C F Systems Dunthorn Calibration

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Getting Linear 16-bit Scans

The ColorNeg plug-in requires a good, clean 16-bit linear scan to work properly and some ColorNeg users have informed us that getting such a clean scan is often quite tricky to do. But users also confirm that ColorNeg works very well indeed when given a properly scanned negative and an appropriate set of film gammas. While the ColorIntegrity plug-in does not require a linear scan, it is at its best when starting with one.

This web page contains instructions for getting a good linear 16-bit scan from several types of systems and scanners. These instructions have been successfully used by current ColorNeg users. Further contributions are welcomed - just e-mail us (cfs.cfs@c-f-systems.com) and they will be added with such minimal editing as required to be consistent with the page, and with or without attribution, as requested.

For scanners that are not specifically covered, looking through these fairly brief instructions may help you understand what to look for with your own software. It appears that scanner software writers often feel it necessary to gild the lily, intentionally distorting color in hopes of impressing the user. While these distortions may fool the eye in a resulting positive image, they can have major undesirable effects when applied to a negative. Some scanner software also misleadingly labels settings or controls. Seeing some examples of these will help you to identify similar tactics in your scanner software. They may even make you look again at the methods you have been using to scan positive images.

Epson
Hewlett-Packard
Imacon Flexcolor
Minolta Dimage Scan-Multi Pro
VueScan
Nikon Coolscan V ED
Using a Digital Camera as a Scanner

Hewlett-Packard

These instructions are based on the HP Scanjet 4670 with transparency adapter using the standard HP TWAIN interface in Photoshop, based on the HP "Photo & Imaging Director" software.

This HP software is implemented in "dot-Net" and is quite flaky, partly as a result of that. One consistent problem is that settings frequently do not "stick." Until you establish a routine that you know works it is always necessary to double-check what you do.

Before opening Photoshop (close Photoshop if it is open), start the HP Photo & Imaging Director. Select Scan Preferences:

to get the following dialog:

On this dialog, make sure "Automatically Adjust Color" and "Use Enhanced Color" and not checked. We prefer to leave "Automatically adjust exposure" unchecked and find that there is no difference in result whether checked or not on our test system, but you may wish to try this if your negative scans are unsatisfactory.

On the Quality Vs. Speed tab you will need to check "scan at maximum pixel depth," which is the setting to get 16-bits/channel.

Then OK and exit from the HP Photo & Imaging Director. Now start Photoshop.

Start the scan using File->Import and select your HP scanner from the list. Note that it is possible to make most of the above settings from the HP TWAIN interface that comes up at this point. However, we have found that some settings made at this point do not stick, sometimes not even for the current scan. You will need to check "Slides from TMA" to get the slide adapter to work. Be sure to select Slides rather than Negatives:

When you have the scanned image preview showing, make sure the preview is negative; else go back and review the above setting. Then make the following settings:

You will need to click the appropriate side-arrows to get the settings to display. Starting from the top, be sure that Scale is 100%. Please don't ask why the default is 300%. Next, we prefer to set the Highlights and Shadows both to zero. Shadows must be set to zero, but Highlights normally can be set to positive values without harm. Midtones is what HP has decided to call gamma and they have given it a completely nonsensical scale as well, going from -100 to 100 and agreeing with no one else in the world. While they give no clue at all exactly how they warp gamma into this form, a value of -67 appears to give a good approximation to a linear scan. Very likely it is not perfect, but it is as close as you will get with this software.

Next, we generally choose not to sharpen, believing that Photoshop does this better where it is needed. The dpi for scanning is of course up to the user requirements.

With these settings we were able to get acceptable results when applying ColorNeg to the image loaded into Photoshop.

Imacon Flexcolor

(Based on Flexcolor 4.0)
The Imacon scanners under Flexcolor appear to add in an uncalled for "compensation" when a straightforward adjustment of gamma back to 1.0 (linear) is specified. This thoroughly distorts shadows in a scan, yielding terrible results as NegPos (ColorNeg) inverts these shadow distortions to spread through the entire image. We have found it necessary to revert to directly using the "3f" raw file created by Flexcolor to work around this. Used with this raw file NegPos (ColorNeg) works very well.

First time only

Open the Setup window. Set the following settings.

General tab	Mode: RGB Descreen: 0 Adaptive light: 0 Film type: Positive Enhanced shadow detail: OFF
Contrast tab	Contrast: 0 Brightness: 0 Gamma: 1.0 Shadow depth: 0
Texture tab	All OFF
ColorSync / ICM tab	Embed profile: OFF Convert: OFF

Save the setup as 'Raw linear scan' or similar.

To scan a colour negative

Scan must be performed using the 3F format.

Select menu item File / Scan 3f. This pops up the Scan 3f control window.
Set film type to Positive
Set Setup to 'Raw linear scan', as saved in the step above.
Turn off 'Auto levels'
Set resolution in percentage of your scanner's maximum resolution.
Click Scan. This saves a file with extension '.fff'

To open the linear scan in Photoshop, you must have the 'Imacon 3f.8bi' plug-in installed (registered Imacon users can download this from the www.imacon.dk site). Open the 3f scan, and run NegPos (ColorNeg) conversion.

Minolta Dimage Scan-Multi Pro

With this scanner we used the DS MultiPRO TWAIN interface software that comes with the scanner or can be downloaded from http://kmpi.konicaminolta.us/eprise/main/kmpi/content/support kmpi.konicaminolta.us/eprise/main/kmpi/content/support

Start Photoshop, then Files->Import and select the DS MultiPro TWAIN driver from the list.

The film size and preferences must be chosen, here for 35mm film and for 6x6 film:

35mm

Here the important setting is for "slide film" rather than for negatives. The remaining settings are user preference, although GEM should be avoided.

Then, set preferences, obtained by pressing the button with the hand pointing to a list in the above control consoles:

The selection of 16bit linear is the important setting here. We find that checking autoexposure works well with color negatives, but checking it is optional. Do not check Color Matching. The remaining settings are according to user preference.

We normally preview, pick a focus spot, and scan. After reading the image into Photoshop, apply NegPos (ColorNeg).

VueScan

Manual: http://www.hamrick.com/VueScan/VueScan.pdf

VueScan supports output of 'raw' scan data. The VueScan manual implies that a raw scan contains the linear scanner data, as required by NegPos (ColorNeg). Empirically, VueScan with Epson flatbed scanners (Epson 3200 and Epson 4870) provide very good input data for well-behaved NegPos (ColorNeg) colour conversion.

VueScan setup

Input tab

Set up VueScan to scan to a 16-bit 'raw' output file.

NB: Although in theory the Media setting should not affect the generated raw data, in practice it does. Experimental evidence shows that much better conversions result from 'Color Negative'. This also has the advantage of making the preview image easier to work with while preparing for the final scan.

Output tab

Turn off the normal TIFF output. Vuescan's attempted colour conversion will not be used. Turn on the Raw output file.

After scanning:

Open the raw file in Photoshop. It will not have a profile attached, but assigning Adobe RGB seems to work.

Convert using NegPos (ColorNeg).

A correspondent has told us that the above procedure does not do ICE corrections on a scan and that the following excerpt from the VueScan manual explains how to do this properly.

Raw output with
(Professional Edition only)

This specifies which operations in VueScan cause the raw scan data to be written to a file.

If set to "Scan" (or "Preview"), the raw file is written at the same time as the scan (or preview). In this case, the raw file has not had infrared cleaning or grain reduction applied.

Assuming that the preview is used primarily to prepare for the final scan, this option should normally be set to "Scan" so that the highest resolution raw image can be saved.

If set to "Save", it is written at the same time as other files are written (i.e. after a scan completes or when the "Save" button is pressed). In this case, the raw file has had infrared cleaning and grain reduction applied.

It's much faster to save the raw file at the same time as the scan, since writing the file is overlapped with scanning the data.

Advanced Option: This option is displayed when "Output | Raw file" is set.

Raw save film

(Professional Edition only)

If this option is set, and if "Output | Raw output with" is set to "Save", then the film corrections are done before the raw file is written.

Advanced Option: This option is displayed when "Output | Raw file" is set and when "Output | Raw output with" is set to "Save".

Nikon Coolscan V ED

It's easy to get good linear, "16-bit" scans of negatives on the Nikon Coolscan V ED if you follow two simple rules:

Don't let the Nikon software provide any enhancements to the scan (with the possible exception of Digital ICE).
Never use the SA-21 stripfilm adapter because it won't work unless the film type is set to "Negative". Instead, use the MA–21 slide mount adapter fitted with an FH-3 film holder. Note that the FH-3 must be purchased separately since it is an option.

You must use the TWAIN interface to properly set the Main Scan Gamma mode (see below). To do this, from the Photoshop File menu, choose Import and then select the Nikon Coolscan. Once the Main Scan Gamma mode setting has been made, the setting will "stick" and you can use the stand-alone scanner app if you want. The initial scanner interface is shown below. Note that the film type menu is set to "Positive" and the colour (color for Yanks) model menu is set to "RGB".

The "Tools" button on the interface brings up the palette below.

The "Layout Tools" and "Crop" Palettes are used in the usual manner. Their only purpose is to determine the size and orientation of the image.

The following tools should never be used:

Curves
Color Balance
Unsharp Mask
LCH Editor
Analog Gain
Scan Image Enhancer

My experience has shown that Digital ICE (Normal) can be toggled on with little or no harmful effect. However, the other options in the "Digital ICE4 Advanced" palette should never be used and left untoggled.

Note that the "Scanner Extras" option must be set at a depth of 14 pixels. This is a high as this scanner will go but 14 pixels seem to be sufficient for NegPos (ColorNeg) purposes and will produce a "16-bit" image file.

The "Prefs" button on the interface brings up the preferences dialog.

The Gamma preferences is where you set up to get the linear scan that is so important for proper operation of NegPos (ColorNeg). "Linear" is the same as "Gamma = 1.0." The easiest way to do this is to set the Main Scan Gamma mode by selecting "Use Preview Gamma" and then set the Preview Gamma to 1.0. Note that you must be using the TWAIN interface to see the Main Scan Gamma mode selection radio buttons - they will not show up in the stand-alone scanner app. Once this has been set, the setting will "stick" and you can use the stand-alone. Remember that if you are scanning an image that is not intended for NegPos or ColorIntegrity (ColorNeg or ColorPos) , you should set the Preview Gamma back to the system value, normally 2.2. If you use the scanner both in TWAIN mode and stand-alone mode or if you use it for other than linear scans it is a good idea to check the Gamma Preferences dialog at the start of each session to be sure the Preview Gamma is set to 1.0, as required for NegPos (ColorNeg) .

It is also possible to select Use Custom Gamma with that set to 1.00, but it seems less convenient. The mechanics of going between the TWAIN and stand-alone scanner app behave differently as well.

Colour Management should be disabled. A colour space (if so desired) can be assigned in Photoshop.

Set Single Scan with Auto focus enabled but disable Auto exposure.

All Automatic Actions should be disabled.

Advanced Color options should be set as shown.

Preview Settings can be set as shown. The preview settings do not effect the ultimate scan but I think it is a good idea to turn off everything except auto focus and Digital ICE.

Sometimes the preview scan displayed on the interface appears to be blurred. This is probably due to the limitations of the scanner when trying to do a "quick and dirty" preview of a very dark negative. However, the definitive scan always turns out sharp.

Using a Digital Camera As a Scanner

A number of users have reported using a digital camera - slide duplicator setup to "scan" color negatives for use with ColorNeg, but so far no one has volunteered to describe a system for this scanner web page. Since there seems to be real interest in this method we will describe what we have learned from successful users and add a few cautions and suggestions of our own. But please understand that we have not used a camera as a scanner ourselves. When we mention specific brand names below it is not to be taken as a recommendation from us of one brand over another - we are just reporting what some successful users have mentioned using.

First of all, the most commonly mentioned cameras in use appear to be Canon EOS, shooting in RAW mode. It seems likely that other digital cameras would work as well, shooting in RAW mode, providing they can be arranged for the necessary close-up imaging. Most users are using slide duplicators of one kind or another, with the Elinchrom mentioned by several.

As it is with any scanner, with a camera "scanning" system the primary problem is getting a good, unaltered 16-Bit/Channel linear image. Many digital cameras will deliver 16-Bit/Channel RAW images, but RAW image converters are normally designed to work with positive images and may apply tweaks to make their results look more impressive. These tweaks may be relatively harmless in positive images but very harmful to color negatives because the often fairly large tweaks intended for the shadows will actually affect the highlights when you are scanning a negative. Even more important, the image is normally converted as "gamma-encoded," as is generally required for positive images on a PC. ColorNeg requires that the negative be left as linear rather than altered to be gamma-encoded. This can be a major roadblock - in particular, we have been unable to make Photoshop RAW deliver a linear image. Worse, the newest Adobe Photoshop RAW converters have a "Curves" tab and under the Curves tab is a "Linear" option on the pulldown. Be aware that this so-called "Linear" curve does not produce a linear image! Do not be fooled by Adobe's misleading use of the term.

The best option, used by almost all of the successful users we have heard from, is to use a third-party or separate RAW converter that does have a linear option. There are several RAW converters available but we have had no personal experience with any of these. Some successful users have mentioned using BreezeBrowser, but we cannot recommend one RAW converter over another. Just be sure that getting a linear image is an option, and turn off any image enhancing features, including "color management," that the converter normally uses.

Although we strongly recommend using a RAW converter that will extract a linear image directly from the RAW data, it is possible - but tedious and in some ways less satisfactory - to work with the gamma-encoded images normally produced by Photoshop RAW. This can be used as a test before investing in a RAW converter.

First set Photoshop RAW to do the least damage possible.

Temperature 6050
Tint 0
Exposure 0.00
Shadows 0
Brightness 50
Contrast 0
Saturation 0

You may find it more satisfactory to set Exposure to -1.00 and produce a very dark image, as Adobe RAW is known to distort highlights. In some versions of ACR Brightness of 0 works better than Brightness of 50 and in place of Temperature and Tint in some versions of ACR it is easier to select a specific light source, like Flash - just be consistent in this.

Run this image through Scantique, a second plug-in that comes with ColorNeg and is normally installed along with it. The default Gamma setting of 2.2 is usually what is required. The result will be as near to a 16-bit linear negative as you can get under these conditions, but will be less accurate than an original linear scan. Run the Scantique result through ColorNeg.

We have had one report of the blue channel (in the negative digital image) being noisy and/or banded, but if this is common, we are unaware of it. If and when this happens the reason is fairly simple. The orange mask present in most color negatives causes the image to be fairly weak in the blue - that is, the (Levels) histogram will be much more narrow for blue than for green or red. Although in theory (and usually in practice) it is not necessary to do anything special about the orange mask, in this case it will help to use a blue filter. This will reduce the intensity of the red and green channels allowing the camera to increase the overall exposure and thus increase the blue channel. At this point we have no specific suggestion for which blue filter to use, but a filter which expands the blue histogram up more nearly to the green should be adequate. Make sure you do not filter out enough red and green so that the blue histogram becomes wider than the red and green histograms. The use of a filter will have no effect on the ColorNeg conversion.

A noisy blue channel is less likely to occur with an original linear scan. The above process we describe for getting Photoshop RAW to work takes a non-linear ("gamma-corrected") image from RAW and then makes it linear using Scantique. Because the actual "scan" is not linear to begin with, the blue channel noise is more likely to occur.

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