1 Introduction

2 Shutter characterization
2.1 Observations and data reductions
2.2 Shutter delay
2.3 Minimum acceptable exposure time

3 CCD linearity

4 Calibration frames
4.1 CCD cosmetics
4.2 Fringing
4.3 Dark frames
4.4 Overscan and bias frames
4.5 Flat fields

5 Lamp flexures

6 Polarization
6.1 The TNG polarization experiment

7 Second-order contamination
7.1 NTT second order correction
7.2 TNG second order correction

8 Conclusions