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Tone Mapping

What is Tone Mapping?

Defined, Tone Mapping is a technique used to map a set of colours to another. For our purposes, it’s mapping differing dynamic ranges from multiple RAW files into a one image. As we discussed earlier in ”Capturing enough Dynamic Range” our three exposures capture a different piece of the tonal range of a single scene. Whereas the 0EV exposure captures mid tones, the -2EV exposure captures the shadow details and the +2EV exposure captures the highlight details, Tone Mapping takes these three sets of tonal ranges and maps them into a single output image. Tone Mapping takes our 32-bit HDR output file and reveals the necessary details contained within the shadows and highlights for editing on a normal computer display monitor. 

Ok, so if you haven’t done so already, click the button clearly marked “Tone mapping”. This will bring up your first visual of your HDR masterpiece. Please keep in mind that what you first see is far from your final HDR image. So don’t worry if things look off. This is just the first step of many in our quest towards a professional looking HDR image. 

 

The Details Enhancer

Photomatix has two methods of processing a 32-bit HDR file, only one of which is of interest to me and the one that will be discussed within this tutorial, the Details Enhancer. So, make sure the Details Enhancer tab is the active tab to follow along in the following workflow. The other tab — Tone Compression — is not something we will be discussing here.

What you’ll see within the Details Enhancer tab — depending on your version of Photomatix — is a long list of sliders and intimidating words that you probably have no idea what they mean. But don’t worry, that’s the goal of this tutorial — to show you how to best utilize the functions of all the tools available for creating a high-quality HDR image. I’m using Photomatix Pro version 3.1 so my screen has all the sliders displayed vertically up and down the left column of the application window with my tone mapped image to the right. Prior versions had these sliders targeted to different tabs and were not visible all at once. Regardless of the version you use, you should be able to follow along easily enough.

The best part about the newest Photomatix Pro 3.1 is that all the sliders are available to the user at the same time. All are logically laid out from top to bottom in a logical workflow pattern. What I mean is, the order in which the sliders are displayed top to bottom is generally the best sequence to follow when editing your HDR file. 

Let’s start from the beginning and work our way top to bottom through the Details Enhancer tab:

Tone-Mapping

  • Strength -  This setting controls the overall strength of the contrast. The maximum value of 100 provides the maximum increase in contrast enhancements. Photomatix’s default setting is 70. I typically increase to between 80 and 100 on most images. 
  • Color saturation - The color saturation slider controls the global color RGB saturation during the tone mapping process. The Photomatix default setting is 46. As tempting as it may be to add saturation to your image during the tone mapping process, I highly urge you to resist and leave this setting somewhere between 40 and 60. Color saturation adjustments have the best results when left to Lightroom and Adobe Photoshop CS3.
  • Light Smoothing – This controls the smoothing of contrast variations throughout your HDR image. A higher value will yield a more natural looking HDR image, while a lower value yields a more artistic — some would argue artificial — look and feel. 
  • Luminosity  - This adjusts the compression of the tonal range, in affect adjusting global luminosity. When you move the slider to the right you will boost shadow detail and brightens the overall image. When moved to the left you will see the opposite effect, giving your HDR image a more natural look. The default setting is 0 and I rarely adjust this slider. 

Tone Tab

  • Black Point / White Point - Both of these sliders set the minimum and maximum values for the tone mapped image. When moved to the right, the sliders to will increase global contrast. When moved to the left, the sliders help reduce clipping at the extremes. I will typically slide both sliders to the right as far as possible before clipping is visible in the histogram. 
  • Gamma – This slider will adjust globally, the mid-tone of the tone mapped image in turn brightening or darkening the image as a whole. The default Photomatix value for Gamma is 1.0.

Color Tab

  • Temperature – Here we adjust the global color temperature of your tone mapped image. Moving to the right, the temperature slider will give a warmer colored (yellow/orange) look. Moving to the left will give your image a cooler and more bluish feel. I tend to like a warmer image and will set this slider to 1 or 2. Remember, color correction is best accomplished in Lightroom and or Adobe Lightroom so as tempting as it may be to slide this a great deal, resist the urge. 
  • Saturation highlights – This will adjust the color saturation within the highlights. A positive number setting will increase the color saturation in the highlights, while a negative value will decrease saturation. A default setting of 0.
  • Saturation shadows - This slider adjusts the color saturation within the shadows. A positive number setting will increase the color saturation in the highlights, while a negative value will decrease saturation. A default setting of 0.

Micro Tab

  • Micro-contrast – This slider sets the level of accentuation of local details
  • Micro-smoothing –  This will help smooth local detail enhancements. Micro-contrast can help reduce noise in areas like sky and will often times give a cleaner look in the final Tone Mapped image. Photomatix’s default value is 2. Depending on the HDR file I am working on, this slider can be very helpful, however, the Loupe may not accurately depict the effect of this slider. 

S/H Tab

  • Highlights Smoothing - This will help reduce contrast enhancements in the highlights and the value of the slider sets how much of the highlights range is affected. The Micro-Smoothing control is useful for preventing white highlights from turning gray and also helpful for reducing halos around objects placed against bright backgrounds. The default setting is 0 and one adjustment that can be very helpful on images with large flat areas like a blue sky.
  • Shadow Smoothing – This slider reduces contrast enhancements in the shadows. 
  • Shadow Clipping - The Shadow Clipping slider determines how much of the shadows range is clipped. This slider can help reduce noise in dark area of an image taken in a low-light situation. The Photomatix default value is 0.

Process the Image – Save as a 16bit TIFF File

Next Step: [Editing your 16bit HDR TIFF File with Lightroom 2]

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