Grunt task recurse files async - help needed

Gruntfile.js

/**
 * I can't figure out why this doesn't work.
 *
 * I've tried using async, but there's no way to know when the exif stuff is done.
 *
 * Please help me understand what I'm doing wrong.
 */

var util = require('util');
var ExifImage = require('exif').ExifImage;

// src/photos contains several photos with exif data
grunt.registerTask('default', function() {
  
  grunt.file.expand('src/photos/*.jpg').forEach(function(el, i, array) {
    // this gets output to the console
    grunt.log.writeln('Attempt to get exif data for ' + el);
    new ExifImage({ image: 'src/photos/' + el }, function(err, exifData) {
      // but neither of these do
      if (err) grunt.log.writeln('Error: ' + err.message);
      grunt.log.writeln(util.inspect(exifData));
      // nor does this
      grunt.log.writeln('Inside new ExifImage');
    });
  });
    
});

grunt.registerTask('default', function() {
  var done = this.async();

  var files = grunt.file.expand('src/photos/*.jpg');
  grunt.util.async.eachSeries(files, function(el, next) {
    grunt.log.writeln('Attempt to get exif data for ' + el);
    new ExifImage({ image: 'src/photos/' + el }, function(err, exifData) {
      // but neither of these do
      if (err) grunt.log.writeln('Error: ' + err.message);
      grunt.log.writeln(util.inspect(exifData));
      // nor does this
      grunt.log.writeln('Inside new ExifImage');

      // Call this to move onto the next image
      next();
    });
  }, done); // done is called when all have completed

});