Even for night time lightning shots I tend to try and keep the exposure time down to a maximum of say 10 seconds, much less if at all possible. This minimizes cloud motion softening the features of the clouds and also light trails etc from passing cars and what not, it also helps keep the sensor cooler and thus minimizes noise in the image.

Below image for instance is at F-11 for 10 seconds.


Vibrant by Orebound Images, on Flickr

F-8 4 second exposure at ISO 100


Magic Hour by Orebound Images, on Flickr

F-13 for 2 seconds ISO 50


Kaboom by Orebound Images, on Flickr

For daytime bolts I'm a bit of a shutter abuser as I'm not really a fan of using lightning triggers as they tend to often miss a lot of the detail in bolts. I generally use a 10 stop ND filter to allow for longer exposures and just lock the shutter open.

Below shot for instance was shot at around 2 pm in bright daylight. Settings were F-16 exposure time 0.5 seconds.


A touch too close! by Orebound Images, on Flickr

Hope this helps.

Cheers