MakeTiff and ColorPerfect's PerfectRAW: On dark greenish Tiff files and magenta highlights


To start processing your RAW photos with ColorPerfect's PerfectRAW you first need to transfer the image data from the RAW file to a regular Tiff file. To make that task an easy one we provide our auxiliary program MakeTiff.

Users who are new to our digital imaging workflow often ask why the resulting Tiff files look as dark as they do and why they are of a greenish color. A third frequent question is why there can be magenta colored highlights when processing the sensor data stored in such Tiff files with PerfectRAW and more importantly how to cure such.

Apart from explaining the actual reasons for these things the key takeaways of this text will be not to worry about the first two questions as PerfectRAW will take care of that and that the magenta highlight situation is caused by sensor overexposure and can be remedied by activating the Smart Clip feature on ColorPerfect's Main panel. If that is what you were looking for you can stop reading here. If you're curious about the details behind these question however you're welcome to read on.

The example photo we chose for this article shows the labor-intensive process of manual linking at a fully-fashioned stocking maker's clothing factory - just in case you were curious about it.

What does MakeTiff do that Adobe Photoshop et al. don't?

We create our software as plug-ins for the host applications Adobe Photoshop, Adobe Photoshop Elements and PhotoLine because that way we don't have to deal with loading files, saving files, layers, selections and everything else these hosts do great already but can focus on what we do best: Color.

To overcome the prevailing color problems in processing digital RAW photos we first had to solve a more trivial problem. That problem was that in order to get the color right we needed to get to the actual sensor data a camera captures. None of our host applications provide this capability. When opening RAW photos there always is automatic image processing involved that distorts the color. Circumventing that proved to be possible using existing and free tools but the required process was so complicated that we decided to develop MakeTiff to make it easy.

The MakeTiff process interpolates the RAW sensor data and transfers the resulting image and original meta data needed for PerfectRAW into a plain Tiff file. That Tiff file can then be opened normally in Adobe Photoshop et al. without any further image processing being applied to it.

Opening such images in the host application leads to a situation that occurs with no other RAW converter. You get to see a graphical representation of the RAW photo before actually "converting" it. That's what the dark green image is. You may not do anything to it before invoking ColorPerfect and using PerfectRAW but you can see it.

Why do the Tiffs created by MakeTiff look that dark?

After opening them in your host of choice the photos look dark because the data stored in them is linear albeit your RGB working space is not. That is perfectly fine and is so by design. When working with PerfectRAW you need to assign the intended output RGB working space profile to the image first. Doing so causes a mismatch between the resulting display settings Photoshop et al. use and the still unprocessed image data. If it were not for this mismatch the photo would appear less dark but greenish nonetheless.

Why do the Tiffs look greenish?

The initial color of such a Tiff depends on the sensor, the light source and maybe filtration. Most often it looks greenish. Camera sensors themselves do not perform any color balancing. Instead the color or white balancing information gets stored as meta data. That means that there are three factors recorded by the camera that define how to produce gray during the RAW data's processing. Of course it also means that precise white balancing is not necessarily crucial when shooting RAW. You can always define these three factors later. In ColorPerfect you'd do that by setting up a suitable CC filter pack.

Why do I get magenta highlights in some of my photos?

Returning to the final version of the example photo we chose for this article we can see that it has a background that was intentionally overexposed using mobile studio lighting. This was a design decision made to clean out elements from the scene that would have distracted from the subject. If we look at the Tiff created with MakeTiff again we'll notice that there is pure white in the off color balance capture of the RAW photo. In the histograms of this linear image file we can thus see that there are pixels for each color channel that have been driven to their maximum value at the right hand side.

When processing this photo with PerfectRAW we can color balance it using the camera's white balance settings and then adjust the Black slider so that the Highlight readout indicates that there is no clipping for the Highlights anymore. This will lead to a preview image that shows the magenta highlight situation that is common for overexposed sensor pixels. Looking at the image's histograms in this state you'll notice that the histogram bins that were in synch for the white areas in our original off color balance RAW capture have now moved apart due to the color balancing. For both the red and the blue color channels the histogram is now populated in places that are beyond where the sensor stopped recording detail for its green pixels. That is where the magenta color comes from.

How can I remove such magenta highlights with Smart Clip?

There is a single option in ColorPerfect that will inhibit such inaccurate color data from getting into the final image and that will also allow you to use highlight compression on such images again. The option is located on the Main panel and is called Smart Clip. The smart thing about it is that it will always set the correct clipping properties depending on your color balance settings as you adjust them. If we activate that setting in ColorPerfect it'll effectively remove the magenta highlights from our image. With the option enabled we can continue processing our image to this final state or a different one that suits our preference.

Of course the best way of avoiding the magenta highlights is to avoid overexposure but some scenes simply have a greater dynamic range than the camera can capture so the photographer will have to decide whether to underexpose the shadows or to overexpose the highlights. For those cases, mishaps that do happen and for specular highlights we have Smart Clip.