Reciprocity failure

[Pfiltz]

I'm new to film. My first film camera 6 months ago is my RB67. My first LF is a Speed Graphic.

If I wanted to shoot a long exposure lets say of a stream or something along those lines, how do I make sure I don't have reciprocity failure, short of shooting B/W.

When I mentioned that I was thinking of shooting some longer exposed work, one photographer mentioned "reciprocity failure".

How is that avoided, or does it really come into play for LONG exposures such as 15 minutes and so on, and even then how are those folks shooting lets say stars at night, and not getting reciprocity failure?

Is reciprocity failure just applied to color film?

TIA

[vinny]

http://www.google.com/search?q=Reciprocity+failure&ie=UTF-8&oe=UTF-8&hl=en&client=safari

[E. von Hoegh]

http://www.largeformatphotography.info/

[Leigh]

Check the datasheet for the film you're using. There's a broad range of characteristics.

For example, Fuji Acros requires no correction up to 120 seconds, and only +1/2 stop up to 1000 seconds.

Reciprocity law failure applies to all sensitized products, both color and b&w.

The reciprocity law states that if you double the exposure time, you double the actual exposure of the sensitized material.
When the law fails, it just means you must increase the time by more than 2x to achieve the same result.
You still get an exposure that increases with time, but the relationship is no longer a simple multiplicative factor.
The same failure occurs with very short exposures, like 1/10,000 of a second, but we seldom work at this end of the curve.

- Leigh

[RichardSperry]

It really is less of a Law than it is a suggestion.



and even then how are those folks shooting lets say stars at night, and not getting reciprocity failure?

You don't use it at that point. You experiment until you get apertures and times that produce results you like. Then just use those. Well, I don't know about you really, or others, but that's how I do it.

[Pfiltz]

Thanks.

A bit over my head, but I'll try to soak it all in.

[Leigh]

It really is less of a Law than it is a suggestion.
Interesting comment.

So you think the entire relationship between film speed, shutter speed, and lens aperture is merely a suggestion?

It happens to be the entire basis for exposure calculations, i.e. the theoretical basis for photography as a science.

- Leigh

[Light Guru]

I'm new to film. My first film camera 6 months ago is my RB67. My first LF is a Speed Graphic.

If I wanted to shoot a long exposure lets say of a stream or something along those lines, how do I make sure I don't have reciprocity failure, short of shooting B/W.

When I mentioned that I was thinking of shooting some longer exposed work, one photographer mentioned "reciprocity failure".

How is that avoided, or does it really come into play for LONG exposures such as 15 minutes and so on, and even then how are those folks shooting lets say stars at night, and not getting reciprocity failure?

Is reciprocity failure just applied to color film?

TIA

First off don't think of it as reciprocity failure, think of it as reciprocity compensation.

Reciprocity does not just happen with color film but also happens with B&W film. In general any exposure over 1 sec with film will need compensation for reciprocity. However the amount of compensation varied for each type of film.

You ask how is it avoided, well simply you expose for less then 1 sec, but reciprocity is not something that you really need to avoid. Just like adjusting your exposure for different filters you just need to adjust your exposure to include the reciprocity.

If you have an iPhone, iPod Touch or iPad there is a great app called Reciprocity Timer that lets you select your film type enter in your metered exposure, and add the filter you are using. it then calculates the actual exposure for you.

[Steve Smith]

It really is less of a Law than it is a suggestion.

Yes. The reciprocity police will not come knocking at your door if you don't follow it.


Steve

[RichardSperry]

So you think the entire relationship between film speed, shutter speed, and lens aperture is merely a suggestion?

It's a continuum. It's not a matter of at some point failure occurs. I do think it's a good enough approximation or estimatation to get usable exposures.


It happens to be the entire basis for exposure calculations, i.e. the theoretical basis for photography as a science.

- Leigh

Many sciences are based on approximations and estimates. I suppose how accurate these are determines how exact a science is.

I am sure you have printed a print with middle of the road, not extreme, reciprocal apertures and times with notably different results. Why do you think film is different?

[RichardSperry]

Yes. The reciprocity police will not come knocking at your door if you don't follow it.


Steve

I dunno, sounds like Leigh is on the police force.

[Leigh]

It's a continuum. It's not a matter of at some point failure occurs.
Look at the Log H graph for any film.

The straight line between the toe and the shoulder is the exposure range over which the reciprocity law is valid.

This is true for any film.

- Leigh

[Leigh]

Yes. The reciprocity police will not come knocking at your door if you don't follow it.
No. They'll come knocking on your film.

- Leigh

[vinny]

where are the google police?
what is google?
a citation for redundancy is in order.

[RichardSperry]

Look at the Log H graph for any film.

The straight line between the toe and the shoulder is the exposure range over which the reciprocity law is valid.

This is true for any film.

- Leigh

If I learn what it is you wrote, how will that allow me to take better photos?

[E. von Hoegh]

If I learn what it is you wrote, how will that allow me to take better photos?

It may not make you take better pictures, but you'll waste less film. (winking smiley)

Post #23. http://www.largeformatphotography.info/forum/showthread.php?90036-News-flash-for-beginners-on-Total-Exposure/page3

[Leigh]

If I learn what it is you wrote, how will that allow me to take better photos?
If you understanding of the photographic process is as pathetically lacking as your posts would indicate, the only hope
is a substantial investment of time in studying the subject, and experimenting with various exposure combinations.

Otherwise, sally forth with your latest p&s, snapping at everything/body that ventures in front of your lens, hoping to
capture some recognizable image, while devouring electrons by the uncountable zillions.

- Leigh

[Pfiltz]

In general any exposure over 1 sec with film will need compensation for reciprocity. .

Stop right there for a minute and let me catch up.

What compensation? Where? The Lab, or in house developing? In camera? Which I wouldn't know where?

Thanks

[E. von Hoegh]

Stop right there for a minute and let me catch up.

What compensation? Where? The Lab, or in house developing? In camera? Which I wouldn't know where?

Thanks

You need to compensate with exposure and often development. It differs according to the film, and length of exposure. Why don't you google "reciprocity failure" and learn for yourself?

[E. von Hoegh]

If you understanding of the photographic process is as pathetically lacking as your posts would indicate, the only hope
is a substantial investment of time in studying the subject, and experimenting with various exposure combinations.

Otherwise, sally forth with your latest p&s, snapping at everything/body that ventures in front of your lens, hoping to
capture some recognizable image, while devouring electrons by the uncountable zillions.

- Leigh

Leigh, he can't "devour" electrons. He'll just use up lots of energy pushing them from one place to another.

[Leigh]

Leigh, he can't "devour" electrons.
Sure he can. Sequestering them within his digital media, thus removing them from circulation and isolating them from their brethren. :D

They don't even get visitation rights on Thursdays. :eek:

- Leigh

[Andrew O'Neill]

pfitz, which film are you using? I typically use HP5 and for exposures that are 1 second I add 1/3 stop more exposure. 2 sec I'll give 3 sec instead; 4 sec I'll give 6 sec; 8 sec I'll give 12... I have a graph that I made. This also applies to FP4. No exposure compensation is given. Some films require more exposure, some less like TMY.

[Light Guru]

Stop right there for a minute and let me catch up.

What compensation? Where? The Lab, or in house developing? In camera? Which I wouldn't know where?

Thanks

Super simple answer is reciprocity compensation is about exposure time.

Read up
http://filmphotographyproject.com/content/howto/2011/10/what-reciprocity-failure

[E. von Hoegh]

Sure he can. Sequestering them within his digital media, thus removing them from circulation and isolating them from their brethren. :D

They don't even get visitation rights on Thursdays. :eek:

- Leigh

But sooner or later the storage media deteriorate - unless he throws it into a particle accelerator/collider the electrons will eventually be back in circulation; perhaps as part of an even more annoying medium.

[sully75]

http://www.google.com/search?q=Reciprocity+failure&ie=UTF-8&oe=UTF-8&hl=en&client=safari

I hate it when people do that. Even if the question isn't that great. If the only thing on this board was topics that hadn't been covered previously AT LENGTH, there would be no discussions...

[E. von Hoegh]

Super simple answer is reciprocity compensation is about exposure time.

Read up
http://filmphotographyproject.com/content/howto/2011/10/what-reciprocity-failure

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

[E. von Hoegh]

I hate it when people do that. Even if the question isn't that great. If the only thing on this board was topics that hadn't been covered previously AT LENGTH, there would be no discussions...

No, Vinny's right. The OP needs something to read while we amuse ourselves. And reciprocity has been covered at length, here and elsewhere.
Personally, I'm done answering questions and explaining simple things to posters who can't be bothered to bestir themselves and look it up.

[vinny]

I hate it when people do that. Even if the question isn't that great. If the only thing on this board was topics that hadn't been covered previously AT LENGTH, there would be no discussions...

Hey, that's not nice. I'm a member of APUG too and that sounds like what you're describing:)

[mandoman7]

The compensations that manufacturers suggest are given with the assumption that you want an image with a normal tonal range. I like to think of RF as an opportunity to get some deep black areas if you don't do the compensation, or maybe just not as much.

[E. von Hoegh]

The compensations that manufacturers suggest are given with the assumption that you want an image with a normal tonal range. I like to think of RF as an opportunity to get some deep black areas if you don't do the compensation, or maybe just not as much.

You can get that by underexposing.....

[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.

-----
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. (http://www.kodak.com/global/en/professional/support/techPubs/f4017/f4017.pdf)



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.

[Pfiltz]

http://farm8.staticflickr.com/7211/7218617410_846744f453_z.jpg

This shot was posted on this forum, the photographer listed

Fomapan 100
R09 1+50 for 8 minutes.

Thread was http://www.largeformatphotography.info/forum/showthread.php?46577-What-did-you-compose-at-Water%92s-Edge/page229

----------------

So with film loosing it's sensitivity, after around 1 second exposure, how do you shoot an 8 minute exposure.

So, for example, a 10 second metered exposure will need approx. 100 seconds. A 4 second might need 8, how does one shoot 8 minutes...?

Was that 8 minutes something quite shorter originally, but then time was added because of Reciprocity Failure playing a influence on the shot?

[E. von Hoegh]

8 minutes is the time the film was in the developer.

[Pfiltz]

8 minutes is the time the film was in the developer.

OH

So I should be able to find some chart for my film, like Arista 100, and see what I should develope an image for, base on it's exposure time, especially if it was exposed for 1 second or longer?

I'll see if I can find that. I'm not sure I'll be developing my 4x5 on a routine bases, but do plan an attempt too when it comes in, just to test to see if I can. I have some "Ecopro to make XTOL, and some Arista Stop Bath coming in, along with my film.

I think I found something that I can use, if need be.

http://home.earthlink.net/~kitathome/LunarLight/moonlight_gallery/technique/reciprocity.htm

and

I did read this which was suggested here on the forum

http://filmphotographyproject.com/content/howto/2011/10/what-reciprocity-failure

[Heroique]

Let’s say 8 minutes was the final exposure choice (not development time).

Here’s how it might have happened:

First, you meter that scene for 1/15th sec.

You decide you want a really long exposure, so you pull out your 10-stop ND filter.

10 stops is 1000x – so 1/15th sec x 1000 is (about) 1 minute.

Next, you consult your reciprocity chart for a 1 minute exposure – and the chart recommends, say, about 7 or 8 minutes.

Go ahead and shoot the recommendation. Bracket w/ a couple more shots, maybe 6 minutes and 10 minutes. Take plenty of field notes. Head home and develop your film. Take additional notes about your processing. Evaluate your final results. Scan your film and share it here. Tell us your story. Let the experts here astonish you w/ their endless wisdom. Then, head back into the field w/ greater knowledge and improved technique. Come back w/ your next round of shots and astonish the beginners with what you now know. Reassure them that you were once a beginner too, and that practice made you the helpful person you are now.

[mandoman7]

... Scan your film and share it here. Tell us your story. Let the experts here astonish you w/ their endless wisdom. Then, head back into the field w/ greater knowledge and improved technique. Come back w/ your next round of shots and astonish the beginners with what you now know. Reassure them that you were once a beginner too, and that practice made you the helpful person you are now.

Totally! Few seem to appreciate the process of exploring and trying things out with all the answers available now via google. Nothing like making an idiot of yourself first, though, to really make a lesson sink in. :)

[Helen Bach]

Fortunately the curiosity to understand something and the enjoyment of practical experimentation and exploration are not mutually exclusive, though some people seem to think that they are.

[Pfiltz]

Few seem to appreciate the process of exploring and trying things out

If that was true, I would have never ventured into Film, especially now.

[mandoman7]

If that was true, I would have never ventured into Film, especially now.

My apologies, as what you say is true. And its smarter, really, to research processing info on this forum before trying out tricky procedures as well. Its an old guy's lament I guess, maybe just a rationalization for all the film I've ruined in the past. :rolleyes:

[Leigh]

...maybe just a rationalization for all the film I've ruined in the past. :rolleyes:
'Tis oft said... "We learn from our mistakes."

That's why I know so much. :D

The procedure is quite simple:
1) Enumerate all possible ways to do something.
2) Through experimentation, identify all of those that are wrong.
3) The ones left on the list are right.

Voilà!

- Leigh

[cyrus]

One of the interesting things about reciprocity failure is that it is hard to OVER-expose.

Once you're in the area of LONG exposures, a bit longer exposure doesn't really make a difference in the result. So, for example you needed a total of 10 minute exposure (including adjustment for reciprocity failure) you can have a 15 minute exposure and the extra 5 minutes of exposure really won't make a whole heck of a lot of difference in the outcome.

If you look at the H&D curve (http://en.wikipedia.org/wiki/File:H%26D_curve.png), you can see why this would be the case: up on the shoulder of the curve, which is the region for the longest exposures, any incremental additional exposure results in only a comparatively small increase in density. And the longer the exposure required, the smaller the effect of exceeding that time limit. So... don't worry about over exposing.

[Leigh]

...up on the shoulder of the curve, which is the region for the longest exposures, any incremental additional exposure results in only a comparatively small increase in density.
While that's true, it's not relevant.

Long exposures are done because the light level is too low to start with.
Even with extended exposure the mid-tones will be on the linear portion of the curve.
Only the highlights (street lights and such) will be on the shoulder.

- Leigh

[Pfiltz]

Back Story: I worked for a printing company for 30 years before they shut the plant. I decided over night to become a photographer, and start up a studio. Bought Camera's, lighting, backgrounds, etc... with NO experience in Photography. Everything I know about it, has been hands on. I never read a book. I never attended a seminar. Back then, 10 years ago, I didn't even know about forums.

Having said that, the reason for my question coming up, was I mentioned on a another forum about wanting to shoot streams with long exposures, and the subject came up briefly.

I can't capture anything technical by reading. It's not in me. I'm more of a hands on guy. When I ask someone for help, all I need is the basic info. Laymens terms.

Someone just today mentioned about a 6x7 format being good for portraits on some street photography I did. OK? I guess. I just take 'em. I've never gotten into the technical background of Photography. I don't plan on creating a darkroom and doing any printing, or at least not in the foreseeable future.

If this reciprocity thing means that I have to tell the lab, that I shot it a x- seconds, and they should develope it based on that, well, OK I guess.
We don't have streams here, so i don't see me doing any milky water looking shots. Having said that, I'm trying to learn 4x5 work, prior to me going up to the Pacific NW in September to visit a friend, and hoping to shoot landscapes, which is not more Forte.

I don't get to travel much, so I hope to get at least 1 good landscape with my 4x5 camera in September on my trip. I know I'll be taking my RB with me, as a backup.

I plan on talking with the lab that is currently developing my color film, so I can get on the right page with them, if there is a need.

Thanks to all that gave me some nibblets to digest on the subject.

[Leigh]

I never read a book. I never attended a seminar.
So you expect us to do all the work for you. :eek:

It's probably no in your best interest to brag about that.

- Leigh

[Brian C. Miller]

I can't capture anything technical by reading. It's not in me. I'm more of a hands on guy. When I ask someone for help, all I need is the basic info. Laymens terms.
...
If this reciprocity thing means that I have to tell the lab, that I shot it a x- seconds, and they should develope it based on that, well, OK I guess.

Laymen's terms: Reciprocity failure = you need more exposure. How much more exposure depends on the film. If the film development needs to be changed, it's noted in the film data.

When you say, "I can't capture anything technical by reading," how can you expect to understand a manufacturer's film reciprocity information?? You need to read! Most film has information about reciprocity. You need to just go and look it up. The information is usually presented as a simple table, so it's very easy to understand. But you won't know what it is if you don't go and read it.

[Helen Bach]

I plan on talking with the lab that is currently developing my color film, so I can get on the right page with them, if there is a need.


If you are sticking to colour neg then there's probably no need to tell the lab anything. I've used Portra 160 (with standard C-41 processing) for exposures of around 20 minutes with no problems. Colour shifts can be corrected at the printing stage.

Best,
Helen

[E. von Hoegh]

Education is what you get from reading the small print. Wasted time is what you get from ignoring the small print.

It is impossible to learn in any efficient manner about a complex field such as photography without doing at least some technical research. Do you read a chart to learn what time and which developer to use for a given film? The reciprocity charts are no more complex.
And, you are reading the responses in this thread. If you can read this thread, you can do basic research.

[cyrus]

I should also (http://www.largeformatphotography.info/forum/showthread.php?92795-Reciprocity-failure&p=909628&viewfull=1#post909628) point out that extending exposure time is only part of dealing with reciprocity failure. You may have to reduce development time too, to deal with the excess contrast that can result.

[Pfiltz]

Ok, folks.

I get it.

[Steve Smith]

If this reciprocity thing means that I have to tell the lab, that I shot it a x- seconds, and they should develope it based on that, well, OK I guess.

You don't need to do that. You compensate for it during exposure so that you can give the film standard development.


Steve.

[E. von Hoegh]

You don't need to do that. You compensate for it during exposure so that you can give the film standard development.


Steve.

That depends upon the film. You can be certain by reading the data sheet which comes with the film.....

[Brian Ellis]

You don't need to do that. You compensate for it during exposure so that you can give the film standard development.


Steve.

Actually as I mentioned on page 4, you would normally reduce development time, at least with b&w film, to compensate for the additional contrast caused by the long exposure (unless of course you wanted the added contrast). I don't know about color film, I've never used it for LF photography.

[RichardSperry]

Ok, folks.

I get it.

Ya, don't ask questions on this forum.

All you will get are insults from old curmudgeons with monopods stuck up their asses.

[Andrew O'Neill]

Pfitz, the bottom line is that you are going to have to do some testing to truly understand your film of choice and reciprocity effects.

[Andrew O'Neill]

Actually as I mentioned on page 4, you would normally reduce development time, at least with b&w film, to compensate for the additional contrast caused by the long exposure (unless of course you wanted the added contrast).

Brian, not so with the films that I use. HP5, FP4, and TMY-2 don't need development time compensation. I've tested them with step wedgies where a piece of film that received reciprocity compensation overlaps almost perfectly over top of a sheet of film that didin't require any exposure compensation.
I have no idea what happens with colour films... don't the colours go all whacky unless you use colour correction filters?

cheers!

Andrew

[Brian C. Miller]

I have no idea what happens with colour films... don't the colours go all whacky unless you use colour correction filters?

Maybe, maybe not. I've used Kodak E100S at 15-20 minutes with no color shift (by full moonlight, don't remember the f-stop). Agfa would change really fast without enough exposure, with an accent on reds.

[E. von Hoegh]

Ya, don't ask questions on this forum.

All you will get are insults from old curmudgeons with monopods stuck up their asses.

Yes, curmudgeons often dislike it when people who know not what they speak of argue with accurate and informative answers. Must be the monopod......

[mandoman7]

Before the internet, getting LF info required learning library filing systems, subscribing to publications, and taking workshops. Now its a matter of wading through personalities.

[E. von Hoegh]

Before the internet, getting LF info required learning library filing systems, subscribing to publications, and taking workshops. Now its a matter of wading through personalities.

When I learned, it was getting books - specifically St. Ansel's trilogy, asking the few (3) local (within 50 miles) practitioners a lot of questions - they were ALL cumudgeons (one looked just like Foster Brooks, another owned a local camera store), and studying, and thinking, and practicing. No local library has any books on LF, never needed a workshop, never subscribed to anything, and I built my own library with references from optics to sensitometry by haunting used bookstores.

The part where the individual who wishes to learn must do work hasn't changed one bit. Research is part of that work; if one is not willing to put in the effort large format is not for you. Period.

[RichardSperry]

Yes, curmudgeons often dislike it when people who know not what they speak of argue with accurate and informative answers. Must be the monopod......

Who's arguing E.?

I asked an honest question(a couple actually), and was summarily insulted. And there were no answers(informative or otherwise) to them, go back and read the thread again.

I gave an example for Leigh, which I ask of you. I am sure you have printed a print with very close and middle of the road reciprocals, did those two prints look the same to you E.? Mine don't.

Why do all the reciprocal "corrections" with film increase continuously as the time gets longer? There are charts above in this thread that show that, I assume that they are correct "enough"; and other charts I have read show the same thing(off hand iirc Simmons has a chart in The View Camera). Does it make sense to you then that, reciprocity "failure" occurs only at either end, and it just clicks itself off in the middle?

Answer this too,E., in the context of long exposures for film(which is the topic of this thread), what is so offensive of my statement that The Law of Reciprocity is more of a suggestion than a Law? Was my suggestion to the OP to experiment(because reciprocal values no longer work), and figure out usable apertures and shutter times offensive?

Go back and read post 5 please. By all means quote what is so offensive about that post, E. or what is wrong with it.

[Leigh]

Does it make sense to you then that, reciprocity "failure" occurs only at either end, and it just click itself off in the middle?
You haven't received an answer to that question because it makes absolutely no sense.

The exposure shown on a graph is given in lux-seconds, where lux is the amount of light and seconds is the amount of time.

The lux value is controlled by the aperture setting, and the time by the shutter speed setting.

Any combination of those values which give the same product when multiplied together will produce
the same density on the film, provided that product falls on the straight portion of the curve.

For exposures on the straight line portion of the curve, if you double or halve that product, the density changes proportionally.

The toe and shoulder are areas where a change of this product no longer causes a proportional change in density.

That is the law of reciprocity, and the basis for photographic exposure.

- Leigh

[E. von Hoegh]

Who's arguing E.?

I asked an honest question(a couple actually), and was summarily insulted. And there were no answers(informative or otherwise) to them, go back and read the thread again.

I gave an example for Leigh, which I ask of you. I am sure you have printed a print with very close and middle of the road reciprocals, did those two prints look the same to you E.? Mine don't.

Why do all the reciprocal "corrections" with film increase continuously as the time gets longer? There are charts above in this thread that show that, I assume that they are correct "enough"; and other charts I have read show the same thing(off hand iirc Simmons has a chart in The View Camera). Does it make sense to you then that, reciprocity "failure" occurs only at either end, and it just clicks itself off in the middle?

Answer this too,E., in the context of long exposures for film(which is the topic of this thread), what is so offensive of my statement that The Law of Reciprocity is more of a suggestion than a Law? Was my suggestion to the OP to experiment(because reciprocal values no longer work), and figure out usable apertures and shutter times offensive?

Go back and read post 5 please. By all means quote what is so offensive about that post, E. or what is wrong with it.

If you had ever bothered to look, you would have found that what you speak of is properly called reciprocity law failure and it is a result of either very low light levels at one end, or very short exposure times at the other end. It is not a suggestion. All of the questions you ask above can be answered by a short study of sensitometry. Read up on it, like I did. http://www.amazon.com/Photographic-Sensitometry-Study-Tone-Reproduction/dp/0871001802

[RichardSperry]

Leigh,

Except with long exposures and very short exposures.

And the "failure" increases exponentially as the time increases proportionately.


You haven't received an answer to that question because it makes absolutely no sense.

It doesn't make sense to me, when there is an obvious change of rate(of needed correction) as time increases that there is no "failure", no matter how small, in the middle. You yourself stated that Failure applies to all photographic media. Its a given that the failure of film, in the middle average values, is imperceptible, so I gave a model of photo paper instead. Print a sheet at f/8 for 10 seconds, print a second at f/11 for 20 seconds...they will not look the same Leigh. You know this is true.

[Leigh]

Except with long exposures and very short exposures.
"Except" what? Your sentence does not reference anything.

The same toe and shoulder curves will result from changes in aperture, although we normally cannot change
that value over the same wide range as shutter speeds due to physical limitations.


It doesn't make sense to me, when there is an obvious change of rate(of needed correction) as time increases that there is no "failure", no matter how small, in the middle.
Then you don't understand the mathematical meaning of the term 'product', which is the result of multiplying two numbers.


Print a sheet at f/8 for 10 seconds, print a second at f/11 for 20 seconds...they will not look the same Leigh.
They look the same on my equipment, provided the times are within the straight line section of the paper's exposure curve.

If they don't on yours, I suggest you get your equipment repaired.

- Leigh

[Lenny Eiger]

Does it make sense to you then that, reciprocity "failure" occurs only at either end, and it just clicks itself off in the middle?

It does. I once had it explained to me by a physicist. (I am not a physicist, so this is for explanation only, I can't say I did this test myself.)

Here's what he said: It has to do with the difference between what happens to one of these grains of silver salts from being hit by photons. If they are hit by enough photons, they move from the "undevelopable" to a "developable" state. We know what happens in the developer....

However, at some levels of energy (less photon strikes) the grain moves to a third state, which is "I don't know". It may like the bowling pin that gets hit by the ball but not with enough force and so tips back and forth, and will either fall over, or right itself.

In the case of "not enough light" this third state rules. Some of the grains move back from the precipice of being developable and become undevelopable again.

The less the amount of light, the more of them are in the state where they might change back, and so there is a predictable rate of reciprocity failure. I don't care what AA said, it's a failure of a grain to turn to the developable state by being hit with photons. Failure is a fine word, IMO. I think the distinction is fairly meaningless.

At any rate, I hope this helps you understand what happens at the toe of the curve, at least. What happens at the top is a different matter.

Regards,

Lenny

[E. von Hoegh]

It does. I once had it explained to me by a physicist. (I am not a physicist, so this is for explanation only, I can't say I did this test myself.)

Here's what he said: It has to do with the difference between what happens to one of these grains of silver salts from being hit by photons. If they are hit by enough photons, they move from the "undevelopable" to a "developable" state. We know what happens in the developer....

However, at some levels of energy (less photon strikes) the grain moves to a third state, which is "I don't know". It may like the bowling pin that gets hit by the ball but not with enough force and so tips back and forth, and will either fall over, or right itself.

In the case of "not enough light" this third state rules. Some of the grains move back from the precipice of being developable and become undevelopable again.

The less the amount of light, the more of them are in the state where they might change back, and so there is a predictable rate of reciprocity failure. I don't care what AA said, it's a failure of a grain to turn to the developable state by being hit with photons. Failure is a fine word, IMO. I think the distinction is fairly meaningless.

At any rate, I hope this helps you understand what happens at the toe of the curve, at least. What happens at the top is a different matter.

Regards,

Lenny

Which is precisely how it is explained in the book I posted the link to above. Available used from $1.98, and it has a host of other great info.

At the top of the curve, for very short exposures, there isn't enough time for the photons to initiate the change in state in all silver grains, and so the compensation - preferably with the aperture.

[RichardSperry]

If you had ever bothered to look, you would have found that what you speak of is properly called reciprocity law failure and it is a result of either very low light levels at one end, or very short exposure times at the other end. It is not a suggestion. All of the questions you ask above can be answered by a short study of sensitometry. Read up on it, like I did. http://www.amazon.com/Photographic-Sensitometry-Study-Tone-Reproduction/dp/0871001802

The book in your link is out of stock. I know what reciprocal law failure is, E. by the way; I have bothered to look.

Anyway,
Of course, the "Law" is not even a good suggestion at very long exposures(which is the topic of this thread). And most light meters don't work reliably there anyway(the Luna Pro SBC being a notable exception).

Add to that, differences between films, say when Acros 100 becomes faster that a 400 film. The law is useless for determining what is an equivalent time for say an f/11 8 minute shot on Acros compared to HP5+, for example. E., how long would you time that HP5 for, using the Law?

[E. von Hoegh]

The book in your link is out of stock. I know what reciprocal law failure is, E. by the way; I have bothered to look.

Anyway,
Of course, the "Law" is not even a good suggestion at very long exposures(which is the topic of this thread). And most light meters don't work reliably there anyway(the Luna Pro SBC being a notable exception). Why it's called "failure"

Add to that, differences between films, say when Acros 100 becomes faster that a 400 film. The law is useless for determining what is an equivalent time for say an f/11 8 minute shot on Acros compared to HP5+, for example. E., how long would you time that HP5 for, using the Law?

For HP5 I would use my LunaSix and compensate per the Ilford datasheet. Films respond differently, but you knew that right?
There are 12 used copies of the book available. It's out of print, so new ones are scarce.

[Leigh]

The film datasheets normally include correction curves for long exposures.

As usual, you would derive more benefit and understanding from reading than by posting nonsense here.

- Leigh

[RichardSperry]

If they don't on yours, I suggest you get your equipment repaired.

Really? I will test it again, on a different enlarger. Thanks for the suggestion.


"Except" what? Your sentence does not reference anything.
I was referring to your previous post, never mind it now.


Then you don't understand the mathematical meaning of the term 'product', which is the result of multiplying two numbers.

When I see an increasing rate of change, I think of differential calculus not multiplication.

[RichardSperry]

The film datasheets normally include correction curves for long exposures.

I have my times for my film memorized, Leigh.


As usual, you would derive more benefit and understanding from reading than by posting nonsense here.

- Leigh

I should go out a shoot some film, and not waste my time with you lot.

[Leigh]

When I see an increasing rate of change, I think of differential calculus not multiplication.
Oh WOW! Calculus! Is that supposed to intimidate us? Sorry... it doen't.

Who mentioned rate of change? Nobody but you.
This is not a rate of change problem in the first place, which is why nobody else mentioned it.
Your comment just emphasizes your total lack of understanding of the underlying subject.


I should go out a shoot some film, and not waste my time with you lot.
That's a marvelous idea. In the process, you can quit wasting our time.

- Leigh

[Helen Bach]

The book in your link is out of stock. I know what reciprocal law failure is, E. by the way; I have bothered to look.

Anyway,
Of course, the "Law" is not even a good suggestion at very long exposures(which is the topic of this thread). And most light meters don't work reliably there anyway(the Luna Pro SBC being a notable exception).

Add to that, differences between films, say when Acros 100 becomes faster that a 400 film. The law is useless for determining what is an equivalent time for say an f/11 8 minute shot on Acros compared to HP5+, for example. E., how long would you time that HP5 for, using the Law?

The reciprocity law is a good and very useful law over the range of exposure times for which it holds* - virtually all exposure meters are based on it. Here we are talking about the failure of the law - ie long exposure times for which the law doesn't hold (in this case, strictly speaking it is the low intensities or illuminances for which it doesn't hold: LIRF). You can't expect a law to be much use once it has failed.

*Between 1/10,000 s and 1 s for the Portra 160 used by the OP, for example.

Best,
Helen

[Heroique]

You can't expect a law to be much use once it has failed.


I think a law that fails is intuitively troublesome to many people.

A law is supposed to “stay” true, they deeply feel.

A legislative law that fails is easier to accept. ;^)

[mandoman7]

Rarely is sensitivity fully linear. Just ask my ex-wife.

[Heroique]

It tends toward logarithmic in this forum.

Or maybe it’s geometric – whichever is worse.

Easy to mix up.

[Andrew O'Neill]

Was my suggestion to the OP to experiment(because reciprocal values no longer work), and figure out usable apertures and shutter times offensive?

Richard, this statement is not offensive at all. It is exactly what all photographers should do if they truly want to understand their film of choice. One doesn't have to be as thorough as I was about testing. One could easily start with the manufacturer's data (which I find to be a bit on the long side exposure-wise :)), try it in the field and see what happens. Adjust accordingly. Keep notes, etc.
Understanding your tools and controling as many variables as possible, makes life so much easier in the field.
Now it's back to ripping up plywood on my deck (which is the roof to my darkroom) for the vinyl guy on Monday.... Man, that's hard work!

cheers
andrew

[Jody_S]

As someone who's done a fair bit of night photography, in all formats (and studied math): experiment with a given film, and then never change films. Fill your freezer if there's any doubt. Reciprocity tables are virtually useless for night photography unless you're in a brightly-lit city (IMHO).

That being said, any time I am forced to use a new film, I do find it useful to use teh Googles and try to find some hints before doing my own tests.

[Helen Bach]

I think a law that fails is intuitively troublesome to many people.

A law is supposed to “stay” true, they deeply feel.

A legislative law that fails is easier to accept. ;^)

Fortunately almost every film photographer is quite happy to trust and make extensive practical use of the reciprocity law without it troubling them one little bit. The entire method of film speed and exposure determination would have to be very much more complicated if the reciprocity law could never be trusted.

It isn't unusual for things that are generally called laws to have specific conditions that define the range of their applicability.

Best,
Helen

[Helen Bach]

Is it worth mentioning that the reciprocity law has nothing to do with the shape of the H-D curve? The H-D curve could have no straight-line section and the reciprocity law could still hold. What the reciprocity law means is that if H (the light energy arriving at the film surface) is constant, the resulting density will be constant. If the reciprocity law fails, that no longer holds: H could remain constant yet D could vary.

In practice I work almost entirely by experience for long exposures at night - knowing f-number and time combinations that work for a particular film in particular circumstances. I have a terrible habit of falling asleep at night no matter how sober, cold and uncomfortable I am, so many of the exposures I have made have been timed by how long I sleep for. It's amazing how many have turned out OK.

Best,
Helen

[Jerry Bodine]

It isn't unusual for things that are generally called laws to have specific conditions that define the range of their applicability.

I certainly agree with that, and I have to say that it made me chuckle as it reminds me of an engineer I worked with many many years ago who always referred to Ohm's Law as Ohm's Opinion.

[Heroique]

[...Chuckle...]

Well, now I'm thinking of poor Newton when things are really small and really fast.

[E. von Hoegh]

I certainly agree with that, but I have to say that it made me chuckle as it reminds me of an engineer I worked with many many years ago who always referred to Ohm's Law as Ohm's Opinion.

AC circuits with capacitive or inductive reactance, the "resistances" will depend on frequency.

[E. von Hoegh]

[...Chuckle...]

Well, now I'm thinking of poor Newton when things are really small and really fast.

Newton and Napier got us to the moon, and more importantly, got us back to earth.

[Leigh]

AC circuits with capacitive or inductive reactance, the "resistances" will depend on frequency.
No. Resistance has no reactive component, and thus is invariant with frequency.

The parameter you're thinking of is 'impedance', which does include a reactive component.

- Leigh

[E. von Hoegh]

No. Resistance has no reactive component, and thus is invariant with frequency.

The parameter you're thinking of is 'impedance', which does include a reactive component.

- Leigh

I know. Hence the quotation marks, I was trying to keep it simple.

[photobymike]

Reciprocity failure My wife says i have it and dont know it..... You really can get an education on photography on LF. Kind of the wiki of opinions about photography... Entertaining also. I dont mind seeing questions like this... but who am i... but you could get more information and fact if you would google this subject.... Google really is a miracle of the internet... searching millions of web pages .. think about ... all that info and porn at your finger tips... My imagination just is not quite big enough to grasp all the info and porn you can find with google....

[E. von Hoegh]

Reciprocity failure My wife says i have it and dont know it..... You really can get an education on photography on LF. Kind of the wiki of opinions about photography... Entertaining also. I dont mind seeing questions like this... but who am i... but you could get more information and fact if you would google this subject.... Google really is a miracle of the internet... searching millions of web pages .. think about ... all that info and porn at your finger tips... My imagination just is not quite big enough to grasp all the info and porn you can find with google....


Wait a minute. Are you saying we can look at porn on our computers? Seriously?!?

[kev curry]

I should go out a shoot some film, and not waste my time with you lot.

Wise words... if you heed them you'll save a lot of valuable time and energy.

If you can manage to stick around here long enough you'll come to realize that this place is never short on assholes. You'll also come to realize that a large proportion of the photographers that hang around places like this dont accually make photographs, they just like to talk as though they do.

The short cut to learning photography is from reading and studying good books and making photographs. A forum is the very last place you should be looking for information especially if your still working on getting the basics down.

[Leigh]

Wow, Kev... strong opinions!

If the forum is so useless... Why are you here?

- Leigh

[kev curry]

I like a bit of S&M now and then...

[Leigh]

If this is how you get off, you're in deep kimchi. :eek:

- Leigh

[kev curry]

Never tried it...but I recognize the smell of bs just fine. Big pharma must be making a mint out of old guys like you.

[perfectedmaya]

i have a 10 stop ND, but never use it on 45.. but i have use my red filter on 45 and exposure of several minutes.. all bw films (Ilford)... i look at the chart for my film and do a rough estimate, so far so good.

[mamypoko]

I've been shooting long exposures on TriX and Shanghai 100 for about a year, paired up with a ND110 in the day and just stopping down at night, I've been taking 20min to 1 hour long exposures.

I followed Kodak's suggestions for TriX, and for Shanghai I based it off TriX but realized it was much slower and now compensate accordingly.

Now moving onto Velvia, longest so far was 10 minutes!

[Vaughn]

I like reciprocity failure -- approached properly, it gives one such a nice boost in contrast (B&W). My exposure times are usually in the minutes under the redwoods. I give just a little more exposure, then develop the heck out the negative for wonderful contrast and feeling of light for my carbon prints and platinum prints.