To measure the narrow gap size with the reticle calibrated at the same setting of magnification 40X (The settings of image resolution and screen display resolution keep unchanged). By moving the microscope with your hand and to draw the position of reticle with your PC mouse you can have the vertical line of reticle cover the tiny gap, and read out the divisions, the width of gap = 4.0 *0.072=0.288mm (See E-area of Figure 5).

                                                                      Figure 5 Picture of a metal part with a narrow gap at 40X

Improvement of image:

In order to capture a clear image of this shiny surface metal part, you need to adjust the setting of exposure time and the setting of Gamma value in software of Future Win Joe to cut away the noise background. You also need to have your metal part be apart from a shiny background material (See D-area of Figure 5, the distinct border between the metal part and the background of a cloth), and to take a picture not containing a shiny point (see B-area of Figure 5). In order to get a wider depth of field, you must capture your image at low power (See C-area of Figure 5).

Inspection in low power and high power:  

                                                    Figure 6 Close view of waviness of the metal part at 240X