Agfa APX 100 reciprocity...

[rob3rt5]

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I just purchased 150 rolls of Agfa APX 100 for use on various projects. On some of those projects I intend to use a HOYA NDx400 filter and long exposures and would like to be able to have a scale that tells me how much time to add for these extended exposures.

So far, I've only found f-stop exposure adjustments and not time adjustments. The information is limited and I could never find the films true rateing (some say 1 others say that the tc is less).

Any and all help would be greatly appreciated.

[giordano]

I just purchased 150 rolls of Agfa APX 100 for use on various projects. On some of those projects I intend to use a HOYA NDx400 filter and long exposures and would like to be able to have a scale that tells me how much time to add for these extended exposures.

So far, I've only found f-stop exposure adjustments and not time adjustments. The information is limited and I could never find the films true rateing (some say 1 others say that the tc is less).

Any and all help would be greatly appreciated.

 

The EV or f/stop data is all you need:

1. Calculate the exposure time for a slightly smaller f/stop than you intend to use.
   
2. Open the aperture by the amount indicated for that time.
   
3. If the resulting aperture is unacceptable, go back to 1 with a slightly different initial aperture.
   

After a bit of practice it'll be easy. You'll probably need to experiment anyway, because highlights are less affected by reciprocity law failure than shadows (obvious, when you think about it) so very long exposures tend to produce more contrasty negs and the manufacturer's recommendations may not be quite right for you.

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[tgray]

apug.org might have some info. Go over there and ask.

[rob3rt5]

Thank you so very much for your time and effort.

[dave_d]

A 1 stop increase is twice as much light so double your exposure time. A 1 second exposure becomes 2 seconds.

 

A 2 stop increase is 4 times as much light so a 10 second exposure becomes 40 seconds.

 

A 3 stop increase is 8 times as much light so a 100 second exposure becomes 800 seconds.

[fotohuis]

http://www.aphog.de/downloads/agfa/apx100.pdf

[stunsworth]

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A 1 stop increase is twice as much light so double your exposure time. A 1 second exposure becomes 2 seconds.

 

Dave, I think the original poster knows that. With very long exposures that system breaks down and you have to expose more than a simple multiplication of time would indicate. I think it's that additional timing that he's looking for.

[rob3rt5]

Dave, I think the original poster knows that. With very long exposures that system breaks down and you have to expose more than a simple multiplication of time would indicate. I think it's that additional timing that he's looking for.

 

That's right Stunsworth- I'm looking for a table of adjusted times and these times are not linear.

[peter_n]

This is the only data I could find on my PC: from Agfa Technical Data Professional Films F-PF-E4 08/2004 4th edition, page 6.

 

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[wontonny]

I just purchased 150 rolls of Agfa APX 100 for use on various projects.

 

I'm curious as to where you bought these? I haven't been able to find any place that carries it

[rob_x2004]

This is the only data I could find on my PC: from Agfa Technical Data Professional Films F-PF-E4 08/2004 4th edition, page 6.

 

 

What are peoples thoughts on this?

[giordano]

 

What are peoples thoughts on this?

 

At first sight the adjustments appear very large, but they are coupled with adjustments in development time. This suggests that in addition to allowing for plain reciprocity failure they are reducing development time to compensate for the increased contrast that comes with it, and increasing exposure to compensate for the reduced development.

 

Anyway: suppose you need f/11 for a shot, the general idea is:

1. See what exposure time the meter says you need at f/11.
   
2. If it's less than a second, go ahead.
   
3. If it's between 1 and 10 seconds, expose for the time the meter says you need at f/16.
   
4. If this takes you past 10 seconds, expose for the time the meter says you need at f/22.
   
5. If that takes you past 100 seconds, take the meter reading at f/32.
   

Adjust the development according to the exposure time you used and - in theory - Bob's your uncle. You may find it worthwhile to interpolate the half-stops. With experience you'll probably refine the adjustments to suit your processing and get the sort of negatives you want.

 

If your film is going to have a mixture of short and long exposures on it you won't be able to adjust the development times for individual frames. In that case you'll need to experiment to get the best compromise. If I was in that situation I think I'd start by using normal development and halving the recommended exposure adjustments.