On Jul 7, 2007, at 7:34 AM, David J. Littleboy wrote: > But you are forgetting to take the other aspects of the format > difference > into account.
This seems like an assumption. ;-) > For the same pixel count (to a rough first approximation, 10 is > about the > same as 12.7), a 4/3 camera's pixels are 1/4 the area, and thus are > two > stops less sensitive. Natch. > And DOF scales with the format size, so you "gain" two stops of > DOF. (Only > at the wide end, at smaller apertures, diffraction kicks in two stops > sooner, so while f/16 on FF results in sharp images, apertures > smaller than > f/8 on 4/3 will show diffraction effects. But since DOF is two stops shallower you don't need to stop the lens down as much to get the same effective DOF. > So that sexy-sounding f/2.0 lens will be functionally > indistinguishable from > an f/4.0 28-70mm lens on FF (with the FF at four times the ISO for > identical > noise/dynamic range). That's assuming a linear comparison of sensitivity where the 4/3 sensor is functionally two stops less sensitive than the FF sensor across its entire ISO range, which in a technical sense it may well be. However, 100 ISO is 100 ISO on both a FF and a 4/3 sensor. From my experience shooting with 4/3 the images from my E-1 looked wonderful at ISO 100-200. The combination of the lovely color rendition of the Kodak CCD used in the camera and the microcontrast qualities of the Zuiko glass conspired to create a beautiful capture device. Where you started losing IQ with the E-1 was at 400 and above. Not terrible at 400. Mostly a luminance noise pattern that looked almost like film grain at 400. At 800 it was starting to contain enough color speckling from the rising curve of the chrominance noise to look more electronic. Which comes back to that issue of high ISO on the 4/3 chips being problematic. That doesn't mean that you're going to suffer at low ISO, though. So a birder, for example, will have a two-stop DOF advantage over a FF guy right out of the gate just because of his format of choice. Add in the faster Zuiko f/2.0 lens at ISO 100 and he can use a higher shutter speed at a lower aperture all day long. You're right, though, when you get to the end of the day and the light starts to fall the extra speed of the lens becomes a crutch that attempts to overcome the limits of the sensor. Still, the high- end Oly glass tends to be very sharp wide open and you don't have to stop them down much at all to hit their sweet spot. > Note that to actually be equivalent, the 4/3 lens has to provide > _twice_ the > resolution (twice the lp/mm at any given MTF, or an MTF curve > shifted up by > a factor of two due to the finer pixel pitch) at f/2.0 than the FF > 28-70mm > lens does at f/4.0. (Interestingly, MTF performance does scale up with > decreasing format sizes, so this point may not be a problem; but > the need > for twice the resolution at a much wider f stop may be problematic.) This is the biggest problem with the format, IMO. You're always going to be fighting that battle. It's the same thing with shooting 16mm instead of 35mm cine stuff. The 16mm gear is lighter, has greater DOF for run-and-gun work and is obviously a lot less expensive to work with. But the frame is roughly a quarter the size of the 35mm frame, so the glass always has to be much better than glass would have to be on a comparable 35mm rig and obviously the grain is going to be magnified on top of that. A grain pattern that looks subtle and wonderful in 35mm may look really bad in 16mm, so you can't even use the same standards of judging what stock to use because 5263 is not the same at the end of the day as 7263 when you take the format into consideration. So that's the rub when you have to decide on buying glass from Olympus now. The 35-100mm f/2 is a really nice lens. Effectively a 70-200mm f/2 lens, but it carries a price tag of $2200. Is it equal to a Nikon 70-200mm f/2.8 on APS? Or a Canon 70-200mm f/2.8 on a FF camera? Hard to say. More than the MTF numbers of the lens play into it, of course. Those Canon FF cameras have a sensor with a diagonal nearly as wide as their lens mount where the 4/3 sensor is tiny in comparison to the 4/3 mount. That allows a lot of advantageous geometry when it comes to lens design and how the light strikes their sensor it a big part of the "4/3 advantage" (to quote the nauseating Olympus PR machine). At the end of the day I think it's about what camera you enjoy using as much as almost anything else, unless you have some particular application that draws you to one camera over another. I prefer CCD sensors and my E-1 and now my D200 both have CCDs. I don't know what options will be available to me in the future, though. I'd love to see the Foveon chips get it together. I'd take full color information over just about any other consideration, but so far I'm unconvinced that they've got that format ironed-out. I really like the highlight and color characteristics of the Fuji Super CCD SR Pro. If Olympus could shove one of those in their new "pro" camera it would probably override any other concerns I had about the format. Not likely, though. -Rob ---------------------------------------------------------------------------------------- Unsubscribe by mail to [EMAIL PROTECTED], with 'unsubscribe filmscanners' or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or body