at arm’s length when photographing (like me), many CSCs also allow you to optionally attach an electronic (eye level) viewfinder (also called an EVF). Some high end CSCs, however, come with an EVF built in apart from the usual LCD monitor.

Picture 1: Schematic of a CSC. The optical path of a CSC is simple. The light passes through the lens and the image is recorded on the sensor.	Picture 2: Sensor (yellow arrow) and the flange (red arrow). Unlike in a DSLR, the sensor is directly exposed. So, be careful!

The shutter in a DSLR is normally kept closed. However, in a CSC the image that is shown before capture is read from the sensor. So, if the shutter is closed blocking the light, no image can be seen. CSCs employ an interesting trick to overcome this. The shutter in a CSC is kept normally open (hence it is shown as a dotted line in Picture 1). When you press the shutter release, the shutter closes and opens again restoring the view. This plus the electronics in the camera help capture an image.

From the description of a CSC you just read, you might have noticed the strong resemblance of a CSC to a digital P&S camera. Alternatively, you can look at a CSC as a P&S camera with interchangeable lenses and a bigger sensor!

Note that due to the absence of a mirror, the distance between the lens mount (also called “flange”, Picture 2) and the sensor, called the flange distance (Picture 2), is considerably less than a DSLR. A short flange distance improves the optical performance of a lens. It also has some other useful ramifications as you will see soon.

Now that you have seen the main characteristics of a CSC, you might be interested in knowing the commercial offerings from various manufacturers. Table 1 summarizes this.

Note (1): Focal lengths mentioned are equivalent to full frame. This has been done to make comparisons easy.

Note (2): The Micro Four Thirds Format also called M4/3 and abbreviated as MFT, traces its origins to the short lived 4/3 format. The MFT format, in fact, kicked off the CSC revolution. It is the only “open” CSC format. “Open” means that, the lens mount, interface details, etc. are available, enabling any manufacturer to develop camera bodies and lenses that are fully compatible and interchangeable. This also allows manufacturers to avoid the costly and risky reverse engineering process. The result is that you get products from different manufacturers that integrate well and function smoothly together.

At present, Olympus and Panasonic produce MFT camera bodies and lenses. Kodak might follow. MFT compatible lenses are also produced by Sigma, Tamron and Tokina. Apart from these, highly reputed manufacturers such as Leica and Voigtlander also produce premium grade lenses for MFT. The latter produces three of the fastest lenses available, with apertures of f/0.95. Another venerable lens manufacturer, Schneider, will also join the fray in 2014. Lenses up to 600mm focal length (after taking the 2X crop factor into account) are available thus giving a great reach in a very compact package.

Another unique feature of MFT systems, as the name itself indicates, is that the aspect ratio of the image is 4:3 rather than 3:2. The latter is used by all DSLRs and other CSCs. The logic behind this is that this aspect ratio is closer to the standard print sizes like 8”X10”, 10”X12”, etc. This means that you don’t waste away pixels by cropping. Another unique feature of MFT bodies (though not all) is the In-Body Image Stabilization (IBIS) feature that gives you image stabilization with any lens.

Lens Adapters: You have seen that CSCs have comparatively small flange distances (Pictures 2 and 3). Due to this it is possible to mount DSLR and even your older film SLR lenses on CSCs with a lens adapter (Picture 3) which is nothing but a hollow tube. One side mounts on the CSC and on the other side you can install a lens from a different system. Adapters are available in two types – dedicated and non-dedicated.

Dedicated Adapters: These are supplied by the respective CSC camera manufacturers. These allow you to use the DSLR lenses from their range on your CSC. For example, Nikon DSLR lenses can be used on Nikon System 1 CSCs with a dedicated adapter supplied by Nikon. Dedicated adapters are expensive but support most of the automation including autofocus, full auto exposure (all modes), image stabilization (if the lens supports), etc. These usually have some electronics built into them.

Non-dedicated Adapters: These are much simpler than dedicated adapters and hence cost very less. For example, you can have a Nikon F mount to MFT adapter, which allows the use all of Nikon F mount lenses on your MFT mount CSC. Likewise you can have a Canon FD to E Mount adapter that allows you to mount Canon FD lenses on a Sony NEX CSC. Note that these are adapters not interchangeable. You need to buy a separate one for every combination – one each for the given CSC and mount. Hence, you need to specify both ends of an adapter when you buy one. Remember though, that they will have some limitations. First, only manual focus is supported even if the lens is autofocus type. Fortunately, most CSCs provide some focusing aides (like a magnifier or focus peaking) to help nail down the focus.

Picture 3: A non-dedicated adapter. This model adapts a Nikon F mount (red arrow) lenses to MFT (blue arrow) mount.	Picture 4: This adapter supports a tilt function (see the inclination, about 8 degrees of the lens) while adapting a Nikon F mount lens to a MFT CSC. It can be used without tilt too!

However, interestingly, even if the lens was designed for the earlier non-auto exposure SLRs, you can still get automatic exposure (usually only aperture priority) even when you use non-dedicated adapters. Metered manual exposure mode will also work. You also need to stop down the aperture when you use these adapters but this will not result in dark viewfinder images since the image gets boosted, as you will read shortly. Now, here is the bonus – your old lenses will get stabilized if your CSC has the IBIS feature!

Once again due to the smaller sensor and lesser flange distance, adapters are available that give you tilt or shift (or even both) functions (Picture 4). Thus, you can get a feature that would cost you a huge amount otherwise (if you buy a dedicated tilt/shift lens). So, you can put all those old, beautifully made lenses that were gathering dust to good use with these inexpensive adapters. You can even buy some old lenses at throw away prices. As a bonus, you will get features like exposure automation, stabilization and tilt/shift features that were not originally available with your old lens. Now, don’t let anyone tell you that you can’t teach your old dog (lens) some new tricks!

So far what you have read just about covers all the salient aspects of a CSC; but how does a CSC compare with a DSLR? Let us look at this aspect in detail, feature by feature.

Viewfinder: The way you view the image to be captured is of course the most fundamental difference between a DSLR and a CSC. Instead of the image formed with the help of optics (mirror and prism), the image you see (either on the monitor or an EVF) in a CSC is generated electronically. Hence, it lacks the crispness of a DSLR viewfinder image due to the lesser resolution. However, being electronic the signal can be boosted and hence it will give you a better image in low light, though it may be bit noisy (grainy). There is also what is called a “lag”. That is, if you quickly pan or move the camera, the image in a CSC may take a fraction to update itself. This is due to the delay in the processing of signals. This may not be perceptible in all but the most extreme cases as advances in electronics have reduced this to a great extent. Further improvements can be expected too.

 

Picture 5: A live colored histogram. The Olympus OM-D E-M5 camera shows blown highlights (in orange, see circle) and blocked shadows (in blue). You can thus give suitable compensation and also maximize dynamic range in real time.

One great advantage of an electronic image is that you can overlay a great amount of information. A useful result of this is the live histogram (possible in some DSLRs but only in live view mode). With this you can see the histogram (Picture 5) before capturing and give any needed exposure compensation rather than guessing it after you take the picture.

Battery life: Since the LCD monitor (or the EVF) has to be on to view the scene (even before you take a picture), the battery consumption is higher with CSCs. This along with lesser capacity batteries that are needed to keep the overall size small means that the battery life is lower than a typical DSLR –something like 400 images for a CSC vs. 900 for a DSLR (per charge). If you are a heavy shooter and want to use a CSC, it is better you keep a charged spare battery on hand.

Size, weight and sound: Due to the mirror, its mechanism, prism, etc., DSLRs are large and heavy (Picture 6). They also make a fairly loud noise due to the mirror slap. Hence, they are not very discreet. If your photography demands stealth, CSCs are the way to go since they are very small and quiet! There is a caveat here though. Some of the CSCs use the same APS-C sized sensors as DSLRs and for these lenses though smaller than DSLR lenses are still large. So, if you are going for a CSC for its compact size, make sure you check the total size (camera + lens + EVF if you need one) before you take a decision.

 

Picture 6: This composite image compares the size of a DSLR (Nikon D600 with an 85mm f/1.8 lens) to a CSC (Olympus OM-D E-M5 with a 45mm f/1.8 lens). After taking into the crop factor the equivalent focal lengths are similar, making it an “apples to apples” comparison. Note the very small size of the CSC camera.

Lens choice: DSLRs evolved from 35mm film SLRs and (most) lenses originally made for 35mm SLRs could be used straight way on DSLRs (from the same manufacturer, of course). Most serious photographers would have made a heavy investment in lenses and thus this feature came in very handy and preserved the investment to a great extent. Lenses designed specifically to support the DSLRs which have the smaller APS-C sensor have been introduced but surprisingly most of them are zoom lenses. Today, there are very few normal and virtually no wide-angle prime (fixed focal length) lenses specifically designed for the APS-C DSLRs!

CSCs started from scratch and hence all the lenses have been designed anew specifically for them. These are generally smaller and lighter (Picture 6). Several high quality prime lenses are available along with extremely compact “pancake” lenses. The latter make some of the CSC systems as small as P&S cameras. One negative point though. Most CSCs (barring MFT) also don’t have any lenses beyond 300mm. As already explained, you can also use your DSLR lenses and many other low cost old lenses with the help of adapters.

System Support: As with lenses, DSLRs inherited a rich legacy of hundreds of accessories (flashes, cables, remote controls, etc.), many of which could be used straight away on DSLRs. CSCs belong to a new breed without predecessors and so they simply cannot match the DSLRs in this aspect. The immense popularity of DSLRs has spawned a large group of third party manufacturers who make cheaper but compatible accessories. This is one area where CSCs simply cannot rival DSLRs currently. However, the situation is changing as CSCs gain popularity.

Image Quality: CSCs with APS-C and full frame sensors virtually match the performance of the DSLRs with the same sized sensors. The same is true with low light performance too. Of the other two CSC formats available, the MFT has very high level of image quality – good for anything up to 20” X 25” enlargements. However, the upper “usable” ISO limit is about 6400, though you can definitely expect this to improve in the future. The Nikon 1 uses a still smaller senor compared to MFT with correspondingly inferior low light performance but this is a specialized camera as you will see shortly.

Video: Video implementation in a DSLR is bit clumsy due to the mirror, its associated extra baggage and a shutter that is designed to be kept normally closed. On the other hand, CSCs are ideally suited for video recording as they don’t have unnecessary hardware and sensors are also optimized for continuous live view operation. It is no then that surprise some of the best video cameras today are CSCs.

Frame Rate: This is measured in FPS (frames per second) and is a measure of how many images a camera can record in one second. The higher the rate is, the better it is for capturing action (sports, flying birds, etc.) DSLRs with moving mirrors and large shutters have some inherent issues with high frame rates. However, CSCs without these encumbrances can give much higher frame rates. It is quite common even for a moderately priced CSC to give up to 9 FPS while this is possible only with really high end DSLRs costing a bomb. The problem with (almost all) CSCs is that they cannot focus continuously (see next section for more details). So, these high frame rates are only possible with autofocus locked at the very first frame.

Autofocus (AF): DSLRs implement AF using the “phase detect” principle. For this they use a separate phase detect sensor. This AF sensor is positioned under the mirror in DSLRs. AF using phase detect is faster and more positive (less hunting). CSCs use an AF principle called “contrast detect” and the AF function is carried out by the imaging sensor itself. While many earlier CSCs were absolutely pedestrian in AF speed, modern CSCs are extremely fast even while using contrast detect. However, contrast detect is inherently poor in focus tracking and hence does not do a good job of focusing moving subjects. The solution to this is to implement phase detect sensors on the main sensor itself. While this technology is not yet wide spread the one implementation that is worth mentioning is on Nikon 1 Model V2 which can do an astonishing 15 FPS with full AF and auto exposure. Right now no DSLR can match this! You can definitely expect more CSCs in future to use this technology.

Price: While some of the CSC top end models are just as expensive as midlevel DSLRs, there are several lower specified models that are cheaper. Lenses are cheaper too, when you take into account the equivalent focal lengths.

A modified approach to CSC: There is one alternative approach possible. Here, the mirror and prism are eliminated from a DSLR (like any CSC) and replaced with a phase detect equipped imaging sensor and an electronic viewfinder. Rest will remain unchanged. Such a system would be more bulky than a typical CSC but can use the same DSLR lenses without any adapter. Only one camera has ever been made like this though you can expect a few implementations of this type in future.

Conclusion: This article has explained you every aspect of CSCs in detail to make your decision making easy. To summarize, at present, DSLRs are best suited for high speed photography like sports, wild life, etc. CSCs being small, discrete and quiet are best for travel, candid and street photography. Some of the CSCs (with a pancake lens) are no bigger than a typical P&S camera with vastly superior image quality equaling that of a DSLR. Plus, you get the versatility of interchangeable lenses. CSC camera sales took off with a bang but have slowed a little of late along with general slowing down of sales of all types of cameras. There are predictions that one day all DSLRs will be replaced by CSCs – either using dedicated lenses or using the same DSLR lenses (see previous paragraph). What will really happen though, only a magic mirror can tell for sure!

So, should you go for a CSC? That is really for you to decide in the end. However, this article gives most if not all the information needed to help you make a good decision.

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All text, diagrams and images © Ashok Kandimalla.