I can't _imagine_ an apple in my hand if you defined the colour, size or weight (for example, purple, 50cm diameter and 100Kg).

In my mind I am recalling a _memory_ of holding an apple in my hand - not imagining the one according to your specifications.

One example I can give is being tasked with rearranging desks in an office. I can't for the life of me _imagine_ what the desks would look like ahead of physically moving them into place.

I can make an educated guess based on their length/width but certainly not "picture" how they would look arranged without physically moving them.

It's like my brain BSODs when computing the image!

The same applies to people - I can only recall a memory of someone - not imagine them sitting on a bench in front of me. I might remember a memory of the person on _a_ bench but certainly not the one in front of me.