Identified advantages
Check the dedicated Olympus E-1 interactive forum

If you have skipped the rather long and detailed Four Thirds standard description page, I really do recommend you read through it to get the best out of this page where I explore the advanatages and disadvantages of both the standard and the first interpretation of that standard, the Olympus E-1.

Size and weight
Four Thirds lenses are half the focal length of equivalent angle of view 35mm system lenses. That, in theory, should mean they will be half the size and weight of 35mm lenses. The E-System Zuiko Digital lenses produced by Olympus so far are, indeed, smaller and lighter, to varying degrees, than 35mm equivalent lenses, especially the Zuiko Digital 300mm f/2.8 telephoto, which is equivalent to a 600mm f/2.8 lens.

As far as I'm aware, there is no 600mm f/2.8 35mm system lens on the market. The nearest lens to the specification of the Zuiko Digital 300mm f/2.8 we could find is Nikon's AF-S Nikkor 400mm f/2.8. This weighs 4.8kg, has a maximum diameter of 160mm and is 352mm long. By comparison, the Zuiko Digital 300mm f/2.8 weighs 3.3kg, is 129mm wide and 281mm long.

The Nikon lens will offer the same 600mm equivalent focal length angle of view as the Zuiko Digital when used on a Nikon Digital SLR calculated using a 50% equivalence factor relating to the Nikon's imager size. Canon's EF 400 mm f/2.8L IS USM is even wider and heavier than the Nikon lens, though it does include optical image stabilisation. The 60% equivalence factor of the slightly smaller Canon imager means a 400mm lens becomes equivalent to a 640mm optic.

Nikon's AF-S Nikkor 600mm telephoto isn't as bright as the Digital Zuiko. Its maximum aperture is f/4, but at 455mm long, it's 62% longer and at 5.9kg, it's 79% heavier. Canon's equivalent lens, also f/4 max, complete with image stabiliser, is slightly lighter and shorter than the Nikkor, but still massively larger and heavier than the Zuiko Digital.

Another point worth noting is that the Canon and Nikon telephotos described above are significantly more (30-60%) expensive than the £5,300 (inc.VAT) Zuiko Digital.

With shorter focal length lenses weight and size is less critical, but the Zuiko Digital lenses still have a useful advantage. The Zuiko Digital 50-200mm f/2.8-f/3.5 zoom (100-400mm equivalent) , is 87x157mm and weighs 1070g with its tripod adapter. The nearest specification lens we could find is the Sigma 120-300 f/2.8 HSM zoom. It weighs 2600g and is 268mm long. It's also nearly £1,000 more expensive than the Zuiko Digital, which is priced £779, (inc.VAT).

It should be noted, however, that the Sigma has a fixed maximum aperture throughout its zoom range, though its zooming range is considerably narrower.

The standard zoom in the current Zuiko Digital range is the 14-54mm f/2.8-f/3.5 (28-108mm equivalent). It is priced £496 (inc.VAT) on its own but is discounted when bundled with an E-1 body. It weighs 435g and is 87.5mm long and 73.5mm wide. Sigma sells a remarkably cheap (£160) 28-105mm f/2.8-f/4 Aspherical zoom and it's only 79.5mm long, 77mm wide and weighs 405g.

Canon doesn't have a lens in this range with a f/2.8 max aperture, but its slower f/3.5-f/4 28-105mm USM lens is about the same size as the Zuiko Digital and about a third lighter. Nikon, too, doesn't have a lens in the 28-108mm range at f/2.8, but its £1300 28-70mm f/2.8 AF-S optic weighs nearly a kilo and is 88.5mm wide and 121.5mm long. This lens has the advantage of a fixed maximum aperture throughout the zoom range.

But what about an equivalent 28-108mm zoom range for small imager Canon and Nikon DSLR? For Canons, you'd be looking for a 17.5-67.5mm zoom range and with Nikon, an 18.7-72mm zoom range. At the time of writing, as far as I can see, there is no comparable lens of the angle of view range anywhere near the Zuiko Digital 15-54.There are some slightly wider but shorter zooms of the same brightness, but all are significantly larger and heavier and most are more expensive and there are some slower examples of the same shorter range, but these are also large and expensive.

No lens compromise
As already identified in the section above concerning the issue of using smaller imaging sensors with 35mm system lenses, the usefulness of wide angle lenses is badly compromised and the availability of 'standard' wide angle zoom lenses with a generous zoom range is virtually non-existent.

But it doesn't stop there. Olympus applies near-telecentric design to its optics to maintain the projected angle of image forming rays into the imager as close to 90 degrees to the focal plane as possible. This minimises corner shading and loss in detail recorded by the pitted photo-diodes in the surface of the imager when the angle of incidence becomes more acute. Olympus points out acute angles are typical of lenses designed for film use.

To enable telecentric lens design the lens mount diameter needs to be relatively large compared to the sensor size in order to accommodate over-size rear lens elements. Olympus says the mount diameter should be double the diagonal of the imager. Ideally, for a full frame 35mm SLR, Olympus says the lens mount should be 100mm wide (2x50mm). Canon's lens mount is 54mm in diameter and Nikon's, which dates back to the 1960s, is only 48mm. The Four Thirds lens mount is about 50mm in diameter, about double the diagonal measurement of the film frame, just as they say is required..

With Nikon and Canon DSLR imagers in the region of 28mm in diameter, if you subscribe to the Olympus theory, you need a lens mount in the region of 56mm wide. Canon is probably OK for its smaller sensor DSLRs but way off the 100mm required for its full frame DSLR and any future full frame DSLR, it should be noted.

The problem for Nikon looks more serious. Even with its small sensor, the lens mount is, according to the Olympus theory, too small. Indeed, the Four Thirds mount is larger than the Nikon one. This pointedly reveals why Nikon appears to have no ambitions to produce its own full frame DSLR based on the current 35mm system. But then again, it ought to be remembered hat Kodak went ahead and did exactly that with its Nikon-based full-frame DCS 14n Pro.

For the time being I'll be keeping an open mind about the telecentric design requirement for electronic image sensors. It sounds convincing on paper, but I'm yet to be convinced of its importance in real life. While the Kodak DCS-14n Pro has been criticised for a lot of things, I haven't seen much criticism to do with corner shading and lost detail towards the corners of the frame. The full frame Canon EOS-1Ds is hardly criticised for anything, apart from its price and certainly not for image quality. However, nobody has yet done back to back exhaustive comparisons with a Four Thirds camera and lens to prove, or otherwise, the telecentric theory, apart from Professor Anders Uschold, who is contracted to Olympus.

Smart lenses
Four Thirds compatible lenses are smart. They have their own microprocessor, upgradeable firmware and the Olympus E-System lenses, at least, all use fly by wire focussing in manual mode, letting you choose which direction you prefer to turn the focus ring towards infinity. You can also manually fine-adjust critical focus using the focus ring even when the camera is set to AF mode, which is really neat.

Not to be confused by digital sensor corner shading, there is the issue of lens vignetting or light fall-off towards the extreme of the image circle. Olympus says lens profiles will tell the camera body about the degree of vignetting, as well as other lens imperfections, like barrel or pincushion distortion, that might require digital correction. Lens distortions are not yet corrected inside the E-1, but Olympus says future cameras will be able to do this. The profile data can be saved with images and be used to dictate post processing of images on a PC, though as far as I can see this will be limited to RAW files only. Even teleconverters and, I'm told, extension tubes, have their own profiles.

User-upgradeable firmware
The potential limits of the new Four Thirds standard and the E-System won't be neared for some time. Continued development will, says Olympus, mean that there will be regular firmware updates for camera bodies and also lenses. New E-System flash units, like the FL-50, are also firmware upgradeable and all upgrades can be undertaken by the users.

Cost
It has already been demonstrated that when compared to premium brand lenses of the same build and, presumably, optical quality, E-System lenses are competitively priced. This is partly because E-System lenses are physically smaller than their equivalent 35mm system counterparts. Olympus may also be banking on the fact that as it's starting out as the exclusive supplier of lenses for the E-System, it can sell a fair number of them, helping it leverage economies of scale. A more cynical view would be that the lenses simply have to be competitive in price for the E-System to succeed.

From the camera body point of view, the most important single component is the electronic imager. The Four Thirds standard has been fixed around an imager of 22.3mm in diagonal measurement. This makes it, in E-1 4:3 aspect ratio form, around 238 sq. mm in area. Its APS sized rivals have an area of around 386 sq.mm, or 60% greater area. In theory, the E-1's CCD imager should be usefully cheaper to make, per unit than APS-sized CCDs, though scale of manufacturing quantity does have an impact on the calculation.

Canon's CMOS imager is clever because it is manufactured using the same process as CPU and memory chips and is significantly cheaper than CCD manufacturing. But Canon's sensor is still around 55% larger than the E-1's CCD, so some of Canon's cost advantage is probably negated.

Olympus has chosen to position its first E-System camera in the mid-low range professional and high-end prosumer sector, so it's not designed or built to be sold as a high volume consumer market camera, like Canon's EOS-300D, for example. But if Olympus chose to enter that market and they say that they will, sooner or later, they should be able to be competitive in terms of cost because of the compact size of the Four Thirds imager.

A lot of people are banking on Canon scaling its affordable CMOS imager to the full frame. Having spoken to various experts in the semiconductor industry, my feeling is that even with CMOS, a full frame sensor will never be affordable in the mass-market sense.

People marvel at the Canon EOS-300D selling today for around £750, discounted, with a lens. Maybe that will fall to £500 in real terms within a couple of years, but even with fantastic improvements in CMOS manufacturing efficiency, I estimate an EOS-300D specification camera with a full frame imager would still cost in the region of £2,000 in the same time period.

In summary
The Four Thirds standard is well thought out and has avoided many of the compromises imposed on other cameras that are based on legacy 35mm systems. Lenses and cameras can be light, compact and relatively good value. In theory, image quality should be optimal for digital shooting. The headache of compromised wide angle lens performance is avoided. The smart communications protocol between lenses, bodies and flash units has tremendous potential.

Check the dedicated Olympus E-1 interactive forum