# Long exposure black & white Film



## benjyman345 (Dec 21, 2006)

Hello,

Im interested in doing some black and white film long exposure photography and was wondering if there were any hints, tips, advice or guidelines i should know for doing this. I haven't done any black and white film photography before but have done lots of colour film photography. I have red and yellow filters.

thanks


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## ThomThomsk (Dec 21, 2006)

benjyman345 said:
			
		

> Hello,
> 
> Im interested in doing some black and white film long exposure photography and was wondering if there were any hints, tips, advice or guidelines i should know for doing this. I haven't done any black and white film photography before but have done lots of colour film photography. I have red and yellow filters.
> 
> thanks


This is book knowledge (I don't generally need exposures of more than a second or two), but it comes from Ralph Lambrecht, co-author of Way Beyond Monochrome, so it should be reliable. It's a chart that shows the results of his testing for reciprocity failure:

http://www.darkroomagic.com/Library/ImageTaking/Reciprocity.pdf

I'm assuming you know what reciprocity failure is, but if not then just shout. In the book he says that the conventional film he used was FP4, but he reckons the times are OK as a starting point for other conventional films too.

Thom


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## benjyman345 (Dec 21, 2006)

I know the meaning of reciprocity failure but i dont really understand any of that.


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## fmw (Dec 21, 2006)

It means simply that film has a tendency to become less and less sensitive to light the longer it is exposed.  With very long exposures, you should add some additional exposure time to compensate for this.

In my experience, with exposures of less than 2 minutes you can ignore the reciprocity failure and compensate in printing.  Beyond that you may want to look at at the RF charts to get a correction factor for your exposure.  Also, exposures this long are often trial and error guesstimates so you can just bracket on the long side as you guesstimate.


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## mysteryscribe (Dec 21, 2006)

I expose a lot of paper neatives which are more critical than film, exposure wise.  

My exposures routinely run in the minutes.  I usually give it less than a full stop adjustment just by the swag method.  Yesterday at eight minutes called for, I gave it ten minutes.  That is about a quater stop.  After a minute I would add some but not a lot of exposure.  Now that is very un reliable it is purely antidotal.


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## myopia (Dec 21, 2006)

well for film, ilford pan-f 50 is a film which often times gives you long exposures if this is something u are looking to improve on. i am doing this right now. just take a few rolls and experiment and note each exp for reference. by refering to yer notes, u will improve twice as quickly. i need to get better at doing this.


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## ksmattfish (Dec 22, 2006)

benjyman345 said:
			
		

> I know the meaning of reciprocity failure but i dont really understand any of that.



Between 1/10000 and 1 sec doubling the exposure time doubles the exposure, but for longer times it doesn't work so neatly.  You'll have no problem spotting the difference between negs exposed for 1/4th and 1/8th of a sec, but negs exposed for 15 min and 30 min may look very similar.  To get twice the exposure as a 15 min exposure you might have to go with 45 min, or even an hour, depending on the film you are using.  So when bracketing don't go with 3 min, 6 min, 12 min; you probably won't get a one stop difference between the shots.  Try something more like 3 min, 10 min, 30 min.

Reciprocity as it concerns aperture does not break down.  A 10 min exposure at f/2.8 is twice the exposure as a 10 min exposure at f/4.

Interestingly, manufacturer recommended ISOs don't always hold up for long exposures either.  For instance, Tmax 100 is actually faster than Tmax 400 (and many other common BW films) for exposures longer than 3 or 4 minutes.


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