A4-Freddy

When preparing b/w bitmap images for printing, the question of resolution and whatnot has always bothered me somewhat.

Goal: When pasting pictures into collateral material (i.e. Word docs, PDF's, etc), the idea is to keep the resulting file sizes as small as possible. But still maintain a decent looking printout. Most often this material is printed on b/w laserjets at around 600 dpi. Mostly small product photos inside of business preso's.

Question: What's the best way to size these images appropriately?

Ridiculous example, If I take a picture I wish to print at 1"x1" within whatever document, make it grayscale, size it to 600x600 pixels, and then convert it to a b/w bitmap (no shade/color in other words), shouldn't this print fine? Because generally isn't the printer only able to print a black dot or nothing for each pixel of resolution?

Or should I instead be leaving it grayscale, but downsampling the dpi and/or total image size to something like 150 dpi and let the printer attempt halftoning/upsampling as it sees fit? In this case, are there normally accepted dpi values for this sort of thing based on the intended application?

Also, along the lines of file formats, is there one that external applications generally handle better than others? I notice GIF's generally saves somewhat smaller than most of the other formats when you get into greyscale territory, but this may not be indicative of anything, just the compression algorithm used here.

Now I have a headache.

omidius

Here's my stab at what I think I hear you saying, but before I being anything, here's a little bit of background:

There is one correlative you are dealing with here: Size vs. Quality. BMP format in either case is NOT the way to go. It is highly inefficient for end-user consumer uses, and within many printing circles it is an outdated and staid format... Printers, whether professional or consumer based solutions do the BEST when dealing with the optimal acceptable input resolution (measured ONLY in px, not DPI). In your case, you mentioned B&W Laserjet printers at 600 ppi. Now when printing everything is done (depending on the print type of course, using a tone method). This allows B&W laser printers to easily acheive half tone by way of halftone screens. Think of halftone screens as the little tiny dots in professionally printer solutions that comprise the image. The thickness of each individual dot as a set will determine the shade of color. Most current laserjet printer's processing unit uses a 150-200 line screen (the higher the number the finer the dot).

Now, this example that you gave, stating if lemme get this straight:
1. Take a photo at 1" squared and convert to grayscale.
2. Size it to 600 PPI squared.
3. Convert to B&W image

Will it print fine? Simple answer is no. The reason? Well that depends on your answer to these couple questions:
-What resolution was the photo taken at? If it already prints on your 600 PPI Laserjet and is 1" square print size, you do not need to do step 2, the resizing. It's already 600 PPI. If it appears as 1 inch on the screen, it's only 72 PPI and will print out very very small, as the printer is set for 600 PPI. Smarter printers will automatically resize the image for you. If you take your 1 inch 72 PPI image and resize it to 600 px, you will have a very very distorted image. The reason: you are taking the information stored in 72px and upsampling to 600px. Here's a metaphor:
Draw a picture with a 10 pack of Crayola crayons.
Copy the same picture using the 100 pack of Crayola crayons. What do you get? The same colors being used in both pictures. There is no more colors (read:information) that can be added with just having more crayons (readixels) in your box (rad:image).
Remember, up/downsampling is converting the existing pixelset to a new one. Downsampling is efficiently taking the pixelset and reducing it while throwing out excess junk. Downsampling will ALWAYS produce better results, you're just throwing stuff out instead of trying to make do with little pixels you have to start with.

PHEW, The last step in that process you had listed had me take the grayscale image and reduce it to black and white. ERR, bad mistake, stop right there. You pretty much answered your own question, although I don't think you see the answer quite yet. In effect you trying to take the roughly 32-64 shades of gray a human being can recognize and reduce it down to two: white and black. The result will look roughly like a line drawing done in black pen. All definition will be lost, all detail and contrast (except between white and black) will be lost. Not a good move. This is NOT to be confused with like a "black and white image or photograph" which is a misnomer, as the image is most likely consisting of shades of grey.

File types: GIF and BMP think of as the bitches of the composed (non vector) image format world. JPEG is the current leader in public consumer image use. It is versatile, optioned, and compresseable. GIF images are defined by a user-set palette of colors. Like saying to Monet, paint your scene with these colors, and only these colors. Image processing suites upon saving in the optimized GIF format like photoshop will take the existing full color image, find the ideal balance of colors (between your set parameters (like 2-512 colors) and compose your image. For certain graphics, consisting of solid patches of color, like logos, charts, etc this is the best format. For photographs, JPEG is the best answer. Unlike GIF formats, JPEG does not rely on the set palette, but actually gets it's colors from a set of 16.5 million colors available to it. The result? A near perfect match (depending of compression quality). The percentage of compression quality will tell the photosuite how conservatively (or not) to publish the image. The less the number, the higher the compression and greater the loss in image quality. This format is ideal for photographs.

Your ideal solution to your quandary (sp?) is to take your full color image convert to greyscale and to reduce it to an even number divisable by the number of ppi of the printer. In your case for 600 ppi, I would pick either 600 or 300. I would save as a JPEG image and import into the document. For fine tuning of the actual image size, I would let the Word engine handle that. As long as there isn't a drastic size difference (increasing), the header information for sizing of images stored in the document is much less than making your image bigger. If you want to make your image smaller in word, why not take it back to photoshop, do it in there and import it in? This way you save filespace and get the image "professionally" resized by photohshop's engine instead of Words'.

phew, hope this answered SOME of your questions.

formerly dennisA4

That said, i prepare images at a max of 350dpi if they are full color or grayscale. Bitmap images are prepared at 900dpi and the frequency and angle of the dot depends on what effect I'm going for.