Preferences of the add-on can be found in Edit > Preferences > Add-ons > Camera: Photographer
Navigate through the different options using the Tabs at the top.

Panel Category and LightMixer Panel Category:
You can change the category name, which is the name of the tab available in the 3D view add-on panel.
Tip: You can type the name of existing categories to merge Photographer panels into an existing tab.

World HDRI: Path where you want to store your 360 HDRIs to be used in the Light Mixer World settings.
Only HDR and EXR files will be recognized in that library.
Thumbnails will be automatically generated for HDR and EXR files that are smaller than 100MB. PNG files with the same name as the HDR/EXR files can be used as thumbnails for large files or to speed up the menu opening.

Optical Vignetting folder: Path where you want to store textures for Optical Vignetting.
Only JPG, JPEG, TGA and PNG files will be recognized in that library.
Default folder: scripts/presets/photographer/optical_vignetting
Photographer comes with a few textures and will install them in the default folder.

Bokeh folder: Path where you want to store textures for Bokeh.
Only JPG, JPEG, TGA and PNG files will be recognized in that library.
Default folder: scripts/presets/photographer/bokeh
Photographer comes with a few textures and will install them in the default folder.

Camera preferences allow you to set some default settings for cameras, so you don't have to set them every time you create a new camera.

Important: These settings only work for cameras created using the 'Add Camera' button in the Photographer panel, or with the Photographer Camera in the Add Menu.

Exposure preferences allow you to set some default settings for cameras, so you don't have to set them every time you create a new camera.
Important: These settings only work for cameras created using the 'Add Camera' button in the Photographer panel, or with the Photographer Camera in the Add Menu.

Lens Attenuation factor: Factor depending on the transmittance of the lens, the vignetting factor, and the angle relative to the axis of the lens to define how much light energy passes through the lens.
The default value of 0.78 will cancel lens attenuation calculations and will match Unreal 4.25 camera exposure.
ISO standard recommends a lens transmittance of 0.65, which is sometimes used by other render engines to match real cameras.

Match Blender ACES to Unreal ACES: If using ACES OCIO config in Blender, you will notice a difference of brightness between Blender and Unreal ACES. Epic apparently applied a 1.45 gain multiplier their ACES ODT.
Enable this setting to apply the same multiplier to Photographer's Exposure. It will only affect Exposure if using the ACES OCIO config.

Use Physical Lights: replaces Blender Light properties with Physical Light properties, adding Color Temperature and Physical Light Units.

Follow Scene Unit Scale: Properly multiplies Physical light intensities with the Scene unit scale.
Only disable to keep retro-compatibility with older scenes.

Keep showing Blender Light panels: Does not hide Blender's light panels when using Physical Lights.
Can be useful if Blender adds new light properties that Photographer hasn't added yet.

Light preferences allow you to set some default settings for lights, so you don't have to set them every time you create a new camera.
Important: These settings only work for cameras created using the 'Add Light' buttons in the LightMixer panel, or Physical Light buttons in the Add menu.