Here you will find all of the information (appropriate links (including Dropbox folder links for homework), notes, reminders, etc.) for Photoshop 101 (Photoshop Basics for Artists) Week Ten.
NOTE: Please respect the work, rights, and privacy of participating artists. You may view the uploaded homework efforts from the class within the Dropbox folder, but you may not download or manipulate their work in any way. Anya and I will be downloading uploaded homework or classwork images when needed/appropriate, but we will never share anyone’s images outside of the class without express permission from the author. All files in the Drobox folders will be deleted at the end of the course. In addition, please know that classes will not be recorded to respect each participant’s learning experience.
If there are files required for the week’s homework, then they will be available in a folder called “WeekX_Resources” in the appropriate week’s folder. You will need to download to files in this folder to complete the week’s homework. However, please be sure not to remove or add anything to this folder.
Here’s a few notes for today’s class:
PS Basics for Artists Week Ten- The Scanning Option
What are scanners?
The basic principle of a scanner is the capturing of an images from materials like photographic prints, posters, magazine pages and similar sources for computer editing and display. Scanners work by converting the image on the document into digital information that can be stored on a computer. This process is carried out by a scanning head, which uses one or more sensors to capture the image as light or electrical charges.
Types of Scanners:
- Flatbed scanners also called desktop scanners, are the most versatile and commonly used scanners.
- Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. A sheet-fed scanner looks a lot like a small portable printer.
- Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorized belt. This type of scanner typically does not provide good image quality. However, it can be useful for quickly capturing text.
- Drum scanners are used by the publishing industry to capture incredibly detailed images. They use a technology called a photomultiplier tube (PMT). In PMT, the document to be scanned is mounted on a glass cylinder. At the center of the cylinder is a sensor that splits light bounced from the document into three beams. Each beam is sent through a color filter into a photomultiplier tube where the light is changed into an electrical signal.
- 3D scanners are a bit different than traditional scanners in that they collect distance point measurements from a real-world object and translate them into a virtual 3D object.
Scanner resolution refers to the number of pixels captured by the scanner sensor and is measured in dots per inch (dpi). The higher the dpi, the greater the scanner’s ability to capture detail.
For example, a scanner with a resolution of 1200 dpi can capture 1200 pixels per inch of an image.
Very high-resolution image scanners are used for scanning for high-resolution printing, but lower-resolution scanners are adequate for capturing high-quality images for computer display.
The scanner’s resolution is determined by the number of sensors in the scanning head.
Specifics that you do not necessarily need to dive into:
The core component of the scanner is the CCD array. CCD is the most common technology for image capture in scanners. CCD is a collection of tiny light-sensitive diodes, which convert photons (light) into electrons (electrical charge). These diodes are called photosites. In a nutshell, each photosite is sensitive to light – the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site.
Here are the steps that a scanner goes through when it scans a document:
The document is placed on the glass plate and the cover is closed. The inside of the cover in most scanners is flat white, although a few are black. The cover provides a uniform background that the scanner software can use as a reference point for determining the size of the document being scanned. Most flatbed scanners allow the cover to be removed for scanning a bulky object, such as a page in a thick book.
A lamp is used to illuminate the document. The lamp in newer scanners is either a cold cathode fluorescent lamp (CCFL) or a xenon lamp, while older scanners may have a standard fluorescent lamp.
The entire mechanism (mirrors, lens, filter and CCD array) make up the scan head. The scan head is moved slowly across the document by a belt that is attached to a stepper motor. The scan head is attached to a stabilizer bar to ensure that there is no wobble or deviation in the pass. Pass means that the scan head has completed a single complete scan of the document.
The image of the document is reflected by an angled mirror to another mirror. In some scanners, there are only two mirrors while others use a three mirror approach. Each mirror is slightly curved to focus the image it reflects onto a smaller surface.
The last mirror reflects the image onto a lens. The lens focuses the image through a filter on the CCD array.
The filter and lens arrangement vary based on the scanner. Some scanners use a three pass scanning method. Each pass uses a different color filter (red, green or blue) between the lens and CCD array. After the three passes are completed, the scanner software assembles the three filtered images into a single full-color image.
The filter and lens arrangement vary based on the scanner. Some scanners use a three pass scanning method. Each pass uses a different color filter (red, green or blue) between the lens and CCD array. After the three passes are completed, the scanner software assembles the three filtered images into a single full-color image. However, most scanners today use a single pass method.
Another imaging array technology that has become popular in inexpensive flatbed scanners is contact image sensor (CIS). CIS replaces the CCD array, mirrors, filters, lamp and lens with rows of red, green and blue light emitting diodes (LEDs). The image sensor mechanism, consisting of 300 to 600 sensors spanning the width of the scan area, is placed very close to the glass plate that the document rests upon. When the image is scanned, the LEDs combine to provide white light. The illuminated image is then captured by the row of sensors. CIS scanners are cheaper, lighter and thinner, but do not provide the same level of quality and resolution found in most CCD scanners.
Resolution, Sharpness, Bit-Depth:
Scanners vary in resolution and sharpness. Most flatbed scanners have a true hardware resolution of at least 300x300 dots per inch (dpi). The scanner’s dpi is determined by the number of sensors in a single row (x-direction sampling rate) of the CCD or CIS array by the precision of the stepper motor (y-direction sampling rate).
For example, if the resolution is 300x300 dpi and the scanner is capable of scanning a letter-sized document, then the CCD has 2,550 sensors arranged in each horizontal row. A single-pass scanner would have three of these rows for a total of 7,650 sensors. The stepper motor in our example is able to move in increments equal to 1/300ths of an inch. Likewise, a scanner with a resolution of 600x300 has a CCD array with 5,100 sensors in each horizontal row.
Most scanners have a scan area that is either letter size (8.5x11 inches, 21.6x27.9 centimeters) or legal size (11x14 inches, 27.9x35.6 centimeters).
Sharpness depends mainly on the quality of the optics used to make the lens and the brightness of the light source. A bright xenon lamp and high-quality lens will create a much clearer, and therefore sharper, image than a standard fluorescent lamp and basic lens.
Resolution terms you many encounter:
Optical resolution: This is the actual number of pixels read by the CCD which measures the intensity of the light that is reflected from the image to be scanned, and converts it to an analog voltage. If a scanner has a resolution of 600 x 2400 dpi, its optical resolution is 600 dpi, which means that it can resolve 600 bits of data per inch.
Hardware resolution: Using a precision stepper motor to double-step or quadruple-step the carriage, the scanner’s sub-scanner resolution can be increased. For example, a scanner can have an optical resolution of 1200 dpi, but a hardware resolution of 1200 x 2400 dpi (because it double-steps the carriage to increase the vertical resolution).
Of course, many scanners proclaim resolutions of 4,800x4,800 or even 9,600x9,600. To achieve a hardware resolution with a x-direction sampling rate of 9,600 would require a CCD array of 81,600 sensors. If you look at the specifications, these high resolutions are usually labeled software-enhanced, interpolated resolution or something similar. What does that mean?
Interpolation is a process that the scanning software uses to increase the perceived resolution of an image. It does this by creating extra pixels in between the ones actually scanned by the CCD array. These extra pixels are an average of the adjacent pixels. For example, if the hardware resolution is 300x300 and the interpolated resolution is 600x300, then the software is adding a pixel between every one scanned by a CCD sensor in each row.
Another term used when talking about scanners is bit depth, also called color depth. This simply refers to the number of colors that the scanner is capable of reproducing. Each pixel requires 24 bits to create standard true color and virtually all scanners on the market support this. Many of them offer bit depths of 30 or 36 bits. They still only output in 24-bit color, but perform internal processing to select the best possible choice out of the colors available in the increased palette. There are many opinions about whether there is a noticeable difference in quality between 24-, 30- and 36-bit scanners.
On your computer, you need software, called a driver, that knows how to communicate with the scanner. Most scanners speak a common language, TWAIN. The TWAIN driver acts as an interpreter between any application that supports the TWAIN standard and the scanner. This means that the application does not need to know the specific details of the scanner in order to access it directly. For example, you can choose to acquire an image from the scanner from within Adobe Photoshop because Photoshop supports the TWAIN standard. Fun fact is that TWAIN is not an acronym. It actually comes from the phrase “Never the twain shall meet” because the driver is the go-between for the software and the scanner.
Ok, back to practical stuff:
General tips/info and link to scanner I use most often:
Again—It is very important to have a scanner in which you can TURN ALL ENHANCEMENTS OFF!!!
Something like Image type options will usually configure settings (auto exposure, resolutions, etc.) that would best serve the average scan of that type. Consider that any selections with scanner software (like a Marquee) may reinitiate auto-enhancements.
Always select somethin akin to ”Professional Mode” in the Mode list if applicable.
Document “Type” options usually fall under the headings of Reflective (for scanning documents or photos) or Film (for scanning film or slides).
- Gutter distortion is a term that most often describes an issue with scanning books in which the book’s gutter (the space down the center of an open book where the pages are bound together) causes a page to scan to be slightly skewed. However, I use this term often to describe distortions that can happen due to noticeable imagining variations that occur at the outermost edge of the glass plate (often when a warpable material (like paper) slightly skews at the scanning “well edge.”
In Photoshop:
The Photomerge™ command combines several photographs into one continuous image. For example, you can take five overlapping photographs of a city skyline, and then merge them into a panorama. The Photomerge command can assemble photos that are tiled horizontally as well as vertically.
Tips for a successful PS Photomerge (Mostly for Photography):
Overlap images sufficiently
Images should overlap by approximately 40%. If the overlap is less, Photomerge may not be able to automatically assemble the panorama. However, keep in mind that the images shouldn’t overlap too much. If images overlap by 70% or more, Photomerge may not be able to blend the images. Try to keep the individual photos at least somewhat distinct from each other.
Use one focal length
If you use a zoom lens, don’t change the focal length (zoom in or out) while taking your pictures.
Keep the camera level
Although Photomerge can process slight rotations between pictures, a tilt of more than a few degrees can result in errors when the panorama is assembled. Using a tripod with a rotating head helps maintain camera alignment and viewpoint.
Stay in the same position
Try not to change your position as you take a series of photographs, so that the pictures are from the same viewpoint. Using the optical viewfinder with the camera held close to the eye helps keep the viewpoint consistent. Or try using a tripod to keep the camera in the same place.
Avoid using distortion lenses
Distortion lenses can interfere with Photomerge. However, the Auto option adjusts for images taken with fish-eye lenses.
Maintain the same exposure
Avoid using the flash in some pictures and not in others. The blending features in Photomerge helps smooth out different exposures, but extreme differences make alignment difficult. Some digital cameras change exposure settings automatically as you take pictures, so you may need to check your camera settings to be sure that all the images have the same exposure.
Homework: (2 points) Join the scanned pieces of the color chart and adjust as you see fit. Submit the joined/edited jpg.
Homework (Part Two-required) (2 points): Please do your best to “correct” the small scanned image provided. Submit the edited jpg.
Bonus Homework: (4 points): If possible, please try to scan one of your own works. Correct as needed and upload a jpg that does not exceed 2MB.
Alternate Bonus: (4 points) For those without access to a scanner: I am uploading a small, (poorly) scanned Christmas-themed alla prima to the Dropbox resources folder for this past week. Combine and intuitively “correct” the Xmas image to capture those bonus points!!! (Upload as a jpg.)