Re: Which image format

Subject: Re: Which image format
From: David Neeley <dbneeley -at- oddpost -dot- com>
To: Wade Courtney <courtney -at- hsq -dot- com>, TECHWR-L <techwr-l -at- lists -dot- raycomm -dot- com>
Date: Thu, 4 Mar 2004 14:45:52 -0800 (PST)


I've been trying to think of some way to say politely what really needs to be said to improve your boss' understanding of graphics formats.

Screens are a bitmap, and thus screen captures are bitmap or "raster" graphics files. Screens are not generated via vector graphics, and thus cannot be captured as vectors.

Raster-to-vector conversion would be severely limited in creating any sort of realistic-looking image.

PNG is a bitmap format, but be sure that your printer is prepared to handle them adequately.

Filesize will vary depending upon many things. I believe the writer who mentioned reducing the finished image size by half to double the resolution is on the right track. However, even better would be to give the printer a graphics file that is an even multiple of the actual *printing* resolution. I would imagine you're using a 133-line screen. Thus, I'd try to get a screen capture of a simple multiple of that number...probably 133 dpi at the printed size, in fact, if I could. Similarly, if you're printing at 150 dpi, you'd work with that figure as your base. The closer to the finished resolution you can get with your capture, the better the results.

Let's say you intend to print the screen capture at 1/4 of the original size in terms of pixels. That means that the capture resolution will be four times the needed output resolution. If your capture tool allows it, you can then set the capture resolution accordingly.

As for file format, if your screen looks all right at 256 colors, your file format may only have to support that many colors. At times, I have actually run the screen at 256 in order to get a very small graphics file size. I find that the fewer processing changes from the original, the easier it is to get high-quality output. Usually, these days I have to use one of the high-color formats--usually I switch to a 15-bit screen color depth for my screen captures.

By using a reduced color set in the screen depiction, the capture software results in a closer rendition to the original. It is also easier to work with the color changes that may be required for the best output when you start with a somewhat reduced palette.

Processing post-capture I generally do in PhotoShop. Normally, I will adjust contrast somewhat to give a crisper result for printing. This is especially true for captures that will be printed in black and white. Colors that have plenty of visual contrast can look very similar in black and white. Thus, I do the transition to black and white in the image that I prepare for the printer, and adjust accordingly to get a pleasing result that will print well.

I know this is a sort of "You only asked for the time and I tell you how to build a watch..." but I would simply indicate that there is much more to it than you may be aware today, if you want the best results.

As for file formats.... You can do low-res prints in your file that will be replaced by the printer with the high-res images (as one example). The original is a "for position only" insertion.

Therefore, I'd produce the files in the format and with any compression settings that the printer specifies as best to work with in his process flow. With recordable CDs and zip disks and the like, you needn't concern yourself with sizes--I have worked more than once or twice with color images for printing that ran over 100 MB, for example.

I would be sure that your printer works customarily with the platform you use. If you're on a PC, I'd be sure they work with PC files; similarly for the Mac or UNIX.

For my screen capture work, I strongly recommend Snag-It from Techsmith (one of the sponsors of this list, in fact.) The ease and flexibility of their screen captures and image handling are the best I have found by far.

I hope this has at least filled in some of the conceptual things.


-----Original Message from Wade Courtney <courtney -at- hsq -dot- com>-----

For those of you who have actual printed manuals that you have
professionally printed...


Which image format: From: Wade Courtney

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