Digital Images

Computer Users’ Group

January 18, 2006


Digital Cameras

Digital cameras vary in size, number of pixels, lens quality, zoom ratio and minimum focus as well as interchangeability. Digital cameras save all pertinent data such as exposure, camera name, date, time in a file called the EXIF data file. Some programs get more from that file than others.

Size: Cameras come in a variety of sizes and formats. You can get one in your phone or portable music player, get one as small as a couple of dominos or large and hefty with multiple interchangeable lenses or just about anywhere in between.

Number of Pixels: How many pixels do you need? A rule of thumb suggests that an image should have 150 pixels per inch to print well (300 is better). So a 6 x4 inch print requires 150x6x150x4=540,000 or half a megapixel minimum. A 12 x8 print requires 4 times that number or 2,160,000 or 2 megapixels. To print that size image at 300 pixels requires about 8 megapixels. (Cameras have either a 4:3 or 3:2 aspect ratio. In 3:2, a 10x8 print requires a 12x8 image with 2 inches cropped off). Most cameras today have adequate pixel counts.

Lenses: Lens quality varies from barely adequate in cheaper cameras to excellent, especially in those cameras that interchangeable lenses. If you have a 35 mm film camera with interchangeable lenses you should seek out a digital camera that will use your existing lenses.

Zoom: Zoom ratio is the magnification that lets you bring the subject closer to you. Use the optical zoom ratio for comparison purposes; any other zoom ratio, such as digital does nothing that you can’t do better in your computer.

Memory: The type of memory used should be considered. Removable memory cards make it easier to move images to your computer using a card reader instead of the usually slower process of dumping them directly from the camera which also uses up batteries. If you own any memory cards, finding a camera that uses them could save you money or at least add additional storage when on a trip.

Image Format: Cameras can save images in several different formats. If yours gives you a choice, consider the following. JPG (JPEG) is a compressed format where some information may be lost. Consider it for images that you don’t plan on processing in your computer. TIF (TIFF) is an uncompressed format readable by both PC and MAC. Best for saving images that will be processed which can later be converted to JPG to save space. Don’t forget to dump the TIF when you save the JPG or you’ll use space and not save it. However, you may want to archive the TIF to a CD to preserve the original which has all of the EXIF data. RAW is a format unprocessed by your camera giving you the greatest latitude for correction and enhancement in your computer.


Scanners

There are basically three types of scanners: Sheet-fed, flatbed or film although there are hand scanners and a camera can be used in a copy stand to simulate a scanner. Scanner resolution is measured in “dots per inch” or dpi similar to “pixels per inch” discussed above. The resolution that you use to scan should be determined by the ultimate use of the image. If the image is to be used without enlargement then 150 to 300 dpi should suffice. If, however, you want to print a 35 mm (1.5x1 inch) slide at 8x10 then you will need to scan at 8x150 or 1200 dpi minimum and preferably 8x300 or 2400 dpi. Preview the image to see what corrections need to be made such as brightness or contrast. Get the image as good as possible with the scanner to preserve all of the data contained in the image.

Sheet Fed: These scanners accept a single sheet of paper so that any bound document needs to be un-bound and books cannot be scanned.

Flatbed: These have a flat class surface on which to place the item to be scanned similar to a copy machine. The most common and most flexible type of scanner. Some may include an adapter for scanning film or slides.

Film: Most can scan slides or film strips. Film can be either positive as in slides or negatives from film cameras. Scanning film rather than prints removes the changes and artifacts introduced by the film processor.

OCR: OCR is optical character recognition in which the scanner and it’s software attempt to turn scanned text documents into digital format text. You can scan any printed text into your computer so that you can edit it and re-publish it. While the process is getting better, some correction is often required but it can save retyping and entire document. Document with unusual formatting are the most difficult.



Printers

Printers come in three flavors; dye sublimation, inkjet and laser. Dye sub printers are not too common but appear as photo printers. Without ultra-violet protection items printed by dye sub printers may fade. Inkjets are the best for producing quality photo images. Inks based on dye will fade with time. Newer pigment inks used in some printers will survive nearly a century. Be aware of the King C. Gillete factor; if you give razors away people will have to buy blades from you. Most printers are sold below cost because all of the money is in the ink. Some use multicolor cartridges where if one ink runs out you have to replace the cartridge. Others use individual cartridges, some using as many as six or eight colors for better color rendition. PCWorld estimates ink costs at between 1 and 7 cents a page for black and 6 to 18 cents a page for color depending on the printer. There are lower cost cartridges for sale by independents and you can also fill your own. You will not void the warranty unless the replacement actually causes the failure. Laser printers are best for text and are good for color graphics but are not up to ink jet or dye sub for photo quality. Color laser prices continue to fall. Lasers tend to be larger than other printers. There are combination devices that combine a

The following comments mostly concern ink jet printers.

Resolution: Generally, resolution is different across the page and down the page and may range from 9600 across the page to 1200 dpi down the page. Ink spreading makes it less significant than it otherwise might be. Your image resolution and printer resolution do not have to match; print images with resolutions of between 150 and 300 dpi; the printer resolution is immaterial as long as it is equal to or better than the image resolution.

Interface: Most printers today use the USB interface. They plug into the USB port of your computer. That is better than the old Centronix interface with the parallel interface cable with the large connectors.

Power: Newer printers so not have to be turned on; they turn on when data is fed to them. Just don’t remove power when the power on light is lit; it needs to park the print heads to prevent them from drying out.

Paper: Printer paper can be plain, high resolution, matte, or glossy. The paper sold by your printer manufacturer may be best but experiment to find the lowest cost approach to your needs. Tee shirt transfers and canvas can also be handled by most printers.

Conclusion: You can find reviews for all of the above at www.pcmag.com , www.pcworld.com and at www.cnet.com. Click on cameras, scanners or printers and also see the buying guides provided there.


Graphics Programs

There are many graphics programs from the $699 Photoshop to the free Paint that came with Windows. Photoshop has a lower cost sibling; Photoshop Elements. Picasa and Irfan View are free and can do limited processing. Another free program that does a lot of what Photoshop does is PhotoPlus 6.0. Serif software made PhotoPlus 6.0 available free after they came out with PhotoPlus 8.0. You need to register to receive emails about new products but that’s a small price to pay for a free program. Go here http://www.freeserifsoftware.com/ and click on PhotoPlus to download it. Another free open source program is GIMP available at www.gimp.org. It’s very complex and requires a support program to install it that is also available at the site. Picture Publisher is sometimes found on the Internet but is no longer made or supported. Most digital cameras come with some limited software. We’ll process an image using some of the above tools.

Learning: No tutorial, especially one as short as this can teach you how to use a graphics program. Many come with a tutorial and all have a Help file. But you can learn best by doing. Open an image in the program that you’ve chosen and immediately do a save as to save it with a new name. That protects the original file from being over written and is something you should do whenever you modify an image. You can delete the original if you like the updated one better.

With the image open, check out the tools in the tool palette to see what each one does. Try them! Experiment! Read the tutorial!

The following will give a brief outline of what can be done. Each program may do it in a different manner.

Brightness-Contrast: There are several ways to adjust these picture parameters. Often there is a function that will attempt to correct everything at once as in Picasa’s “I’m Feeling Lucky”. Others may have Auto Contrast and Auto Brightness which will attempt to correct the condition. Most have a manual control where you can move a slider to reach the desired effect. Many have a histogram where you can see the value of each intensity level. This can aid in setting the adjustments.

Color Balance: Very subjective but precise work requires the monitor to be calibrated and all external light to be excluded. Then getting the printer colors to match the monitor is another whole subject. Try to do the best you can making the sky blue, the grass green and the skin flesh colored..

Sharpness: Programs have a way of sharpening an image. Often the best way is with the tool called the unsharp mask. Too much sharpening can lead to artifacts so be careful.

Effects: Effects that can be applied to an image vary from program to program but generally include water color, oil painting and canvas; pattern removal for images scanned from a printed document; framing; diffusion; blurring; de-speckling; distortion and many others. Some programs may refer to them as filters.

Clone Tool: Many programs have a way of copying one part of an image to another part of the image. As the tool is moved both the source and recipient tools move together to copy good data over a blemish. Only Picture Publisher lets you know where both tools are at all times.

Layers: Many programs have layers that can be added over the original (background layer). Each can accept modifications, enhancements or embellishments and the number of layers can be large. When all modifications are complete, the layers can be collapsed onto the original to complete the image. Images can be saved with layers intact for further processing by saving the image in the program’s native format.

Size or Resize: Programs give you the option of changing both the size and the resolution of an image. If you scan an image at 600 dpi and want to print it at 150 dpi you need to change the resolution from 600 to 150. Depending on the program, you may have to change the size in inches to be 4 times the width or height. Picture Publishers permits you to select Maintain Image Size so that changing the resolution automatically adjusts the size and vice versa.

Convert: You can convert an image to grayscale like a B&W photo or to line art such as text or line drawing. Sometimes scanning text as grayscale and then converting to line art produces better results than scanning as line art. Grayscale can have brightness and contrast adjusted before conversion. Try it both ways to see which is best.

Format: Images to be manipulated should be in an uncompressed format. TIFF and BMP are uncompressed, JPG is compressed. When you are done with editing, you can save the image as JPG to save space. Note that when saving to JPG, you will be asked how much compression to apply. More yields a smaller image size at the expense of some loss of image quality. Because the compression usually affects small areas that the eye can’t discern very well, compressing of images may not be noticeable. Try several compression ratios and see if you can tell the difference then use the one that offers the smallest size with the best results. Remember to either dump the TIFF file or archive it to disk to save the original. During processing you may want to save a file with all of the layers intact. Then you must use the program’s native format (PSD or PDD for Photoshop).

Selection: There are selection tools that can outline a portion of an image that can then be copied and pasted into a new location, just removed or pasted into a new image. Tools can be free hand, magic that follow a boundary, rectangular or elliptical. You can make a selection and then use the edit menu or use CTRL-X to delete, CTRL-C to copy and CTRL-V to paste. Santa has been done that way for many years. Just paste him in and adjust him for the proper size.


Good digital cameras can be had for as little as $150 and what you save on film and processing will more than pay for it and you’ll have the ability to be creative with the images you’ve captured. Prints can be obtained on line, at most stores such as Walgreens or you can print you own. And you only have to print what you want. Scanners can help take all of your old prints and negatives and burn them to a cd and the old shoe box can be thrown away. Using an image processing program you’ll get images that satisfy you and can be manipulated to achieve what you desire. All you need to do this is the desire to try. There is no special talent or ability required; just the willingness to experiment and to learn.