Web Tools Review--Scanners

The Web Tools Review on Scanners

which is loosely related to Chapter 4 of Database Backed Web Sites

Rule 0: don't scan from prints, use the original negs or slides

Computer monitors are low resolution but they have much better dynamic range (difference between darkest black and brightest white) than a photographic print. Thus, it is sometimes true that an image will look better on-screen than in a print. Of course, by the time a print is made, most of the information in the original neg or slide is already lost. This is why you must go back to the original slide or neg if you hope to have a competitive image on the Web.

Rule 1: don't scan, use PhotoCD

Good quality scanners cost over $10,000. Great scanners can cost $100,000. You will get better quality from a PhotoCD than from anything you can afford, especially if you haven't gotten hardcore about dust control in your office.

If you absolutely must have a desktop neg/slide scanner for convenience then check the reviews in photo.net. The HP PhotoSmart and the Nikon Super Coolscan are nice toys but I wouldn't have had time to scan my 6000-image on-line library with either one.

Rule 2: get a drum scan when PhotoCD isn't good enough

The PhotoCD scanners are CCD-based and can't see as deep into the shadows as the $100,000 drum scanners with photo multiplier tubes used by service bureaus. The PhotoCD system has many practical advantages, but it isn't the last word in quality. If your image has a lot of dynamic range, you may be better off with a 12-bit scan from a drum scanner (PhotoCD has 8 bits of luminance information).

See my Publishing Flashpix tutorial for some example drum scans.

Rule 3: don't obsess about flatbed scanner resolution

Flatbed scanners are useful when you want to scan in an artifact that isn't exactly a photograph. I did this in the third chapter of my Summer '94 travelogue (about 75% of the way down in the document).

Forget about the bogus interpolated resolution numbers that you see in advertisements. All you should care about is optical. And you really needn't care about that if you're doing Web publishing. An ancient Apple Color OneScanner's 300x300 dpi resolution is more than adequate 99% of the time. You'll probably want to present material at roughly original size so in fact 75 dpi (typical screen resolution) is adequate. Much more important than resolution are dynamic range, linearity, and color fidelity.

A good source for information on the latest scanners is DTP Direct ((800) 643-0630). My personal current choices are the HP ScanJet 4c (under $1000) and the UMAX PowerLook II (over $1000).

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philg@mit.edu

Reader's Comments

It is not quite fair to say that PhotoCD is 8-bit when a drum scan is 12-bit. PhotoCD is 8-bit log-scale when a drum scanner is 12-bit linear. PCD is more like 10-bit linear with more efficient coding.

-- Robert SIlvers, November 11, 1997

One thing I would add to flatbed resolution comments is that, while it is true that 72dpi or 300dpi is enough for most files, a scanner is not a perfect device and adds noise to each pixel. If you scan at a high (say 600x600dpi) resolution and then downsample, you average this noise out and get a cleaner file. I would NEVER scan at less than 150dpi -- even if you want 72dpi. Clean files also compress better.

-- Robert SIlvers, November 11, 1997

Most of us cannot afford the approx. $1000 scanners. We need the best available/affordable. I had to research this because my wife wasn't about to let me spend $500, much less $1000 for a scanner. I needed a good all purpose scanner to scan old family photos, slides and negatives (1890 thru 1960 vintage). I found the Epson Perfection 1200 PHOTO that has a transparency adapter, that will scan at 1200x2400 DPI opptical, which is $299 at www.scanneroutlet.com. These are the scanners that the commom folk need recommended.
Phil

-- Phil Dziki, January 30, 2000

It's easy to say that we should use negatives or slides when scanning, instead of prints. Regrettably to scan a slide or negative accurately you cannot use one of the abundant $200-$300 scanners that most people buy.
So I use my scanner for getting quick snaps of photographs into my system.
Now however I have a Nikon Coolpix 950 Camera. Excellent camera, 1600x1200 resolution. I use it more and more... I used to have an Minolta D'Image-V camera (expensive and with 640x480 and very limited battery life) but this was not more useful than for putting small thumbnails on a web-site or for utilitarian purposes as when we were househunting.
The Nikon, I actually use next to my regular camera. It's got lots of goodies, such as spot metering, manual control, great battery life, external flash connection, etc.
The resolution 1600x1200, whilst not as high as PCD or high-end negative scan, certainly exceeds what you would get from a flat-bed scanner with a negative or slide adapter. I have printed pictures blown up to 5"x7" on an Epson colour printer on expensive paper, and these look great. Given that 150 dpi is usually enough for a good photo-printer to do it's work, you should be able to enlarge this up to 11"x8".

-- Peter van Es, April 3, 2000