Using Levels with a histogram.... Scary?

It sure is when you are not accustomed to them.
Many of you are very knowledgeable, but every day we get new people joining us, so a gentle refresher.
In an 8 bit image, the span from Black to white runs from 0 to 255; with zero being black, and 255 being white.
What you see in that histogram box is what the camera saw with so many pixels in each shade between zero black, and 255, white.

The taller the 'mountain' at a given point along the span, the more pixels at that level of brightness.
So if I had a tall spike in the center of my histogram, it would indicate I had a lot of middle gray stuff.

So suppose our image was shot on a gray day and needed to be pepped up a bit with more contrast.
Levels can do this for us quickly and easily.
Levels breaks the image up into three parts.
The Shadow part. The bright or Highlight part. The middle part
What do we want?
More contrast!
How do we get it?
Make Black blacker, and white whiter

Keep in mind that when moving the Shadow slider from zero to 25, you are saying to the image...  from now on, pixels that have a brightness value of 25 will be changed to zero or black. twenty five will be the new black.... and it follows that pixels that had a value of 35, would now be as dark as 10.
So the dark part of the three parts has become darker.
Now it's time to watch the video.
Please make it full screen so it will change to High Definition.

https://youtu.be/YmBCbDLCw28

Enjoy your Qimage Ultimate

Fred

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Fred & Terry

You've done a marvelous demonstration about levels!

Thanks
Ya Me

I missed that pun!
It's up and down dunes and perspective; the old post is almost vertical.

Terry

Jeff,

Was looking for Jeff's response to your challenge to produce an ad.  Instead I clicked on this levels thread.

Very good!  It made me brush up on some techniques.

Vlady