Perhaps the light is not hitting the entire object or, at the other end of the spectrum, maybe the light needs to be focused at the center of the field of view. Here is how to solve this.
Fresnel lens
When used in combination with a white ring light, the fresnel lens will focus light at the centre of the field of view. This can be useful if you only need a relatively small area of an object illuminated.
The fresnel lens comes in 3 sizes (50 mm, 100 mm and 200 mm) depending on the lens you’re using it with.
Diffusor filter
Using a white ring light can also cause the point light to be too sharp. An optical difussor filter can then be used to get a homogenous illumination of surfaces. The diffusor filter available through TAGARNO can be used for working distances from 150 mm. Besides changing where the light should focus, you can also eliminate shadows and reflections created by lighting with light accessories from TAGARNO.