Defish

描述

This effect can transform footage shot with a fisheye lens to look like it was shot with a rectilinear lens, and vice versa. It can also be used to straighten the video that was shot with one of these wide angle converters, which are only slightly curvy, or with a semi-fisheye camera, like the GoPro Hero.

參數

參數	數值	描述
De-Fish	開關	If checked, the transform direction is from fisheye to rectilinear, when not checked, it is rectilinear to fisheye.
類型	選取	Selects the fisheye angular mapping function used
縮放	選取	Select the scaling method
Straighten all Edges of Video Frame	開關
Interpolation	選取	Select which interpolation method to use. Options: see below.
Aspect Type	選取	Select the pixel aspect type[1].
數量	整數	Controls the amount of (de)distortion applied to the video. More details below.
Fix Camera Scaling Between 4:3 and 16:9	整數
Scale Y to Affect Aspect Ratio	整數
手動處理程度	整數	Scales the video. Range is 0 to 1000 (divided by 500 to get scaling factor).
手動處理趨勢	整數	Controls directly the pixel aspect ratio. Range is 0 to 1000 mapped to from 0.5 to 2. Only used if Aspect Type is set to manual.

可以使用以下選項：

Type

Equidistant
Orthographic	Straighten all edges of video frame
Equiarea	預設
立體投影（Stereographic）

Scaling

適中	no cropping but there will be blank area at the borders
手動	see Manual Scale

Interpolator

Nearest neighbor
雙線性	預設
Bicubic smooth
Bicubic sharp
Spline 4x4
Spline 6x6
Lanczos 16x16

Aspect Type

方形	預設
PAL DV	1.067 ratio
NTSC DV	0.889
HDV	1.333
手動	see Manual Aspect

Parameters explained

Interpolation:: The seven different interpolation methods allow making a quality/speed trade-off. The interpolators are ordered from fast, low quality to (very) slow, high quality. The spline interpolating polynomials are from Helmut Dersch. For real-time use, Nearest neighbor is the fastest because, in fact, it is equal to no interpolation. In most cases Bilinear should be good enough, and on a decent machine should still run in real time. Beyond Bicubic, the quality gain is marginal for a single resampling. Lanczos takes an eternity!
數量:: Controls the amount of (de)distortion applied to the video. It controls the ratio of fisheye focal length to image half diagonal, but in an nonlinear inverse way, to make the control more 「comfortable」. It can be adjusted beyond 「reasonable」 values (which differ between the mapping function types), to produce some looney effects. When exploring this range and the image disappears, check the scaling as it could be that the image became too big or too small to see. For some unreasonable values the image might indeed disappear, when there are math overflows or imaginary results (Type Equidistant and Orthographic are more prone to image vanishing). When working in the 「special effect」 range, it is always worth to try manual scaling. If the video contains zooming through a curvy wide angle adaptor, the needed amount will vary. In this case use keyframing.

備註

Tweaking the parameters for best defish

Take a shot of something like a brick wall or bathroom tiles, that has a lot of horizontal and vertical straight lines. Be careful to keep the optical axis as perpendicular as possible to the wall (i.e. keep a maximally symmetrical image in the viewfinder). Use this image to tweak the parameters, primarily amount, type and aspect.

Some examples of effect abuse

These were tried with PAL DV. These examples work best when there is some interesting action near the center of the image.

For a kind of roundish kaleidoscope, try this:

數量

775

Defish

關閉

類型

equidistant

縮放

手動

手動處理程度

300…400

Another crazy distortion:

數量

921

Defish

關閉

類型

stereographic

縮放

手動

手動處理程度

191

For an effect reminiscent of some scenes from the 「2001 Space Odyssey」 movie try this:

數量

900

Defish

開啟

類型

立體投影（Stereographic）

縮放

填充