Install the lens with the minimum focal length.

Place the camera so that its optical axis is perpendicular to the surface of the Distortion grid.

Make sure that the edges of the frame are completely covered with a chess pattern.

• Double-check with the camera operator that the coverage is based on the effective sensor area – not the internal frame that can be set in the display settings

• Don’t try to fit the entire grid within the frame – let it extend beyond its boundaries if necessary.

Сlose the iris to its maximum value.

• Shooting Distortion grids for different focus distances is important because when adjusting the focus ring, the ‘lens breathing’ effect occurs, which also affects its distortion, especially pronounced in anamorphic lenses. 

• Now you understand that it’s important to shoot focus distance AND gather this information on the set for each shoot, because only together they will work correctly.

• Most likely, a closed iris will significantly darken your image, therefore:

Reduce the FPS to the minimum value.

Set the shutter speed to the maximum (shutter 360).

If necessary, increase the ISO.

• After that, we recommend turning the focusing ring to make sure that the grid is in focus and covers all of the frame at the all focus distance values.

Set the minimum focus distance on the lens.

Ensure that the grid is in focus.

Next, record the following information on a sheet of paper:

• Camera model

• Frame format (shooting resolution)

• Focal length

• Focus distance

Shoot the frame.

• Attach a sheet to the grid and press REC.

• If you are recording at a rate of 1 FPS, then after a couple of seconds, remove the sheet from the frame and, making sure that the grid image is evenly illuminated and without shadows, stop recording.

• For your convenience, magnetic stickers are included with XYZ.Grids to record this information, which you do not need to remove from the frame.

After that, change the focus distance.

• The step is determined independently based on your needs: the smaller the step, the more accurate the lens distortion profile will be, and the more time it will take to shoot.

• For example: Hawk V-Lite Anamorphic 28mm (minimal focus distance 0.8m):

  80 – 100 – 130 – 180 – 200 – 250 – 350 – 450 – 600 – 800 – 1500 – ထ

• ATLAS 32mm (minimal focus distance 0.55m):

  55 – 65 – 75 – 85 – 100 – 120 – 140 – 200 – 250 – 300 – 450 – 1000 – ထ

• As you can see, the change in focus distance is non-linear. This is because the shorter the distance, the more the distortion parameters change
Try to maintain a similar dependency as in our example.

Repeat steps 10–13 until you reach the “infinity” focus distance value (this also needs to be captured).

After reaching the “infinity” focus distance value,

install the next lens and repeat steps 9–14.

• Please remember that we perform the shooting from a shorter to a longer focal distance lens.

  In that case we will get a slightly larger grid spacing in the frame, but in most cases this is enough – it helps to minimize camera movements.

If we use zoom lenses, the algorithm is similar to shooting a Distortion grid for fixed focal length lenses, only instead of changing the lens, we rotate the focus distance adjustment ring and repeat steps 9–14.

• It is important to note that the non-linear dependence, as with the focus distance, no longer works here, so we take steps based on classical focal length values:

  8 – 14 – 18 – 24 – 32 – 35 – 50 – 65 – 80 – 100 – 135 – 140 – 200 – 300 – 400 – 600

• In some cases, when the focus distance range does not allow you to move the camera far enough away from the grid, you may get a large grid size in the frame. For this you need to use a grid with halved grid spacing.
  If you are using XYZ.Grid, just magnetize an additional mini grid on top of the main one. The principle here is the same – the new grid should completely overlap the frame.