Capturing the image: Pixels and image size / quality
Digital cameras do not take sharp images. This is nothing to do with the focusing. It is caused by the interpolation of colour data. Each pixel is only able to record a single colour - red, green or blue. To record the information for the missing colours, it takes the data from adjacent pixels that are sensitive to these colours. But as the colour data is increased, so the sharpness suffers.
Fortunately, it is relatively simple process to increase the apparent sharpness of these images. It is not the actual sharpness that is increased, but the contrast at the borders between light and dark tones. A measure of the density gradient across the border is called the acutance. If you have ever processed black-and-white films, you may have come across high-acutance developers, such as Paterson Acutol, which increased this gradient by chemical means.
With digital images, the sharpening can be done at various stages, either in the camera or on a computer. Most digital cameras aimed at the consumer market do the sharpening in camera. This is why an image from the PowerShot G7, for example, looks so sharp and vivid when you come to print it. Canon assumes that images from a digital compact camera will normally go to an ink-jet printer, so in-camera processing optimises them for this purpose.
The situation is different with professional cameras. Here, the final destination of an image might be a web site, an ink-jet print, a newspaper or a magazine - or a combination of these. Each needs a different set of parameters applied to the image file for the best results. This means that it is necessary to keep image processing within the camera to a minimum.
Digital cameras capture RGB images - that is, an image composed from different ratios of red, green and blue light. If the image is to be published in a magazine, it must be converted to CMYK (cyan, magenta, yellow, black). For the best print quality, any sharpening should be applied after the CMYK conversion. Sharpening done in the camera cannot be removed at a later stage, so it is best to apply little or no sharpening until after the file is converted to CMYK. The images from your camera will look a little soft when you first see them on a computer monitor,
However, if your images are not destined for publication, you might want to boost the sharpness with the in-camera processing. This is easy to do. Simply go the Parameters on the Camera menu and increase the sharpness to a level between ‘1’ and ‘5’.
If you have moved from the EOS-1D to the EOS-1D Mark II, you might find that the images look less sharp. There are two reasons for this. First, images captured with the EOS-1D Mark II have less noise than images from the earlier model.
This provides a smoother gradation, which can give the impression of reduced sharpness. Also, the EOS-1D does not have a phase plate. This makes the images look sharper, but can increase the level of false colours. If you want images from the EOS-1D and EOS-1D Mark II to be similar, set the sharpness parameter on the EOS-1D Mark II to ‘1’.
Even after making these changes, images from more recent EOS professional digital cameras can still look softer than those from earlier models. This is because recent models have more pixels, which means that pixel size is smaller (11.5µm on the EOS-1D; 7.2µm on the EOS-1Ds Mark II). Smaller pixels are more sensitive to camera shake, as a smaller movement will cause the image to move across more pixels. You need to hold the camera steadier - ideally on a tripod.
For the same reason, sports photographers also need to re-think their shutter speeds, as blur from subject movement will be more apparent on cameras with more pixels. Where possible, consider increasing the shutter speed, even if this requires an increase in ISO speed.
However, if you shoot RAW images, rather than JPEG, none of these camera settings will have any effect. The RAW image receives little processing within the camera, leaving you with a ‘digital negative’. You apply the parameter settings when you open the RAW image in programs such as Digital Photo Professional or Adobe Photoshop. The file is always opened as a copy, leaving the original RAW file untouched. This means you can experiment with different parameter settings to obtain the result you want - and can apply different settings if the image file is going to be used for different applications.