Why Astronomical Zooms Are Needed

2011.03.07

Optical zooms now reach a whopping 36X. A few years back, the word ultra-zoom was coined to describe fixed-lens cameras with an optical zoom of 10X or more. It seemed like a huge range at the time, yet people kept asking for more powerful zooms. As time passed and digital cameras reached 18X optical zoom and beyond, the number of people asking for more powerful zooms greatly declined.

This decline, of at least 80% as observed at Neocamera, should signify that zooms are long enough, yet camera makers have since doubled the range! So why are optical zooms still growing?

The easy answer is marketing. Just like megapixels, optical zooms are summarized by a single number such as 20X, 24X, ... 36X, etc. Single numbers are easy to compare and let advertisers boast about bigger numbers.

Marketing is only part of the answer. The truth is that ultra-zooms need those astronomical optical zooms to survive. Every camera class needs a distinguishing factor and the advent of relatively small SLDs, such as the Panasonic Lumix DMC-GH2 pictured here, is cornering ultra-zooms with nothing but their optical zoom numbers to hold on to.

Shown above on the left is the Fuji Finepix S100FS, arguably the best-performing ultra-zoom built to date. This Fuji features an 11 megapixels SuperCCD HR with outstanding image quality for its class and a 14X mechanical optical zoom lens, equivalent to 28-400mm. The compactness of its lens, compared to a DSLR, is essential to the compromise offered by ultra-zooms. Despite its high image quality for its class, the Fuji S100FS cannot deliver image quality comparable to that of DSLRs at high ISO or even in large prints.

Enter SLDs, which often use the same sensors as DSLRs, to shake things up. Ignoring the fact that they support interchangeable lenses, SLDs actually work exactly the same way as ultra-zooms. Many of them even look like ultra-zooms and their feature set is almost always a superset.

Olympus and Panasonic both use Four-Thirds sensor for their SLDs which have a crop-factor of 2X compared to full-frame DSLRs. This is the smallest size among DSLR sensors but is far larger than sensors used in ultra-zooms. This means that the image quality of SLDs is far closer to that of DSLRs. This relatively small sensor size lets Olympus and Panasonic build the smallest lenses in their class. This contributes to a great reduction in size compared to a DSLR while maintaining similar image quality.

The image above shows that the GH2 when equipped with a 10X lens, equivalent to 28-280mm, is actually smaller than the Fuji S100FS. There are smaller ultra-zooms but there also are smaller SLDs. The point is that the reduction in total size for cameras with high image quality is forcing ultra-zooms to distinguish themselves even more.

Small sensors used in ultra-zooms may be a liability in terms of image quality but they give the ability to provide an extreme zoom range in a single lens. Indeed, no interchangeable lens presently has a zoom factor of more than 15X, yet 35 ultra-zooms cover such a range and more. To keep existing as a class of digital cameras, ultra-zooms must keep pushing the limits of their lenses.

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