Examples of High ISO Images With Canon 40D
ISO refers to the sensitivity of a camera's film or digital sensor to light. The Canon 40D, a digital SLR (single lens reflex) camera, has a maximum ISO setting of 3200. The ISO number itself does not reveal anything about the particular sensitivity (i.e., ISO is not a unit), but ISO values can be compared to determine sensitivity. An exposure made at 3200 ISO, for example, is twice as sensitive to light as an exposure made at 1600 ISO.
Exposure
A high ISO value makes the Canon 40D's digital sensor more sensitive to ambient light. This means that a photograph can be taken with a relatively lower shutter speed and still allow for proper exposure. Canon 40D High ISO images can be identified by the qualities of the exposure. For instance, if a fast-moving subject such as a sports player appears well-exposed and not blurry despite an apparently low amount of ambient light, the photograph was probably taken with a high ISO setting.
Noise
Noise refers to the amount of grain in a photograph. A very noisy image will have off-colored pixels scattered over the surface of the image. Noise increases as ISO value increases; a low ISO image will produce relatively little noise, while a high ISO image will produce a lot of noise. While noise reduction software can be helpful in reducing the pixelation in an image, you can still identify high ISO images from the Canon 40D by the presence of noise.
Sharpness
The Canon 40D's noise reduction software that helps reduce the effects of noise at high ISO values causes some loss of sharpness in noisy areas. This is typically most apparent in the edges of the subject, which tend to be blurrier than the same edges in a low ISO image. Fine details such as wrinkles on a person's skin or the texture on the surface of a basketball will also be noticeably blurry in high ISO images.
Color Banding
High ISO images taken with a Canon 40D will also exhibit a bit of color banding. Color banding refers to the choppiness of color, whereby a color gradient appears as distinct bands of color rather than a smooth transition between two colors. Color banding can also be the result of highly compressing a digital image, however the banding present in high ISO images will show characteristic noisy patches at the borders of the color bands.
Prints
Prints of high ISO images taken with a Canon 40D will show grain similar to high-grain film of non-digital cameras. While digital grain caused from high compression will tend to be patchy, grain in prints from high ISO images will be more uniform. The effects of grain can be minimized by reducing the dimensions of an image prior to printing, and Canon 40D high ISO images (even up to 3200 ISO) will display almost no grain on a full-resolution image reduced to an eight- by 10-inch print.
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