Scanners and Photoshop
March 15, 2011
Today we will use Photoshop to process images. First we will see how photos, maps and other "hard copies" of images can be converted to digital format appropriate for inserting into reports, PowerPoint presentations and Web sites.
My students and I use scanners to convert aerial photographs into digital format that can be set up for use in a geographical information system (GIS), enlarge selected sections for printing and improved stereo views, and printing multiple copies at a fraction of the cost of photographic reproductions.
The image to the left is of Cajón Pass, where Interstate 15 climbs from San Bernardino, California to the Mojave Desert, crossing the San Andreas fault near the point where the 1857 Fort Tejón earthquake rupture terminated. Aerial photographs are taken as an aircraft flies at a constant elevation in a straight line, using a special large-format (9 inch square) film, taking pictures that overlap by about 55%. Because consecutive images are taken at different angles with respect to ground features, viewing a pair of adjacent images with special apparatus (mirror stereoscope) allows the viewer to see the topography, trees and cultural features in 3-D. Because photographic film (and paper for prints) is based on light-sensitive silver salts, and because the camera and aircraft require skilled technicians, aerial photography is not cheap. I recently heard the price quoted for using new aerial photographs to produce a contour map (2 foot contour interval) of 2 square miles at $24,000. This print cost $18 in 1988, when the price of silver was significantly less than it is today.
Aerial photographs have been part of flood control and soil conservation projects since World War II, when aerial reconnaissance developed into a critical military asset. After that war, this technology was used to photography much of the USA. One of my students used old aerial photographs to investigate hazardous waste sites in southern California, tracking several sites from the time before waste disposal operations began until the present. There are condominiums build over old oil field waste lagoons near La Habra, California, something most residents of that development probably do know realize.
Aerial photos are useful but expensive and sometimes unique and irreplaceable. Therefore, when working with aerial photos, I scan the photo and keep the original on file, working with the electronic copy or a print from the laser printer.
I used to scan my photographs (printed on Kodak paper) but now use a digital camera. Trade-offs in buying a camera and setting it up for photos include:
Size of image - large number of rasters yields detail but uses up memory faster, small images allow you to store more images but details are lost.
Optical zoom - digital zoom is useless, the image looks bigger but you get the same raster problem as if you simply magnify a digital image.
Storage - memory cards, mini-CDs, several options available
Software for downloading
SLR or display to view/frame picture
PHOTOSHOP
Photos, scanned or taken with a digital camera, are seldom precisely what you want. Today we will examine some of the features I use to get my mediocre photographs to look more or less decent when I post them on the Web or insert them into PowerPoint presentation.
Click on either photo to see the enlarged image, then right click on that image and "save as" to your usual location. If you prefer, locate another photo on the Web or open a photo from your own file of digital photos, and use that photo for your experimentation.
I'll describe my biases, please contribute your experiences to the in-class discussion.
In the first photo, the prof is looking for a rock. In the second, erosion is occurring in the background. In the third, the prof is pointing at an exposure of the San Andreas fault.
Open Photoshop and open a photo - any photo that includes at least one person. I will demonstrate some tools useful for modifying photographs.
Rotate image
Image - Adjust - Levels
Lighten or darkens entire image
Image - Crop
After selecting that part of image you wish to retain,
usually with Rectangle tool
Dodge and Burn tools
Lighten and darken selected parts of an image
Clone stamp (Alt-click)
Duplicates offset rasters into selected space.
Resize image:
The image to the left was sent, along with 4 others, from an associate working to solve a flooding problem. My problem with this image is, it is TOO BIG - too many rasters. You might need high-resolution digital images when photographing a wedding with the intention of printing glossy, large hard copy prints, but when the intention is viewing the image on the computer monitor, such large files are overkill. This particular set put my email inbox over my allocated mailbox size limit, making it impossible for me to send email until I had moved the attachments and saved the message to a private folder.
Always "save as" under a different file name. You can never recover what has been thrown away during image processing, and you can never add resolution or colors to an image that were not there to begin with except by painting over things. Filters remove information. I keep my original scans and digital photos on file in case I need to redo my work.
For making backgrounds -
Layers menu - duplicate
layer
Turn off original layer
Use 'opacity' sliding bar to make duplicate layer more
'transparent'
"Save as" your favorite image file type, to your Backgrounds
folder.
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Your assignment: either use one of your favorite digital photos (does everyone out there have a cat but me?) or find a photograph on the Web and download that photo. Use Photoshop or Photo Editor to significantly improve it as you see fit (crop, color balance, sharpen, resize to fit screen nicely, etc.) and save the result. Then use Photo Editor to abuse it (stained glass effect, too sharp or smudged, paste a mustache on the candidate, be creative) and save the result. Fox News (sic) reports that candidate Clinton's campaign used digital technology to darken her opponent's skin and whiten his teeth for one ad.
Attach all 3 photos (original, improved, tortured, in .jpg format) to an e-mail message and them to me.
Please try to complete assignment by noon on Friday, March 18.
