Friday, June 1, 2007
Turning On The Brights With DxO Optics Pro
DxO Optics Pro's Highlight Recovery brings overexposures back to life
DxO Optics Pro image-editing software works in an alternate way to restore clipped highlights in RAW images. The program uses downloadable Correction Modules—camera and RAW personalities specific to the equipment used to take the shot—to customize performance to match the image on which you're working. Optics Pro's Lighting and Highlight Recovery adjustments take over from there.
In many images, even in the histogram, portions of an image may seem to be overexposed when they're actually not on RAW data. In these cases, only one or two of the three RGB channels may be saturated (reaching maximum value), while the other one or two still have readable color information. Optics Pro's Highlight Recovery corrects for this eventuality by analyzing the remaining information in the channels left unsaturated and reducing the balance of the blown-out channel or channels to even out the total exposure of the three channels.
For instance, in daylight conditions, there's more light emitted in the green wavelengths than in the red and blue wavelengths. Consequently, the green channel has a higher probability of overexposure.
In situations like this, standard RAW conversion would increase the balance of the lowest saturated channels (in this case, the red and blue channels) to match the levels of the highest (in this case, the green channel). This leads to oversaturation of all three RGB channels, of course, instead of just one.
Optics Pro's Lighting and Highlight Recovery, on the other hand, takes advantage of the data available and reconstructs essentially in the reverse. A negative exposure-value bias is calculated by automatically compensating through a DxO Lighting adjustment, which then reduces the saturated channel or channels to equal the saturation value of the active channel or channels.
The negative exposure compensation is then balanced by DxO Lighting to ensure that the EV level doesn't affect shadows and midtones negatively. From there, the luminance of the newly reconstructed pixels is modulated, and color reconstruction is done, with a concentration on avoiding undesirable reconstituted color casts on the neutral “gray” areas of the image (snow, for example).
All of this is performed quickly and nondestructively, recorded as a set of processing instructions in a small .dxo file. Only at the final rendering stage will the files be combined to create the new file.
DxO Optics Pro Elite maintains support for JPEG and RAW files for most popular D-SLR manufacturers, including Canon, Nikon and Sony; it's Mac- and PC-compatible. Estimated Street Price: $299.
For more information and a complete list of cameras and lenses supported, visit the DxO Website at www.dxo.com.
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