Happy to, Brent. Most of the time, people shoot with their cameras in the program or "P" mode. The camera is going to select for you an average shutter speed and an average aperature that will most of the time yield an acceptable (read average) photograph. Another factor that comes into play is the type of film being used. Print film is by far more popular than slide film. While I have nothing in particular against print film, I do have a problem with the way that the images are printed most of the time. They're either done by a machine run in an auto mode or by a human who decides to make the image look "normal." If you shot it on a bright sunny day, this would be fine. If you shot it well after sunset or in the predawn, that probably wouldn't be at all what the image should look like.
Print film is a forgiving medium for the amateur photographer. In most instances, a photograph anywhere from about -2 stops to +3 stops can be printed to make it look "normal." Slide film, on the other hand is much less forgiving. Your exposure latitue is probably about +/- 2/3 stop. In other words, you're more prone to over or under expose an image if you're not careful with what you're doing.
Slide film, while far less forgiving in terms of exposure, will yield intensely saturated colors, some films more so than others. Examples of highly saturated slide films are Fuji Velvia (iso 50) and the Kodak Ektrachrom 100VS. I use a lot of the former and none of the latter -- I don't like the color palette or reciprocity behavior of Kodak film but that's a personal choice. Many other professional photographers swear by it. People should use what they find pleasing to their eye and compatible with their photographic style. Another good choice is Fuji Provia 100F. Not quite as saturated but still good saturation and it can be push processed to iso 200 very well in a professional lab.
As light levels go down, a relationship known as the Rule of Reciprocity breaks down. Quite simply, the rule of reciprocity dictates that if you double the exposure time you have to close down the aperature of your lens accordingly so that the correct amount of light gets to your film. Under normal conditions, an exposure of 1/125th sec at f/8 equals 1/250th at f/11 or 1/60th at f/5.6 and the Rule of Reciprocity is satisfied and any of those three exposure conditions would give you the correct exposure based on the accuracy of your camera's light meter.
Generally speaking, longer exposure times (you'll need to shoot off a tripod to do this!) and small aperatures yield the intensely saturated colors that you see in a lot of my photography.
When shutter speeds either become extremely short or extremely long, the Rule of Reciprocity breaks down and the relationship is no longer a linear one. For example, if you were shooting at 15 sec at f/4 to get an exposure in low light, this would equate to an 8 minute exposure at f/22. When your light levels are such that your exposure goes beyond about 30 sec with Fuji Velvia or beyond 60 sec with Provia 100F professional slide films, for example, the Rule of Reciprocity goes out the window! With some experimentation and note taking, you can learn to push the saturation of your film and to take advantage of breakdowns in the Rule of Reciprocity, which are know as Reciprocity Failure or RF. I know that most of the national photo mags have had articles in them in recent months on how to avoid reciprocity failure. All well and good if that is your intent, but personally I find it a useful photographic tool.
As an example, the photo below won first place in the color photography category of the Door County Maritime Museum's annual juried photo contest in 2001. This was shot about 9:20 PM in late June looking across the Sturgeon Bay ship canal to the Sturgeon Bay North Pierhead light. The sky at that time of night in Wisconsin at that time of year is darned near BLACK! This was a 4 min exposure at f/22. I was stopped down, knowing that I was going to get reciprocity failure and that the nearly black sky and nearly black waters of the ship canal would render in something around cobalt blue, which they did. The 4 min exposure was there to give me plenty of cycles of the light in the lantern room to insure that I'd get a nice reflection of it on the waters of the ship canal, which was by no means glass smooth that evening. The long exposure also flattened out the appearance of the surface of the ship canal giving the smooth look that it has in the image. The small aperature gave me the star radiating from the light in the lantern room.
Here's another shot, this time of the outer pier light at St Joe shot from the south pier about 2 weeks ago. This photo was taken on Provia 100F as a 40 sec exposure at f/32 using a 300 mm f/4 lens.
At the hour this was taken, pushing 10 PM, the sky was more toward deep blue/black than rendered in this image - the lightening caused by RF starting to occur. BTW, yes the outer light is leaning to the left. It does after being pounded by waves sweeping off the lake for decades. You'll notice, however, that the horizon is dead level. When you're getting images ready to post or print, check your horizon and level that. Many lighthouses lean this way or that!
I hope that some of this helps. If you still have questions, don't hesitate to ask.
Gary
Don't hurt me.
