How to reduce a photo in Photoshop without losing quality?

Question

Adobe Photoshop

Tell me how to reduce a large photo 1200x800 px to a small 150x150px without quality loss, so that there is no graininess in the photo.

Answer 1

Try to reduce it in the vector editor... Yes, yes, in the vector editor.
Lebedev wrote about this somewhere, but now he hastily found it.

Answer 2

I just already did it without quality loss in Photoshop here is bir-moto.ru , now I started to do it, there was graininess

Answer 3

Ok, you probably know how to take a 300dpi 800x800 image and turn it into a 600dpi 400x400. A correctly asked question contains at least half of the answer!