Contrast means many things but I think in this context it means the dark areas of the negative (highlights in the print) are very dense or black. The shadows (the light areas of the negative) are very clear. Of course the trouble with this is there is very little in between. I think of this in terms of information but also gain or slope of a curve. As I have posted elsewhere if one takes a high contrast negative one has a very steep gain curve. (Sorry I am an engineer by training so this is a bit mathematical.)
The graph below attempts to illustrate this. A high contrast image has a very steep light curve. That is a small change in light in put on the horizontal axis results in a large change in light transmitted to the paper. This can be thought of in terms of exposure where a small change in exposure time results in a lot more light on the paper. This makes it inherently hard to control the exposure as you may be faced with quarter stop or smaller steps to achieve a 'good' exposure. This is especially true where the high contrast filters are concerned. These filters introduce (mathematically they multiply) another steep curve making control more difficult.
|High contrast or steep curve|
|Example #5 filter test strip|
|Low contrast curve|
First the split grade print. Most of the detail in the kachina is present in the shadow while rendering the cabinet mostly black. Plenty of subtle detail in the highlights.
|frame 3A #5 32 sec #00 45 sec f16|
From now on I will develop at 20% less development time.