Creating good prints Part II - Scanning

So, you have these *awesome* photographs you took while meandering down the streets of Toulouse France, Sao Paolo Brazil, or NYC - incredible shots of an abandoned building tagged with incredible spray painted images - and the shots came out pretty good - now what?

Well, for this post, we'll assume your pictures are photographs, ya know, the traditional "chemical" process prints that you have developed and get back as prints. Now what?

Well, in our case, you must digitize the images - get them from the physical prints into digital format that can then be cleaned, cropped, maybe enhanced, and then printed. So the gist of this post will be scanning.

SCANNERS

There a few types of scanners available, notably drum scanners and flat-bed scanners. Used to be, in the pre-press and art world, drum scanners were the first and last word. They were technically superior to the flat-bed scanners of those days - and they were prohibitively expensive! A good drum scanner could top $50,000!!!

(FWIW- the term "drum scanner" referred to a cylindrical drum that the picture to be scanned was mounted on. This drum then spun at high speed, while a light was focused on it, and read through a shutter.)

Oh, how times have changed! You can buy a flat-bed scanner at Staples or CompUSA for less than $100 today that surpasses the performance and speed of a $20,000 drum scanner of just a few years ago!

Still, if your objective is "museum-quality prints" such as those we sell at graffitipix.com, then you still need something beyond an "all-in-one" printer-copier-scanner-fax machine!

One of the chief differences between a drum scanner and today's flat-bed scanners is how they acquire the image. Drum scanners use something called PMT (Photo Multiplier Tubes), whereas flat-bed scanners use CCD (Charge-Coupled Device) technology. CCD's are essentially chips that convert light into data, and are what made camcorders, digital camera's and the like possible. Just like other chips i.e. memory, CPU's, etc., CCD's came in a wide range of "sizes" and capabilities.

Optical scanning via a flat-bed scanner is measured by a number of criteria: bed size, spatial resolution, and color-depth. Bed size is just what it sounds like, namely how large a picture it will take. Most can accomodate 8 1/2" x 17" (ours is a larger bed that scans up to 18"x24"). Next is spatial resolution, which is basically like the dots-per-inch of a printer. The higher the spatial resolution, the more data the scanner sees, the better the resulting image file. 600 dpi x 1200 dpi is common on low-end scanners. Higher-end scanners can go as high as 4,200 dpi and higher. Last is color depth, a measure of how fine gradiations the scanner sees. 24-bit is a functional minimum, the scanner we use is a 32-bit scanner.

Lastly, and perhaps most importantly, are the optics. Just like on a 35mm camera, the higher quality of the lenses, the better the picture. And, again like camera's, this is what seperates the good from the great. Once again, like with camera's, this is where the majority of the cost comes from.

Ok, thats the 5-cent scanner lesson; next we'll look at what happens once you scan, or acquire the image.

Molly