MultiscaleAdaptiveStretch version 1.1 comes with two new features. Now, we can fine tune the Contrast Recovery option using the Intensity slider. Contrast Recovery allows to have a contrast level similar to a delinearization using a midtones transfer function while preserving the star profiles. Now, we can choose how much we want to recover the contrast.
A good example is the Orion nebula. Without Contrast Recovery, we can compress the dynamic range to preserve the structures inside the nucleus. But this comes at the cost of decreasing the overall contrast in the image. Using the Intensity slider we can reach an intermediate solution, as shown in the following figure:
At left, the Intensity parameter was set to 0; on the middle to 0.6; at right to 1.0. Usually, when we increase the Intensity parameter, we'll need to decrease the Aggressiveness parameter to compensate for the increase in contrast. The image at right has an aggressiveness of 0.9, 0.8 on the middle and 0.7 at right.
MAS 1.1 comes also with a Background Reference section that allows to define a custom background region in the image. Up to now, the Target background parameter was defined by the median of the entire image. Using a background region of interest we can define where the Target background is calculated. For instance, the default 0.15 value gives a very dark result in this M42 image. But, using a background region in the bottom right corner allows to define the illumination level in the darkest area of the image:
The following images show the improvement using this new feature. In the first image, Target background is referred to the entire image, so the stretched image has a median value of 0.15. In the second image, we used the background area on the corner, so the stretched image has a median value of 0.15 on that specific area.
Referring the background to a specific area in the image is also useful when we have very dark objects in the image. In the following example we have a dark nebula,which can be easily clipped using an automated delinearization tool like MAS. We can set a Background Reference area inside the darkest area of the nebula:
Without using the Background Reference option, we clip the nebula, as can be seen below:
Using the Background Reference option, we avoid clipping significant information in the image:
This results in an image without significant loss of information where we can then manage the contrast using other tools like CurvesTransformation.
As a side note, it's important to point out that the background reference area in MAS does not necessarily have to be a true sky background area, but the darkest area in the image. In the last example, the reference is the dark nebula, which is indeed darker than the sky background.
A good example is the Orion nebula. Without Contrast Recovery, we can compress the dynamic range to preserve the structures inside the nucleus. But this comes at the cost of decreasing the overall contrast in the image. Using the Intensity slider we can reach an intermediate solution, as shown in the following figure:
At left, the Intensity parameter was set to 0; on the middle to 0.6; at right to 1.0. Usually, when we increase the Intensity parameter, we'll need to decrease the Aggressiveness parameter to compensate for the increase in contrast. The image at right has an aggressiveness of 0.9, 0.8 on the middle and 0.7 at right.
MAS 1.1 comes also with a Background Reference section that allows to define a custom background region in the image. Up to now, the Target background parameter was defined by the median of the entire image. Using a background region of interest we can define where the Target background is calculated. For instance, the default 0.15 value gives a very dark result in this M42 image. But, using a background region in the bottom right corner allows to define the illumination level in the darkest area of the image:
The following images show the improvement using this new feature. In the first image, Target background is referred to the entire image, so the stretched image has a median value of 0.15. In the second image, we used the background area on the corner, so the stretched image has a median value of 0.15 on that specific area.
Referring the background to a specific area in the image is also useful when we have very dark objects in the image. In the following example we have a dark nebula,which can be easily clipped using an automated delinearization tool like MAS. We can set a Background Reference area inside the darkest area of the nebula:
Without using the Background Reference option, we clip the nebula, as can be seen below:
Using the Background Reference option, we avoid clipping significant information in the image:
This results in an image without significant loss of information where we can then manage the contrast using other tools like CurvesTransformation.
As a side note, it's important to point out that the background reference area in MAS does not necessarily have to be a true sky background area, but the darkest area in the image. In the last example, the reference is the dark nebula, which is indeed darker than the sky background.
