In the case of my field, 19th-century French painting, there is no question that certain artists used optical aids like the camera lucida.

Some parts are so small that they have to be made under a microscope by anyone else whereas you can do it without optical aids.

Training and practice in the use of optical aids is critical to success.

It is also equipped with modern optical aids like periscopes and night vision.

But it can be difficult or uncomfortable to view without optical aids.

Hockney began wondering whether other artists might similarly have used optical aids and kept quiet about it.

The side-by-side method is extremely simple to create, but it can be difficult or uncomfortable to view without optical aids.

I'm with Hockney here, if there were optical aids available it would be natural for artists to use them.

Risk of injury increases when viewed with optical aids.

With optical aids, "you're still doing things the way you used to."