Digital imaging basics - Foundations

Optimal foundations

Instead of a chemical film, a digital camera like the Epson R-D1s uses a light-sensitive chip. Each of its 6.1 million diodes controls a pixel, which together make up the motif, like a mosaic. These pixels are arranged on the surface of a 17 by 25.5 APS film. The fact that the digital camera is oriented to a classic set of dimensions has beneficial effects on image quality.

The sensor sets the frame

A compact camera is forced to focus as sharply as possible on a tiny chip, even with the shutter wide open. The usual artistic effect of a wide aperture can't be easily achieved, resulting in the blurriness of one plane of the image. This stylistic aperture effect is desirable, for instance, in order to gently suppress the background of a portrait. A larger sensor, such as that used in the Epson R-D1s, allows you this freedom.

You will notice in many pictures that the sky and other surfaces are relatively free of noise pixels. These colourful little irritants occur when the chip reacts with too much sensitivity, for instance due to longer exposure times or higher ISO values. This can be the case at twilight, for example, when the light sensitivity must be increased.

Happily, sensors in the APS-C size are not simply packed with more photodiodes, but their sizes are also increased. On these larger diodes, logically, more light can fall, so they needn't overshoot the sensitivity target, like their smaller, noise pixel producing cousins.

High-quality raw materials for pictures

At optimum resolution, an image from an Epson R-D1s consists of 6.1 million pixels. Thus it must be greatly enlarged in order to see the individual components. That would be the case, for instance, if the photo were viewed in Photoshop enlarged one hundred times. You would see coloured rectangles, the so-called pixels - a word created from the words "picture" and "element".

In the enlargement, you can see the
pixels which make up the image.

Each of these colour dots is mixed using the three primary colours red, green, and blue. The mixing ratio is expressed in computer language with up to 36 digits of 0s and 1s, i.e. 36 bits. This allows nuances of 2 to the 36th power, a palette of 68,719,476,736 (over 68 billion) colours! The Epson R-D1s, too, has this same richness of colour.

The sheer amount of pixels and colours can naturally only be stored in correspondingly large files. These have the advantage that even in poster size, they exhibit thorough colour gradients and the finest detail. However, a storage card which can contain only a few megabytes of data will quickly fill up. If you are intending to save the pictures in a small format anyway, you should dial down the image quality a little in the camera menu, perhaps to a resolution of 2240 x 1488.

Packing photos into formats

The Epson R-D1s uses two file formats, each of which sets a standard for practical or high-quality use of image data: JPEG and ERF. The TIF format is seen equally often in the world of digital photography. Each of these formats has its own advantages and limitations.

JPEG

JPEG is now the standard format used by digital cameras. In this form, image information can be compressed, so that the file size shrinks. This allows more images to be stored on a single storage card. How greatly they are compressed can be set either in the menu of the digital camera or in nearly any image editing program. However, the information losses will also reduce the image quality to the same extent.

RAW

Raw data with the file extension ERF ("Epson Raw Format") stores the information from the image sensor with no changes at all. There are different RAW formats used by different vendors, and they have different file extensions. Most image editing programs can't normally read this image information, so Epson Photo Raw is available instead. You can also process them using the power Photoshop image editing program, since Epson provides a plug in for this purpose. Thanks to the true fullness of detail of the RAW format, shadings are more finely recorded and, unlike the strongly compressed JPEGs, rich detail appears. However, the photos must be balanced afterwards.

TIFF

TIFF files are normally saved without compression. Each pixel contains the full information delivered by the digital camera. This leads to large file sizes, but at the same time, no loss of data. A further advantage of the TIFF format is that, like JPEG,it can be used by almost any program.

From the camera to the hard drive

Unlike film, you can easily empty a Secure Digital Card (SD card) quickly when you need fresh storage room for pictures. Usually, the pictures are stored to a hard drive in a computer and printed to photo paper at the same quality as their chemical predecessors. In the computer, they are archived or creatively manipulated using an image editor program.

The easiest way to work is by either using an Epson printer with cardslot to read the data or purchase a separate reader for the card. It is often connected to the computer using a USB cable. Once it is successfully installed, operating systems like Windows XP detect when a storage card is inserted into the device, and then automatically offer to transfer the pictures into a folder on the hard drive.