Just below, the Sony Alpha A100 is compared to its closest competitor, the Pentax K10D. The top row presents the overall scene at ISO 100. Below that are 100% scale crops taken from full-resolution images at each ISO setting from its respective camera. These shots were taken at night using aperture priority, automatic white-balance and set ISO sensitivity.

The Sony Alpha A100 shows low noise levels below ISO 400. At ISO 400, noise become noticeable at 100% but has little effect on image details. ISO 800 and 1600 images from the A100 show increased noise and reduced details. This is where the performance of the Alpha A100 is below that of the average DSLR.

Although the A100 and K10D share the same sensor, image noise characteristics and sensitivity differ. The night crops below show that the K10D preserves more details at all ISO and shows a little less noise starting at ISO 400. In this setup, the measured exposures are the same but the A100 produced a slightly brighter image. This is because the sensitivity gain is higher on the Alpha. In other words, when it is set at ISO 100, the Sony Alpha A100 captures an image with a lightly higher sensitivity.