Tips for Digital Imaging

JPEG or GIF And Monitor Settings
For displaying photographs on the web JPEG is much preferred over GIF file format. This is because GIF is limited to only 256 colors. GIF is fine for clip art and logos but most photographs will look layered where a color needs to blend from one shade to another. You should be using 24 or 32 bit color (also called 'true color') to see photographs in JPEG file format at their best. You will need to check your computer's screen setting adjustments to see if you can run 24 or 32 bit color depth at the screen resolution of your choice. If you are using Windows, just right click on any empty space on your desktop. Select properties from the drop down window and then select settings. In the lower right hand corner of this dialogue you will see a screen resolution setting slider. On the lower left hand side you will see the color selection drop down menu. Use the color selection drop down menu to select 24 or 32 bit True Color. Some newer graphics display cards offer 32 bit color as the only 'True Color' setting. See a screen capture image of Windows monitor properties setting dialogue box.

Monitor Calibration
In order to produce digital images that will print with colors and a tonal range that approximate what you see on your monitor, you'll need to do a basic monitor calibration. The simplest way to accomplish this is to adjust your monitor's gamma. To check and adjust your monitor's gamma level and color depth settings click on the following link to see a Gamma and Color Settings Check Chart. You should be able to see each individual shade from pure black to pure white and all the colors smoothly blending together without any banding or speckle like effects. You will probably need to use more than the test page's recommended 25% for brightness. I've found 50-80% brightness to be a more likely average setting. After this basic calibration is done it's usually not very difficult to get a feel for the adjustments you'll need to make with your imaging program's color and tonal range tools and your printer's tools to get a decent match between the printed output and the color and tonality of the image represented on your computer screen.

If you need to have exact color matching, you may want to consider buying a monitor calibration software/hardware solution. Monaco Systems, Eye One and other companies offer color calibration products that allow you to make an ICC profile based on your monitor's actual color characteristics. You can read more about ICC profiles and ICC color managed workflow two headings below in this document.

Those of you who are contemplating buying a flat panel monitor should know that mid to low end flat panels are a very poor choice for serious image editing due to the narrow angle of view, mediocre color accuracy and limited contrast range. Flat panel monitors intended for advanced image editing should have a contrast ratio of 500 to 1 or higher and have some sort of advertised 'wide angle view' capability.

Color Space, Color Bit Depth
The RGB (red, green, blue) color space is the default for all consumer scanners and digital cameras. Another example of a color space is CMYK (cyan, magenta, yellow and black). CMYK is the color space of all printers that use inks. There are several calibrated versions of the RGB color space that encompass different areas and amounts of the visible color spectrum.

Scans done with the RGB color space produce image files consisting of these three colors blended together to produce all other colors as well as the different shades of red, green and blue. For the web and home digital darkroom RGB is the only color space you need to be familiar with. One of the newest calibrated versions of RGB is sRGB. The sRGB color space is a shared project of Microsoft and Hewlett-Packard. It is designed to help make color matching between computer screens and the latest generation printing devices easier to do. sRGB has a color gamut that doe not match the color gamut of most types of commercial printing inks very well. It may not be the best choice when the output will be for offset press generated publications. Microsoft and Hewlett-Packard think sRGB solves a lot of color matching problems in a home digital darkroom environment that is not using ICC color management. sRGB is certainly the best choice when your output is going to be used mainly for presentation from a computer monitor (web site placement, email, PowerPoint etc ).

You will need an imaging program that has color management options to be able to choose between sRGB and other calibrated RGB color spaces. The lower end programs may use either sRGB or their own un-calibrated version of RGB without telling you which of these color spaces is actually being used. Programs that have color management options will usually allow you to choose the exact color space you want to work with. I find that I prefer to work in sRGB for my web imaging and Adobe RGB for my Epson printers. sRGB does make the best color match for computer screen viewing in graphics viewers and web browsers. Some of the home photo printers by both HP and Epson are actually optimized for sRGB images. If you aren't using an ICC profile workflow, try sending the same photo to your printer in sRGB and Adobe RGB and see which print you like best. We will discuss calibrated color spaces and ICC workflow in more detail in the next section of this article.

There is also a "bit depth" to digital image files. Each pixel recorded during the scan has color information assigned to it. Each pixel's color information is saved as a number of bits (8 bits = one byte) for each color channel (red, green, blue). Depending on the quality of the scanner it can save from 8 bits to 16 bits per color channel for each pixel recorded. Most of the consumer scanners save 12 bits per channel. Multiply this figure by 3 (for each color channel red, green and blue) and you get the color bit depth of the scanner. A scanner that can save 12 bits of color information for each color channel per pixel is a 36 bit scanner. A scanner that can save 14 bits of color information for each color channel per pixel is a 42 bit scanner. All of the current 12 and 14 bit scanners are 'interpolated' up to 48 bit color output (16 bits per color channel). We will discuss the merits of 48 bit color in more detail in the next paragraph of this document. The higher color bit depth scanners can produce a broader range of colors and tonality.

Since computers can only deal with multiples of 8 bit "computer words" (1 byte), scanners must interpolate the number of bits up or down and/or add null bits (zeros) to make the scanned pixel's color information available to the computer and imaging program as either 24 bits (three 8 bit words or 3 bytes) or 48 bits (6 bytes). A 30 bit color scanner will produce 24 bit color files. A 36 or 42 bit scanner can interpolate up or down to produce either 48 bit or 24 bit color files.

48 bit color can only be saved as TIFF files. Working with 48 bit color images is only supported by a few high end imaging programs like Adobe Photoshop and PhotoImpact ( limited 48 bit color editing in PhotoImpact). Adjusting your image color and tonality while it is in 48 bit color will provide smoother gradations between colors. After all color and tonal range adjustments have been completed the image can be converted to 24 bit color for printing or monitor presentation. This conversion down to 24 bit does not negate the advantage of adjusting color and tonal range while the image is in 48 bit mode.

It doesn't take a math genius to see that 48 bit image files are twice the size in kilobytes or megabytes as 24 bit image files. 48 bit color is the future of digital imaging. All of today' scanners and almost all of the high end digital cameras that can output RAW files are capable of producing 48 bit color image files. As computers become more powerful and hard drives become larger, the larger file sizes of 48 bit images and the longer image processing times are just not the issues they used to be. I find it hard to believe that so few of today's image editing programs support editing in 48 bit color mode. For now, editing in 48 bit color is most appropriate for fine art photographers and photographic service bureaus that can afford Photoshop.

Scanners and computer screens and digital cameras operate in the RGB color space but printers use inks in the CMYK color space. Fortunately for the home digital darkroom enthusiast, converting RGB to CMYK and producing accurate color prints is not the nightmare it used to be. All current home color printers accept RGB data from your imaging program and convert to their CMYK output automatically. Professionals preparing scanned images for offset press output may still do this conversion manually.

Comments On Some Image Editing Programs
Four programs that I recommend for digital imaging are Adobe Photoshop, Adobe Photoshop Elements, Paint Shop Pro and PhotoImpact

Photoshop at 6 through CS2 has an excellent selection of tools and professional level features for the RGB imaging enthusiast. The quality of Photoshop's tools and the ability to work with 48 bit images, handle calibrated color spaces and support an ICC profile color managed workflow make Photoshop the best choice for professional photographer. Photoshop is also suitable for amateur photographers who need or want the best imaging program available today. Cost; retail boxed list about $600.00

Adobe Photoshop Elements has most of the basic tools that Photoshop has but will not edit 48 bit images (converts to 24 bit color upon opening). Elements has limited color management workflow tools. Elements seems to have the same excellent image manipulation algorithms as Photoshop. Elements 3 now includes a camera raw file converter. Cost; retail boxed about $100.00

Paint Shop Pro will open most 48 bit images but coverts them to 24 bit upon opening. Paint Shop Pro has limited color management workflow tools. Paint Shop Pro has a very full featured toolbox. Cost; retail boxed about $90.00 downloaded about $80

PhotoImpact has a huge variety of tools, options and extra features. PhotoImpact will allow color and tonal adjustments on 48 bit images. It also has limited color management workflow tools. This program is a bit of a memory and resource hog. Don't buy this program if you don't have at least 512mb of RAM and a PIII of 400mhz or faster. I'm sure it will work with less RAM and a slower processor but it might be 'painfully' slow in getting most jobs done with high resolution files. Cost; retail boxed about $90.00 downloaded about $80

There are also image viewing and cataloging programs. These programs allow you to quickly find and view the images you have stored on your hard drives or CDROM's without waiting for a complex image adjustment program to open on your PC. Two of the best of these are ACDSee and ThumbsPlus

I'm currently using Photoshop CS2 for all of my image editing and printing needs. Many of these programs are available as downloadable evaluation software. You can try a program for free and decide if it is appropriate for your needs before having to pay for the program. You can click on any of the product links above to learn more about each of these program's features or download a time limited evaluation copy of the software.