It is not an optical effect to make people feel good.

An optical effect might be used to place actors or sets against a different background.

At first they seemed to be optical effects, as though the eye itself were playing tricks.

The only clothes he owned were of expensive natural fiber, with no optical effects at all.

Then you can argue about optical effects of one object framed against a smaller body.

Through his mastery of the lens several optical effects were created.

The time of day and weather change the optical effects.

The optical effect has to do with how much light is reflected.

No optical effects or other "cosmetics" are allowed and only one added light source, if absolutely necessary.

A rainbow is an optical effect dependent on the position of the observer.