underexposure with halogens?

[andrew_luke2]

So I shot 4 rolls of fuji 800z the other day using 4 500w halogen lamps. I used

several different light setups with totally different positions and directions

of light (ie some with all 4 direct, some with umbrella, some bounced of

ceiling, etc). I also was using a hoya 80A filter to bring the colors back to

daylight and factored the extra stop in by metering at 400 with the sekonic.

 

I shot all manual as I always do with metering on my sekonic L-358 set on

incident. I double checked some of these with the on camera spot meter on my

f100 and they were within a fifth of a stop pretty much every time. all 4 rolls

I got back were underexposed identically about a full stop. no matter the

lighting conditions or room i was in, they were all the same. is there

something I missed about this? the meter is dead on in daylight as I shot

several rolls of 120 on my hasselblad a month ago and the exposure was perfect.

I'm kinda pissed because now I have to scan them and see if I can salvage many.

the model loved like half the shots and I've got nothing unless the one roll of

120 comes back ok.

 

they were processed at a lab using C-41 if that makes a difference. I'm

wondering if they didn't expose the film correctly.

[john tonai]

An 80A needs 2 stops compensation.

 

Also, labs don't expose the film-you do.

[ericf1]

John nailed it, but the good news is your meter remains spot on.

 

Good luck.

[andrew_luke2]

you know I looked into this yesterday and found the factor for the filter is an extra 1.5 stops, not the 1.0 I was told at the counter (that's what I get for listening to a salesman).

 

I realize the exposure is in my control but the amount of time the film is left in the developer well change the exposure.

[john tonai]

Andrew,

 

The compensation is 2 not 1.5. While with C41 that should make much difference, the person who told you that was also wrong.

 

Also, developing affects the development. Exposure affects the exposure. Although under exposing and under developing both result in a thin negative, they are not the same thing.

[andrew_luke2]

I understand now that I screwed up by not testing first. I just wasn't sure if it was possible the lab botched on accident.

 

as far as 2 stops, the filter factor from hoya says 2.4. it's my understanding that that means 1.4 stops compensation. I may have that wrong too...I'm new to this balancing tungsten to daylight thing. I've mostly shot strobes and natural lighting in the past. I've honestly never used any filter except for UVs for protection.

[helenbach]

I've seen Hoya Optics data that suggests 1.5 stops for their version of the 80A, but I wouldn't use anything less than a 2 stop compensation. The Kodak data for a Wratten 80A suggests 2 stops.

 

Best,

Helen