public TwainImageEffectsFlags Flags { get; set; } 
Flags that indicate the method behavior
If the NegotiateHighlight is set, then the ImageEffects property will get/set Highlight property
If the NegotiateContrast is set, then the ImageEffects property will get/set Contrast property
If the NegotiateBrightness is set, then the ImageEffects property will get/set Brightness property
using Leadtools;using Leadtools.Twain;public void ImageEffectsPropertyExample(IntPtr parent){TwainSession session = new TwainSession();session.Startup(parent, "manufacturer", "productFamily", "version", "application", TwainStartupFlags.None);TwainImageEffects imgEffects = session.ImageEffects;imgEffects.Flags = TwainImageEffectsFlags.NegotiateBrightness | TwainImageEffectsFlags.NegotiateContrast | TwainImageEffectsFlags.NegotiateHighlight;float contrast = imgEffects.Contrast;float highlight = imgEffects.Highlight;string msg = String.Format("Image Contrst = {0}\nImage Highlight = {1}", contrast, highlight);MessageBox.Show(msg);imgEffects.Brightness = 100;session.ImageEffects = imgEffects;TwainAcquirePageOptions pageOpts = session.AcquirePageOptions;pageOpts.PaperSize = TwainPaperSize.A4;pageOpts.PaperOrientation = TwainPaperOrientation.Landscape;session.AcquirePageOptions = pageOpts;session.Shutdown();}