For your example, this is quite valid, as with four third lenses f 8 is the diffraction limit, as with canon lenses is about f 11. F 16 degrades the sharpness of the picture. So with the olympus f5,6-8 is an ideal aperture for the same DOF as 8-11 with a canon camera and yes less high iso is needed. But this approach has limits and is only valid as long as you can open the aperture. As long as you compare apples with apples like E-3 with D300 the E-3 is not an bad option, but if you need high iso the E-3 has no chance with a camera like Nikon D3. [a href=\"index.php?act=findpost&pid=153570\"][{POST_SNAPBACK}][/a]
If you campare the previous 4/3rds models with Canon's cropped format cameras such as the 10D, 20D, 30D and 400D, the Olympus cameras could not compete in terms of noise or resolution at high ISO.
In terms of DoF, the 4/3rds format has a 2/3rds stop advantage (compared with the 20D). But for purposes of noise comparison, (ie. using an ISO 2/3rds of a stop lower and an aperture 2/3rds of a stop wider for the same shutter speed) this doesn't quite work because the Canon ISO ratings are inflated. ISO 1600 is really ISO 2000 and ISO 3200 is really ISO 4000.
Therefore, whilst you can use an aperture 2/3rds of a stop wider for the same DoF, you would only get about 1/2 a stop ISO advantage to lower noise, if you needed the same shutter speed.
Since Canon DSLRs always have had, at least until recently, much lower noise at high ISO than Olympus 4/3rds models, that 1/2 stop advantage of previous 4/3rds models was never enough to even nearly compensate for the inherently higher noise, something that BJL tended to overlook.
However, the new E-3 appears to change things. Apart from some very marginal resolution advantage of the Nikon D3 and Canon 5D due to those extra couple of megapixels, the 2 stop advantage in DoF and ISO should more or less equalise matters. I believe Nikon ISO ratings are also fairly accurate, as is the Canon 40D.
When comparing the D3 with the E-3 under conditions of equal DoF and equal shutter speed, one should be comparing ISO 1600 on the E-3 with ISO 6400 on the D3. Having just seen some comparison shots between the 40D and the E-3 at Imaging Resources (on their Comparator), I could believe that the E-3 at ISO 1600 would be at least the equal of the D3 at ISO 6400.
Of course, Olympus does not have a monopoly on fast lenses. A D3 or 5D with an equally fast lens will have an advantage but at the cost of greater shallowness of DoF and greater weight. The greater shallowness of DoF might sometimes be desired, but never the greater weight.
What we appear to have now from Olympus is a cheaper and lighter package that can (perhaps?) equal the quality of some current full frame 35mm DSLRs in every respect except dynamic range. The DR of the E-3 might have been improved as a result of lower noise, but it's really too much to expect a smaller sensor with smaller pixels to match the DR of a significantly larger sensor of about 4x the area.