Jon Sachs is the creator of Photo Matters, an educational resource for photographers who want to learn about creative photographic variables. Most of my readers are professional and semi-professional, and may consider an educational website such as this one to be for beginners...but that would be a mistake. Photo Matters is different, and aims at all levels of photography proficiency.
It's true what Sachs says on his website. Many times, we reach for a lens, or adjust the shutter speed/aperture value without even thinking...and can't explain it. We just know...or just feel it. However, Photo Matters explains it visually.
Trust me...you'll like this website. A lot.