Super Corrected Lens system

I inquired with Canon USA regarding the issue of chromatic aberration with the SX30IS and here is an excerpt from their prompt response.

“Lateral Chromatic Aberration (LCA) or more commonly known as fringing results in loss of sharpness and white light objects or areas having
colored halos (commonly a reddish or purple cast) around the edges.

LCA is caused by light which is made up bands of different wavelengths (as seen when light passes through a prism). These bands focus at different points and different magnifications. Since a camera lens can only focus light at a single point, wavelengths falling on either side of that point will be slightly more diffuse and less focused. Only through the use of specially ground lens optics which are generally found only in professional grade lenses can LCA be controlled.

LCA is most often seen in areas of high contrast or areas with a great difference in exposure levels. You may wish to try switching your Photo

Effects setting to NEUTRAL, this setting will help in such settings.

Another cause of LCA can be that a lens has an optic that is out of alignment and would require servicing.  I have included service information if you would like to have your camera checked out.”

Based upon what this Canon service tech is saying, the issue is either the result of the limitation of the lenses themselves or it is the alignment of the lenses.

It may be the unavoidable limitation of the super wide angle/super telephoto setup that results in a trade off of quality vs. versatility.

Because it was a service tech who responded and not one of the engineers, it is hard to say what the real issue is.  Suffice it to say that the aberration is a lens issue.  Either it is an issue in the quality of the manufacturing (grinding) of the lenses themselves, or in the assembly of the lenses, or in the limitation of the high powered telephoto configuration, or any combination of the above.

Since the fabrication and grinding of lenses is computer controlled, the quality is probably not as much an issue as the assembly itself.  Beyond that, the configuration of the lenses may have certain limitations that are unavoidable.

Afer reviewing “Digital Camera Review” online review of the SX30IS, they had this to say about chromatic aberration and image sharpness.

“When light rays pass through a camera lens they separate into various color waves and dispersion (all colors don’t focus at exactly the same point) can become a problem. Dispersion causes axial chromatic aberration - the fuzzy colored edge blurring image degrading phenomenon popularly known as purple fringing. The SX30’s f/2.7-5.8 4.3-150.5mm (24-840mm equivalent) zoom is constructed of 13 elements in 10 groups and includes one Hi-UD element, one UD element (to reduce chromatic aberration), and one double-sided aspherical element.

A 35x zoom designed for a DSLR would be so long that you’d need a pick-up truck to transport it and so heavy that it would require three men and a boy to carry it. Canon’s technical folks did a remarkable job - this lens is amazingly compact and astonishingly light-weight. But this is a super corrected lens, and as optical complexity increases, lens faults and optical aberrations are magnified exponentially. Images do show some visible corner softness and barrel distortion (straight lines bow in toward the center of the frame) at the wide-angle end of the zoom range is noticeably above average. Pincushion distortion (straight lines bow in toward the center of the frame) is (as expected) above average at the telephoto end of the zoom. Chromatic aberration (purple fringing) is also above average, but not as much above average as expected.”

I think this last comment should answer my above question.  The SX30IS appears to be at its own design limitation with a super corrected lens system.  Apparently, the chromatic aberration is less than expected (“not as much above average as expected”) for that much lens correction.

So this seems to be my answer.  It is apparently a legitimate trade off between image quality and extreme versatility.  That being confirmed, I can now go and purchase this camera knowing that it is not an exercise in smoke and mirrors.  For this much versatility, there is a bit of an image quality trade off under certain circumstances.

A larger CCD might get rid of some of the high resolution noise but there is no certainty of that given the very highly corrected lens system.  In other words, there is no guarantee that a larger CCD would make any affective difference in low light high resolution noise in this camera.  This appears to be as good as it gets.

BY:GORDON