LensDistortion

The image sequence to apply lens distortion to or remove lens distortion from.

Choose your output type depending on whether you want to distort the input image directly or just preserve the distortion information to use it on another image:

• Image - Choose to distort or undistort the input image.

• Displacement - Choose to leave the input image alone and store the pixel displacements corresponding to the calculated distortion in the UV channels, so they can be used by the STMap node. Choosing the Displacement option enables you to analyze the distortion on one image or grid and use the STMap node to apply that distortion to another image.

Select your lens type. You can choose between Spherical and Anamorphic lenses.

The first radial distortion term. This is proportional to r^2, where r is the distance from the distortion center. You can define this manually, or use image analysis, grid analysis, or line analysis to fill it out automatically.

The second radial distortion term, proportional to r^4. You can define this manually, or use image analysis, grid analysis, or line analysis to fill it out automatically.

The values for the center of the radial distortion.

The anamorphic squeeze value. If you select an anamorphic lens, the distortion in x will be scaled by this amount.

This control is only available if you have set Lens Type to Anamorphic.

Enter values to define asymmetric distortion to correct for slight misalignments between multiple elements in the lens.

This control is only available if you have set Lens Type to Anamorphic.

When enabled, the Image Analysis and Grid Analysis modes skip their initial estimation steps and instead use the current parameter values as an initial guess from which to estimate the distortion. If you already have a rough idea of the distortion present, this can speed up the estimation, particularly for the Image Analysis mode.

When enabled, LensDistortion applies the inverse of the current distortion.

Resets the controls for zero distortion.

Select the filtering algorithm to use when remapping pixels from their original positions to new positions. This allows you to avoid problems with image quality, particularly in high contrast areas of the frame (where highly aliased, or jaggy, edges may appear if pixels are not filtered and retain their original values).

• Impulse - remapped pixels carry their original values.

• Cubic - remapped pixels receive some smoothing.

• Keys - remapped pixels receive some smoothing, plus minor sharpening (as shown by the negative -y portions of the curve).

• Simon - remapped pixels receive some smoothing, plus medium sharpening (as shown by the negative -y portions of the curve).

• Rifman - remapped pixels receive some smoothing, plus significant sharpening (as shown by the negative -y portions of the curve).

• Mitchell - remapped pixels receive some smoothing, plus blurring to hide pixelation.

• Parzen - remapped pixels receive the greatest smoothing of all filters.

• Notch - remapped pixels receive flat smoothing (which tends to hide moire patterns).

• Lanczos4, Lanczos6, and Sinc4 - remapped pixels receive sharpening which can be useful for scaling down. Lanczos4 provides the least sharpening and Sinc4 the most.

Select either:

• Scale to Input Format - to scale to your input format.

• Choose Format - to choose another format. You might want to select this, for example, if you have previously undistorted an image and changed the format to match the undistorted image size, and then want to reapply the distortion later.

If you have set Distortion Scaling to Choose Format, you can use this menu to select a format that you want to use to scale your image.

Card Parameters

Equivalent value for the scale control on the Card node, needed to reproduce the horizontal scale.

This allows you to use the calculated lens distortion values to distort an image projected onto a card in 3D.

Equivalent value for the a (r^3) control on LensDistortion tab of the Card node. Defines a cubic term that affects the radial distortion of the texture applied to the card, and the edges of the card.

This allows you to use the calculated lens distortion values to distort an image projected onto a card in 3D, for example, to simulate camera lens distortion effects, such as barrel distortion.

Positive values make the card rounder, negative make the corners sharper.

Equivalent value for the b (r^2) control on LensDistortion tab of the Card node. Defines a square term that affects the radial distortion of the texture applied to the card, and the edges of the card.

This allows you to use the calculated lens distortion values to distort an image projected onto a card in 3D, for example, to simulate camera lens distortion effects, such as barrel distortion.

Positive values make the card rounder, negative make the corners sharper.

Equivalent value for the c (r^1) control on LensDistortion tab of the Card node. Defines a linear term that affects the radial distortion of the texture applied to the card, and the edges of the card.

This allows you to use the calculated lens distortion values to distort an image projected onto a card in 3D, for example, to simulate camera lens distortion effects, such as barrel distortion.

Positive values make the card rounder, negative make the corners sharper.

Image Analysis Tab

Sets the range of frames in the sequence to analyze:

• Source Clip Range - the entire sequence including all frames.

• Specified Range - a particular frame range selection from the sequence. Enter the start and stop frame in the Analysis Start and Stop fields.

The first frame to analyze.

This control is only available if you have set Analysis Range to SpecifiedRange.

The last frame to analyze.

This control is only available if you have set Analysis Range to SpecifiedRange.

Sets what type of camera movement to expect:

• Free Camera - expect a freely moving camera that is rotating and translating.

• Rotation Only - expect a still camera that is rotating only.

If you don’t want to analyze all regions of your image, for example if there are moving objects in the image, you can provide a matte in the Mask or Source input and use this control to select the matte channel:

• None - no matte is used and the entire Source image is analyzed.

• Source Alpha - the alpha of the Source input is used.

• Source Inverted Alpha - the inverted alpha of the Source input is used.

• Mask Luminance - the luminance of the image connected to the Mask input is used.

• Mask Inverted Luminance - the inverted luminance of the image connected to the Mask input is used.

• Mask Alpha - the alpha of the image connected to the Mask input is used.

• Mask Inverted Alpha - the inverted alpha of the image connected to the Mask input is used.

Track features through the input sequence and estimate the lens distortion present. When the analysis is complete, this will set the controls on the LensDistortion tab in order to undistort the sequence.

After analyzing, you can choose:

• None - to not display an overlay in the Viewer.

• Features - to display the features that were detected on the current frame in a Viewer overlay.

• FeaturesandTracks - to display the features and tracks that were detected on the current frame in a Viewer overlay.

Choose the type of grid you want to use, Checkerboard or ThinLine grid.

Calculate the lens distortion present. When the analysis is complete, this will set the controls on the LensDistortion tab in order to undistort the sequence.

Check to correct for perspective distortion caused by the grid not being shot square-on to the camera. In other words, you can align the grid lines with the image edges.

After analysis, you can choose to display the Original or UndistortedGrid lines over the image.

Check this to begin drawing lines along features in the input that should be straight. Draw a line by left-clicking along the feature at intervals and finish a line by clicking the right mouse button. You need at least three left-clicks to make one line, and at least three lines to initiate the distortion.

Choose the number of distortion terms to estimate. With only a few lines, sometimes better results can be achieved by estimating only the first radial distortion term.

Choose whether you want to estimate the distortion center. If the lines are not evenly distributed around the image, the center estimate is unlikely to be very good and you may get better results to approximate it by using the image center instead (the default).

Click to estimate the lens distortion from the current lines. When the analysis is complete, this will set the controls on the LensDistortion tab in order to undistort the sequence.

Delete the last line drawn. Repeat to delete the previous line, and so on.

Delete the last point drawn. Repeat to delete previous points that are not yet part of a completed line.

Hide the line overlay.