Long exposure on film - help!

[bobiscuit]

I'm running my first roll of film through my new Holga WPC. I went for Velvia 100, which the wisdom of Google suggests is good for long exposures.

So how do I work out metering? My exposure meter only goes up to f32 but the WPC is f135. So there's about 4 and a bit stops difference? f32 -> f45 -> f63 -> f87 -> f122

Is that all I need to do, then? Work out the f32 value using the light meter and slow the shutter by a bit over 4 stops?

Thing is, though... I was out earlier in sunny but not really bright conditions, and the meter was reading 1/8s for f32 and ISO 100. So 4 stops slower is 2 seconds - that doesn't sound long enough. The guide on the back of the Holga says 7-9 seconds for sunny weather.

Help :shrug:

 

[RaglanSurf]

I've checked on my pinhole and 8 secs looks about right.

 

[timbo46]

It's because of reciprocity failure of film; see this http://www.geofflawrence.com/photography_tutorial_reciprocity_failure.htm

 

[bobiscuit]

The Fuji factsheet for Velvia 100 states that there is no need for adjustment up to 1 minute.

So if my exposure meter read 1s for f32, what would I use for f/135?

 

[timbo46]

You could meet in the middle at 4 seconds, but it's always better to overexpose colour negative film than underexpose, and the reverse for slide film.

 

[TheBigYin]

Pinhole Exposure Guide

The guide on the back of the 120WPC tends to overexpose by about 1.5 - 2 stops. I was out shooting last wednesday with mine, and it was around 8 elephants with Delta 100 and a red filter over the lens - so say 2.5 seconds-ish.

I think that they've made it over-expose, to try and cover the light fall-off to the outer edges of the frame, especially when shooting with the 12x6 frame in place.