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Dynamic Range

The dynamic range of a sensor is defined as the ratio of the highest value and smallest non-black value that sensor can capture at the same time.

In a linear 8 bit sensor, this definition gives a value of 28-1 / 1 = 255. In a 12 bit linear sensor the dynamic range is 212-1 / 1 = 4095, 16 times larger, what allows you to distinguish more different gray levels.

The deconvolution process increases the dynamic range of the image. This means that in a restored image you can distinguish more different levels of intensity that in the original one. This is linked to the increase of the intensity range while spread light (blur) is taken back to the sources: bright points become brighter and background regions become darker.

Do not limit the dynamic range of your detector and measure with as many bits as possible, that will also help not to limit the Signal To Noise Ratio (SNR).

Visualization consequences

Since the Huygens Software auto-scales the image between the maximum and minimum intensity when displaying it on the screen, the background features will appear darker. (You may adjust the Gamma Correction to highlight the darker features in the image). But this does not imply a loss of information!!! Read more on Huygens Deconvolution and at RestoredImagesLookDimmer.


Data exporting consequences

Notice that you can loose the gained dynamic range when saving your images for example to TIFF.

Imagine for example that you have a Float Type result image with a maximum intensity of 220, and some other pixels have intensities like 219.0, 219.2 and 219.6. The maximum of 220 is smaller than 255, thus it could be stored directly in a 8 bit TIFF, but then the other mentioned values would have to be rounded to either 219 or 220, loosing the intensity resolution. This happens even if you save the intensities directly in a 16 bit TIFF.

By applying a contrast stretching and exporting to 16 bit TIFF you can preserve the contrast, at least partially. If you scale the maximum up to 65535, the other mentioned values could be 65237, 65297 and 65416 respectively, and you can still distinguish them. Read more about Tiff Scaling.

See also important information for Ratiometric Images.

Artifacts

Reducing the dynamic range of an image can cause Posterization Artifacts.

Contact Information

Scientific Volume Imaging B.V.

Laapersveld 63
1213 VB Hilversum
The Netherlands


Phone: +31 (0)35 64216 26
Fax: +31 (0)35 683 7971
E-mail: info at svi.nl

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