Some scanners such as those of Nikon provide additional features:

• Autofocus: the image is focused all along the film, an indispensable feature; a must-have.
• Image Correction and Enhancement (ICE): scratches and emulsion digouts are filled with colour (but not grain). This saves a lot of time later in case the originals have been damaged somewhat. However because scratches are not filled with grain, they may later still need to be treated by cloning. Note, however, that prints are not very sensitive to repaired scratches without grain. The ICE technology was developed by Kodak who discovered that an infra-red scan of the image pierces through all colour layers to see scratches, dust and lint. The infra-red image is then used to remove scratches by filling the image from neighbouring pixels.
• Restoration of Colour (ROC): the image is restored according to loss of colour with age. This can also be achieved in the photo editing software. I have noticed that my earlier slides (20 years old) benefit from this option but the colour correction can entirely be achieved with your photo editor, which has become my preferred method as it gives more control.
• Grain Elimination (GEM): in theory, a scanner should be able to apply the most sophisticated techniques to eliminate graininess but in practice this boils down to various forms of blurring, which should be done at a late moment in the editing process and not at the very beginning. My advice: don't use it.
• Sharpening: not helpful since this must be the last step in the editing process.
• Multiple sampling: the image is scanned several times to reduce noise. A good scanner won't need this and just scans more slowly to achieve consistent results with dark images.
• Tone curve tool: this is perhaps the most important tool in the digital darkroom. By scanning for a soft image, keeping the blacks out, the highest degree of colour fidelity is achieved. See further on this page.
• Colour correction: useful where large corrections need to be made, such as for some negatives. Not of practical use for slides since colour correction is an elaborate phase in the editing process.
• LCH editor: images can be corrected by Luminosity (B/W intensity), Chromaticity (amount of colour) and Hue (colour code). Chroma or colour intensity correction is an important tool for fine-tuning the result but can easily be overdone. However, it is true that all colour films due to imperfections in their dyes, suffer from colour dilution which can be compensated for by increasing the chromaticity slightly. Telephoto lenses also dilute colour and images obtained with them benefit from increased chromaticity. Likewise images obtained with wide angle lenses may need to be de-saturated (reduced in chromaticity). Leave it for the last step.
• Analog gain: most film scanners allow you to tweak the analog gain for each channel, which allows for colour correction and film base colour correction at its most basic level. This is the preferred method for calibrating your scanner and film using the greyscale image below. Make sure you are working in manual mode rather than auto-levels or white balance.

Calibrating the scanner You have to calibrate the scanner for each type of film you are using. Click on the calibration sheet to print a larger version and keep it in your camera box. Make one of the black boxes even blacker by sticking some black velvet or other very black material on (or shading it with your hand when photographing it). Stick the sheet on non-transparent cardboard. For each film type take a photo of this test pattern. Blur the image by disabling autofocus and defocusing it. In this manner the graininess of the paper won't show through. the idea behind this is that all black to white neutral densities have equal values for RGB. Thus (40,40,40) is neutral dark grey; (120,120,120) is neutral mid grey; (240,240,240) is neutral almost white.

Last but not least, print the scanner manual and reread it several times. It contains good information and you must become a confident and professional scanner operator - the best.

Scanner manufacturers must provide calibration curves for each brand and type of negative film. Instead, they often apply an automatically adjusting logic whereby the lightest point in the photo is assumed to be white and the darkest black. Between these two points the colour curves are 'calibrated' automatically. Although this often produces near-satisfactory results in snappies, it is a pain for those photos that have no black or white points (like underwater). Then the scanned result is nasty, requiring extensive colour correction before and afterwards. The diagram shows how to correct such problems. Use the (calibrated by you) tone curves for each colour until highlight white and/or mid tone greys are balanced. Since these are major signal corrections, they must be done during scanning and not later on.

Note that this is not a disadvantage of negative film but a shortcoming of the scanner's logic, its inbuilt software. For the time being it appears something one has to live with, a symptom of colour technology's infancy. However, users of negative film will find the digital darkroom techniques of more value than those shooting slides.

A major colour shift may also occur in case some of the scanned image does not cover the film base which is coloured for negative films. Make sure the scanner does not see the cut edges.

Scanners need maintenance too because atmospheric dust and grime settle onto optical surfaces, causing unwanted blurring. Once every two years the unit must be serviced and cleaned. Make sure you buy a scanner with good service backup. Scanners with electrical ventilators for internal cooling particularly suffer from this problem. With modern technology it is not necessary for a scanner to have a cooling fan.
 
 

1. mounting and cleaning: start with a clean image. Buy some isopropyl alcohol (50ml lasts a long time) from the paint shop or local chemist because it dissolves grease and acts like alcohol without affecting the emulsion layer. Get some white gloves from the photographic supplier. Gently wipe the image clean with the glove or your oldest handkerchief. Mount it in the slide/neg holder. Use a manual blower brush to puff-wipe it again. Use isopropyl only as a last resort!
2. scanning with major corrections: in the scanner software use the tone curve tool to approach the log-lin curve (depending on the subject). Produce a soft image for highest colour fidelity and in order to be able to correct the density of bright objects (the sky) by masking. Save the image in a systematical way. See filing and backup below. From here on, use your photo editing software. Enable the scratch removal option.
3. cropping: Where an image needs to be cropped, do it now, since this requires less cleaning. Look carefully at the edges for any black or white intrusion. Crop them off with the image/paper size or canvas tool. Use the crop tool or rectangular mask (followed by crop to mask) to crop off large parts.
4. cleaning with the clone tool: your image is a bit bleak at this stage, which shows blemishes clearly. Set the enlargement scale to 1:1 for one pixel on screen = 1 image pixel or better (for fine scratches 2:1 or 200%). Scan from left to right and top to bottom and remove impurities. See the use of the clone tool below. Save the image to be able to fall back to in case further editing ends in disaster.
5. colour/density correction with mask: this advanced technique will be discussed in the chapter on masking techniques. The idea is to do it here since the image has enough colour fidelity to allow for partial density corrections. Use the tone curve tool to adjust partial density. The brightness/contrast tool requires more care for this.
6. colour correction: the main colour corrections are done now although fine tuning may occur later on. See the chapter on colour correction below. If the image looks very weak, do some density correction first.
7. density correction: the whole image is now adjusted for the final look. Blacks are created, but preferably near-blacks for your archival storage. There's no way back.

See the chapter on density correction below. It pays to make a checkpoint (temporary backup) now in case of later editing mistakes.
8. chroma correction: weak images improve by intensifying colour chroma slightly (5-10%). For slides that have lost chroma in the darks and the highlights, chroma correction with a density dependent mask may be necessary. Use chroma correction with care. It is also provided in the Brightness/Contrast/Intensity (BCI) tool as intensity.
9. gamut test: just to make sure, apply the gamut test to see whether any colours have been pushed outside the printable range. Culprits to watch are chroma correction and density correction.
10. blurring and resampling: so far, the image has benefited from maximal noise which renders colours more truly, as multiple pixels average out to represent true colour. Now the noise needs to be reduced as at the same time sharpness is increased. These are two opposing requirements which must be handled with skill and care. A mask may be necessary. Resampling may be needed to arrive at the minimal allowable file size. See the chapter on blurring and sharpening.
11. sharpening: several sharpening tools exist but two have most use: the unsharp mask and the adaptive sharpening. Skilful use of these leads to largely improved results. See the chapter on blurring and sharpening.
12. web pictures and screen images: once the master image has been made and saved, it can be reduced to much smaller sizes and compacted further than an original. See the chapter on resampling.

• reduce the visibility of the blemish: it is not always possible to remove it completely, but softening its impact may already be enough. Think about the soldier's face he is not able to hide, but he can hide its characteristics by painting it disruptively. Make a blemish look less like one. This is particularly important for hiding back scatter in underwater photography.
• replace the blemish by something that is very similar: this is essentially what cloning aims to do.
• replace it with somethig that is different but acceptable: a difficult technique but often done. It requires skill, inventiveness and insight. It allows large parts of the image to be replaced, if need be, even from an image stored on file (clone from file).

In principle, the cloning must be done with the smallest brush, approximately three times the size of the width of a scratch or half the size of a blotch. Begin cloning all the small spots and skip the larger ones to be done with a larger brush, which also needs already cleaned territory and a less detailed view. A brush size of 15-20 pixels is quite useful at the beginning. Set opacity to 75% (transparency 25%) and soft edge to no more than 50%. This is necessary to retain graininess. Otherwise cloning becomes more like polishing and the polished patches stand out like a sore thumb. Select the nearest similar patch to clone from. Brush across the line between the two patches. If you move towards, you will clone a repetitive pattern becoming smoother as you go, which is wrong. If you move away, something similar but less disturbing happens. Change direction frequently and for larger patches, nibble away at their edges working from the outside inward.

During the second pass with the larger brush, set brush size to match the background sharpness or unsharpness rather. This will make it easier to tackle the larger blemishes.

To replace part of an image with something totally different, be artistic and inventive. Set brush size to the largest affordable, about 1/4-1/3 of the patch. Now brush the main bits in without overstepping boundaries. Then decrease the brush size without changing the distance to the cloned patch and work on the details of the outline. Make sure graininess is as expected.
 
 
 

Film processors' first reaction to complaints is that they never caused the scratches, but that they are the fault of you and your camera. Nobody ever complains. Don't believe it. Here is how they make all the scratches on your films:
The film is yanked out of the cassette and taped onto the processing conveyor. This threatens your first frames (and at the end of the film a few more). As it moves through the processor, a chance of scratching is minimal but new threats appear in the form of dust and even lint, when the filters are not cleaned regularly. The processing chemicals can also leave streaks on both sides of the film. But the main problems occur when the 'dried' film is handled.
When the 'dried' film exits the developer, the emulsion is still soft. It takes in fact over 24 hours for it to harden sufficiently to stand handling. Worse still, when the film is printed immediately and then sleeved, the emulsion is still able to fuse with the sleeving material, bonding bits of paper to the emulsion. Needless to say that this destroys your film. Professional laboratories do not use paper sleeves but transparent plastic sleeves which do not have this problem.
So, most labs handle the 'dry' film when its emulsion is still unfit for handling. Operators are always in a hurry and the film is rough-handled to meet time schedules. Worse still, most machines have not been polished such that all sharp edges on chromium-plated guides and pathways have been securely smoothed. As a result, the film gathers numerous scratches from printing alone. Ironically, the prints do not show these scratches but reprints do.
Then the film is sleeved by a sleeving machine. You would not believe that any film handling equipment has rollers touching the image rather than the sprocket path, but sleeving machines do. They have rollers that engage with the images and spew the film four or six frames at a time, but not precisely. So the operator pulls back on the film now and then, which causes short deep scratches at each fourth frame or so.

Here is what you should have your laboratory agree to, in order to prevent scratching:

• Make them aware that you are serious about scratches and that your film is more special than anyone else's. Make them aware that you know how and when scratches arise. Report back any scratches with solid evidence of such, like a print-out of the infrared channel.
• After developing, have the film hung and dried for a full 24 hours or at least over-night. This is by far the most significant act to avoid scratching!!
• Do not accept the use of a sleeving machine but have your films cut and sleeved manually.

• Regularly check the pressure plate in your camera for smoothness and clean it with a soft cloth. Scratches caused by the camera show as straight 'telephone lines', sometimes interrupted but always precisely at the same place.
• Do not change film in a sandy/ dusty environment.
• Always handle your film with cotton gloves.
• Give the emulsion extra time to harden before handling your processed films.
• Run your fingers over every part of the film guides in your scanner and polish any sharp edges with the finest of emery paper.
• Write the first two frames off (use them for colour calibration), and do not take the last frame of the film for this causes the camera to wind hard on before discovering that there is no more film.

Find out what the short-cut key is to sample the RGB of a square of pixels because you will use it a lot. Try to memorise the values for RGB, but particularly how many points they differ. This forms the basis for your colour correction. The colour correction has a number of components:

• shadows: the eye does not tolerate colour cast in the shadows. Attempt to bring them to neutral dark grey so that they can turn into neutral black when increasing contrast later. But exceptions apply. Play around with colour casts by deliberately introducing them into the shadows and printing the results of a test image.
• mid tones: colour correction delivers most pronounced results in the mid tones. If neutral mid-grey is not available, use your eyes to judge what is right. In general watch out for red. Mid tones can be fine tuned at a late stage but do the highlights and shadows now.
• highlights: the eye is not very sensitive to colours in the highlights and these become bleached in the printing process anyway. But it is good practice to adjust the highlights to neutral white, except for special lighting conditions like sunsets.

So the best way of adding yellow is by reducing blue, because red + green = yellow. The best way of adding cyan is by reducing red because cyan = green + blue. It sounds a little confusing but this is how additive colours works. Note also that red can make a landscape picture somber but it makes skin tones glow. Yellow makes a picture look dirty.
 
 
 

Remember that photography is a multiple stage process unlike our eyes which convert the real world directly into an image in our brains. By comparison, a photo usually takes another step (slide) or two steps (photo) or three steps (neg/slide, scan, print). In the process some of the original colour intensity may get lost, and this happens also when slides and negatives age or when they are underexposed. Use the chromaticity editor with care to restore colour. It can easily be overdone and when gamut is exceeded, your image remains damaged.

The hue editor is of little practical value, except that it can be used to warm or cool the image somewhat. Used to excess, it becomes a powerful creative tool. You may find it useful in creating sunset effects.
 
 
 

You have to learn to understand the histogram to see how the luminance is spread between black and white. It is somehow a photographic sport to push a photograph out between these two margins without losing detail, at least that was the game of black and white photography. However, in colour photography we are guided more by how to make the image look like the real thing. It pays to try to make your photo look real so that you can adapt it later for creative reasons.
 
 
 

The standard brightness/contrast tool is important for using the available colour space (256 levels) and to come close to what the image should look like. However, this tool keeps the same contrast level throughout the range (straight line) and is not suitable for softening or hardening one part of the scale. In the diagram the effect of these tools is shown. The brightness tool shifts the whole histogram left or right even when it clips. In the example the highlights will be affected by the black line. The contrast tool rotates the curve, which has the effect of widening the histogram, darkening the dark parts while equally brightening the bright parts. In the example some highlights will be clipped. Note that in some editing software the tone curve tool can be used for this purpose by placing the straight lines visually as desired.

The tone curve tool is the most versatile tool in the tool box and you will use it already when scanning. As the above example shows, the classical contrast and brightness tools can be done with this tool too. But you can do more.  linear: the linear 'curve' is there for reference as it forms the starting position and has no effect. You can slide the top node of this 'curve' down its vertical axis, thereby reducing contrast. log-lin: the theoretical density correction to make densities look more natural, but consider this curve as the envelope beyond which one seldom goes. It is done intuitively by placing two nodes on the linear curve and pulling both up and sideways. This curve will make the image rather washed and dull and needs to be followed up with the s-curve, allowing one to shift humps in the histogram to the density of maximal interest while making the image peppy again.

• brighten: by placing a node in the middle of the tone curve and pulling it up, the mid tones will be brightened. At the same time it decreases contrast (softens) the highlights while also increasing contrast in (hardens) the shadows. Note that it shifts the middle of the histogram to the right. Shifting the mid tones is the most used brightness correction, as it does not shift the darks and highlights and does not lose colour information.
• darken: by placing a node in the middle and pulling the tone curve down, the mid tones of the image will be darkened while at the same time contrast increases in the highlight and decreases in the shadows. It creates the 'slide look' with high contrast, but unlike slides it retains soft detail in the shadows. Note that it shifts the middle of the histogram to the left.
• s-curve: by placing nodes at 20% and 60-80%, pulling the first one down (slightly) and the second one up, the mid tones are made more contrasting while at the same time both the highlights and the shadows are softened. This is a most important curve for shifting contrast and brightness to where it is matters most. Place the two points judiciously and study their effect before applying the result to the whole image. This is perhaps the most important tone curve that you will also use most. The s-curve makes your image look sunny. It widens the middle part of the histogram while compressing and softening the end parts.
• z-curve: it doesn't really look like a z, but I have named it this way to distinguish it from the opposite s-curve. It is a tricky effect that brings the highlights down and at the same time the shadows up, while increasing contrast on both. However, the mid tones become dull. So it is of importance only to those images that have two important humps in their histograms, located too far apart, such as the sky and the field in nature photography, with nothing of importance in between. The z-curve is then an indispensable tool to improve the image. A steep z is usually followed by a shallow s-curve to compensate for lost contrast in the mid tones.

The z-curve is particularly helpful after an autoadjust, or after scanning contrast-rich slides. But remember that it increases contrast in the highlights and the shadows, which is undesirable. Autoadjust NEVER gives the BEST result!

Phew! That was an extensive treatise on this powerful tool, but it has more tricks in store!
What did I say before? Don't make blacks until at the very end of the process. Once a pixel becomes black or near-black, it loses all colour information and there is no way back.
 
 
 

A Fujichrome 50 slide scanned without correction using a linear tone curve, as is customary.

The same slide scanned with the log-lin curve. Shadows and darks show detail but the image looks dull, yet all colour information is there. Notice the halos in the blacks, could be caused by dirty optics/dust.

Colour corrections applied and contrast placed where it matters, using the s-curve. The image looks natural and sunny with soft shadows and highlights.The wave-wash provided neutral white.

A Fujichrome 50 slide scanned without correction. The image would improve considerably from brightening, but shadow detail becomes gritty.

The same slide scanned with the log-lin curve looks dull but the detail in the shadows looks smooth.

After colour correction and contrast adjustment with the tone curve tool, the image looks natural and sunny.

creative tone curves The tone curve tool can be used to create stunning colour effects similar to solarisation in the darkroom. Solarisation happens when a photographic print is exposed again during development. This darkens and inverts the highlights while also creating edge effects. The solarisation curves shown here do not precisely achieve this but they achieve what cannot be done in the darkroom, see photographs below.

The original image, a diver coming down a fresh water cave. The image consists almost entirely of two colours.

Inverse: the image becomes a negative. Cyans become reds.

Solarise1: a strong s-curve which inverts highlights and shadows somewhat.blacks, reds and blues.

Solarise2: inverts the mid tones. New colours appear.

Solarise3: inverts the highlights and shadows.

Solarise4: inverting the mid tones to highlights.

solarise5: inverts the shadows to the mid tones.

Mid-tones: a density-dependent grey scale mask for blurring and sharpening. See use of masks below.

Edge detect and invert creates the mask for smart sharpening.