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Get the Best Digital Images Possible What’s it all about anyway? Lorna Olsen Information Get the Best Digital Images Possible What’s it all about anyway? Lorna Olsen Information Technology Services North Dakota State University

Issues to Consider Resolution n Image Size n File Size n Intended Use of Issues to Consider Resolution n Image Size n File Size n Intended Use of the Image n File Formats n

Issues to Consider n Image size u Pixel dimensions of original image (width x Issues to Consider n Image size u Pixel dimensions of original image (width x height) determine maximum size the image can be without losing quality

Issues to Consider n File Size u The more pixels in an image – Issues to Consider n File Size u The more pixels in an image – the larger the file size u Larger file sizes mean: t longer Web page load times t Longer print times for printed images

Issues to Consider n What’s the intended use of the image? u Print t Issues to Consider n What’s the intended use of the image? u Print t Print dimensions are more important than pixel dimensions t Higher resolutions produce better quality printed image

Issues to Consider u Online viewing t File size is the most important consideration Issues to Consider u Online viewing t File size is the most important consideration t Pixel dimensions determine approximate viewing size

Resolution n What IS resolution? u Ability to resolve detail (changes in contrast between Resolution n What IS resolution? u Ability to resolve detail (changes in contrast between pixels) u More commonly used to describe total number of pixels in captured image u The greater the number of pixels captured, the better the resolution – but – u More pixels means larger file sizes

Types of Resolution n Image Resolution u # of pixels per unit of length Types of Resolution n Image Resolution u # of pixels per unit of length measured in pixels per inch (ppi) u A high resolution image contains more pixels than an image of the same dimensions with a low resolution

Types of Resolution n Monitor Resolution u # of pixels per unit of length Types of Resolution n Monitor Resolution u # of pixels per unit of length on a monitor measured in pixels per inch (ppi) u Image pixels translate directly into monitor pixels t If image resolution is higher than monitor resolution, image appears larger on screen than it prints

Types of Resolution Common Monitor Resolutions u 640 X 480 u 800 X 600 Types of Resolution Common Monitor Resolutions u 640 X 480 u 800 X 600 u 1024 X 768 u 1280 X 1024 n Newer monitors can have even higher resolutions n

Types of Resolution The same image displayed at two different monitor resolutions will appear Types of Resolution The same image displayed at two different monitor resolutions will appear at different sizes n The monitor’s physical size also influences the size the image appears at n

Types of Resolution n An image displayed on a 19” monitor set to display Types of Resolution n An image displayed on a 19” monitor set to display 1024 X 768 pixels looks much larger than the same image displayed on the same monitor at 1280 X 1024 pixels

Types of Resolution n Output or Printer Resolution u # of ink dots per Types of Resolution n Output or Printer Resolution u # of ink dots per inch produced by printer measured in dots per inch (dpi) u Higher resolution printers combined with higher resolution images generally produce the best quality

Print Resolution n Appropriate resolution for printing is determined by both the printer’s resolution Print Resolution n Appropriate resolution for printing is determined by both the printer’s resolution and the screen frequency (lines per inch – lpi) of the halftone screens used by the printer to produce images

Getting the Right Print Resolution n Computer Graphics Rule of Thumb: u Scan image Getting the Right Print Resolution n Computer Graphics Rule of Thumb: u Scan image at 1. 5 to 2 times the screen frequency used by the printer t Screen frequency is usually 133 lpi u 133 lpi x 1. 5 = 200 ppi correct scanning resolution to use

Digital Cameras Camera resolution is measured in terms of the maximum number of pixels Digital Cameras Camera resolution is measured in terms of the maximum number of pixels the image sensor is capable of capturing n Megapixels – 1 megapixel = 1 million pixels n 3. 1 megapixel camera produces images with 2048 X 1538 pixel dimensions n

Digital Cameras n Assume you need at least a 150 ppi image resolution for Digital Cameras n Assume you need at least a 150 ppi image resolution for good print quality u To get a good 4 X 6 print – you need to capture at least 600 X 900 pixels (150 X 4, 150 X 6) u For 8 X 10 print – you need at least 1200 X 1500 pixels

Digital Cameras Some cameras have multiple resolution settings (pixel dimensions) available n Use lower Digital Cameras Some cameras have multiple resolution settings (pixel dimensions) available n Use lower resolutions for smaller file sizes if you don’t need to enlarge the image for printing n

Image Size n Best to create the image at the final size you want Image Size n Best to create the image at the final size you want to use u You can always resize images smaller without loss of quality u Resizing the image larger later can degrade image quality

Image Size n Digital Cameras u Start with camera set at highest resolution setting Image Size n Digital Cameras u Start with camera set at highest resolution setting if you’ll need to print a larger image t Use image editing software to resize print dimensions/increase image resolution u If image will be used on Web page, reduce the camera resolution setting to reduce the file size and image dimensions when viewed on screen

Image Size n Scanners u Set scanning resolution as high as necessary t Scan Image Size n Scanners u Set scanning resolution as high as necessary t Scan at higher resolutions for both print and online viewing for best quality u Choose the desired print dimensions before scanning t Best to scan larger and rescale smaller, than to scan small and then try and resize larger

Image Size n If you’ve scanned at a higher resolution (200 -300 dpi): u Image Size n If you’ve scanned at a higher resolution (200 -300 dpi): u If image is to be used online, use image editing software to lower image resolution to 72 -96 ppi t Image detail captured by higher resolution scan will still be there, but file size will be smaller t Improves quality of images printed from Web pages

File Formats n JPEG (. jpg) Joint Photographic Experts Group u Image is automatically File Formats n JPEG (. jpg) Joint Photographic Experts Group u Image is automatically compressed so file size is smaller as camera saves the image as a JPEG file u Most digital cameras use the jpg format by default u Some cameras use a proprietary file format you’ll need to convert to useable formats using image editing software

File Formats u When editing JPEG images, save in another format while editing – File Formats u When editing JPEG images, save in another format while editing – each time you resave a JPEG image you lose more data, lowers image quality

File Formats n n Many digital cameras have different quality settings u Hi – File Formats n n Many digital cameras have different quality settings u Hi – usually uncompressed TIFF files u Fine – lowest compression JPEG file, larger file size u Normal – more compression, smaller file size u Basic – most compression, smallest file size Each setting compresses the image with more or less loss of data – affects file size and image quality, not image resolution

File Formats Most scanners allow a choice of different file formats to save the File Formats Most scanners allow a choice of different file formats to save the final scanned image n Choose the format that’s best for the intended use of the image n JPEG is best for online images due to image compression – smaller file sizs n TIFF is often best for printing images – no image compression, no loss of data n

Questions? ? ? Questions? ? ?