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Recognizing continuous tone (contone) vs. dot pattern images

From: Scanning Techniques for Photography, Art, and Design

Video: Recognizing continuous tone (contone) vs. dot pattern images

One special image evaluation issue that you need to pay attention to and this is kind of a sneaky one is whether your original image is a true continuous tone image and I like to use the word contone, like a photograph or if it's an image that's built out of dot patterns. Because they may look similar to the human eye, in fact, they are designed to look similar to the human eye. But in fact when we get to the scanner, they are not the same at all. Let me show you the difference between a true contone or continuous tone photographic image, and one that is built-out of patterns of dots.

Recognizing continuous tone (contone) vs. dot pattern images

One special image evaluation issue that you need to pay attention to and this is kind of a sneaky one is whether your original image is a true continuous tone image and I like to use the word contone, like a photograph or if it's an image that's built out of dot patterns. Because they may look similar to the human eye, in fact, they are designed to look similar to the human eye. But in fact when we get to the scanner, they are not the same at all. Let me show you the difference between a true contone or continuous tone photographic image, and one that is built-out of patterns of dots.

On the right, we have an image that was scanned from a true continuous tone photograph. The building blocks are actually microscopic. In fact, they are atomic in size and dimension. They are either a film-based emulsion type building block or they are a silver halide crystal if it's an old grayscale photograph, and the crystals are literally on the size of the atoms. It's just a collections of small atoms, much, much smaller than the resolution in which you're scanning your images. So your scanner will never ever actually see those building blocks. Let's take a look, let's just zoom in on this image here on Christina's forehead, no matter how close we get, you see you don't see any building blocks of the image at all.

It's a true continuous tone, particularly when you can look at something very smooth like someone's skin tone, you don't really begin to see any building blocks until you actually see the scanned building blocks, the pixels. So the process of scanning an image or capturing it with a digital camera actually reduces the resolution of a continuous tone photograph. It takes something that is very, very super high resolution and breaks it up into pixel-sized building blocks, in this case, one three-hundredth of an inch on a side. That's what a continuous tone image looks like. Notice, there's no original pattern in that image that we have to worry about at all.

No matter what scale you look at it, it's true continuous tone. The only thing you change is, is just a tonal value of the image itself. On the left on the other hand, we have a scan of a book, and there is a type of course and then there's a " photographic image" that has been reproduced. And let's zoom in on that like we did the previous image and notice as we start to zoom in, it looks like a continuous tone image, except for as we begin to zoom in more and more and more you start to see that dot pattern. You see because printed images are not printed as continuous tone unless they are actually a photographic print.

When an image is printed on a printing press or a laser printer or an Inkjet printer, any of the standard printing devices that you and I use today, the image is actually reproduced as a pattern of dots. There are several terms that are used to describe this, the most common one is the most ancient one. It's called the halftone dot. In the process of reproducing a photographic image as a printed image to allow us to reproduce it cheaply at very little cost and multiple, multiple many, many copies is using this halftoning process. Conventional halftoning looks like this where you see you have an equal spacing of dots and we vary the size of the dots in order to create the perception of a grayscale to the human eye when we zoom out.

That's the way a conventional commercial printing works, with a lot of printers like laser printers and particularly Inkjets, instead of varying the size and having equal spacing, they vary small halftone dot and they vary the spacing. But in either case, you end up with a dot pattern. This is a very obvious one because it's a fairly coarse grained halftone dot pattern. But the result is you don't end up with a smooth continuous image like we do over here with the Santa Claus image, you end up with actually a pattern of dots. As you move down the production path things get worse.

This halftone dot image when you scan it, not only reproduces the halftone dots, but if you notice at various enlargements here, you see the pattern that's coming across on screen here, let me go down a little bit more. That pattern changes and you get this very obvious black and white pattern. That's all being created by the interaction of the halftone dot pattern in the scanned image that's been reproduced by the scanner. And the pattern or array of pixels that you have actually displayed on your screen, the same thing happens when you take this halftone dot scanned image and try to reprint it with another pattern of dots. Ooh! Things get real ugly in a hurry.

So it's very important that you recognize if your image is built-out of a dot pattern versus a true continuous tone photograph before you start your scan process, which is one of the reasons why I recommend that if you are going to be doing much scanning at all and particularly of printed images, you should always have a little magnifying glass with you and you can look and see if you have a true continuous tone or if you've got halftone dot pattern. You would be able to see that pattern with the 10 power magnifying glass. Obviously, during the scanning process, our goal is going to be to remove this halftone dot pattern as much as possible, so we don't end up with all this interaction on screen or even worse, when we go to reprint this image again.

Show transcript

This video is part of

Image for Scanning Techniques for Photography, Art, and Design
Scanning Techniques for Photography, Art, and Design

58 video lessons · 8672 viewers

Taz Tally
Author

 
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  1. 6m 48s
    1. Welcome
      1m 11s
    2. What you should know before watching this course
      3m 54s
    3. Using the exercise files
      1m 43s
  2. 1h 0m
    1. Scanners and digital cameras
      3m 6s
    2. Types of scanners
      5m 2s
    3. Scanner location
      3m 19s
    4. What scanners and digital cameras create
      7m 22s
    5. Understanding grayscale values and channels
      3m 19s
    6. Understanding pixels and vectors
      4m 1s
    7. Choosing pixels or vectors
      2m 27s
    8. Resolving resolution
      6m 32s
    9. Working with interpolation
      3m 31s
    10. Understanding the effects of compression
      2m 4s
    11. Evaluating and correcting images with histograms
      8m 26s
    12. Saving to different file formats
      7m 4s
    13. Color management
      4m 23s
  3. 33m 22s
    1. Cleaning your scanner
      7m 31s
    2. Cleaning your images
      7m 47s
    3. Calibrating your scanner
      9m 13s
    4. Creating and applying a color management profile
      8m 51s
  4. 20m 55s
    1. Evaluating your scan challenges
      9m 46s
    2. Reproducing vs. assigning colors
      6m 20s
    3. Recognizing continuous tone (contone) vs. dot pattern images
      4m 49s
  5. 36m 32s
    1. Understanding bit depth
      8m 49s
    2. Selecting a scan mode
      8m 20s
    3. Sharpening and its effects
      10m 40s
    4. Creating and assigning color management profiles
      8m 43s
  6. 2h 25m
    1. Taking the Tazmanian Oath!
      3m 38s
    2. Choosing your weapon
      4m 2s
    3. Setting up your scanning preferences
      12m 14s
    4. Performing a prescan
      2m 53s
    5. Assigning a scan frame
      5m 40s
    6. Determining scan resolution
      7m 57s
    7. Choosing a scan mode and bit depth
      5m 53s
    8. Naming images
      1m 49s
    9. Scanning simple logos and line art
      12m 21s
    10. Scanning complex line art
      7m 33s
    11. Scanning grayscale contones
      13m 22s
    12. Scanning color contones
      13m 54s
    13. Sharpening
      9m 39s
    14. Scanning printed/screened or patterned images
      7m 1s
    15. Scanning positive transparency film
      12m 33s
    16. Scanning negative transparency film
      9m 11s
    17. Capturing high dynamic range (HDR) scans
      1m 47s
    18. Setting up wet scans
      14m 29s
  7. 1h 48m
    1. Scanning, converting, and using simple line art
      5m 32s
    2. Scanning and using detailed line art
      10m 52s
    3. Scanning landscapes
      15m 50s
    4. Scanning product shots
      11m 58s
    5. Scanning combo/complex images
      9m 3s
    6. Adjusting distressed images
      11m 12s
    7. Scanning images with no neutrals
      11m 57s
    8. Post-scan touch-ups
      2m 7s
    9. Scanning images for multiple uses
      10m 44s
    10. Automatic scanning
      10m 40s
    11. Streamlining big jobs with batch scanning
      5m 22s
    12. Using your manufacturer's scanning software
      3m 14s
  8. 27s
    1. Goodbye
      27s

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