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Scanning Colour Negatives 

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By Ian Lyons

 

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A Computer Darkroom Tutorial

 

One of the main advantages of using Negative type film is the ability to capture a wider dynamic range than can be achieved with Reversal types (slide/chromes). Unfortunately the image data is usually compressed into a much smaller density range. The big trade-off is our inability to immediately see the information due to the orange mask.

Most film scanners are supplied with software that is capable of scanning both Reversal and Negative type film. However, not all scanner software is created equal and some is just plain useless at scanning negatives. I see little point in using a negative type film only to have the scanner software trash a fair percentage of the highlight and shadow detail in an attempt to get a visually pleasing image straight from the scanner. It's much better to manually tune the image so as to extract every last "bit" of detail. Needless to say this is easier said than done - or is it?

The following is a technique used by many who find themselves doing battle with inadequate scanner software. With care this technique has the potential to produce results equal and occasionally superior to those obtained from even the most expensive scanner applications.

23 October 2002 - It has recently been brought to my attention that some view the technique discussed below as flawed or at best less - than perfect. The implication being that other more effective techniques exists. This may be so, and since I haven't suggested that the technique discussed below is anything other than an alternative to less than perfect scanning software - I'm not arguing with them. However, at no time did I suggest that anyone should consider this technique as their primary method of scanning colour negatives. The following information should clarify any settings that may be causing their confusion: 

  1. You should ensure that any Automatic Exposure systems within the scanner software are disabled.

  2. Ideally the scanner Gamma should be set somewhere between 1.5 and 2

  3. The key to success is getting a scan that does NOT clip the highlight or shadow in ANY colour channel.

If after trying the following method you still get poor scans from your negatives then you might wish to try VueScan from http://www.hamrick.com

An Adobe Acrobat version of this tutorial can be downloaded by clicking the following logo.

Step 1

  • Scan the negative as positive making sure that no image corrections are made. Ideally your scanner should support 48bit colour mode - if it does use it! 

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Scanned Negative

Step 2

  • Choose Invert from the Photoshop Image Menu. The telltale orange mask of the Negative will be replaced with a low contrast image having a blue cast.

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Inverted Negative

Step 3

  • Select Levels from the Photoshop Image menu. As in the example shown below the histogram for the combined RGB Channel is usually not full-scale. For the time being don't be tempted to make any adjustments to the RGB Channel.

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RGB Channel

Step 4

  • Select the Red Channel

  • Drag the Highlight and Shadow Input sliders so as they just touch the end pints of the histogram

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Red Channel Corrections

Step 5

  • Repeat step 4 but this time select the Green Channel.

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Green Channel Corrections

Step 6

  • Repeat step 4 but this time select the Blue Channel.

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Adjusting the Blue Channel

Step 7

  • Return to the RGB Channel. If the adjustments associated with steps 4 to 6 were done correctly you should find that the RGB Channel histogram is spread out more than the original. In the example shown below I have managed not to clip Highlight or Shadows.

  • Adjust the Shadow and Highlight sliders as required.

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The  RGB Histogram

The majority if not all colour casts will have been removed. If they haven't make the necessary adjustments in the normal way using either Levels, Curves or Colour Balance. For examples of how this can best be done see Tutorial 3

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Nearly Complete

Step 9

  • Using the Photoshop Curves tool adjust the image contrast. A simple S-curve as shown below is a good starting point. I also increased Saturation a little. Each image will require unique adjustments and the screenshot shown below is only one of many options.

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Increase Contrast

Although no master piece the final image is shown below. Not bad for about 5 minutes work.

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The Final Image - Townhouse, Dublin

 

 

 

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