diff --git a/camerad/archon.cpp b/camerad/archon.cpp
index 0a691ad6..d0825ad7 100644
--- a/camerad/archon.cpp
+++ b/camerad/archon.cpp
@@ -88,6 +88,8 @@ namespace Archon {
     this->frame.buftimestamp.resize( Archon::nbufs );
     this->frame.bufretimestamp.resize( Archon::nbufs );
     this->frame.buffetimestamp.resize( Archon::nbufs );
+
+    image_output_type = "disk";
   }
 
   // Archon::Interface deconstructor
@@ -95,6 +97,14 @@ namespace Archon {
   Interface::~Interface() = default;
 
 
+  ImageOutput* Interface::get_image_output() {
+    if (!image_output) {
+      output_handler = ImageOutputFactory::create_image_output(image_output_type);
+      image_output = dynamic_cast<SaveToDisk*>(output_handler.get());
+    }
+    return image_output;
+  }
+
   /**************** Archon::Interface::interface ******************************/
   long Interface::interface(std::string &iface) {
     std::string function = "Archon::Interface::interface";
@@ -1340,7 +1350,7 @@ namespace Archon {
    *
    */
   long Interface::load_acf(std::string acffile) {
-    std::string function = "Archon::Interface::load_acf";
+    const std::string function("Archon::Interface::load_acf");
     std::stringstream message;
     std::fstream filestream;  // I/O stream class
     std::string line;         // the line read from the acffile
@@ -1750,11 +1760,13 @@ namespace Archon {
       logwrite(function, "loaded Archon config file OK");
       this->firmwareloaded = true;
 
-      // add to systemkeys keyword database
+      // add firmware filename and checksum to systemkeys keyword database
       //
-      std::stringstream keystr;
-      keystr << "FIRMWARE=" << acffile << "// controller firmware";
-      this->systemkeys.addkey( keystr.str() );
+      this->systemkeys.addkey( "FIRMWARE=" + acffile + "// controller firmware" );
+
+      std::string hash;
+      md5_file( acffile, hash );
+      this->systemkeys.addkey( "FIRM_MD5=" + hash + "// MD5 checksum of firmware" );
     }
 
     // If there was an Archon error then read the Archon error log
@@ -3300,7 +3312,7 @@ namespace Archon {
               logwrite( function, message.str() );
               #endif
 
-              error = this->fits_file.write_image(fext, this->camera_info); // write the image to disk
+              error = this->get_image_output()->write_image(fext, this->camera_info);
               this->camera_info.extension++;                                // increment extension for cubes
               if ( fext != nullptr ) { delete [] fext; fext=nullptr; }            // dynamic object not automatic so must be destroyed
 
@@ -3326,7 +3338,7 @@ namespace Archon {
             }
 
 //          error = fits_file.write_image(fbuf, this->fits_info);   // write the image to disk //TODO
-            error = this->fits_file.write_image(fbuf, this->camera_info); // write the image to disk
+            error = this->get_image_output()->write_image(fbuf, this->camera_info);
             if ( error != NO_ERROR ) { this->camera.log_error( function, "writing 32-bit image to disk" ); }
             delete [] fbuf;
         }
@@ -3339,7 +3351,7 @@ namespace Archon {
         if (this->camera_info.datatype == USHORT_IMG) {                   // raw
           cbuf16 = (uint16_t *)this->image_data;                          // cast to 16b unsigned int
 //        error = fits_file.write_image(cbuf16, this->fits_info);         // write the image to disk //TODO
-          error = this->fits_file.write_image(cbuf16, this->camera_info); // write the image to disk
+          error = this->get_image_output()->write_image(cbuf16, this->camera_info);
           if ( error != NO_ERROR ) { this->camera.log_error( function, "writing 16-bit raw image to disk" ); }
 
         } else if (this->camera_info.datatype == SHORT_IMG) {
@@ -3349,7 +3361,7 @@ namespace Archon {
           for (long pix=0; pix < this->camera_info.section_size; pix++) {
             ibuf[pix] = cbuf16s[pix] - 32768;                             // subtract 2^15 from every pixel
           }
-          error = this->fits_file.write_image(ibuf, this->camera_info);   // write the image to disk
+          error = this->get_image_output()->write_image(ibuf, this->camera_info);
           if ( error != NO_ERROR ) { this->camera.log_error( function, "writing 16-bit image to disk" ); }
           delete [] ibuf;
 
@@ -3925,7 +3937,7 @@ namespace Archon {
       #ifdef LOGLEVEL_DEBUG
       logwrite( function, "[DEBUG] opening fits file for multi-exposure sequence data cube" );
       #endif
-      error = this->fits_file.open_file(this->camera.writekeys_when == "before", this->camera_info );
+      error = this->get_image_output()->open(this->camera.writekeys_when == "before", this->camera_info );
       if ( error != NO_ERROR ) {
         this->camera.log_error( function, "couldn't open fits file" );
         return error;
@@ -4006,8 +4018,7 @@ namespace Archon {
           // reset the extension number and open the fits file
           //
           this->camera_info.extension = 0;
-          error = this->fits_file.open_file(
-                  this->camera.writekeys_when == "before", this->camera_info );
+          error = this->get_image_output()->open(this->camera.writekeys_when == "before", this->camera_info );
           if ( error != NO_ERROR ) {
             this->camera.log_error( function, "couldn't open fits file" );
             return error;
@@ -4028,14 +4039,14 @@ namespace Archon {
 
         if ( error != NO_ERROR ) {
           logwrite( function, "ERROR: waiting for readout" );
-          this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+          this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
           return error;
         }
 
         error = read_frame();                                           // then read the frame buffer to host (and write file) when frame ready.
         if ( error != NO_ERROR ) {
           logwrite( function, "ERROR: reading frame buffer" );
-          this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+          this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
           return error;
         }
 
@@ -4045,7 +4056,7 @@ namespace Archon {
           #ifdef LOGLEVEL_DEBUG
           logwrite( function, "[DEBUG] closing fits file (1)" );
           #endif
-          this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info ); // close the file when not using datacubes
+          this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
           this->camera.increment_imnum();                           // increment image_num when fitsnaming == "number"
 
           // ASYNC status message on completion of each file
@@ -4076,13 +4087,13 @@ namespace Archon {
 
       this->copy_keydb();                                           // copy the ACF and userkeys databases into camera_info
 
-      error = this->fits_file.open_file(this->camera.writekeys_when == "before", this->camera_info );
+      error = this->get_image_output()->open(this->camera.writekeys_when == "before", this->camera_info );
       if ( error != NO_ERROR ) {
         this->camera.log_error( function, "couldn't open fits file" );
         return error;
       }
       error = read_frame();                    // For raw mode just read immediately
-      this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+      this->get_image_output()->open(this->camera.writekeys_when == "after", this->camera_info );
       this->camera.increment_imnum();          // increment image_num when fitsnaming == "number"
     }
 
@@ -4092,7 +4103,7 @@ namespace Archon {
       #ifdef LOGLEVEL_DEBUG
       logwrite( function, "[DEBUG] closing fits file (2)" );
       #endif
-      this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+      this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
       this->camera.increment_imnum();          // increment image_num when fitsnaming == "number"
 
       // ASYNC status message on completion of each file
@@ -4917,7 +4928,7 @@ namespace Archon {
           #ifdef LOGLEVEL_DEBUG
           logwrite( function, "[DEBUG] opening fits file for multi-exposure sequence data cube" );
           #endif
-          error = this->fits_file.open_file(
+          error = this->get_image_output()->open(
                   this->camera.writekeys_when == "before", this->camera_info );
           if ( error != NO_ERROR ) {
               this->camera.log_error( function, "couldn't open fits file" );
@@ -4999,7 +5010,7 @@ namespace Archon {
                   // reset the extension number and open the fits file
                   //
                   this->camera_info.extension = 0;
-                  error = this->fits_file.open_file(
+                  error = this->get_image_output()->open(
                           this->camera.writekeys_when == "before", this->camera_info );
                   if ( error != NO_ERROR ) {
                       this->camera.log_error( function, "couldn't open fits file" );
@@ -5021,7 +5032,7 @@ namespace Archon {
 
               if ( error != NO_ERROR ) {
                   logwrite( function, "ERROR: waiting for readout" );
-                  this->fits_file.close_file(
+                  this->get_image_output()->close(
                           this->camera.writekeys_when == "after", this->camera_info );
                   return error;
               }
@@ -5029,7 +5040,7 @@ namespace Archon {
               error = read_frame();                                           // then read the frame buffer to host (and write file) when frame ready.
               if ( error != NO_ERROR ) {
                   logwrite( function, "ERROR: reading frame buffer" );
-                  this->fits_file.close_file(
+                  this->get_image_output()->close(
                           this->camera.writekeys_when == "after", this->camera_info );
                   return error;
               }
@@ -5040,7 +5051,7 @@ namespace Archon {
                   #ifdef LOGLEVEL_DEBUG
                   logwrite( function, "[DEBUG] closing fits file (1)" );
                   #endif
-                  this->fits_file.close_file(
+                  this->get_image_output()->close(
                           this->camera.writekeys_when == "after", this->camera_info ); // close the file when not using datacubes
                   this->camera.increment_imnum();                           // increment image_num when fitsnaming == "number"
 
@@ -5072,14 +5083,14 @@ namespace Archon {
 
           this->copy_keydb();                                           // copy the ACF and userkeys databases into camera_info
 
-          error = this->fits_file.open_file(
+          error = this->get_image_output()->open(
                   this->camera.writekeys_when == "before", this->camera_info );
           if ( error != NO_ERROR ) {
               this->camera.log_error( function, "couldn't open fits file" );
               return error;
           }
           error = read_frame();                    // For raw mode just read immediately
-          this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+          this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
           this->camera.increment_imnum();          // increment image_num when fitsnaming == "number"
       }
 
@@ -5089,7 +5100,7 @@ namespace Archon {
           #ifdef LOGLEVEL_DEBUG
           logwrite( function, "[DEBUG] closing fits file (2)" );
           #endif
-          this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+          this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
           this->camera.increment_imnum();          // increment image_num when fitsnaming == "number"
 
           // ASYNC status message on completion of each file
@@ -6044,7 +6055,7 @@ namespace Archon {
       this->add_filename_key();                                      // add filename to system keys database
       this->camera_info.systemkeys.keydb = this->systemkeys.keydb;   // copy the systemkeys database into camera_info
       if (this->camera.writekeys_when=="before") this->copy_keydb(); // copy the ACF and userkeys database into camera_info
-      error = this->fits_file.open_file(this->camera.writekeys_when == "before", this->camera_info );
+      error = this->get_image_output()->open(this->camera.writekeys_when == "before", this->camera_info );
       logwrite( function, "untimed exposure trigger enabled" );
       return error;
     }
@@ -6052,8 +6063,8 @@ namespace Archon {
     // For "disable" there's nothing more to do right now (except close any open FITS file)
     //
     if ( error == NO_ERROR && this->trigin_state == "disable" ) {
-      if ( this->fits_file.isopen() ) {                              // "untimed" could have opened a FITS file
-        this->fits_file.close_file( false, this->camera_info );      // close the FITS file container
+      if ( this->get_image_output()->is_open() ) {                              // "untimed" could have opened a FITS file
+        this->get_image_output()->close( false, this->camera_info );      // close the FITS file container
         std::remove( this->camera_info.fits_name.c_str() );          // remove the (empty) file it created
       }
       logwrite( function, "untimed exposure trigger disabled" );
@@ -6094,7 +6105,7 @@ namespace Archon {
       if (error==NO_ERROR) error = this->wait_for_readout();         // Wait for the readout into frame buffer,
       if (error==NO_ERROR) error = read_frame();                     // then read the frame buffer to host (and write file) when frame ready.
 
-      this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info ); // close the file when not using datacubes
+      this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info ); // close the file when not using datacubes
       this->camera.increment_imnum();                                // increment image_num when fitsnaming == "number"
 
       // ASYNC status message on completion of each file
@@ -6145,7 +6156,7 @@ namespace Archon {
       // Open the FITS file now for cubes
       //
       if ( this->camera.datacube() ) {
-        error = this->fits_file.open_file(
+        error = this->get_image_output()->open(
                 this->camera.writekeys_when == "before", this->camera_info );
         if ( error != NO_ERROR ) {
           this->camera.log_error( function, "couldn't open fits file" );
@@ -6177,7 +6188,7 @@ namespace Archon {
               return error;
             }
             this->add_filename_key();                                     // add filename to system keys database
-            error = this->fits_file.open_file(
+            error = this->get_image_output()->open(
                     this->camera.writekeys_when == "before", this->camera_info );
             if ( error != NO_ERROR ) {
               this->camera.log_error( function, "couldn't open fits file" );
@@ -6193,7 +6204,7 @@ namespace Archon {
           if (error==NO_ERROR) error = read_frame();                  // then read the frame buffer to host (and write file) when frame ready.
 
           if ( !this->camera.datacube() ) {                           // Error or not, close the file.
-            this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info ); // close the file when not using datacubes
+            this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info ); // close the file when not using datacubes
             this->camera.increment_imnum();                           // increment image_num when fitsnaming == "number"
 
             // ASYNC status message on completion of each file
@@ -6210,16 +6221,16 @@ namespace Archon {
         error = this->get_frame_status();                             // Get the current frame buffer status
         if (error==NO_ERROR) error = this->camera.get_fitsname( this->camera_info.fits_name ); // Assemble the FITS filename
         this->add_filename_key();                                     // add filename to system keys database
-        if (error==NO_ERROR) error = this->fits_file.open_file(
+        if (error==NO_ERROR) error = this->get_image_output()->open(
                     this->camera.writekeys_when == "before", this->camera_info );
         if (error==NO_ERROR) error = read_frame();                    // For raw mode just read immediately
-        this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+        this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
         this->camera.increment_imnum();                               // increment image_num when fitsnaming == "number"
       }
       // for cubes, close the FITS file now that they've all been written
       //
       if ( this->camera.datacube() ) {
-        this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+        this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
         this->camera.increment_imnum();                               // increment image_num when fitsnaming == "number"
 
         // ASYNC status message on completion of each file
@@ -8006,7 +8017,7 @@ namespace Archon {
           // open the file now for datacubes
           //
           if ( this->camera.datacube() ) {
-            error = this->fits_file.open_file(
+            error = this->get_image_output()->open(
                     this->camera.writekeys_when == "before", this->camera_info );
             if ( error != NO_ERROR ) {
               this->camera.log_error( function, "couldn't open fits file" );
@@ -8042,7 +8053,7 @@ namespace Archon {
           }
           this->add_filename_key();                                     // add filename to system keys database
 
-          error = this->fits_file.open_file(
+          error = this->get_image_output()->open(
                   this->camera.writekeys_when == "before", this->camera_info );
           if ( error != NO_ERROR ) {
             this->camera.log_error( function, "couldn't open fits file" );
@@ -8065,7 +8076,7 @@ namespace Archon {
         if (error==NO_ERROR && ro) error = this->read_frame(Camera::FRAME_IMAGE);  // read image frame directly with no write
         if (error==NO_ERROR && rw) error = this->read_frame();                     // read image frame directly with no write
         if (error==NO_ERROR && rw && !this->camera.datacube()) {
-          this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+          this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
           this->camera.increment_imnum();                                          // increment image_num when fitsnaming == "number"
         }
         if (error==NO_ERROR) frames_read++;
@@ -8076,7 +8087,7 @@ namespace Archon {
       // (or any time there is an error)
       //
       if ( rw && ( this->camera.datacube() || (error==ERROR) ) ) {
-        this->fits_file.close_file(this->camera.writekeys_when == "after", this->camera_info );
+        this->get_image_output()->close(this->camera.writekeys_when == "after", this->camera_info );
         this->camera.increment_imnum();                                            // increment image_num when fitsnaming == "number"
       }
 
diff --git a/utils/utilities.cpp b/utils/utilities.cpp
index a4311ef5..b732fbf2 100644
--- a/utils/utilities.cpp
+++ b/utils/utilities.cpp
@@ -747,13 +747,9 @@ long md5_file(const std::string &filename, std::string &hash) {
         }
 
         instream.close();
-    } catch (std::ifstream::failure &e) {
-        std::cerr << "md5_file( " << filename << " ): " << e.what() << "\n";
-        hash = "ERROR";
-        return 1;
     }
     catch (std::exception &e) {
-        std::cerr << "md5_file( " << filename << " ): " << e.what() << "\n";
+        std::cerr << "ERROR md5_file( " << filename << " ): " << e.what() << "\n";
         hash = "ERROR";
         return 1;
     }
@@ -772,7 +768,6 @@ long md5_file(const std::string &filename, std::string &hash) {
 
     return 0;
 }
-
 /***** md5_file *************************************************************/