Great question! Scanning in color has been a reality for some time so why are most folks not storing images in color.... The short answer is because the image files are VERY LARGE. It is a bit like the difference between a photograph and a Oil Painting. If you by a digital print of an oil painting often called a Giclee is beautiful, single piece of paper that can be rolled up and shipped and shared with anyone. The ORIGINAL PAINTING has so much more, the brush strokes and the way the light hit it is so much better, but it is hard to share, ship, move. In the Document Imaging world, the Original Image scanned in color contains much more information and the size of the file reflects this. I know of an archivist that requested all of his images to be scanned in color at 1000DPI. The image was wonderful and about 150 Meg each. This allowed him to put 4 pages on a CD and that is just not practical. Can you imagine trying to view one of those images on the internet? It would take minutes to hours to download and see 1 image. Although that is a true story the archivist learned the hard way there is such a thing as overkill. That is the whole point. Why do you need color is the better question. Are the originals so bad you have no other option to convert them? Is the color of the information important? Do they just look pretty and that is important? There are practical ways to convert to color images and still maintain a file size that makes sense. 1: Pick a LOWER resolution. Color has 24 times as much information as black and white so you need less resolution to achieve the same effect. 2: Reduce the color content where you can. Color is often 24bit or more. If that is confusing it is simple. it is the DEPTH of the color or how many computer bits does it take to make a color on the screen. You can wiki or google Color Depth and get a very complicated explanation but the difference between an image scanned in pure black and white and a 24 bit color image is that the 24 bit image has 24 times more information. That is 24 times the raw size as well. Computers are switching devices and 1 switch hold 2 states, on and off. In our case that 1 switch holds BLACK(off) or White(On). Think of 1 bit = 1 switch. The human eye can discriminate more than 10 million colors. To represent those colors we need 16,777,216 variations of color or 24 switches (2 to the 24 power= ~16Million). Big difference. And you need that difference for every dot on the screen. You have to store that switch state or the COLOR for each dot. If you have a 8.5 inch X 11 inch page scanned at 300 dpi then in color there are ((8.5" * 11") * 300DPI) *24bits of color=673,200 pieces of RAW information Compare that to a black and white scanned image ((8.5 * 11) *300) * 1=28,050 pieces of RAW information. 1/24 of the size of the color image. So reducing color could be converting to 256 colors instead of 16 million. It sound ridiculous but reducing the number of colors is a very good way to reduce the size of the files. 3: Try Grayscale/Greyscale. Grayscale is a pallet of grays designed to represent the reflected light from the image. It is 8 bits deep so it is 1/3 smaller than color and 8 times bigger than black and white but it is still a good compromise 4: TEST IT Test it. I do not mean just scan it and look at it. Scan a real sample of the work you do. If a FOIA packet is 900 pages scan 900 pages. Now can you work with this document? Can it be emailed? Stored? Opened? Copied? Delivered in a timely manner on your computer network. In more than one case I have had users tell me that color is perfect and no matter what I would say they would use color, until 1 file would not fit on a DVD, or someone wanted to see the thumbnails of the images and it took 15 minutes to get them all and paint them to a screen. All of the above are real client issues we have encountered over the years and there are cases where it is VERY hard to convert the images to black and white. So try it then have the users test it and see if the choice you have made works as well as looks good. so REDUCE/REDUCE/REDUCE and test are my recommendations! Reduce Resolution Reduce Color Reduce size and Test it all to see if it works! You may have noticed I did not mention compression engines and what they do. Compression is all relative to the actual image. Some images compress well and others not so well;BUT, one this is true the starting image is the same. Start with 24 times more information and you will have a substantially larger file no matter what compression you choose. Happy scanning! |