You don't need to use the convert.exe program anymore. Almost all the functionality from ImageMagick is available in Magick.NET. And if it is not please tell me so I can try to add it.
You can set the compression method like this:
Adding those two new methods is not much work and you are probably not the only one that could use it. With your help Magick.NET will become a better product for everybody.
You can set the compression method like this:
using (MagickImageCollection images = new MagickImageCollection()) { images.Read("first.tiff"); images.AddRange("second.tiff"); // You only need to set this for the first image in your collection. images[0].CompressionMethod = CompressionMethod.Group4; images.Write("outputfile.tiff"); }