Digital picture information and techniques

  1. Batch Scanning
  2. Archival Image Quality
  3. Cropping to a specific aspect ratio
  4. Drag and drop picture fragments

Batch Scanning

I am so pleased with the use of the Batch Scanning feature in Irfan View, that I just had to share it with you. It really simplifies the process of Batch Scanning, except for the cases which were already simple, sheet fed material and a scanner with a sheet feeder. But those cases are rare.

With Irfan View 3.91 or newer (and many of these features are available in the last several releases, but I first tested them with version 3.91), unless you are scanning with an automated sheet fed scanner, you should go to Options/ Properties, choose the "Misc. 1" tab, and unchecked the option "Close TWAIN dialog after acquire (disable it for batch scanning)".

Then choose the appropriate scanner (if you have more than one possible scanning device).

The batch scanning process can be found on File/ Batch Scanning. Answer the questions on the first dialog (the answers will persist across sessions, so you can start and restart scanning of, say, a whole book or album), and it will then launch the scanner driver. You place the material to be scanned in the scanner, do the Preview scan, adjust the marquee(s) as necessary, and then do the final scan. (With some types of material, the positioning and coloration is consistent enough that preview scans are not needed on every page.... for example, high contrast black and white unbound material). After each scan Irfan View saves the scan, increments the page number, and is ready for the next scan.

Archival Image Quality

Scanner selection

The quality of the scanner is important. One of the least advertised measures of scanner quality is something called optical density, which is measured on a scale of zero through 4, where 4 is the highest possible quality. The only under $500 scanner that has a "nearly perfect" score, is the Epson Perfection 4870 scanner. So if you are in the market for a new scanner, and/or are planning to do archival scans, the Epson Perfection 4870 scanner is highly recommended. It is limited to letter size and A4 scans, however, so for larger material, you must either sacrifice optical density or price or both.

Bitonal (Text, Line Art, Black and White)

The most compact way to save bitonal (NOT black and white photographs, which are actually gray scale) material is TIFF with CCITT FAX Group 4 compression. This is the latest technique developed for FAX transmissions, and it excels at compressing black and white documents. It doesn't even work for gray scale or color documents. I generally recommend a minimum scanning resolution of 300 dpi. For text and line art documents, a 8.5x11" page of material seldom exceed 80 or 90 KB, and is often less.

Gray Scale and Color

The most compact lossless way to save color material (gray scale, photographs, etc.) is JPEG with a quality factor of 100. The quality factor of 100 causes the JPEG compression algorithms to use only lossless compression. Using lossless compression best preserves the material. I generally recommend a minimum resolution of 300 dpi for normal size pictures, but maybe 600 dpi when the original pictures are smaller than 4x6 (if they are sharp and clear), to allow for quality enlargements. 35mm slides and film can usually be scanned at 3200 dpi, but numbers from 2000 dpi to 4000 dpi are possible, depending on the grain in the film (which is usually a function of cost and film speed). Of course, there is little point to exceeding the optical resolution of your scanner.

Not all software supports Lossless JPEG and some folks don't think Lossless JPEG is really Lossless... and those sort of folks recommend using a quality factor of 95 as the maximum.

Of course, you can save more space by choosing other quality factors, but they really do affect the quality. Compression artifacts don't generally become noticeable until you drop below a quality factor of 75 or so. Doing a batch conversion to have a copy with a lower quality factor or a lower resolution, to save hard disk space and to speed viewing is fine.

If you don't believe in Lossless JPEG, or don't have software that supports it, the TIFF format, with LZW compression, is the next most compact format for Lossless compression, and there are no arguments about whether it is truly lossless... but it takes significantly more space.

Cropping to a specific aspect ratio

Irfan View can be used to crop pictures to a specific aspect ratio to prepare for printing them. First, view the image of interest. Next, choose the Edit / Create custom selection menu option. If you want one of the standard dimensions in the bottom left panel, you can choose one, but those all match specific screen sizes, so are not practical for cropping for printing. The ratios in the upper right panel are ok for printing, but only control the ratio when typing numbers into the boxes in the upper left panel, as far as I can tell. Because the selection of ratios is quite limited, and because the math is easy, I leave that collection of radio buttons set to None.

Now it is hard to estimate the number of pixels that you actually want to use for cropping, especially if the picture is viewed at a ratio other than 100%. Fortunately, you don't have to. You can follow the procedures outlined below, to make custom crops, using only simple math, and adjusting things with on-screen feedback.

As far as I am concerned, then, the top left panel contains all the useful features of this option. Make sure the setting is in pixels (or adjust the numbers in the following discussion appropriately). The top boxes, labeled X-Coord and Y-Coord, I fill in with 100 and 100. This is generally wrong, but is a starting point that you can see, as it is generally not smack dab up against the edge of the picture, yet most pictures are big enough that it doesn't exceed their bounds. These settings persist, so after the first time, these boxes and the radio buttons can also be ignored

For the boxes labeled Width and Height, this is where you choose your desired aspect ratio. For any given desired aspect ratio, simply multiply it by 10 (or 100), and enter the numbers in the boxes. For a landscape mode 4x6 picture, simply enter 60 and 40, or for a 5x7 portrait, enter 50 and 70. Now the notes in the bottom right panel are the key to finishing the job. Read the notes, and then click the box "apply to image". A selection bounding box will appear overlaid on your image, generally toward the upper left corner. Use the right mouse button to drag it to a corner of your desired crop area, and then hold the Control key down, and use the left mouse button to drag any of the edges of the bounding box to the desired positions--note that an adjacent edge will also move to keep the aspect ratio constant. If at any point you forget to hold down the Control key while dragging, the aspect ratio will be changed.

These manipulations allow you to pre-crop your images to an exact ratio before submitting them to be to a service bureau for printing, and thus avoid the unknown effects of cropping by the service bureau. This pre-cropping is useful even if you print pictures on your own color printer, if you wish to use standard size frames and album pages.

It is always good to leave a little background around the main point of the picture, so that if the service bureau crops a little off all aronud, or the frame covers a little all around, you don't lose the main features of the picture.

Drag and drop picture fragments

Irfan View has no obvious way to select a fragment of a picture, and reposition it somewhere else... but it is a straightforward combination of other operations, once you figure it out. This is useful for eliminating a piece in the middle, or to fill an area.

The key observation is that you can drag selection frames. So the trick is to select exactly what you wish to drag and drop; then Edit/Copy (Ctrl-C), then drag (right click and drag) the selection box to another position, and Edit/ Paste (Ctrl-V) the previously copied selection.

To extend this technique to copying a fragment from one file to another, do the following:
  1. Open one file and select the area you wish to copy from.
  2. Edit / Create custom selection and click on Save values and exit.
  3. Edit / Copy.
  4. Open another file.
  5. Edit / Create custom selection and click Save and apply to image.
  6. Right-click and drag the frame to the desired location.
  7. Edit / Paste