SPOT 4.1 Basic and Advanced Software Manual for SPOT Insight ...

Ch. 5 – Preparing to Take a PictureNote: Gamma adjustments in live imaging are controlled exclusively via the Live ImageControls dialog. If you are using the Snap option to capture an image via the Live Imagewindow, the Gamma Adjust setting that you enter on the Image Setup window has no effect onthe final image capture.To automatically gamma adjust an image after it is captured, follow these steps:1. Check the Gamma Adjust box on the Image Setup window.2. Enter a gamma value between .1 and 4.0. Although there is no formula for determining a gammavalue, gamma values are typically between 1.3 and 1.7Note: Although the gamma adjust option is typically used to lighten the mid-tones of an image,entering a value between .1 and 1 will darken the mid-tones.3. Select one of the following options: HSL, HSV, or RGB.InsightB/WIf you are using an Insight B/W camera, the color space options are not available. Gamma adjustment isautomatically set to use RGB, the recommended color space for monochrome image editing.HSL (Hue Saturation Luminance), HSV (Hue Saturation Value), and RGB (Red Green Blue) are threedifferent color spaces. A color space is any coordinate system that is used to mathematically representcolor.−−The HSL color space is an intuitive model based on the three attributes that are common to allcolors: hue, saturation, and luminance. The HSL color space assigns a value for each colorattribute (e.g., hue, saturation, and luminance). In this color space the brightest saturated color isconsidered to be 50 % luminance. Above 50 % luminance, saturated colors transition throughpastel shades before reaching pure white at 100 % luminance. This process mimics the naturalperception of objects illuminated by broadband light sources.The HSV color space is similar to the HSL color space except that it uses value instead ofluminance. In this color space, the brightest saturated color is considered to be 100 % value.This allows you to modify images that contain only saturated colors (e.g., fluorescence) withoutchanging the bright, saturated areas to pastel or white.−The RGB color space assigns a red, green, and blue value to each pixel in an image. This is themethod that color computer monitors use to display images.The process by which the program applies gamma to an image capture differs according to the colorspace that you select. The following table briefly describes how gamma is applied in each of the threecolor spaces and lists situations where the use of one color space would be preferable to another.Color Space Gamma Adjustment Process Recommended UsageHSL 1. RGB pixel values are translated to HSL (hue,saturation, and luminance) values.2. Gamma is applied to the luminance.The HSL option is ideal for allcolor images exceptfluorescence images.3. The HSL values are translated back to the RGBpixels.HSV 1. RGB pixel values are translated to HSV (hue,saturation, and value) values.The HSV option is ideal forfluorescence images.RGB2. Gamma is applied to the value.3. The HSV values are translated back to the RGBpixels.Gamma is applied separately to the red, green, and bluepixel values.The RGB option is ideal formonochrome images.User Guide to the SPOT Insight Camera 109