Image Metadata List (camera maker) struggling to achieve this in mvvm pattern

public class CameraMakersViewModel : ObservableObject //2nd VIEWMODEL - Create Collection For Camera Manufacturers
    {
        private ObservableCollection<string> _FoundManufacturers; //The COLLECTION/LIST OF CAMERA MANUFACTURERs
        public ObservableCollection<string> FoundManufacturers
            {
            get
            {
                return this._FoundManufacturers;
            }
            set
            {
                if (this._FoundManufacturers != value)
                {
                    this._FoundManufacturers = value;
                    OnPropertyChanged(() => this._FoundManufacturers);
                }
            }


        }


        public CameraMakersViewModel(FileInfo f) //Model Get MetaData And Add To Collection
        {
            FileStream fs = new FileStream(f.FullName, FileMode.Open, FileAccess.Read, FileShare.Read);
            BitmapSource img = BitmapFrame.Create(fs);
            BitmapMetadata md = (BitmapMetadata)img.Metadata;
            this.FoundManufacturers = new ObservableCollection<string> { md.CameraManufacturer.ToString()};
        }

        public CameraMakersViewModel() //Get Current Selected Drive
        {
            
        }

    }

This will probably look like a mess to some, I'm new to mvvm, to explain I have 2 List Boxes, 1 combobox, the combobox lists available hardrives, when one is chosen the listbox is filled with thumbnails, that works fine, the other listbox I want to list the various camera maker metadata from the listed pictures, i.e a list that says "sony, cannon, Nikon" whatever brands it can pick up from the photos, I'm struggling to achieve this so much help would be appreciated