digitalizar negativos com scanner normal

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Scanning Colour Negatives for Maximum Quality

By Ian Lyons © 2002

One of the main advantages of using Negative type film is the ability to capture a widerdynamic range than can be achieved with Reversal types (slide/chromes), although this isusually compressed into a much smaller density range. The big trade-off is our inability toimmediately see the information due to the orange mask.

Update: 3 October 2002 - It has recently been brought to my attention that someview the technique discussed below as flawed or at best - less than perfect. Theimplication being that other more effective techniques exists. This may be so andsince I haven't suggested that the method discussed below is anything other than anALTERNATIVE 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 theirprimary method of scanning colour negatives. The following information should clarifyany settings that you may be causing their confusion:

1. You should ensure that any Automatic Exposure systems within your scannersoftware are disabled.

2. Ideally the scanner Gamma should be set for anything between 1.5 and 2.3. The key to success is in 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 thenyou might wish to try VueScan from http://www.hamerick.com

Most film scanners are supplied with software that is capable of scanning both Reversal andNegative type film. However, not all scanner software is created equal and some is just plainuseless at scanning negatives. I see little point in using a negative type film only to have thescanner software trash a fair percentage of the highlight and shadow detail in an attempt toget a visually pleasing image straight from the scanner. It's much better to manually tune theimage 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 inadequatescanner software. With care this technique has the potential to produce results equal andoccasionally superior to those obtained from even the most expensive scanner applications.

Step 1

• Scan the negative as positive making sure that no image corrections are made.IdeallyIf your scanner supports 48bit colour mode - use it!!


Scanned Negative

Step 2

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

Inverted Negative

Step 3

• Select Levels from the Photoshop Image menu. As in the example shown below thehistogram 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.


RGB Channel

Step 4

• Select the Red Channel

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

Red Channel Corrections

Step 5

• Repeat step 4, but select the Green Channel.


Green Channel Corrections

Step 6

• Repeat step 4, but select the Blue Channel.

Adjusting the Blue Channel

Step 7

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

• Adjust the Shadow and Highlight sliders as required.


The RGB Histogram

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

Nearly Complete

Step 9

• Using the Photoshop Curves tool adjust the image contrast. A simple S-curve asshown below is a good starting point. I also increased Saturation a little. Each imagewill require unique adjustments and the screenshot (Curve adjustment) shown belowis only one of many options.!


Increase Contrast

digitalizar negativos com scanner normal

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