user: Show practical ways to work with Properties in a Blender add-on or script – include code.

assistant: ### Lens

Type

The camera lens options control the way 3D objects are represented in a 2D image.

Perspective
:   This matches how you view things in the real world.
    Objects in the distance will appear smaller than objects in the foreground,
    and parallel lines (such as the rails on a railroad) will appear to converge as they get farther away.

    Focal Length/Field of View
    :   The [Focal Length](../glossary/index.xhtml#term-Focal-Length) controls the amount of zoom, i.e.
        the amount of the scene which is visible all at once.
        Longer focal lengths result in a smaller FOV (more zoom),
        while short focal lengths allow you to see more of the scene at once
        (larger FOV, less zoom).

        |  |  |
        | --- | --- |
        | ../_images/render_cameras_traintracks-perspective-BI.jpg   Perspective camera with 35 mm focal length. | ../_images/render_cameras_traintracks-perspective-telephoto-BI.jpg   Perspective camera with 210 mm focal length instead of 35 mm. |

        Lens Unit
        :   The focal length can be set either in terms of millimeters or the actual [Field of View](../glossary/index.xhtml#term-Field-of-View) as an angle.

            [image reference removed]

Orthographic
:   With *Orthographic* perspective objects always appear at their actual size, regardless of distance.
    This means that parallel lines appear parallel, and do not converge like they do with *Perspective*.

    [image reference removed]

    Render from the same camera angle as the previous examples, but with orthographic perspective.

    Orthographic Scale
    :   This controls the apparent size of objects projected on the image.

        Note that this is effectively the only setting which applies to orthographic perspective.
        Since parallel lines do not converge in orthographic mode (no vanishing points),
        the lens shift settings are equivalent to translating the camera in the 3D Viewport.

        [image reference removed]

Panoramic
:   Cycles Only

    This type covers a variety of panoramic projections.
    See the Cycles [panoramic camera](cycles/object_settings/cameras.xhtml#bpy-types-camera-panorama-type) settings for more information.

Custom
:   Cycles Only

    Custom cameras enable user-defined behavior through the use of OSL code.
    See the [Cycles custom camera documentation](cycles/osl/camera.xhtml) for more information.

Shift
:   Allows for the adjustment of *vanishing points*.
    *Vanishing points* refer to the positions to which parallel lines converge.
    In these render examples, the most obvious vanishing point is at the end of the railroad.

    |  |  |
    | --- | --- |
    | ../_images/render_cameras_traintracks-perspective-lens-shift-BI.jpg   Horizontal lens shift of 0.330. | ../_images/render_cameras_traintracks-perspective-rotate-BI.jpg   Rotation of the camera object instead of a lens shift. |

    Notice how the horizontal lines remain perfectly horizontal when using the lens shift,
    but do get skewed when rotating the camera object.

Clip Start and End
:   The interval in which objects are directly visible.
    Any objects outside this range still influence the image indirectly,
    as further light bounces are not clipped.

### Depth of Field

Real-world cameras transmit light through a lens that bends and focuses it onto the sensor.
Because of this, objects that are a certain distance away are in focus,
but objects in front and behind that are blurred.

[image reference removed]

Example of DOF bokeh effect.

The area in focus is called the *focal point* and can be set using either an exact value,
or by using the distance between the camera and a chosen object:

Focus Object
:   Choose an object which will determine the focal point. Linking an object will deactivate the distance parameter.

Focal Distance
:   Sets the distance to the focal point when no *Focus Object* is specified.
    This distance can be visualized in the 3D Viewport by enabling *Limits* in the camera’s
    [Viewport Display](#bpy-types-camera-show) panel.

#### Aperture

F-Stop
:   F-Stop ratio that defines the amount of blurring.
    Lower values give a strong depth of field effect.

Blades
:   Total number of polygonal blades used to alter the shape of the blurred objects
    in the render, and render preview. As with the viewport, the minimum amount of
    blades to enable the bokeh effect is 3, resulting in a triangular-shaped blur.

Rotation
:   Rotate the polygonal blades along the facing axis, and will rotate in a clockwise,
    and counter-clockwise fashion.

Ratio
:   Change the amount of distortion to simulate the anamorphic bokeh effect.
    A setting of 1.0 shows no distortion, where a number below 1.0 will cause a horizontal distortion,
    and a higher number will cause a vertical distortion.

### Camera

These settings adjusts properties that relate to a physical camera body.
Several [Presets](../interface/window_system/tabs_panels.xhtml#ui-presets) can be chosen to match real-world cameras.

Sensor Fit
:   Adjusts how the camera’s sensor fits within the outputs dimension adjusting the angular field of view.

    Auto:
    :   Calculates a square sensor size based on the larger of
        the [Resolution](output/properties/format.xhtml#bpy-types-rendersettings-resolution-y) dimensions.

    Horizontal:
    :   Manually adjust the *Width* of the sensor, the *Height* is calculated based on
        the aspect ratio of the output’s [Resolution](output/properties/format.xhtml#bpy-types-rendersettings-resolution-y).

    Vertical:
    :   Manually adjust the *Height* of the sensor, the *Width* is calculated based on
        the aspect ratio of the output’s [Resolution](output/properties/format.xhtml#bpy-types-rendersettings-resolution-y).

Size / Width, Height
:   This setting is an alternative way to control the field of view, as opposed to modifying the focal length.
    It is useful to match a camera in Blender to a physical camera and lens combination,
    e.g. for [motion tracking](../movie_clip/index.xhtml).

### Safe Areas

Safe areas are guides used to position elements to ensure that
the most important parts of the content can be seen across all screens.

Different screens have varying amounts of [Overscan](../glossary/index.xhtml#term-Overscan) (especially older TV sets).
That means that not all content will be visible to all viewers,
since parts of the image surrounding the edges are not shown.
To work around this problem TV producers defined two areas where content is guaranteed to be shown:
action safe and title safe.

Modern LCD/plasma screens with purely digital signals have no [Overscan](../glossary/index.xhtml#term-Overscan),
yet safe areas are still considered best practice and may be legally required for broadcast.

In Blender, safe areas can be set from the Camera and Sequencer views.

[image reference removed]

Red line: Action safe. Green line: Title safe.

The Safe Areas can be customized by their outer margin,
which is a percentage scale of the area between the center and the render size.
Values are shared between the Video Sequence editor and camera view.

Title Safe Margins X/Y
:   Also known as *Graphics Safe*.
    Place all important information (graphics or text) inside this area to
    ensure it can be seen by the majority of viewers.

Action Safe Margins X/Y
:   Make sure any significant action or characters in the shot are inside this area.
    This zone also doubles as a sort of “margin” for the screen which can be used
    to keep elements from piling up against the edges.

#### Center-Cut Safe Areas

Center-cuts are a second set of safe areas to ensure content
is seen correctly on screens with a different aspect ratio.
Old TV sets receiving `16:9` or `21:9` video will cut off the sides.
Position content inside the center-cut areas to make sure the most important elements
of your composition can still be visible in these screens.

Blender defaults show a `4:3` (square) ratio inside `16:9` (widescreen).

[image reference removed]

Cyan line: action center safe. Blue line: title center safe.

### Background Images

A background picture in your camera can be very helpful in many situations:
modeling is obviously one, but it is also useful when painting
(e.g. you can have reference pictures of faces when painting textures directly on your model…),
or animation (when using a video as background), etc.

Background Source
:   The source of the background image.

    Image:
    :   Use an external image, image sequence, video file or generated texture.

    Movie Clip:
    :   Use one of the Movie Clip data-blocks.

        Active Clip
        :   Display a Movie Clip from the scene’s [Active Clip](../scene_layout/scene/properties.xhtml#bpy-types-scene-active-clip).

        Render Undistorted
        :   Display the background image using undistorted proxies when available.

        Proxy Render Size
        :   Select between full (non-proxy) display or a proxy size to draw the background image.

Color Space
:   The color space the image or video file uses within Blender.

View as Render
:   Apply the [color management](color_management/displays_views.xhtml#render-post-color-management) settings when displaying this image on the screen.

Opacity
:   Controls the transparency of the background image.

Depth
:   Choose whether the image is shown behind all objects, or in front of everything.

Frame Method
:   Controls how the image is placed in the camera view.

    Stretch:
    :   Forces the image dimensions to match the camera bounds (may alter the aspect ratio).

    Fit:
    :   Scales the image down to fit inside the camera view without altering the aspect ratio.

    Crop:
    :   Scales the image up so that it fills the entire camera view,
        but without altering the aspect ratio (some of the image will be cropped).

Offset X, Y
:   Positions the background image using these offsets.

    In orthographic views, this is measured in the normal scene units.
    In the camera view, this is measured relative to the camera bounds
    (0.1 will offset it by 10% of the view width/height).

Rotation
:   Rotates the image around its center.

Scale
:   Scales the image up or down from its center.

Flip
:   X
    :   Swaps the image around, such that the left side is now on the right, and the right now on the left.

    Y
    :   Swaps the image around, such that the top side is now on the bottom, and the bottom now on the top.

### Viewport Display

[image reference removed]

Camera view displaying safe areas, sensor and name.

Size
:   Size of the camera visualization in the 3D Viewport. This setting has **no** effect on
    the render output of a camera. The camera visualization can also be scaled using
    the standard Scale `S` transform key.

Show
:   Limits
    :   Shows an orange line indicating the *Clip Start* and *End* values,
        as well as a yellow cross indicating the *Focus Distance*.
        If the *Focus Distance* gizmo is enabled in the 3D Viewport’s
        [gizmo settings](../editors/3dview/display/gizmo.xhtml),
        this cross can also be dragged with the mouse to adjust the distance.

    Mist
    :   Toggles viewing of the mist limits on and off.
        The limits are shown as two connected white dots on the camera line of sight.
        The mist limits and other options are set in the *World* panel,
        in the [Mist section](eevee/world_settings.xhtml#bpy-types-worldmistsettings).

    Sensor
    :   Displays a dotted frame in camera view.

    Name
    :   Toggle name display on and off in camera view.

Passepartout
:   This option darkens the area outside of the camera’s field of view.
    The opacity of the passepartout can be adjusted using the value slider.

#### Composition Guides

*Composition Guides* enable overlays onto the camera display that can help when framing a shot.

Thirds
:   Adds lines dividing the frame in thirds vertically and horizontally.

Center
:   Center
    :   Adds lines dividing the frame in half vertically and horizontally.

    Diagonal
    :   Adds lines connecting opposite corners.

Golden
:   Ratio
    :   Divides the width and height into Golden proportions (about 0.618 of the size from all sides of the frame).

    Triangle A
    :   Displays a diagonal line from the lower left to upper right corners,
        then adds perpendicular lines that pass through the top left and bottom right corners.

    Triangle B
    :   Same as A, but with the opposite corners.

Harmony
:   Triangle A
    :   Displays a diagonal line from the lower left to upper right corners,
        then lines from the top left and bottom right corners to 0.618 the lengths of the opposite side.

    Triangle B
    :   Same as A, but with the opposite corners.

Color
:   Sets the display color and opacity (alpha) used for all composition guide overlays.
    Useful for adjusting visibility depending on the brightness or contrast of the underlying shot.