Reciprocity failure

[Heroique]

I'm new to film…

I’ve shared this starter’s chart before, and I’m happy to share it again – I presume that it will be more helpful than another indignant “Do a search” remark, but I’ll leave that judgment up to you.

It’s for times under 2 minutes for traditional b/w films (not T-grain), until one becomes more familiar w/ personal equipment & film, darkroom processing habits (such as “N-1” or “N-2”), and preferred results. As you learn more, adjust to your taste:

• Metered 2 sec. – use 4 sec (2x)
• 4 sec – use 12 sec (3x)
• 8 sec – use 32 sec (4x)
• 15 sec – use 75 sec (5x)
• 30 sec – use 3 min (6x)
• 60 sec – use 7 min (7x)
• 120 sec – use 16 min (8x)

Over time, my personal reciprocity charts for various films depart more and more from the chart above, and from manufacturing suggestions, but not by a very significant amount.

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Master’s note:
“This is commonly known as ‘failure of the reciprocity law’,” AA says in his book, The Negative, “but I prefer the term reciprocity effect as it is not actually a ‘failure.’ ”

[Lenny Eiger]

These numbers don't make sense to me. I have always used the 1 sec, 10 sec, 100 sec rule, which sates if you have

1 sec add 1 stop
10 secs add 2 stops and
100 secs add 3 stops.

This worked well for me for many years, with traditional film. With the TGrained films, it is much less. 4 seconds becomes 5, it doesn't get to a full stop until about 8 seconds.

Everyone's results are different.... and so is each different film.

There can be no rules except those that you discover yourself...

Lenny

[mandoman7]

You can get that by underexposing.....

I'm not sure its the same. I was under the impression that the brighter tones were less affected than the lower tones at long exposures. Charts don't mention it nowadays, but it used to be that N-1 or -2 development was recommended for the longer exposures.

[Pfiltz]

Thank you all for the info.

I think i have my head around some of this.

Back to your regular scheduled programming.

P.S. Btw,, someone was asking about film.

RB67 - I've been shooting Porta 160
SG - Portra 160, and the next box due up is Arista I believe. It's been ordered, and I'm awaiting it.

[Light Guru]

It's also often about development. With color materials, filtration rears it's knobby head.

That's why I said super simple answer.

[Andrew O'Neill]

P.S. Btw,, someone was asking about film.

That were me. Sorry, never used colour so cannot even begin to help you.

[RichardSperry]

Leigh,

Why the need to resort to insults?

It was a cordial discussion.

[Helen Bach]

I'm not sure its the same. I was under the impression that the brighter tones were less affected than the lower tones at long exposures. Charts don't mention it nowadays, but it used to be that N-1 or -2 development was recommended for the longer exposures.

Yes, it's dependedent on the illuminance* at the film plane, so dark areas depart from reciprocity more than the brighter areas for low intensity reciprocity failure/departure (but not for high intensity reciprocity failure, which is the other way round).

*'brightness' of the arriving light - light (or radiant) power (rate of arrival of energy) divided by area - the lower the local rate of arrival of energy, the less chance there is of forming a stable latent image, at film plane illuminances for which the reciprocity law doesn't apply.

The change in developing is still mentioned by Kodak in their tech notes for their B&W films. Here it is for Tri-X: Tech. pub. F-4017, dated 2007.

Master’s note:
“This is commonly known as ‘failure of the reciprocity law’,” AA says in his book, The Negative, “but I prefer the term reciprocity effect as it is not actually a ‘failure.’ ”

The logic of that puzzled me - why would you use 'reciprocity effect' to describe situations in which the reciprocity law doesn't apply? Later, however, he calls it 'reciprocity law departure', which seems much clearer, and more accurately descriptive.

Best,
Helen

[Brian Ellis]

It's also often about development. With color materials, filtration rears it's knobby head.

It's most definitely about development time with b&w film. Unless you want the additional contrast that accompanies the exposure increase given to compensate for reciprocity failure you decrease development time, the greater the exposure increase the greater the reduction in development time. Test to determine the decrease or find a table of reduction times such as the one John Sexton hands out at his workshops.

I don't know about color materials or what you mean by "filtration rears its knobby head."

[Helen Bach]

Because the different sensitive layers in a colour film can have different behaviours at low intensity, manufacturers sometimes recommended filtration as well as exposure change for long-ish indicated exposures (often quite short compared to B&W film reciprocity departure onset exposure times), particularly for some reversal films - eg CC05R for Kodachrome 64 and CC10Y for Kodachrome 200.