For example, I would reduce the image quality if it meant that I could prevent motion blur in my photo. Digital photography for beginners can be confusing. You also have to learn about how your camera looks at light. Metering modes are there to tell your camera how you want it to look at a scene.
The picture below was taken on spot metering mode. If you were to take the same photo using the evaluative mode, you would end up with a completely different exposure.
This is also covered in my free video training. Understanding this basic photography point might be the key to understanding why your photos are coming out underexposed or overexposed. The histogram shows you a mathematical review of exposure after the photo has been taken. It tells you how evenly exposed a photo is. New photographers often find it frightening to understand.
But it is easy, and I tell you how. How do you work out which one you should be using? When you understand what each mode does, the one that will be suitable for your situation becomes a lot clearer. But this has a major side effect. A shallow depth of field. You can use this in a creative way. So that the whole scene remains in focus. This tutorial walks you through everything you need to know about choosing the right aperture and the DoF for the right situation.
I look back on some photos now and wonder what I was thinking. The white balance changes the colour cast of the entire photo. It is responsible for the overall warmth. It can determine whether your photo appears blue or orange, cold or warm.
Especially with tungsten light. The sooner you learn about this basic photography idea, the more accurate your photos will look. Or why people use longer focal lengths for portraits? It also influences the perspective. I cover which focal length you would want to use in different situations.
As well as their possible side effects. This means that your sensor is much smaller than professional SLR cameras. It is cropping your image. The crop factor has a range of effects on your photos. It creates a narrower viewing angle and will influence your lens purchases in the future. For those beginner photographers, research what lenses will help your field of photography first.
Polarizing filters only allow light into the lens from a certain direction. This results in the removal of glare and reflections from non-metallic objects.
Water and glass are the most affected, as well as haze from the sky. Cutting out these reflections and anomalies will make for more natural saturated colours. This looks fantastic and it cannot be replicated in post-production.
Photography beginners, I will walk you through the 10 step process of taking sharp photos like a professional. It covers everything from choosing the right aperture and shutter speed to shooting in RAW. Topics include everything from self-portraiture and creating a body of work at home to curating a photo essay and how to unify poetry and photography.
Visit: Leica Akademie UK. Canon has launched a pair of online initiatives to reach out to customers during this time. Canon Connected is a free content hub that's designed to be inspirational, educational and entertaining.
Videos come from Canon ambassadors, filmmakers, experts and influencers across Europe, including Pulitzer Prize-winning Daniel Etter and year professional sports photographer Eddie Keogh. The manufacturer has also launched Canon Live, an online portal to get advice on all Canon imaging products from cameras to printing.
A team of product experts are available, seven days a week, via the manufacturer's new Live Chat Service.
In addition, it will showcase free online live events from both Canon and its retail partners featuring ambassadors such as Wanda Martin, David Newton and Richard Walch on everything from lighting to vlogging to print. Visit: Canon Live. DxO is hosting a series of free live webinars throughout April and May, enabling you to watch along as experts share their step-by-step workflows on shooting and processing images — and you have the opportunity to ask questions in real time.
Visit: DxO Webinars. There are always some great Adorama deals available on photographic kit, but the retailer has gone the extra step in supporting creatives during the coronavirus crisis with a series of daily Facebook Live programs called Coffee With Creators. Hosted by photographer Seth Miranda, the idea is to bring creators together for fun, laid-back conversations to stay inspired and motivated.
As an added bonus, there will be surprise live giveaways at the end of some broadcasts based on the hashtags Adorama and CreateNoMatterWhat — a community campaign to engage creators who are stuck indoors, and to bring the artistic community together and to encourage each other.
Visit: Adorama on Facebook. Each week the company will be sharing new tips, exercises and techniques for you to try out at home, alongside FAQ sessions with Fujifilm product specialists, and asking photographers to involved and share their images using the FujifilmFromHome hashtag.
Visit: Fujifilm X Stories. One of the most fun and informative series comes from Laowa, which is hosting a weekly Meeting Macro Masters session on Facebook. Taking place every Friday night in April and May, nine macro photography specialists will discuss macro techniques, tools and tips.
Everything from macro hacks to ideas to shoot at home to photographing insects in the wild. When the Control panel opens, double-click the Display icon or command to display the Display Properties dialog box, then click the Settings tab on the dialog box and check the Screen Area setting.
If you have a 14" monitor and 21" both set to x pixels, the pixels per inch are different. The same pixels are spread across a larger screen on the larger monitor so the pixels per inch falls. Imagine the image printed on a balloon. As you inflate it, the image gets larger. Measure the width of the screen display and enter it on this line.
Enter the horizontal resolution your screen is set to on this line. In the illustration above it divides by 14 for a ppi of In the illustration above it divides by 57 for an image width of 14 inches.
Exercises 1. If your image is x , how large will it be when displayed on a 72ppi screen? Will it fit on a 14" screen? If your image is x 8, how large will it be when displayed on a 72ppi screen? Will it fit on a 10" screen? The Arithmetic of Printing Images Printer resolutions are usually specified by the number of dots per inch dpi that they print.
Generally ppi—pixels per inch—refer to the image and display screen and dpi—dots per inch—refer to the printer and printed image. In this course we sometimes use them interchangeably For comparison purposes, monitors use an average of 72 ppi to display text and images, ink-jet printers range up to dpi or so, and commercial typesetting machines range between 1, and 2, dpi.
Since image sizes are described in pixels and photographic prints in inches, you have to convert from pixels to inches. To do so, you divide the image's dimension in pixels by the resolution of the device in pixels per inch ppi. However, if the output device prints ppi, the result changes to a 2. At 72 ppi it's 8. Exploring Print Sizes This figure and Part 3a on the Excel worksheet "Image Size Calculator" calculate the size of print you can expect from a given file size and printer resolution.
Enter the width of the digital image in pixels on this line. Enter the height of the digital image in pixels on this line. Enter the number of dots per inch dpi printed by your printer on this line. If your printer prints dpi, how wide will an image have to be in pixels, to get a 6-inch wide print?
That task is handled by the software program you use to print the image. For example, if you place an image in a program such as QuarkXpress or PageMaker, its printed at the size you specify in those programs. Pixels begin to show when the print is enlarged to a point where the pixels get get so big that the pixels per inch ppi fall too low. If your printer can print a sharp image only at or more pixels per inch, you need to determine if the size of the image you plan on printing will fall below this level.
Let's say you have a scanned image and want to print it at a certain size. When you enlarge or reduce an image like this, the ppi change. To find out what the pixels or dots per inch becomes, you convert from the image's original size in pixels to its pixels per inch.
Exploring Print DPI This figure and Part 3b on the Excel worksheet "Image Size Calculator" calculates the dpi of a print when you use a program that automatically resizes a file for printing.
Enter with desired width of your printout on this line. A formula on this line calculates the height of the print so it has the same aspect ratio as the digital image. To come The Arithmetic of Color Depth Resolution isn't the only factor governing the quality of your images. Equally important is the number of colors in the image. When you view a natural scene, or a well done photographic color print, you are able to differentiate millions of colors.
Digital images can approximate this color realism, but whether they do so on your system depends on its capabilities and its settings. How many colors there are in an image, or how many a system can display is referred to as color depth, pixel-depth, or bit depth.
Older PCs are stuck with displays that show only 16 or colors. However, almost all newer systems include a video card and a monitor that can display what's called bit True Color. It's called true color because these systems display 16 million colors, about the number the human eye can discern. To see if your Windows system supports True Color not all do , display Window's Start menu, point to Settings to cascade the menu, and then click Control Panel.
When the Control panel opens, double-click the Display icon or command to display the Display Properties dialog box, then click the Settings tab on the dialog box and check the Color palette setting. How do bits and colors relate to one another? It's simple arithmetic. Here's a table to show you some other possibilities.
Name Bits per pixel Formula Number of colors Black and white 1 21 2 Windows display 4 24 16 Gray scale 8 28 color 8 28 High color 16 65 thousand True color 24 16 million Black and white images require only 2-bits to indicate which pixels are white and which are black. Gray scale images need 8 bits to display different shades of gray.
Color images are displayed using 4 bits 16 colors , 8 bits colors , 16 bits 65 thousand colors called high color, and 24 bits 16 million colors called true color. Some cameras and scanners will use 30 or 36 bits per pixel. These extra bits are used to improve the color in the image as it is processed down to its bit final form. Review: Bits and Bytes When reading about digital systems, you frequently encounter the terms bit and byte.
The bit is the smallest digital unit. It's basically a single element in the computer that like a light bulb has only two possible states, on indicating 1 or off indicating 0. The term bit is a contraction of the more descriptive phrase binary digit.
Bytes are groups of 8-bits linked together for processing. Since each of the eight bits has two states on or off , the total amount of information that can be conveyed is 28 2 raised to the 8th power , or possible combinations. Exploring Color Depth This figure and Part 4 on the Excel worksheet "Image Size Calculator" calculate the total number of pixels in an image when you enter the images width and height in pixels.
Enter any bits per pixel from the table of color depths on line 7 and following on this line. A formula on this line calculates the number of possible colors by raising the number 2 to number of bits per pixel. File sizes are shown in bytes, kilobytes, and megabytes.
All you need to do is have your slides, negatives, or prints scanned. You can do this yourself if you have a scanner, or you can have them scanned onto a CD disc or floppy at your local photofinisher or lab. The resolution of these images is much higher than you get from all but the most expensive cameras, so if quality is an issue this is really the best route to take.
Most scanning services are available when you have your film developed. The problem with this is that you pay to scan the good, the bad, and the ugly. Scanning Basics Color scanners work by creating separate red, green, and blue versions of the image, and then merging them together to create the final digital image.
Some scan all of the colors in one pass while others take three passes, a slower but higher quality method. Which method is used depends on the scanner's image sensor. Most scanners use linear CCDs arranged in a row. Those that require three passes use a single row of photosites and pass different filters red, green, or blue in front of the sensor for each pass or use three different light sources.
As the image is scanned, a light source travels down the photo some print and document scanners instead move the document past the light source. The light source reflects off a print or passes through a transparency and is focused onto the image sensor by a mirror and lens system.
Because of this mirror and lens system, the sensor does not have to be as wide as the area being scanned. The horizontal optical resolution of the scanner is determined by the number of photosites on its sensor. However, the vertical resolution is determined by the distance the paper or light source advances between scans.
Reflective or Transparency Some scanners are designed to scan photos and other documents, called reflective copy. Others are designed to scan slides and larger transparencies. Transparency scanners scan 35mm slides and negatives and some go much larger. As the size increases, so does the cost. Resolution and Resolving Power As you saw in Chapter 2, there are two types of resolution. Optical resolution is the "native" resolution of your scanner as determined by the optics in your scanner hardware.
Interpolated resolution is resolution enhanced through software, and is useful for certain tasks such as scanning line art or enlarging small originals. However, in photography interpolation adds no new detail to the image yet makes the file size a lot larger. For these reasons, you should never scan a photograph at a setting higher than the scanners optical resolution.
The true resolution of the scanned image depends on more than the scanner's resolution. It's ability to capture details is known as its resolving power. This resolving power is determined not just by resolution but also by the quality and alignment of it's lenses, mirrors, and other optical elements and the accuracy with which it moves along the image when scanning. It's possible for a very well designed scanner with a lower resolution to outperform a cheaper one with a higher resolution.
Dynamic Range Scenes in the real world are full of bright light and deep shadows. The extremes are referred to as the dynamic range. Film doesn't have anywhere near the dynamic range of nature, so it's always a struggle to accurately capture a scene on film. It's like trying to squeeze one of those coiled snakes back into the can after you've taken the lid off to let it pop out. Ansel Adams Zone System was developed to make this easier with black and white film, but color film can't be manipulated in the same way.
When film is turned into prints, they have even less dynamic range so something is always lost. Display screens have a dynamic range closer to slides than to prints. That means that when you scan images for the Web, you need to be sure you capture the full dynamic range. How much dynamic range you can capture depends on its ability of the scanner's ability to register tonal values ranging from pure white to pure black. It must also be able to accurately map the tones on the original to tones on the digital image.
If the scanner doesn't have enough tonal range, details will be lost in shadow areas, highlights, or both. A scanner's dynamic range can be measured and given a numeric value between 0. Common flatbed scanners typically register values from about 0. New or bit scanners claim a dynamic range up to around 3. Although image density ranges from pure white to pure black, no detail can be seen in those areas. As you progress from pure white into slightly darker areas, detail emerges.
The point at which a scanner can detect this detail is called DMin minimum density. The same is true at the other end of the spectrum. The point at which detail can be detected before the image goes to pure black is called DMax maximum density. The dynamic range is calculated by subtracting DMin from DMax. For example, if a scanner has a d-min of 0. Color depth As you saw in Chapter 2, color depth refers to how many bits are assigned to each pixel in an image. The best scanners use 36 bits 12 for each color red, green, and blue to produce 6.
When these files are processed down to bit files, they contain images with more subtle gradations of color and more color accuracy. The quality of the colors in a scanned image depend not just on depth but on their registration. Since the colors are being captured by different sensors or at slightly different times, they may not overlap perfectly.
If they don't color fringes will appear around details in the image. Everyone had their own proprietary set of protocols that made scanning possible with their hardware or software and a few other products that they choose to support. The problem with this approach was that scanners from different manufacturers were incompatible with many application programs. Before buying a scanner, you had to check if your applications worked with it. If you had a scanner, you had to be sure applications would work with it before you bought them.
They all spoke different "languages. These standards are embedded in a device driver that is installed on your system. This standard has been so widely adopted, you'll find that most are. Film Scanners The highest quality scans are from slides or negatives because they have a much higher dynamic range than prints. Special film scanners also called slide or transparency scanners have been designed to scan film and the results are outstanding.
By using the included filmstrip holder, strips up to 6 frames in length can be scanned, one frame at a time. In fact, Photo CDs are created on high resolution film scanners such as these. Because slides and negatives are so small and must be enlarged so much, these units must have very high resolutions to be really useful. Even at dpi, a print on a dpi printer would be less than 2 inches wide.
Konica's Q-Scan scans 35mm and APS film at bit depth and a resolution adjustable from to 1, dpi in 70 seconds or less per frame. Courtesy of Konica. Some of the best film scanners use a software program called Digital ICE from Applied Science Fiction to eliminate dust and scratches on the surface of the scanned film. Flatbed Scanners Flatbed scanners are reflective scanners useful for scanning both black and white and color prints.
Flatbeds are excellent for scanning old photographs for restoration purposes. The print should be removed from any frame to make flat contact with the scanner glass.
Make sure the glass on the flatbed is clean. One advantage of flatbed scanners is that they do double-duty. They are ideal for copying documents of all kinds and many even come with OCR optical character recognition software that converts printed text to an editable digital form. The Epson Expression color scanner delivers 36 bit scanning at dpi. It has an optional transparency adapter so you can scan slides and negatives. Courtesy of Epson. Many flatbed scanners come with optional transparency units that allow you to scan slides.
A transparency adapter is a scanner cover that diffuses light evenly through the transparent media. It sits in place of the copyboard cover that is included with the scanner. Generally, the resolution of these units is below those of units designed to scan transparencies. Paper materials can still be scanned with the transparency adapter in place.
A transparency adapter allows you to scan slides and film. Courtesy of MicroTek. When first encountering a copy machine, many people have tried copying money, photographs, and other objects.
Some even go so far as to press their nose or other parts of their anatomy against the glass to capture an image. Basically, they are using the copier as a lensless camera. You can do the same with a flatbed scanner and the results can be interesting.
One trick is to try different background materials laid on top of the objects to be scanned. These can range from other image to black velvet. By laying some coins on the scanner glass and then placing a hand over them, it looks like a handful of change.
Print Scanners Print or photo scanners are specifically designed to scan snapshot-sized photos. The quality you get from scanning prints isn't as great as from scanning slides or negatives.
However, some of these small scanners also allow you to scan negatives, slides, and prints. The Epson PhotoPlus color photo scanner will scan a photo in less than 60 seconds. Drum Scanners When price is no object and quality is paramount, you need to have prints or transparencies scanned on a drum scanner.
On these scanners the transparency or print is affixed to a glass drum. As the drum spins, the image is read a line at a time by a photomultiplier tube instead of a CCD. A bright pinpoint of light is focused on the image and its reflection prints or transmission transparencies is measured by the tube. Their dynamic range is so high they can capture detail in both deep shadows and bright highlights and they also capture subtle differences in shading.
These expensive scanners are available at service bureaus where you pay by the scan. The cost of the scanner, computer time, and labor involved with a drum scan demands a higher charge. Drum scan resolutions are sometimes identified with the term RES. For example "RES 30" denotes 30 pixels per millimeter which could be compared to ppi pixels per inch. The higher resolution scans create very large files that would prove difficult to work with even with a high-end workstation.
Kodak Picture Makers If you don't have a scanner and want to make prints, all you have to do is locate a dealer with a Kodak Picture Maker. To operate these self-serve machines, you point to items on a touch-sensitive screen. Some models even accept Photo CD disks and flash memory cards from cameras. The printer in these units is a dye-sublimation printer. You'll see in Chapter 10 that this is the finest type of printer available for photographs.
The Kodak Picture Maker scans prints, slides, and negatives so you can make prints using a touch screen. You can even save the scanned image onto a disk. Courtesy of Kodak. Getting Images Scanned When you want high image quality, you can have your slides or negatives scanned onto FlashPix or Photo CDs at your local camera store or any service bureau that offers this service. Each CD comes with a series of thumbnail images that let you quickly locate any image you want.
The quality of these scanned images is much higher than what you get from the most expensive digital cameras. Once scanned onto the disc, the images can be displayed on a TV using a Photo CD player or copied into your computer from any CD drive that supports the Photo CD format almost all now do. Photo CD's are covered in detail in Chapter 7. FlashPix CDs The FlashPix format stores images in a number of resolutions and each resolution is subdivided into square tiles. FlashPix aware applications work with the resolution that works best for a given application.
This can greatly speed things up for you. For example, you can edit a low resolution version and then apply those changes to a higher resolution version when ready to print. Also, since the images are broken into tiles, only the section of the image you are using needs to be updated on the screen as you work on the image.
This reduces the time you sit around waiting for the screen to update. A FlashPix file contains the same image at a number of different resolutions.
You can view the image at one resolution on your computer screen and download a different resolution for printing. This greatly speeds up your viewing time and outputs high-quality images.
Both are available in The Digital Photographer's Toolbox. The FlashPix format is covered in detail in Chapter 7. At the low end of the scanning market are floppy disk scans. Although generally limited to low resolutions, these services are both cheap and convenient. There is hardly a system anywhere that can't read a floppy disk. PhotoNet dealers can scan your images onto a floppy disk or even posted on the Web. Image courtesy of PictureVision. The images are x pixels with bit color.
You can have these images scanned at your photo dealer when you have your film processed, or at any later time. Kodak Picture Disk Viewer software included on each disk allows you to view the images. It also allows you to organize your images into albums, and crop, rotate, and print them. The result is large file sizes that are better for high- quality prints. You can have prints, negatives, or slides scanned onto these disks at stores that have a Kodak Image Magic Print Station or Enhancement Station.
The images are usually X pixels with bit color. The number of images that can fit on a disk varies between 40 and , depending on how well each compresses.
The disk contains a program that displays your images singly as in a slide show, or as a multi-image contact sheet. You can also rotate and zoom the images or enter up to 32, characters of text for each picture. PictureVision's PhotoNet service scans your film or slides and posts them on the Web where you can view them. Software is included so you can view the images. Scanning Images Yourself When you first start scanning and printing images, it seems like there is a black art involved.
Actually, it's not that at all, you just have to understand some relationships between pixels and inches. Here we'll try and explain those relationships so they're understandable.
To follow these discussions better, and to calculate your own scanning and print sizes, download the Scan Calculator by clicking the link below. It was created with Excel Download Excel Scan Calculator Scanning and File Sizes When scanning, your goal is to get a digital image file that contains all of the detail you need without the file being too large to work with.
If you scan at too low a resolution, you'll lose detail. If you scan too high, you're file will be too large. When you scan an original image—either a slide or a print—the file size depends on a number of factors including the area being scanned, the resolution of the scanner, and the color depth, or number of bits assigned to each pixel.
Let's take a look at this step-by-step as you'd calculate file sizes using the downloadable scanning calculator—Part 1.
Enter the width in inches of the art to be scanned. Enter the depth or height of the art to be scanned. Enter the scanner's optical resolution or the resolution to intend to scan at. The scanned pixels horizontally are calculated by multiplying the scanner's resolution line 3 times the horizontal size of the original line 1. The scanned pixels vertically are calculated by multiplying the scanner's resolution line 3 times the vertical size of the original line 2.
The total scanned pixels is calculate by multiplying the horizontal scanned pixels line 4 times the vertical scanned pixels line 5. The color depth is where you enter the number of bits assigned to each pixel. The file size in bits is calculated by multiplying the number of pixels in the image line 6 time the color depth line 7.
The file size in bytes is calculated by dividing the file size in bits line 8 by 8. The file size in kilobytes is calculated by dividing the file size in bytes line 9 by 1, The file size in megabytes is calculated by dividing the file size in kilobytes line 10 by 1, Printing a Digital File of Known Size Most of the time, you have an image of known size, perhaps directly from a camera, and want to print it out. In these case, you want to know the size of the print you'll get at various printer resolutions.
Enter the width in pixels of the digital file. Enter the depth in pixels of the digital file. Enter the printer's output resolution in dots per inch dpi. Horizontal size of output is calculated by dividing the number of pixels horizontally in the original line 1 by the output resolution.
Vertical size of output is calculated by dividing the number of pixels vertically in the original line 2 by the output resolution. Scanning an Image for Printing at a Specified Size There are times when you know what size you want a print to be and need to calculate backwards to what size the image file should be.
For most purposes, you can expect to get photorealistic quality with a print having about dpi. This means, a 4 x 6 print needs an image file of x , and an 8 x 10 print needs one x Because the number of pixels in the image don't change, the dots per inch have to.
For example, let's say you placed an x image on a page and it was 2-inches wide. If you print it out at that size, it will print at dpi divided by 2". If you now stretch the image to be 4 inches wide, the dpi drops to divided by 4". If you want the image 4" wide AND dpi, best scan it so it's pixels wide before you import it.
However, if it's to be printed on a printing press, the rules change and become more complex. You should scan the image so its sots per inch are twice the lines per inch lpi at which it will be printed. Enter one of the the printer's output resolution in dots per inch dpi. The horizontal size of the original is calculated by multiplying the desired horizontal size of the output line 1 by the desired output resolution line 3. The vertical size of the original is calculated by multiplying the desired vertical size of the output line 2 by the desired output resolution line 3.
Enter the color depth of the image. The file size in bits is calculated by multiplying the horizontal by the vertical size of the original lines 4 and 5 to calculate the total number of pixels in the image and then multiplying those by the color depth line 6. The file size in bytes is calculated by dividing the file size in bits line 7 by 8. The file size in kilobytes is calculated by dividing the file size in bytes line 8 by 1, The file size in megabytes is calculated by dividing the file size in kilobytes line 9 by 1, Scanning an Image for Screen Display Scanning an image for the screen is the same as scanning one for printing except the output is usually specified in pixels, not inches.
Although the actual number of pixels per inch on a monitor vary depending on its size and resolution, images are generally scanned at 72 ppi for screen display although they are sometimes scanned up to 96 ppi. Making them any larger doesn't add any information to the image and just makes the files larger. Enter the width in inches of the image to be scanned. Enter the depth or height of the image be scanned. Enter the screen's resolution in dots per inch dpi.
This is normally 72 dpi on average. Enter the desired width of the image in pixels. The vertical size of the image is calculated by dividing it's width on line 4 by the ratio of the original's width to height calculate by dividing line 1 by line 2. Scanning Black Magic Scanning on one level is simple, plop a print on the copyboard and click the Scan button.
However, to get the best results, there are lot's of little things that need tweaking. Here are some of them. This has been done to add a little confusion to all discussions. However, there is a point of diminishing returns at which the image file just gets larger without any noticeable effects on the image.
CCDs are not really good at this. When the image is scanned, pixels in the image often overlap or are blurry because the scanning process isn't perfect. Sharpening cleans up the boundaries between colors to make things appear sharper. Most photo editing programs have a filter called an unsharp mask that allows you to sharpen just parts of the image based on their radius and threshold. Sharpening, and even oversharpening, is especially important when you are dramatically enlarging a file.
Philip Greenspun recommends using Photoshop's Unsharp Mask filter by setting the Amount to and the Threshold to 2. The Radius setting then varies depending on the size of the image file—doubling as the width doubles. Using Photo CD resolutions as example, he suggest 0.
For dye-sub printers see Chapter 9 a resolution that gives you dpi or even less will work if the print is to be viewed at a normal viewing distance of 10 inches or so.
On any printer that uses dithering, such as an ink-jet, you need 3 to 4 times as much—perhaps dpi. To reduce these, use a Gaussian blur filter in your photo-editing program. This is based on the screen they used to break a halftone image such as a photography into small dots what we computer people now call pixels. Historically, these screens halftone line screens had straight lines that varied in width. Although the screens changed at the turn of the century to grids that break the image into dots, the old label of lines per inch has stuck.
Screen printers for PostScript printers range between 85 and lpi. The lower figure is used for newspaper printing and the higher one for quality books and catalogs. When scanning photographs for later screening, you should scan so the image has twice the dots per inch as the lines per inch it will be printed at.
For example, if the image will be printed with a line screen, scan it so it has dots or pixels per inch. A Short Course in Digital Photography 5. Over the years, a number of different bitmap image formats have been developed. Each has it's own unique characteristics which determine when and where you might choose it over the others. However, most of these have fallen into disuse or are encountered only in special circumstances. As new demands arise, such as displaying images on the Web, new formats emerge.
Some, such as Photo CD, gain wide acceptance. Others generate a lot of excitement and then disappear because they are found to have flaws or just don't get critical mass. In this section we explore those formats you are most likely to use or encounter. However, whatever format you choose, there are programs that will convert it to any of the other formats. Bit-Map Vs Vector Images All of the still images that you see on the Web, or in multimedia programs, and many that you see in print, have been created or manipulated on a computer in a digital format.
There are two basic forms of computer graphics: bit-maps and vector graphics. The kind you use determines the tools you choose. Bitmap formats are the ones used for digital photographs.
Vector formats are used only for line drawings. Bit-mapped images Bit-map images are formed from pixels—a matrix of dots with different colors. For example, a x image contains pixels and pixels in horizontal and vertical direction respectively. If you enlarge a small area of a bit-mapped image, you can clearly see the pixels that are used to create it. When viewed normally, the small pixels merge into continuous tones much as the dots used to create newspaper photographs do.
Each of the small pixels can be a shade of gray or a color. Using bit color, each pixel can be set to any one of 16 million colors.
All digital photographs and paintings are bitmapped, and any other kind of image can be saved or exported into a bitmap format. In fact, when you print any kind of image on a laser or ink-jet printer, it is first converted rasterized by either the computer or printer into a bitmap form so it can be printed with the dots the printer uses. To edit or modify these bitmapped images you use a paint program. Bitmap images are widely used but they suffer from a few unavoidable problems.
They must be printed or displayed at a size determined by the number of pixels in the image. Printing or displaying one at any other size can create unwanted patterns in the image. Vector graphics Vector graphics are really just a list of graphical objects such as lines, rectangles, ellipses, arcs, or curves—called primitives. Draw programs, also called vector graphics programs, are used to create and edit these vector graphics.
These programs store the primitives as a set of numerical coordinates and mathematical formulas that specify their shape and position in the image. This format is widely used by computer-aided design programs to create detailed engineering and design drawings. It has also become popular in multimedia when 3D animation is desired. Draw programs have a number of advantages over paint-type programs. Vector graphics always print at the best resolution of the printer you use, no matter what size you make them.
When working with a draw program, you can display the image in two views: wire frame view or shaded. In wire frame view, you see just the underlying lines—a skeletal view of the image. The image is displayed this way because it can be manipulated on the screen a lot faster. To see what the finished model looks like, you can apply colors to the wire frame and display it with the wire frame covered by these shaded surfaces. The camera is shown in shaded view left and wireframe view right.
The ability to shift between these two views is characteristic of vector draw programs. Bitmap file formats fall into two subclasses; native and transfer or exchange formats. Native Formats As new programs are introduced, developers have a tendency to create proprietary, or native formats that can be read only by their programs.
Part of this desire is to have a competitive advantage.
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