18-250mm Superzoom Lens Group Test: Compact Comparison
The Case for a Compact Superzoom
The biggest zoom ranges for stills photography are offered by lenses that are fitted to compact cameras. That being the case, it is worth considering whether a hybrid compact camera might actually be a better choice than carrying a DSLR fitted with an all-purpose lens.
If the answer is to be ‘yes' then the hybrid's lens must be capable of recording images that have a level of quality comparable to that obtained from DSLR lenses.
Testing the Theory
To test this, a typical hybrid compact, Casio's EX-FH20, was put through the DSLR resolution testing routine. The results were interesting...
The first thing to note is that the aperture settings offered by the compact are much more limited than those provided by a DSLR lens and are not in-step with conventional aperture values. In addition, the number of aperture settings provided by Casio's compact decreases as the focal length increases, dropping from three F-stops to two (in one-third F-stop increments).
This is not necessarily a bad thing given that tiny aperture settings tend to produce poor images. In fact, curtailing the aperture range might actually be a means of maintaining image quality. And that is exactly what the MTF curves appear to suggest.
Although Casio's compact has a 20x zoom range, its lens was only tested over a range of focal lengths equivalent to 26mm (its widest setting) to 270mm. The resulting graph shows a very consistent set of MTF curves bunched between 0.20 and 0.25 cycles-per-pixel. The group is positioned a little lower than ought to be ideal but it shows much less variation than any of the DSLRs could manage.
Encouraging though this is, the record must also show that the compact camera sometimes failed to focus accurately on the test chart, especially at its longer focal-length settings, and if the lens fails to focus on a subject then no amount of theoretical resolution will record a sharp image.
The best thing about this quick test is that readers who are avid users of sophisticated compacts can find encouragement in these results whereas fans of DSLRs still have room to feel that theirs is the better choice.