called a "modal" function, while localized response is called "zonal". Actuator coupling shows how much the movement of one actuator will displace its neighbors. All "modal" mirrors have large cross-coupling, which in fact is good as it secures the high quality of correction of smooth low-order optical aberrations that usually have the highest statistical weight. Response time shows how quickly the mirror will react to the control signal. Can vary from microseconds (MEMS and magnetics mirrors) to tens of seconds for thermally controlled DM's. Hysteresis and creep are nonlinear actuation effects that decrease the precision of the response of the deformable mirror. For different concepts, the hysteresis can vary from zero (electrostatically-actuated mirrors) to tens of percent for mirrors with piezoelectric actuators. Hysteresis is a residual positional error from previous actuator position commands, and limits the mirror ability to work in a feedforward mode, outside of a feedback loop. Deformable mirror concepts Segmented concept mirrors are formed by independent flat mirror segments. Each segment can move a small distance back and forth to approximate the average value of the wavefront over the patch area. Advantageously, these mirrors have little or zero cross-talk between actuators. Stepwise approximation works poorly for smooth continuous wavefronts. Sharp edges of the segments and gaps between the segments contribute to light scattering, limiting the applications to those not sensitive to scattered light. Considerable improvement of the performance of the segmented mirror can be achieved by introduction of three degrees of freedom per segment: piston, tip and tilt. These mirrors require three times as many actuators compared to piston segmented mirrors. This concept was used for fabrication of large segmented primary mirrors for the Keck telescopes, the James Webb Space Telescope, and the future E-ELT. Numerous methods exist to accurately co-phase the segments and reduce the diffraction patterns introduced by the segment shapes and gaps. Future large space-based telescopes, such as the NASA Large UV Optical Infrared Surveyor will also possess a segmented primary mirror. The development of robust methods to increase the contrast is key for the direct imaging and characterization of exoplanets. Continuous faceplate concept mirrors with discrete actuators are formed by the front surface of a thin deformable membrane. The shape of the plate is controlled by a number of discrete actuators that are fixed to its back side. The shape of the mirror depends on the combination of forces applied to the faceplate,