Why's SD -> Ethernet Card -> Webbrowser so slow?

it makes sense in my code i have

int16_t c;
          while ((c = file.read()) >= 0) {
client.print((char)c);
          }

adapting it with the information you provide, is something like

byte clientBuf[64];
            int clientCount = 0;
              clientBuf[clientCount] = file.read();
              clientCount++;

              if(clientCount > 63)
              {
                // Serial.println("Packet");
                client.write(clientBuf,64);
                clientCount = 0;
              }
            
            //final <64 byte cleanup packet
            if(clientCount > 0) client.write(clientBuf,clientCount);            
            // close the file:
            file.close();

is this right?