Quote Originally Posted by mporter012 View Post
OK. So if my light meter reads f/8 at 2s, this will be inaccurate then and I need to use one of these charts? Dammit, there goes a ton of long exposures down the drain!
At two seconds measured exposure you could still be within acceptable exposure latitude of most films - for a technically perfect negative. If you shoot HP5+ for example, it may be that you needed 2.5 seconds, and that's not going to make an enormous difference in your negatives. If you were measuring for 30 seconds and needed 70 seconds according to the chart, then you're more in trouble.

But keep in mind that just because a negative isn't technically perfect doesn't necessarily mean it will not yield a good print!
So process your film and learn from your experience, just like everybody else has had to do. If you don't use a multitude of films it's only a matter of time until you know how to compensate for reciprocity failure. We all learn some of our lessons the hard way.