100 or 400 ASA fro light trails?

100 or 400 ASA fro light trails?

 

I havea asked this somewhere else already, but should I use 100 or 400asa for light trails that's roughly 10-15 seconds long? I'm already using 800asa for 120, so I'm thinking fro 135. Also, I'll be shooting at night. Thanks

Maybe car light trails?

 

If you do this with ISO800 120 film, how are the results? If they're fine, then just repeat the same for 35mm. The change in format doesn't change exposure.

I know, but I never tried doing light trails with film (cars), only tried once with digital. Heard you should be fine with 400 and 800. Search ultimate exposure computer, they have chart nearly at the end of the page

Will do, thanks :) Will wait till I;m the UK as theres no stars here in hong kong

Film, unlike digital, suffers from Reciprocity Law Failure. Long exposures have less than a proportional effect on the exposure level. Sometimes the product specification sheet will give some guidance in this respect.

 

A possible alternative is to take several long exposures, scan and stack the rules. Stars "move" 30 degrees per hour, and 30 minute exposures are easier to manage and less risky than one exposure, hours long. On the other hand, if you want stars to appear as pinpoints, even a 10 second exposure will show significant elongation with a "normal" lens, unless you use a clock drive.