Tuesday, 5 August 2008

Micro FourThirds: Should they have started with it?

Since the date of the announcement of the FourThirds system, experienced photographers often ask: why does a compact camera system not exists with this sensor size? Such a combination would have ment an ideal compromise between image quality, depth of field and the physical size of the equipments.

There is a big inconsistency in the FourThirds system. The E-1 was not regarded as a top dSLR from an image quality point of view when it was announced, and now the E-3 is walking in same shoes what clearly visible in its price - it is the cheapest really professional dSLR. At the same time, the pricing strategy of Zuiko lenses is not based on the lenses' optical parameters and the size of the lens elements, but on their equivalent focal length, so sometimes their prices seem to be irrealistic and many customers are discouraged as they just do not see the benefits behind the high cost.

One of the problems of the FourThirds is that the flange focal distance (the distance between the plane of bayonet and sensor) was not decreased propotionally to the image size. There are many reasons for this. In comparison to 3:2, the 4:3 aspect ratio means relatively higher image and consequently higher main mirror in the mirror box. Because of this, the size of some mechanical elements could not be decreased too. This effect is liable for that the Focal Length Multiplier is 2.0 to the 35mm system, but the flange focal distance is 38.67mm what is hardly smaller than at other 35mm cameras. As a result, relatively large diameter bayonet and strongly retrofocus design for wideangle and normal lenses is required. The common consequence of this design is that "ordinary" FourThirds lenses with smaller than normal field of view are not smaller than their 35mm "FullFrame" equivalents.

The Micro FourThirds offers a real solution to this problem. The dedicated lenses of the new system can not be as telecentric as the older ones but perhaps the new Panasonic sensors are not as sensitive to the direction of rays as older CCDs were. Leica and Kodak in M8 shift the microlenses a bit at the edge of the sensor to prevent strong vignetting but the focal length range is very limited at the telephoto end so this solution is not suitable for Micro FourThirds.

Clearly, current mainstream camera design in the semi-pro and pro market is dictated by the viewfinder design, leading to the dominance of dSLRs. The main question is: therefore if Olympus wanted to produce a new system six years ago, was it really necessary to use optical TTL viewfinder? The first concern is the quality and usability of viewfinder, but we have to be careful in jumping to conclusions as we know very little about an EVF what could be manufactured on the cost of a TTL optical viewfinder. Still, considering the size of a really high quality viewfinder, such as the one used in Panasonic's Genesis cine camera, there must be considerable engineering challenges to face in this area.

In digital still cameras, we mostly meet EVFs in compact cameras as auxillary service. I am not referring to the now dominant back LCD only solution, as the size and quality requirements are very different. The only one quasi 1-megadot EVF was built into an old Minolta camera, and its quality was significally better than in simpler devices. Compared to a dSLR, a camera with EVF has no moving main and auxillary mirror, focusing screen, pentaprism or pentamirror, very complex AF modul and focal plane shutter. These are the most expensive elements in a dSLR and from their cost it is possible to make a high resolution EVF with high picture-frequency, that is comparable to optical viewfinders. The evolution is continous, for example: OLED - EVF, etc.

One of the features of SLR cameras that there is the possibility to use AF system based on phase-difference detection. When the FourThrds system was started, the contrast detection AF were incomparably slower than phase-difference detection AF because only the latter could give information immediately about the amount and direction of necessary lens-movement. There was no chance to sell a new interchangeable lens system with an AF what ten times slower than competitors. The situation is not much better today but looking at the AF performance of Olympus E-420/520 in LiveView mode when it is switched to contrast detection mode. The shutter lag is still too long because Olympus can not solve the precise light-metering without moving the mirror, but if we look at only the length of the AF process, the improoving is significant. This improvement is one of the factors which allow the starting of the Micro FourThirds. There is a note in news that tells us to be careful. Some functions of new system will not work if we use the MFT/FT adapter and traditional FourThirds lenses. If there will really be only contrast detection AF in the new cameras, maybe it means that the AF will not work or it will be slower. On the other hand, the adapter is an extension-tube what restores the flange focal distance for normal FourThirds lenses so there is no lens in it and it has no effect to the image quality.

The switching between aspect ratios is a very interesting possibility opened up by the new standard. Unlike many review site, the Micro FourThirds whitepaper not give information the horizontal and vertical size of the sensor, only on the diagonal size. This is very important because Panasonic, one of the founders of this new standard, announced the LX3, an interesting new compact camera only a couple of days ago. It has larger image sensor than coverable by lenses so it can switch the aspect ratio from 4:3 to 16:9 without loss of resolution. Based on the available information, I predict that we will face this solution in Micro FourThirds cameras so the width of the sensor will be about 20mm instead of 17.3mm with unchanged height and the number of effective pixels will not decrease when it is used in 16:9 or 3:2 mode. If this really is the case, the lens hood of some normal FourThirds lenses will cause a little vignetting in this modes.

The whitepaper also stresses that the recording of movies is one of the features of the standard, and the two new pin on the bayonet was designed for this reason. Panasonic has great experience in manufacturing amateur and professional video equipment. Probably all Micro FourThirds camera will be able to record movie but maybe a videocamera-system with interchangeable lenses is among the main goals of Panasonic. We have to remember that Panasonic has announced its experimental HDR sensor which have more than 20 EV dinamic range. Combination of this sensor and the size advantages of the new system could produce a high quality movie solution at a price never seen before.

There are other effect of switching to a non-mirror/EVF solution, namely:
- contrast detection AF is still much slower than phase-difference detection AF
- light-metering can be slower too
+ precision of AF does not depend on many mechanical elements which often cause AF errors
- delay of EVF is added to shutter-lag
- higher power consumption
+ simpler and cheaper normal and wideangle lenses
+ totally noiseless functioning is very useful feature for many photographers (nature, theatre, people, etc.)
+ live histogram
+ viewfinder boost in darkness
+ unlimited number of AF fields
+ 100% viewfinder is easy realiseble
+ magnification is possible in viewfinder

This is all very nice, but every FourThirds user has now a question: what is the future of their beloved system, already purchased and planned to be purchase lenses? If Micro FourThirds can not win new customers, there is real chance to the new system will fail with the old one. It is clear that Olympus will kill the 4x0 camera-series by Micro FourThirds but it is also dangerous to Pro bodies and lenses. The chance of a simple upgrading from entry level camera will be lost due to lens incompatibility and this would be not an attractive feature of any camera makers' product palette. Still, the amount of sold Pro/Top-Pro lenses and other accessories is very large so I at least hope that new semi-pro or professional FourThirds cameras will be designed in the future. We just know too little to draw any conclusions right now.

I fell in love with Micro FourThirds at first sight because I wanted to decrease the size and weight of my photo-equipment. I wonder which group of customers will be targeted with the price and external design of cameras. The whole Micro system has a point only if its price is competitive so probably we will get simpler and cheaper products for the first time, but I would really like to have an elegant, "Zeiss Ikon like" camera option. I am sure this would be very well received by demanding, semi-pro and pro photograpers.

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