Digitisation workflow.

As a general rule scan your originals once at a very high resolution. Save these scans then work on copies of them. Resizing to a smaller images or lower resolution is comparatively easy and fast. Getting a higher resolution than your archived copy without losing optical quality means a whole new re-scan - much time, effort and possible damage to your original.

Handling originals.

The recommendations for safely handling originals at the digitisation point are:

• The digitisation area must be as clean and as dust free as practical and you should try not to touch any of the original material surfaces. Ideally protective lint-free gloves should be worn when handling originals to protect them from your as much wear as possible as well as the oils in your skin. Slides and other transparencies can get quite dusty and hairs can become attached. These can be removed with careful application of a clean air device such as a puff brush.
• The capture device and PC should be arranged to ensure maximum ease of access. You should also ensure ample layout table space so as to reduce handling accidents when placing originals in the equipment.

Loading the scanner

It is preferable to use multi-frame holders for 35mm slides and negatives as this often enables quicker transfers. Even some better flat bed scanners with transparency hoods will come with these and often with other holders for medium format transparencies too.

Scanning

In the very first instance it is recommended that the first scan of a new item and media type is done at a quite low resolution and the results assessed for colour and tone fidelity against the original. This will provide useful guidance for further high quality scanning from the collection and save time if any adjustment is required as a really high resolution scan will take much longer.

Scanning Images

Resolution

A higher resolution will represent the original more accurately because it captures more pixel information. Since the physical size of collection items will vary, it is important to adjust the spatial resolution to get optimal results.

For example the final image after processing, resizing etc should be a minimum of 300dpi (300 to 600 is ideal for print) so if I have a 6x4" postcard and wanted to eventually print out a very high quality (600dpi) 12x8" print (twice the size) I would have to scan the original 6x4 in at 1200dpi.

Quite often people worry about the large size an scanned image looks like on their computer screens when viewed at 100%. Don't be! Your screen almost certainly has a resolution of 96dpi. This means that at 100% the above 1200dpi scan would look about 12 times its real size. If you want to see all the image on your screen don't resize the image, simply reduce its screen magnification using the zoom out command in whichever image manipulation package you are using.

Bit Depth.

The greater the bit depth, the greater the number of tones (greyscale or colour) that can be represented. It is therefore recommended to scan images at the highest setting your scanner is capable of but bear in mind that many image packages can only handle 24 bit images (24 bit is 16 million colours and will suffice for almost anything).

Colour Space

The colour space of an image determines how the colours will be represented in different mediums, it is important to use the same colour space (correctly calibrated) throughout your work flow, a good standard colour space to use is the Adobe RGB (1998).

Processing Images

It is important to do any corrections to the digital images such as colour changes whilst the original is available for comparison. Dust and scratch removal however doesn't always require the original to be viewed. It's also worth checking your scanner's default scanning settings - it's not unknown for scanners to artificially sharpen images by default as well as have automatic dust and scratch removal. If, for instance, you're scanning an aerial view of woodland - do you really want the scanner to try and remove things it thinks are specks of dust or scratches on the film or would you rather see all your leaves and small branches?

Saving to disk

The recommended format for the Archived high quality image is an RGB Uncompressed TIFF. If your image manipulation package allows it it's sensible to have the thumbnail option activated too.

Each file name should be unique to each digital image and should make the image identifiable. No file names should be repeated otherwise confusion about the identity of the image will result.

For example the digital image could be named with the acquisition number followed by the image number eg. OP697-01.tiff

Adding technical image metadata

Technical image metadata is the data which describe the digital image itself, e.g. format, resolution, file-size etc. They can also include 'capture' details, such as creation date, creator (scanner/operator).

Other metadata is also very useful for locating particular images. Keywords are particularly helpful.

Storage of captured images

Because the archive images will be rather large and the hard disk space on production machines is, to an extent, precious it may be required to write the data to another storage device or portable storage medium on a regular basis to free production resources. This will also serve as a backup system.

I know that hard disks often quote a life-spans in millions of hours but I've rarely had one last more than three years. If a 500GB disk fails on you it means your likely to lose a mass of valuable images. With huge disks now available for buttons there's really no excuse for not regularly backing things up. (If you start to here clicking noises emanating from any of your hdds back up immediately!)

CD or DVD burners are fairly standard, but each disk can take a number of minutes to write, the failure rate for the media is quite high and large data volumes would create a very large number of disks. I'd recommend that if your backing-up onto these silver wonders you choose reputable manufacturers to start with, store them in a fairly cool place ad out of the light - and duplicate these discs yearly - unfortunately they can fail over time.

Recording Information

Assuming you have one it is important to also insert the image path (where the scanned image resides) into a relevant collections management system (Adlib, Modes etc.)