What are the advantages and disadvantages of grids vs. snoots for light control?

Question

Both are, in general, used to control the area that's lit.

What are the relative advantages and disadvantages of both? When would you prefer one over the other?

Answer

In general snoots give more gradual falloff than grids. Grids are effectively a collection of very tight snoots next to each other, as a result they spill much less light at the end and give you a more direct narrower beam. They are used when you really need to control the light to highlight an object/detail and restrict it to a specific area.

In addition to differences in the quality of light, shoots are much easier to manufacture in an emergency from objects you happen to have to hand!

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How to offset the positioning of the Preview Gridlines in GIMP?

Question

When rotating an image with GIMP, there is an option to superimpose gridlines on the image. The number of lines is settable but the offset is not. I'd expect that when changing the center of rotation, the grid will be moved as well, but it is not.

Why would I want to do so? When rotating in Corrective mode, I want to align the grid with a supposedly horizontal/vertical line in the image to get perfect leveling. However, when the reference line in the image is not at the place of a gridline, it is more difficult. I found out that increasing the number of gridlines gets me close to this, but I wonder -

Is it possible to change the offset of the grid?

While we are at it - how to automatically adjust the canvas after rotation in GIMP, when Clipping is set to Crop?

Answer

AFAIK there is no way to offset the grid. However, there is a simpler way to straighten the photo: simply drag a guide from the ruler at the edge of the image until it lies along the horizon (or whatever else you want), then rotate as normal.

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