JPEG/TIFF Image Size & Quality

The 6900Z provides nine different image size / quality combinations. There are four image quality settings at 6 megapixels (2832 x 2128), including TIFF, two each at 3 megapixel and 1 megapixel and a single VGA mode. Because of the honeycomb structure of the 6900Z's SuperCCD none of these can truly be considered the cameras 'native resolution', however the 2048 x 1536 size is nearest to the quoted number 3.3 million pixels on the CCD.

Standard Test Scene

To give an impression of what some of the combinations of image size and quality produce the table below is a cross reference of some of them:

• 6mp: 2832 x 2128 HI (TIFF)
• 6mp: 2832 x 2128 FINE
• 6mp: 2832 x 2128 NORMAL
• 3mp: 2048 x 1536 FINE
• 1mp: 1280 x 960 FINE
• VGA: 640 x 480 NORMAL

Images below are cropped 240 x 100 area of the image magnified 200% (nearest neighbour).

	2832 x 2128 (6mp)
HI TIFF	17,720 KB (Not available for download)
FINE JPEG	990 KB
NORM. JPEG	677 KB
BASIC JPEG	329 KB
	2048 x 1536 (3mp)
FINE JPEG	595 KB
	1280 x 960 (1mp)
FINE JPEG	460 KB
	640 x 480 (VGA)
JPEG NORM.	293 KB

Images at the processed 2832 x 2128 6 megapixel 'processed' resolution do look soft and generated (not sharp and detailed as you'd see from native resolution). The NORMAL compression ratio doesn't introduce very much in the way of JPEG artifacts (compared at least to FINE) and looks like the best choice for most. The images get sharper and more detailed at the lower resolutions, the 2048 x 1536 3 megapixel images look considerably more detailed and cleaner (obviously I'll talk more about image quality later in this review).

ISO (Sensitivity) Adjustment

ISO equivalence on a digital camera is the ability to increase the sensitivity of the CCD to allow for faster shutter speeds and/or better performance in low light. The way this works in a digital camera is by "turning up the volume" on the CCD's signal amplifiers, nothing is without its price however and doing so also amplifies any noise that may be present and often affects colour saturation.

The 6900Z features four selectable ISO sensitivities of 100, 200, and 400. To give you an idea of the amount of noise to expect at different sensitivities under different lighting conditions we now shoot our simple test target under both good and low light.

Good light (9 EV)	Low light (3 EV)
ISO 100, 1/30 s, F4.0	ISO 100, 1.6 s, F3.2
ISO 200, 1/60 s, F4.0	ISO 200, 1 s, F3.2
ISO 400, 1/147 s, F4.0	ISO 400, 1/3 s, F3.2

The 6900Z produces relatively noise free images at ISO 100 (though there are a few exceptions, which I'll cover in the Image Quality section of this review) and also performs well at higher ISO sensitivities. ISO 200 is perfectly usable for day to day shots in lower light situations, going to ISO 400 ramps up the noise so that it begins to affect detail, I'd only use it in extreme circumstances.

I was also surprised to see hot pixels in the low light test shots (above), these weren't particularly long exposures, nor was the camera warm, yet clearly visible stuck pixels are sprinkled all over the images (even at 1/3 sec on the ISO 400 shot).