Digital cameras have a filter you will never find on a film camera. The purpose of the filter is to make the image less sharp. The filter is called a low pass filter and it is part of the sensor assembly.

Digital images can suffer from moire patterns and the filter on the sensor is there to eliminate moire patterns, which it does by reducing sharpness.

Sharpness is not the same as focus or lack of blur. You can apply sharpening to an out of an out of focus or blurred image and it will still look bad. Sharpness in digital images is achieved by adjusting the contrast of edges. If it is over done you end up with halos or bright white lines around objects in your picture. There are many techniques for sharpening.

If your camera makes JPEG files, you should examine the setting for sharpening, and perhaps increase the sharpness. If your camera makes raw files, you can adjust sharpness when converting from raw to JPEG, which seems to have its devotees as some professionals have suggested a work flow with sharpening at three separate stages. Others prefer to have sharpening turned off, or at least turned down, until the final step before output to a rendering device (monitor, printer, etc.). When an image is resized, the resampling affects edge contrast so regardless of whether you sharpen along the way or not, the final step should be to apply sharpening.

Original photo

Same photo as at left with contrast and
sharpening applied in Photoshop


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