An important aspect of digital photography
In order to get the right exposure for your digital photographs you will need to check the level of reciprocity factor that that film has. This will then give you clues as to the minimum exposure that you need in order to return great photographs. You might also benefit from the purchase of a modern electronic light meter to help you with the selection process for the right level of exposure when you are working. You might also need to take in to consideration the reciprocity failure for the different slide films that you may be working on. As you increase the exposure time the possibility for failure increases by four times. Thus the formula that is given is that when you double the exposure, the compensation must be quadrupled. These might seem to be pedantic details but they make a difference in the way that the photograph eventually comes out.
There are specific points at which you might begin to see deterioration in the picture quality that you are getting. You have to be careful with the times and the level of exposure or the photograph will not turn out as planned. Experimentation is a good way to find out the right levels at which you might be operating at optimum. The star trails indicate that you might not be getting to the right amount of exposure on the film. Some people say that eight minutes is enough for negative four EV. The color correction is entirely dependent on the personal tastes of the photographer. Some people wait until the film has come back from the lab before they commit to anything. An initial trial with the filters will help you decide the right exposure for the camera that you are using and the conditions in which you are operating.
There are certain bespoke formulas for calculating using the star trails. For example some people have found that they turn to 180 degrees in twelve hours and you keep counting down until you have the minute figure. This is not an exact science so you should expect to compromise on certain aspects of your procedures. A smaller aperture will reduce the trails but with a larger aperture you get the trails that are much brighter. The direction that you are facing or using might have an impact. The North is centered while the South needs an arch. Color shifting can happen when you shoot during the day but you will need to work with the samples until you get the kind of image that you were looking for.
If you are in any doubt about the exposure or related matters then the internet is a very good place to do your research. There are many amateur and professional photographers that like to share their knowledge in the niche forums. The information that you get can be very useful in terms of improving the chances that you have of getting the right image in the right situations.