MP and long exposure

[mervynyan]

I had tried several rolls of color prints iso400 inside the bars, street lights, etc. they tends to be underexposed at least 1 stop or more. I used B and counted seconds in my head, I suppose this method is not workable at all. I will try some 800 or 1600 films next time, just want to see how you guys deal with this? I have seen a mechanical shutter timer few years ago, any one using it?

- Cheers, Mervyn

 

[Bryce]

Did you compensate for reciprocity failure?

 

[ClaremontPhoto]

Reciprocity Failure

With longer than typical exposure times film needs more exposure than we would expect.

If the indicated exposure time is more than 1 second it it necessary to calculate and adjust for reciprocity failure like this...

1 second or more give double the indicated exposure
5 seconds or more give 5 times the indicated exposure
50 seconds or more give 10 minutes

See Wikipedia

 

[mbisc]

As others already stated, it's reciprocity failure. Rather than simple rules-of-thumb, I would check the technical information for your particular film on the additional exposure time (www.kodak.com, if it is Kodak film), since the required adjustments vary substantially between different films -- e.g. the adjustments for TMax100 are different from PlusX...

Regards,
Mike