Idea Digital Imaging

Forget transparencies, the negative is the "real" test of your scanning and colour editing skills.?

Why bother scanning negs??

A considerable amount of information is lost when a negative image is printed to photographic paper. Scanning negatives gives us access to that information.?

Negative film will always be popular with photographers - particularly those who are shooting in environments where they don't have precise control over exposure.?

Many negative stocks have an exposure range that exceeds 4.0 log - so you can get your exposure completely wrong and still get an image that is printable!?

Are negatives difficult to scan?

From a purely technical point of view, negatives are easier to scan than transparencies.

High-end drum scanners are designed to retrieve detail from the densest transparencies. This capability is wasted on negatives and usually leads to very flat results.

Although the exposure range is large, the density range of a negative is small - therefore the cheapest scanners can faithfully record the darkest and lightest tones on a negative.

So why do some scanner operators avoid negatives?

The biggest problem with the negative is that you can't "see" what the image should look like before you do the scan!

The image is reversed and orange. It was also designed to be printed on to another photographic stock before being viewed.

This is a real pain for the scanner operator. They have to take on the additional skills of a "photographic printer" to get the best results from the negative.

How do negatives work?

Believe it or not, negatives are created in the exact same way that transparencies are...

You have 3 layers of chemicals that are sensitive to blue, green and red light. They even have the same yellow filter layer as transparencies to improve the sensitivity of the green and red layers.

The only difference is that negatives produce their dyes in direct relation to the amount of light that they are exposed to, whereas transparencies have an inverse relationship between dye formation and exposure.

Why are negatives orange?

The coloured dyes used to absorb and react to specific wavelengths of light in transparency and negative films are not "perfect".

In a perfect world, the cyan dye would only absorb red light and the magenta and yellow dyes would only absorb green and blue light respectively.

In real life the dyes tend to overlap in their absorption - in particular the magenta dye is prone to absorb significant amounts of blue light.

Both negative and positive films have a yellow filter layer separating the cyan and magenta/yellow layers to cut down the "cross-talk" between the dyes.

The fact that negatives were never meant to be viewed directly meant that additional control could be used to eliminate "cross talk" by introducing "coloured couplers".

To avoid unwanted green and blue absorption in the red wavelengths, the cyan dyes are "coupled" to a magenta-yellow dye. Likewise, to avoid unwanted blue absorption in the magenta layer a yellow coupler is used.

The combination of "coloured couplers" causes the orange colour of the negative stock.

Scanning considerations

Remember that negatives are "intermediary" images. They only produce a recognisable and believable image once they have been subjected to a further processs - the photographic printing process.

In other words, you can't measure colour values directly from the negative and relate them to specific output values on your final image. Operator interpretation is needed - which is why we said that you need to have the skills of a photographic printer to get a good result from the negative.

The lack of density in the negative requires steep tonal adjustments to add contrast to a very "flat" image. These adjustments are not intuitive to scanner operators who are used to scanning transparencies.

Transparencies normally require a delicate tonal adjustment to flatten the image so that both highlight and shadow detail are held. Negatives require strong edits and decisions made on what shadow and highlight detail should be sacrificed to give the subject "impact".