PaintShop Histogram


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A PaintShop histogram is a graphical representation of the brightness levels of the pixels in an image and every digital image on your computer has one.

As a matter of fact most quality digital cameras have the ability to display this graphical representation of image brightness for each image and every one of the quality digital editing programs prominently display the image histogram.

Understanding what it's telling you may be a great help in your projects.  There's really no such thing as a perfect PaintShop histogram - really they are a guide that will help you decide which adjustments are appropriate for each image

Lots of Numbers


paintshop histogram balanced histogram



This is, more or less,  a balanced PaintShop histogram (I really had to look long and hard to find one that was close to balanced).  Balanced means the curve starts on the bottom left, gracefully increases in size to about the middle of the screen and then falls down gracefully to the bottom right.

In your editing you'll find thousands or different configurations of the curve.

So let's take a look at the curve ...

The Ends

  • Left End - Shadow end - this is where the darkest tones live.  Numerically the extreme left end is 0 - and the RGB designation for Black is Red=0, Green=0, Blue=0.

  • Right End - Highlight end - this is where the lightest tones live.   Numerically the extreme right end is 255 - and the RGB designation for white is Red=255, Green=255, Blue=255.

  • The area roughly one-third from the left to one-third from the right are the mid-tones where most of the image detail lives.  The exact middle of the curve is middle gray which is an important term in photographic metering and is represented by Red=128. Green=128, Blue=128.

In the image represented by this histo (not shown) the majority of the pixels are in the mid-tone area with a nice representation of both shadows and highlights so it is a nicely balanced image.  Without even seeing the picture you know that there's lots of detail with nice contrast - see how useful it is already!

Tonal Range

Ideally in a balanced image every Lightness level between 0 (Black) and 255 (White) will be represented on the PaintShop histogram.  Of course some levels will be represented more than others - that's what gives the height of the histogram.

The higher each vertical band - the more pixels are present at that particular level of lightness.  


painshop histogram green valley

paintshop histogram
Some Comments;

There are no completely black pixels in the picture.

The highest point is at brightness level 67 and there are 4,041 pixels at this level.

Only brightness levels are represented on this histo.  Other options have not been selected.


If you run your cursor over the curve, you'll see the numbers on the right side of the palette change.

The total number of pixels and the amount of pixels at each brightness level are not important - just interesting unless of course you are some kind of math geek.  What is important is the shape and where the end points are located.

Middle Gray

The metering of every digital camera light meter and every hand held light meter is standardized to set the cameras f-stop and speed based on an object that is middle gray at approximately 18% luminance.  If the camera is pointed at a very dark subject then the meter will assume that the surface is 18% gray (no matter how dark it is) and make the settings accordingly - this is the main reason for both under exposures and over exposures so be careful when you are metering.

  • This is this reason that quality camera stores sell 18% neutral gray cards to help photographers get the metering correct right in the camera.

  • On the curve the middle gray point falls at brightness level 128 - half way between 0 (black) and 255 (white).

  • When working with Levels, middle gray is labeled as 128 (below the middle diamond) and if the image was exposed incorrectly the mid-point slider can make up the difference.

  • When working with curves the middle of the curve line is middle gray.  The mid point can be pulled up or down to change the middle gray point.
.

Different Histograms


There really is no such thing as a bad PaintShop histogram because each image has its own purpose. Here are some examples and some observations.


paintshop histogram motorcycle histogram paintshop histogram motorcycle
Motorcycle

A predominance of dark pixels and very few light pixels.

It's not necessary to be balanced to have an effective picture.
paintshop histogram high key paintshop histogram high key
High Key

This one is all bunched up on the right (white) side of the histogram.

It's not at all balanced and it's still a great picture.
paintshop histogram cooling paintshop histogram cooling


Cooling the Soup

This is a fairly balanced histogram with a nice contrast (which can be seen in the nice wide histogram).

This shot also looked great when it was converted to black and white





Adjustment Affect

When you apply an adjustment to a photograph the change in the appearance can be easily seen on the histogram.

Take the following picture for instance - it was a quick shot (no time to do anything other than press the shutter) taken with a film camera from a bus in France way back then.

The negative was flat and the top picture is a scan of the original image.  No contrast with most pixels clumped about middle gray.

100% of the pixels are contained from level 80 to level 231 which is a far cry from 0 to 255 for a normal, balanced histogram (that's easy to figure out by left clicking at one point and dragging up to the highest point - the palette tells you all kinds of neat information).

Some high end math demonstrated that this image contains pixels in only 59% of the available lightness positions - not much, really.


paintshop histogram castle histo
paintshop histogram castle in France



After adding a Curves Adjustment layer we've got a substantially different PaintShop histogram and a much more pleasing image ...


paintshop histogram curves
painshop histogram after curves

Some things to note ...

  1. The PaintShop histogram is now stretched from 0 to 255.
  2. About 25% of the pixels are located in that one high area (from brightness level 75 to 101).
  3. The curve is no longer as solid as it was in the original.  When either a curves or levels adjustment is done on an image the curve changes.  In this situation it's because the existing range of brightness of the original (narrow) is now stretched to cover the complete range of brightness.
    This creates "holes" - areas of brightness where there are no pixels.  You cannot see the holes in the image but they are missing nonetheless.
This discussion could go on and on but the best thing is for you to make it a habit to compare the histogram to its image.


Additional Options


painshop histogram palette options

There are a lot of check boxes at the bottom of the palette.

The most common use of the curve is to look at the brightness levels (Lightness) and checking Use All Layers is useful as well - heck, leave it checked all of the time..

You can probably come up with a reason to check out the brightness levels of a selection as well.

With a color picture and everything checked the curve is kind of pretty.  Here's a view of the curves for the motorcyle shown earlier ...


paintshop histogram all checked


It's kind of tough to make anything of that, isn't it? 

Go ahead and have some fun with the PaintShop histogram!



On-Page links

Numbers

The Ends

Tonal Range

Middle Gray

Some Examples

Adjustment Effects

Additional Options


Normal Curve

histogram normal curve









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