whoops! my first image was somewhat unhelpful. That was to show the way I modified the speedlight, not to show the lighting setup. The setup was: the camera, mug and flash in a straight line, flash pointing towards the camera through the steam. Then, looking through the viewfinder, I moved the flash to my right until I no longer saw it in the image, (turning it at the same time to keep the light on the steam)
Sorry, I meant that in 5 minutes I assembled the little paper thingy on my flash- the whole thing took longer than that. Yes, you’re right! The goal of the paper is to prevent light from spilling where I don’t want it to. The little folded up pieces inside is to ensure the light striking the steam is all at the same angle.
A gridded light is any light source used with a grid such as this: https://www.adorama.com/pp900849.html (never mind the price, Profoto stuff is like that. it just happened to be the first item I found on Adorama with an image that showed the grid well) They (grids) are mainly used on beauty dishes and hard light reflectors, but occasionally also on softboxes. Their purpose is to ensure that all the light rays from a given light source are travelling parallel to each other, or to put it another way, all in the same direction- regardless of the size of the light source. For example in the case of a large softbox, the light coming from one corner is hitting the subject at an angle very different to the light coming from the opposite corner to the same point on the subject. This gives a softer look to the subject, at the expense of defined edges. A grid will cause the light to be less scattered thus giving more definition, but maintaining the size of the light source, and thus preserving softness.
You could probably do something similar to what I did, but with your desk lamp and some black construction paper!
