New Post: TIFF Correction (color space & bit depth)

I'm trying to write a function that will convert any TIFF into a set format acceptable by third party imaging software. The accepted formats are bitonal, 8-bit grayscale, and 24-bit RGB. In particular, I'd like to change 32-bit and 16-bit to the expected bit depths as well as non-RGB color spaces (specifically CMYK) to RGB. Here's my current code:

using (var frames = new MagickImageCollection(source))
{
    var isCmyk = frames[0].ColorSpace == ColorSpace.CMYK;
    int depth = frames[0].BitDepth();

    if (depth == 32 || isCmyk)
    {
        foreach (var frame in frames)
        {
            frame.Format = MagickFormat.Tif;
            frame.CompressionMethod = CompressionMethod.LZW;
            frame.ColorSpace = ColorSpace.sRGB;
            frame.Depth = 24;
        }

        frames.RePage();

        return frames.ToByteArray();
    }
    else if (depth == 16)
    {
        foreach (var frame in frames)
        {
            frame.Format = MagickFormat.Tif;
            frame.CompressionMethod = CompressionMethod.LZW;
            frame.ColorSpace = ColorSpace.GRAY;
            frame.Depth = 8;
        }

        frames.RePage();

        return frames.ToByteArray();
    }
    else
    {
        return source;
    }
}

From what I can tell, the problem is that the color space is always sRGB, and the bit depth is always 8, regardless of what I see in the detail properties of the image file.

Am I going about this conversion the wrong way?