More Silly Numbers: The UltraZooms
March 25, 2010
As someone who rarely photographs sports or wildlife, the world of long-zooms is not one I pay much attention to.
But there’s trouble brewing lately, in the “bridge camera” market; and it’s reached a point even I can’t ignore.
Yes, just as with megapixels, camera makers have launched another numbers race—this time over zoom range.
Currently, bragging rights go to Olympus, with their SP-800UZ (“ultrazoom,” geddit?). While it shares an alarming 30x zoom range with Fujifilm’s HS10, the Oly is biased more towards the telephoto end. And so, the SP-800UZ wins the zoom war with a zany maximum of 840e!
The outsized lens makes the SP-800UZ one rather odd-looking camera. And despite the SLR-ish hump on top, there is actually no eye-level viewfinder. You must frame using the back LCD—holding the camera away from you.
Now, for those who photograph birds, zoo animals, stadium sporting events, etc., I’ll admit the handiness of having a long zoom range.
But 840e is getting into crazy-magnification territory. Just locating the subject will be a challenge (especially with unsteady arms-length viewing). For reference, we’re talking more than double the magnification you would typically buy in binoculars.
Needless to say, aggressive two-stage antishake becomes mandatory in UltraZoom cameras. Even so, you’d better pray for strong sunlight to keep shutter speeds brief. And once your subjects are really in the distance, no lens will remove the milky haze of the atmosphere itself…
Nonetheless, all the major camera makers are now cranking up their UltraZoom specs. (Panasonic is being the most conservative, with “only” 18x on their FZ35.)
The styling of UltraZooms usually mimics the serious look of a DSLR. But in fact, all of these models employ the same little trick:
The imager in these cameras is nowhere near the APS-C format found in DSLRs. In fact, it’s under 8% of their sensor area. (A so-called 1/2.3″ chip is approximately 4.6 x 6.2 mm.)
This lets camera makers scale down all the lens dimensions by the same proportions. So, a focal range that would require a bazooka-like barrel on APS-C can be made smaller than a beer can instead.
And the volume of glass required for a given lens design (and thus, its weight) shrinks even more dramatically—to almost 1/40th. You can see why camera makers became so fond of this little gimmick.
Also recall that the “brightness” of a lens (its widest f/stop) is actually a ratio: f/numbers are the focal length divided by the aperture diameter.
The physical diameter of the glass limits the second number; so as you zoom in, lens brightness drops. The Olympus SP-800UZ lens specs are 5.0–150 mm focal length; f/2.8–5.6 in aperture. That’s right—you sacrifice two whole f/stops at the long end of the zoom range.
In the case of the Olympus SP-800UZ, this raises another troubling question. To cram 14 megapixels into such a small sensor, each one can only measure 1.44 microns across.
So when you’re fully zoomed in, how sharp can your photo even be? The smallest point of light theoretically possible smears across a dozen pixels. And this is before considering lens aberrations (which are probably significant too, at the extremes of the zoom range).
So if an UltraZoom is what you need, don’t let me stop you from buying one.
But just don’t expect it to rewrite the laws of physics.