Understanding Reciprocity Failure

[thegman]

Hi all,
I was out yesterday taking a few night shots on ISO 100 film, some Fujifilm Acros, and some Veliva 100f. With such slow film, and failing light, my exposures were often well over 5 seconds. I didn't want to use faster film as my aim was to get some good fine grain tripod shots. I bracketed by up to 2 stops each way, so I hope I'll get something worth keeping...

Today, however, I've read on Wikipedia that reciprocity failure generally kicks in on film after about 1 second.

Is this something I need to consider for long exposures? Are there good rules of thumb about this?

I'll be sending off the film tomorrow, so I'll see how it went soon enough.

Also, my ZI meters up to 8 second exposures, is a cheap handheld meter a good investment, in case I need to go longer?

Cheers

Garry

 

[bmattock]

Reciprocity failure is a departure from exposure that can be reliably predicted based on the film's rated speed. Therefore, reciprocity values vary based on the film. Manufacturers put a lot of effort into determining the appropriate values for both high and low speed reciprocity values, and those are generally available to the public. If it could be easily calculated, there would be no need for such things. It is also an unfortunate fact that some meters do not respond well in very low light situations, so readings taken by them can lead to inaccurate settings for exposure. A high-quality meter is generally capable of better low-light performance that a built-in meter in a camera, but I do not know the capability of the ZI meter.

Here is a blog that purports to have a Velvia reciprocity chart. I do not know how accurate it is:

http://www.brucepercy.com/blog/?p=47

 

[Pickett Wilson]

Reciprocity failure is a result of films decreasing sensitivity during long exposures. It varies from film to film and can sometimes become an issue at times as short as 1/10 second, but is mainly a concern over one second. You can download product sheets from the film makers web site that usually provide a chart showing the reciprocity characteristics of the film.

 

[Pickett Wilson]

bmattock, great minds and all. 🙂

 

[not_in_good_order]

Each film is different in its reciprocity characteristics. You should always consult the manufacturer's data sheet for more information. For example, here is Velvia 100F's data sheet from Fuji's website:

http://www.fujifilm.com/products/professional_films/pdf/velvia_100f_datasheet.pdf

On page 2 it states that exposures between 1/4000 sec and 1 minute need no adjustments for reciprocity failure.

 

[sepiareverb]

My general rule for most films is:

1S give 2S
2S give 4S
4S give 10S
8S give 20S
15S give 40S

This gives me pretty good results with normal development- though I'd reduce agitation a bit if most of the roll is in low light.

These conversions came from years working with the view camera under tungsten lights, so I'm not sure how relevant they would be outdoors at night.

And of course, I'd say bracket if you can to be sure.

 

[thegman]

I see, Velvia makes it simple at least...

sepiareverb: So you're saying if your meter says 1 second, you'd expose for 3 seconds? If that's the case, then I'm not expecting great results from my latest films!

 

[not_in_good_order]

This is Fuji's data sheet for Neopan Acros 100:

http://www.fujifilmusa.com/shared/bin/NeopanAcros100.pdf

On page 1, in the section titled Reciprocity Characteristics, it states that no changes need to be made for exposures lasting between 1/1000 sec and 120 seconds.

If your exposures were around 5 seconds for both the Velvia 100f and for the Neopan Acros 100 then you did not need to make any adjustments to your exposure according to the manufacturer. Many films from Fujifilm, including the ones you used, excel in their ability to not require adjustments for long exposures.

What you read about reciprocity failure occurring after exposures lasting longer than a second is only true for certain films. Every film has its own reciprocity characteristics.

 

[bmattock]

sepiareverb: So you're saying if your meter says 1 second, you'd expose for 3 seconds? If that's the case, then I'm not expecting great results from my latest films!

My suggestion would be that using published reciprocity data would be superior in most cases to guessing, even if the guesswork is based on experience using something else altogether in altogether different circumstances. I'm not sure why a person would wish to ignore what the manufacturer has spent time & money to create accurately in order to depend upon a 'rule of thumb' that in the case of reciprocity, is stated not to exist?

 

[Mablo]

I wouldn't be so downbeat. I guess your negs will be just fine. I've been using cheap fixed lens rangefinders like Yashica Electro 35 or Olympus XA when the needle in my Seconic Twinmate no more reacts to the dwindling light. I get great shots every time.

 

[fergus]

I see, Velvia makes it simple at least...

After reading this thread I went looking for the reciprocity data on two films I use, Astia and Provia 400.

I found the data sheets here.

These seem to have similar characteristics to Velvia mentioned above, no adjustment for up to 1 minute.

Perhaps b&w films need adjustment at much shorter exposure times?

 

[Philly]

This is Fuji's data sheet for Neopan Acros 100:

http://www.fujifilmusa.com/shared/bin/NeopanAcros100.pdf

On page 1, in the section titled Reciprocity Characteristics, it states that no changes need to be made for exposures lasting between 1/1000 sec and 120 seconds.

Confirmation.
I've used this film extensively for long exposures with pin-holes and zone-plates. There are no problems out to beyond 2 minutes so the OP should have no worries with his Acros shots.🙂

 

[Disaster_Area]

a somewhat similar question... is reciprocity cumulative? ie: is the film not able to register long exposures of light all at once because of some chemical threshold gets reached? As a metaphor... you can't pour a beer into a glass all in one go because foam builds up, but you can pour the beer into the same glass if you do it in short spurts with no problem. So one, three second exposure would suffer from reciprocity but would a dozen quarter second exposures on the same frame also be subject to reciprocity?

 

[aizan]

yes, it would also have reciprocity failure, as long as the total exposure time is outside the normal range. the foam doesn't settle down with film. =)

 

[Dwig]

Several additional points:

1. Reciprocity failure occurs on both the short and long exposure end of the scale. Extremely short exposures can exhibit a similar failure, with the film being "slower" than its base ISO predicts.

2. Reciprocity failure in color films is not uniform in all three layers. In addition to speed loss there is also color shift.

3. Because reciprocity failure is actually the result in non-linearity based on light intensity rather than exposure time (the time relationship is coincidental). With long exposure failure, the failure is greater in the shadows than in the highlights. For this reason, many correction tables for B&W film include adjustments to processing to compensate. With color films, the color shift is not uniform across the image's tonal range. With long exposures there will be more color shift in the shadows, where the light is weaker, than in the mid-tones which will be greater than in the highlights. Non-digital means of correcting this are very limited in their scope and very difficult.

4. Traditionally, Kodak has balanced their tungsten and PhotoFlood balanced films in such a way that the optimum exposure range is shifted to the long side. They fail less, at least in terms of color accuracy, with long exposure but fail sooner with short exposure.

 

[ulrich.von.lich]

Nice thread, a lot of information here. I used to do a lot night photography with digital. Now I'm thinking to try it with film.

For starting, is there any recommendation for color films which suffer less from the reciprocity failure?

As to the metering, my R3a can only calculate until 8 seconds. Should I buy a meter or do the math? (Not sure if it will work: if I set the highest ISO and widest aperture, get a shutter speed recommendation, then count stops to compensate the new ISO and aperture?)

One off topic question: is there any other tungsten calibrated film other than the Fuji T64?

 

[JoeV]

Acros is a great film for avoiding reciprocity failure. It works well in applications like pinhole cameras where long exposure times are the norm. In fact, Acros 100 in a pinhole camera can be faster than a traditional 400 speed film, due to reciprocity failure with the traditional film.

~Joe

 

[not_in_good_order]

For starting, is there any recommendation for color films which suffer less from the reciprocity failure?

One off topic question: is there any other tungsten calibrated film other than the Fuji T64?

Fuji's Provia 100F would meet your criteria. Here is the data sheet for more information:

http://www.fujifilm.com/products/professional_films/pdf/provia_100f_datasheet.pdf

The only other tungsten balanced film that I am aware of is KODAK EKTACHROME 64T which was recently discontinued, but is still available (in other words, if you want to try it, buy it now or lose the chance forever).

 

[mackigator]

Just curious then - so what films handle reciprocity failure poorly - require compensation after only a short period of time, etc?

 

[not_in_good_order]

Just curious then - so what films handle reciprocity failure poorly - require compensation after only a short period of time, etc?

Ilford's Pan F Plus requires compensation for exposures longer than 1/2 a second. Their data sheet gives you an awful graph to try and figure out how to handle longer exposures:

http://www.ilfordphoto.com/Webfiles/2006216115811391.pdf

Kodak recommends adjustments for exposures longer than one second with Plus X, but at least they give you a little more information to go by in their data sheet:

http://www.kodak.com/global/en/professional/support/techPubs/f4018/f4018.pdf