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Digital slide scanners and scanning

by Brian Pitkin

April 2002

INTRODUCTION

The majority of underwater photographers take 35 mm print or slide film, although there are a few using medium/large format film or digital cameras. At the current time no reasonably priced digital cameras produce good enough results for large size reproduction, although many, particularly the 3-5,000 pixels per inch models, are adequate for producing small digital images for a web site, e-mail transmission and prints up to 6 x 4". But if you are taking pictures to sell or to print them A4 or larger for your own use, then film is currently the best means of capturing the original image.

Once captured on film it becomes possible to digitally scan your pictures at high enough resolution to be able to reproduce them at a reasonable size. However the process of digitally scanning a transparency or negative does require skill and lots of time, not to mention money.

Nikon 4000ED

SCANNERS

There are quite a number of different makes, models and types of scanner on the market. Large A4 flatbed scanners are not generally suitable for scanning film, even if they do have a slide adapter. You really need a dedicated slide scanner. These come in two basic types, drum scanners such as the Shiraz 490 and FlexTight 311 and standard slide scanners such as the Nikon LS4000 and

Nikon 8000ED

If you can afford one, then drum scanners will give consistently better results as they cope better with high contrast images, often a feature of underwater wide-angle shots, where the sun or surface is in the picture.

The results you get from a standard scanner will depend very much on how it is set up and how it is adjusted for each individual slide or film type and of course how skilful you are at using it. Having said that, I have used a CanoScan 2700F for a couple of years now and find it adequate for producing small digital images for this website.

Scanner resolution is usually quoted in dots per inch (dpi). The higher the number of dpi, the greater the quality of the resulting image. Most scanners allow what is called interpolation, where the scanner fills in the detail between scanned points. Interpolated images, at up to double the dpi of the optical scan, may not be as good a quality as an optically scanned (un-interpolated) image of the same resolution.

Colour depth is usually quoted in bits. The higher the number, the greater the colour depth.

Prices of standard slide scanners range from �120 for a 1800 dpi, 36 bit scanner up to £3,000 for a 4000 dpi, 48 bit scanner. Drum scanners cost considerably more!

COMPUTERS

Whatever your choice, you will need to purchase a scanner that is compatible with your computer. Most modern computers such as PCs running Windows 95, 98, 2000 or XP and MACs use a USB (Universal Serial Bus) or Firewire port to connect with peripherals such as scanners. However, if you have a computer running Windows NT, then you may need a scanner that connects via a SCSI or Ultra SCSI card, as my CanoScan 2700F currently does on my old Windows 95 computer.

You will also need a fast processor (1 GHz or more), a minimum of 256 Mb RAM and a high capacity hard disc drive (40 Gb or more) in order to manipulate and store the scanned images, unless you don't mind waiting many minutes each time you make a change to your image . You will also probably need a CD-Writable or DVD-Writable drive to store copies of your digital images. The latter are usually supplied with suitable software to enable the drive to 'burn' digital data onto a disc.

A large (17" or more) monitor will enable you to manipulate your images more easily. Then of course you will probably want a decent colour printer! This package will set you back around �1,500 to �2,000, but specifications change rapidly and prices have been falling at a similar rate, so that the same system twelve months on will be noticeably cheaper or you'll get faster processing, larger hard drive capacity etc for the same price.

SCANNING

Standard slide scanners usually come complete with scanning software, which has to be installed on your computer before you can get down to scanning your favourite pictures. If you are using a SCSI interface, then you will need to install the appropriate software and SCSI card first or get your computer supplier to install it for you.

The scanning software is usually quite easy to install and use, enabling you to select film type, image resolution in terms of dots per inch, and gives you some control over contrast and brightness. The scanning software usually interfaces with image manipulation software, normally purchased separately, so that you can capture an image via the manipulation software.

Before you start scanning, however, it is very important to calibrate your monitor so that the colours you see on screen are the same as those on your transparency. For this you can use calibration software such as OptiCal 3.3. If you are using a PC, set the gamma at 2.2 and the colour temperature to 5,500K, which is similar to a light box.

Although it is tempting to push the resolution beyond the optical limit of your scanner using interpolation, where the software fills in the detail between individual scanned point, you should, if hoping to sell the results, check with your photographic agency as to whether they will accept such images.

All images should be saved as 24 bit RGB TIF format using Adobe RGB (1998). This file format does not lose detail with subsequent manipulation like JPEG format. If you subsequently need to reduce file size for web-deployment always keep the TIF file as an archive and name copies appropriately.

It is vital that all shadow and highlight detail in the slide is retained in the scanned image. Assuming you are using Adobe RGB (1998) then the RGB 'density' reading for shadow should not be much less than 10 while the highlight detail should be around 240.

Ideally the finished file size should be 50-60 Mb, or larger if you are intending to sell your digital images through an agency, or if there is relevant detail or scanning medium/large format film. If you are scanning to generate A4 or smaller prints then a file size of 20-25 Mb may be adequate. If selling your pictures as digital images and your agency is using PCs than they may only accept PC compatible files.

MANIPULATION

Once captured, you may want to manipulate the image, to increase or decrease sharpness, contrast, brightness, colour saturation etc and perhaps to crop the image to improve its composition. Manipulated images can produce stunning results, but again if you are selling your pictures through an agency, you should check that such images are acceptable.

The most popular image manipulation software is probably Adobe PhotoShop 6.0 (cost approx. �560 for Windows; �575 for Mac) , followed by JASC's PaintShop Pro 7 (cost approx. �90.00, Windows only). The latter is considerably cheaper. However, Adobe PhotoShop Elements, a cut-down version of Adobe PhotoShop is slightly cheaper still (cost approx. �70.00).

These image-manipulation software programmes can do most things that could be achieved in the darkroom and much more. The results you can obtain are limited only by your imagination and skill. If you really are serious about manipulating your scanned pictures then I recommend that you attend one of the many courses that are becoming available.

If you cannot afford either the time or money, then you could consider sending your images to a bureau, but bear in mind that you get what you pay for.