Bright Field (BF) Imaging:
• Select the objective lens To focus on the sample.
• Adjust the condenser lens To ensure the electron beam is converging onto the sample (you can use the condenser aperture for finer control).
• Set the objective aperture Wide open, allowing the unscattered (direct) electrons to pass through.
• Focus on the sample.
• Capture the BF image, Which uses the transmitted, unscattered electrons. These electrons create the image of the sample where contrast is typically based on the sample thickness and atomic number.

Switch to Dark Field mode:
• Using the selected area diffraction (SAD) aperture, select a diffraction spot corresponding to a particular crystallographic plane or feature you want to observe in the image.
• Center the diffraction spot in the diffraction plane by adjusting the selected area aperture.
• Use a smaller objective aperture to block out the transmitted (zero-order) electrons, and allow only the diffracted electrons (from a specific crystal plane or lattice) to pass through.