02/03/09 © Vic Dohar, 2009 1

Introduction to Digital Images

Presented and Written by

Vic Dohar

02/03/09 © Vic Dohar, 2009 2

Purpose

• To provide you with the basic concepts and understanding of digital images

• Explain why knowing about digital images is important in today’s technical environment

• Demonstrate some basic editing tasks that even you can perform on software that is free

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Why Do I Need To Know About Digital Images?

• It is important to have a basic understanding of digital images for:

– Advertising images of your artwork by uploading them to the internet/web page

– Participating in juried exhibitions that only except digital submissions

– Editing your digital images (crop, rotate, resize)

– Managing an inventory of your images as a reference for subject matter

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Juried Digital Submissions

• Jury only accepts digital images:

“The image submitted should not exceed 72 dpi and the image should fit proportionally within 6″x6″ dimension thus if the image is not a square do not stretch the image to make it fit as a square. However, the image should fill most of the area within 6″x6″ appropriately.” (source RBC Canadian Painting Competition)

• You will have to know how to create a digital image that is 6″ x 6″ at 72 DPI.

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Juried Digital Submissions

• Jury accepts digital images following strict rules and guidelines

– File format

– File size (dimension)

– File name

– Image requirements

(source TWSA Prospectus and Entry Instructions 2009)

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Uploading to Web Page

• Limits or restrictions for posting images on web galleries (source www.canartscene.com)

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Image Quality in Digital Images

• Understanding quality plays an important role in manipulating digital images for different requirements

– You want to make prints or Giclees (very high quality)

– You want to create cards or book marks to sell at exhibitions (high quality)

– You want to email your latest set of paintings to prospective buyers or galleries (medium quality)

– You want to personalize your business card by incorporating the design from one of your paintings (low to medium quality)

– Upload images to the web (low quality)

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Now It’s Time to Get Technical

• Brace yourselves … relax … get comfortable

• Pretend you’re back in school

• Try and think like a computer geek

• You may even learn something new tonight

• Please ask questions at anytime

• Are you ready?

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What is a Digital Image?

• Representation of a picture or photograph (analog) by digital means obtained either from a digital camera or scanner

• A digital image is comprised of columns and rows each containing any number of pixels defining its dimension

• Each pixel has a colour

• A digital image is stored as a file in various formats(e.g. JPG, TIFF, GIF, BMP, raw, etc…)

• Image dimension and compression are important properties that define the size and quality of a digital image

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Let’s Begin With The Pixel

• A coloured square that is the smallest part of a digital image

• Sometimes referred to as a dot or a cell

onepixel

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The Mega Pixel

• A mega pixel simply means 1,000,000 pixels(something times a million)

• Mainly associated with digital cameras defining the maximum number of pixels in a digitalimage

• MS Explorerprovides infowhen a file isselected

Dimensions: 2048 x 1536Date Picture Taken: 09/05/2005 9:19 AMCamera Model: Canon PowerShot A70Type: JPEG ImageSize 2.12 MB

Taken from a 3.2 MP digital camera, because image contains 3,145,728 pixels (2048 x 1536)

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The Mega Pixel Myth

• “My 8MP camera is twice as good as a my old 4MP camera.” TRUE / FALSE?

2000 pixels

20

00

pix

els Total number of pixels

= 4,000,000 (4MP)

4000 pixels

40

00

pix

els

Total number of pixels= 16,000,000 (16MP)

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The Mega Pixel Myth

• To obtain an image with a quality twice as better, the mega pixel count has to be 4x greater(e.g. 16MP compare to a 4MP)

• Therefore there is not a significant difference in image quality between a 8MP and 10MP camera

• What does this mean? It means you can save some $$$ when shopping around for a digital camera.

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The Mega Pixel Myth

• For example, these two Nikon cameras have the same internal workings, but one has a higher MPand a slightly better lens

• Keep the money in your pocket for cameras with similar features but offer different MP ratings

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OK – Now What?

• You now know what comprises a digital image. We will now go through the steps in how to obtain, edit and save a digital image and prepare it for a web gallery and/or juried submission

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Digital Imaging Steps

1. Obtaining digital images of your artwork

2. Performing edits on the digital image

3. Saving the digital image

4. Preparing digital image for various needs

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Obtaining Digital Images of Your Artwork

• Sources:

– Ask for a Photo CD when developing film

– Scan existing pictures/slides of artwork

– Scan artwork directly

– Take a picture with a digital camera

• Ask a friend that has all these toys to help!

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Using a Digital Camera

• Read the camera’s manual to ensure picture is taken with the highest quality (image compression) and highest resolution (maximum image dimension)

• Use tripod along with timer setting

• If digital camera has manual settings, bracket several shots with varying exposures

• Use adequate lighting and if possible adjust camera setting to correct white balance

• Do not use a flash

• Make sure artwork is not behind glass

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Issues with Images from Digital Cameras

• Uneven/poor light distribution (brightness)

• Keystone/distortion around perimeter

• White balancing is off (warm or cool)

• Usually require to crop image

• Majority of these issues can be corrected when editing the digital image

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Using a Scanner

• Recommend using a see-through scanner allowing to place scanner on artwork rather than placing artwork upside-down on a flat-bed scanner

• Can scan at various resolutions, but recommend 300 DPI providing a good quality

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Issues with Images from Scanners

• May contain noise due to surface textures, however it provides even light distribution

• Images from scanners usually require more disk space

• Multiple scans from a large format painting will have to be digitally stitched together(Hint! Use camera’s panoramic software)

• If image has to be rotated do so during the scanning process

• Require to crop image, but the image dimension and resolution will be accurate

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Demonstration #1

• Digitally stitch together images scanned in multiple sections using software that came with digital camera

• Use Google’s Picasa 3 to compare images taken with a digital camera with one that is scanned

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Digital Imaging Steps

1. Obtaining digital images of your artwork

2. Performing edits on the digital image

3. Saving the digital image

4. Preparing digital image for various needs

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Digital Image Editing Software

• Numerous software applications available for editing digital images

– Free/shareware applications from internet (Google’s Picasa 3, PhotoFiltre, GIMP, …)

– Purchase (Adobe Photoshop, Corel Paint, Paint Shop Pro, …)

• Also look at the abilities of software that comes with camera and scanner

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Software Musts

• Ability to rotate and crop image

• Ability to resize/re-sample image, change or scale dimension and/or resolution (each have their own terminology, practice to get familiar)

• Ability to adjust image

– Remove noise (smooth image) from a scanned image

– Lighten/darken image (auto-adjust image)

– Correct colour

– Adjust white balance

• Almost all software now-a-days has these features

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Basic Editing Steps

i. Rotate image to correct orientation (if required)

ii. Crop image (if required)

iii. Adjust/edit image (if required)

iv. Save image with a meaningful name

If you perform these basic steps, you will have a master image from which to apply adjustments and create other images at different sizes or resolutions.

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Demonstration #2

• Using Google’s Picasa 3 to perform the following on a digital image taken from a camera

– Rotate/straighten image so it is square

– Crop image

– Adjust image (brighten, darken)

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Editing With Picasa• From the library of thumbnail pictures, double-

click on an image to edit

• Basic edits are available from theBasic Fixes menu

• Remember to save edits betweena crop and/or rotation

• Save edits by returning to thelibrary of thumbnail images and pressing the Save to Disk button

• When saving edits, a backup of theimage is saved in the Originalsfolder allowing you to undo edits

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Digital Imaging Steps

1. Obtaining digital images of your artwork

2. Performing edits on the digital image

3. Saving the digital image

4. Preparing digital image for various needs

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Saving Digital Images

• Each digital image is stored as a separate file

• The most common file format from digital cameras is JPEG or JPG (Joint Photographic Experts Group)

• Professional cameras also store in RAW or their native format

• Assign meaningful names to files

• Always have a “master” file from which variations can be created

• When saving JPG files on some applications, you have to specify the degree of image compression

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Image Compression

• Compression reduces the file size on disk by joining pixels with similar value/colour

• All JPG files have a certain degree of compression; once compressed you can not revert back to its original state (this is known as lossy compression) … unless you save a copy of the original image!

• Follow this general rule comparing compression, quality and file size on disk

– High compression = lower quality = smaller file size

– Low compression = higher quality = largerfile size

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Comparing Degrees of Compression

Low compressionHigh quality

250 KB

High compression

OK quality

71 KB

Extreme compressionPoor quality

7 KB

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Why is Compression Important?

• When submitting digital images to a jury, want high quality so as not to loose any detail

• High quality images are not required when displaying images on the internet/web pages

– Saves on disk space

– Displays/downloads/uploads faster

– Public does not have access to your high-quality images

• Resolution for images on the web can be 96 DPI

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Demonstration #3

• Using Google’s Picasa 3 to perform export an image at a higher compression/lower quality

– Export image to another folder

– Specify image dimension and quality

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Exporting Image From Google

• From library of thumbnails, select images and select Export Picture to Folder from the File drop down menu

• Specify location and name of folder

• Select image size(longest dimension)

• Select quality(preset or custom)

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Quick Review

• This is what you have learned so far:

– Digital images can be used for various purposes

– Know what is a pixel and mega pixel

– Mega pixel ratings is really not that important comparison between digital camera models

– Obtain digital images from cameras or scanners

– Basic editing steps

– Why compression of digital images is important

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Digital Imaging Steps

1. Obtaining digital images of your artwork

2. Performing edits on the digital image

3. Saving the digital image

4. Preparing digital image for various needs

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Preparing a Digital Entry for a Jury

• Ensure you know what is required for digital entry

– High quality image

– Pixel dimensions

• Calculate image dimensions based on size requirements

– 4”x 6” image at 300 DPI

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Image Size

• Image size is referred to the size of the image when it is displayed (usually in inches)

• The size can be any since the image can easily be enlarged or reduced (zooming)

• Base your calculations on the image dimension or number of pixels

– 4”x 6” image size at 300 DPI (resolution)

– In pixels this is 1200 x 1800 pixels

• Resolution is the number of pixels per unit of measurement (e.g. one inch)

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The Image Formula

• All three properties are related as follows:

Dimension (pixels) = Resolution (DPI) x Size (inches) Size (inches) = Dimension (pixels) ÷ Resolution (DPI)Resolution (DPI) = Dimension (pixels) ÷ Size (inches)

DIMENSION(pixels)

RESOLUTION(DPI)

SIZE(inches)

÷ ÷x

1200 x 1800 pixels

300 DPI 4 x 6 inches

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One Word of Caution

• When submitting digital images to a jury, avoid “over”-editing the digital image using tools like smoothing, burring, sharpening, removing blotches or errors, etc…

• Adjustments that do not accurately portray the original piece of artwork may disqualify entry in a juried show

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Demonstration #4

• Using the export function from Google’s Picasa 3 to prepare an image for the TWSA submission

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Image for TWSA Submission

– File format must be JPG, highest quality, no compression (error)

– Entry image should be no smaller than 900 pixels in the longest dimension

– Also prepare entry for catalogue, high-resolution 4”x 6” at 300 DPI

– Name file accordingly

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Review & Tips

• Read camera manual to determine the maximum pixel dimension of an image and set camera accordingly

• Be aware of compression/quality settings on camera High quality = low compression = large file sizeLow quality = high compression = small file size

• Familiarize yourself with software’s resizing/re-sampling methods of digital images

• Have at least one master image at the highest resolution possible from which other images at lower resolution or different dimensions can be created

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Review & Tips

• Give meaningful names to your digital files:RideauCanal_Scan300DPI.jpgRideauCanal_Master.jpgRideauCanal_Camera.jpgRideauCanal_Thumbnail.jpgRideauCanal_400x250.jpgRideauCanal_MAA_Web_Gallery.jpg

• Consider investing in software to manage and organize your digital images (Google’s Picasa)

• Practice, practice, practice and have fun!

• Contact me for help: vicdohar@rogers.com