convert tiff to jpg format

Since a TIFF can contain multiple frames but JPG can't, you need to convert each single frame into a JPG.

Taken from Windows Dev Center Samples:

public static string[] ConvertTiffToJpeg(string fileName) 
{ 
        using (Image imageFile = Image.FromFile(fileName)) 
        { 
            FrameDimension frameDimensions = new FrameDimension( 
                imageFile.FrameDimensionsList[0]); 

            // Gets the number of pages from the tiff image (if multipage) 
            int frameNum = imageFile.GetFrameCount(frameDimensions); 
            string[] jpegPaths = new string[frameNum]; 

            for (int frame = 0; frame < frameNum; frame++) 
            { 
                // Selects one frame at a time and save as jpeg. 
                imageFile.SelectActiveFrame(frameDimensions, frame); 
                using (Bitmap bmp = new Bitmap(imageFile)) 
                { 
                    jpegPaths[frame] = String.Format("{0}\\{1}{2}.jpg",  
                        Path.GetDirectoryName(fileName), 
                        Path.GetFileNameWithoutExtension(fileName),  
                        frame); 
                    bmp.Save(jpegPaths[frame], ImageFormat.Jpeg); 
                } 
            } 

            return jpegPaths; 
        } 
} 

using System.Drawing;
using System.Drawing.Imaging;

Bitmap bm=Bitmap.FromFile("photo.tif");
bm.Save("photo.jpg",ImageFormat.Jpeg);