Humpy Histograms!

[Bryan Kennett]

Evening all,
Having done some studying, especially frm ' The Missing Manual' for PS4, i thought I was doing quite well with tuning the histograms to fairky good effect.

However, Just recently I have produced shots in which the histogram consists of two distinct humps separated by a small space along the base axis. I have been unable to 'join' them up or get really satisfactory results.

This usually occurs when photographing aircraft, on the take off run as a rule. I use a Canon PS721IS and an Olympus SP500UZ.

Does anyone have any idea what causes it and what, if anything, I can do about it.

Incidentally, a few weeks ago I read about the Smart Curves download here, and promptly did; it works very well and has merged perfectly with PSE4.

Regards to all,

Bryan.

[RobertSchuldenfrei]

Evening all,

However, Just recently I have produced shots in which the histogram consists of two distinct humps separated by a small space along the base axis. I have been unable to 'join' them up or get really satisfactory results.

This usually occurs when photographing aircraft, on the take off run as a rule. I use a Canon PS721IS and an Olympus SP500UZ.

Does anyone have any idea what causes it and what, if anything, I can do about it.


Hi Bryan,

It helps to know what the histogram is in order to give you some help. Simply put, the histogram is a bar chart of all the pixels in your image. The X axis represents intensity from darkest (0) to lightest (255). Instead of darkest and lightest pretend you have a black and white image. Then we can talk about the left most column as black and the right most column as white (and the center column as gray). It is easier to talk about black and white.

The Y axis is the number of pixels of each value. For example, if the image has 250 pixels of pure black there would be a representation of this number in column 0 of the graph, the pure black column. And if there were 200 pixels of value 1, almost black, the height of column 1 would be a little less. Note that we computer types talk about the first column as o and not 1.

Now to your problem. Because there is a gap in the middle of your histogram there are no gray (or midtone) pixels. An extreme case of this is if you had an image of a black square and a white square, all of the histogram would be in column 0 and column 255. Your gap would be really large:).

Now I don't think there is anything wrong with your camera, but a good test is to take a picture of a Macbeth color checker. You don't have to spend the $60+ dollars for a real one. Just print one off of the Internet.

Take a picture of the card and take a look at at the histogram and see if it makes sense.

Cheers,

Bob