Sharpshootin' 8-megapixel pieces-is one right for you?
What's with the noise?
Can the image quality from an 8MP EVF ever match the quality from an 8MP-or even 6MP-digital SLR? Some "experts" claim that EVF and compact digital cameras float-belly up because of digital noise-the term for image-degrading patterns and mottling, which is most evident in even-toned areas like sky, skin tones, or shadow areas.
That popular theory derives from a genuine fact: The smaller imaging sensors used in EVF and compact cameras are crowded with much smaller pixels. For example, on four cameras in this roundup, the 2¼3-inch CCD sensors feature 2.7 micron pixels, compared with 7.8 microns on the APS-sized CCD in the Nikon D70.
Two things happen with smaller pixels. First, the base ISO sensitivity of the sensor drops because more light is needed to fill the ultrasmall pixel wells. To compensate, cameras offer higher ISO modes, which unfortunately boost noise levels in the process of increasing low-light sensitivity (see ISO 100 vs. 400 shots at left). Second, the physical characteristics of the sensor, especially the materials used to create the boundaries between pixels, are less able to prevent electronic background noise from interfering with the signals from individual pixels. Thinner, more transparent walls between small pixels also allow angled light to strike adjacent pixels, causing noise, color fringing, and softer edges-especially with wide-angle lenses set to their widest apertures.
Sound like a dire situation for 8MP EVF models? It isn't for the images they capture at ISO 50-64 settings in normal lighting. That's because manufacturers have come up with some ingenious solutions to the noise problem. For example, many CCDs now use a microlens on each pixel to direct angled light toward the sensor, improving sensitivity and signal-to-noise ratio. Sony's 8MP CCD goes even further, incorporating a double internal lens (DIL) to further direct light toward the sensor. Other advancements in image-processing circuits and noise-reduction technologies also help keep noise in check.
But there's no avoiding the reality of increased noise levels found in these five 8MP EVF models at higher ISOs, and it's this hurdle that may slow down the megapixel race in EVF and compact digital cameras for the near future.
Konica Minolta USA:
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