question about long exposure increased contrast

[esearing]

I read a Fred Pickler article where he stated Long exposures (> 1second) will have roughly 1 stop more contrast than a short exposure, given same amount of light . This statement interests me because most of my waterfall shots are exposed between 3 and 15 seconds and over time i have adjusted my processing for my typical images. Wondering if I need to expand time when using short exposures.

Should I expect more contrast for long exposures? This is a a simple yes or no question for a given film based on your experience and process.
Examples:
FP4+ yes;
TMAX no

Parameters:
Assume I expose 2 sheets or frames of a scene, that meters 5 stops SBR, and process them together (Same Tank, same NORMAL developer, same stop, same fixer, same wash):
1) f32 @2 seconds (+adjustment for reciprocity)
2) f11 @ 1/4 seconds.

[Neal Chaves]

Do your own test for reciprocity failure. I spoiled a lot of good negatives blindly following "compensation" advice from Picker and The Great Yellow Farter. Finally, when I did test, I found no loss of speed or contrast changes out to 30 seconds for Tri-X.

[Corran]

Increase in contrast scales with reciprocity loss. So depends on what film.

[Steven Ruttenberg]

I have used tmax100 out to 30 minutes. Twice the time I estimated the exposure to be with no reciprocity. I used reciprocity timer for iphone as a guide. I get good results so far just doubling exposure when using tmax100 for times 2 minutes and longer. Less for 30 seconds to 2 minutes. I sorta go by feel too.

[Bob Salomon]

The rule has always been that exposure controls density and development controls contrast.

Long exposures May result in reciprocity failure which would then require exposure compensation.

[Mark Sawyer]

The theory is that long exposures in low light cause reciprocity failure, but the same length exposure in brighter light does not suffer the same rate of reciprocity failure, as these areas build to a "normal" exposure sooner. That means, in theory, the highlights will build even more exposure than the shadows relative to the light that's there, resulting in increased contrast.

That's the theory, but as a great Yogi once observed, "In theory, practice and theory are the same. In practice, they're not."

And of course, dim light often means softer light...

[Vaughn]

John Sexton also mentions the added contrast one can get from long exposures.

If you like the contrast you are getting with any particular film with long exposures compensated with additional exposure but normal development, then the answer is yes with just about any film. The needed increase will vary from film to film. I've used that property with most brands/models. I do not plan on much long-exposure-contrast-bonus, for example, when I am using Acros...extra development gets more effect, but with FP4+, TriX, HP5+, Bergger200 and other assorted films (including TMax100), I can take advantage of it.

I tend to undercompensate to let the deepest shadows go clear -- I contact print and the areas are too small to expect/see detail in. I give more development than 'normal' since I use alt processes, so my actually experience may not be fully applicable to your work.

One film I use this does not work at all for the above...Kodak Copy film -- when I can find it. One develops for the shadows/midtones and exposes for the highlights -- and almost no reciprocity failure...far better than Acros. Fun film -- builds contrast like nobody's business! Pity they do not make it anymore.

[Doremus Scudder]

Contrast does indeed increase with long exposures and reciprocity failure. As mentioned above, when a film goes into reciprocity failure, the lower values, i.e., those getting less light, need a longer exposure to be rendered in their "normal" place than the higher values, where more light is hitting the film. Kodak used to (maybe still does) recommend development adjustments for very long exposures.

The thing is, every film has different reciprocity characteristics Many newer films (T-Max, Delta) have better reciprocity characteristics than older "conventional" films and need very little development compensation until exposure times get very long.

And, every photographer has different ways of determining their "long" exposures. If you base your exposure on shadow values à la Zone System, then, if you expose correctly, you'll get good shadow detail and an increase in contrast proportional to the length of exposure. This you can test and compensate for.

If you use an averaging meter or other method of exposure (e.g., a table for night-time exposures) then the results will be different. Getting to know your film and how it works with your metering method and E.I. takes a bit of time and testing.


FWIW, I'll use an ND filter sometimes to push my film into reciprocity failure just so I can take advantage of the contrast increase, which has a different look than increased development (the shadows separate more with reciprocity failure while increasing development separates the high values).

Best,

Doremus

[Joe O'Hara]

Every now and then Doremus comes up with a real gem. This is one:

"FWIW, I'll use an ND filter sometimes to push my film into reciprocity failure just so I can take advantage of the contrast increase, which has a different look than increased development (the shadows separate more with reciprocity failure while increasing development separates the high values)."

That is a good thing to have in your bag of tricks.

[Steven Ruttenberg]

I keep an ND16 in my bag. That increase your actual exposure time by 2^16*tv. I like to have people out of my city scapes. This could be a 2 hour exposure in broad daylight at noon.

[esearing]

thanks all - Consensus seems to be yes but may or may not need to be compensated for and varies according to light (dim vs bright)
and thanks to Doremus we all now have a way to increase contrast in the field vs development for low contrast scenes. Should be useful for Rocks and Roots scenes.

Guess I will be testing on my next outing to see how FP4+ responds in my usual exposure times vs shorter.

[Steve Sherman]

Reciprocity does most have it's most impact in the mid tones, however, don't think for a minute by applying a ND filter of significance will replicate the gains of an exposure made during the low light levels of dawn or dusk, the light is simply different as the sun arches across in the sky. Photography, especially film photography will always be most impacted by the Quality of Light. There are resaons outdoor TV commericals are filmed in Sweet Light. As mentioned on FB, Sexton devoted an entire book to Quiet Light.

[John Layton]

On the subject of using heavy ND filters in sunlight...I've noticed, on the rare occasions when I actually do this - that I sometimes will get some strange artifacts resembling astigmatism, especially when using wider anger lenses. Using high quality B+W ND's. Never seems to happen in overcast conditions, and less so with longer FL's even in bright conditions. Anybody else ever notice this?

[Steve Sherman]

On the subject of using heavy ND filters in sunlight...I've noticed, on the rare occasions when I actually do this - that I sometimes will get some strange artifacts resembling astigmatism, especially when using wider anger lenses. Using high quality B+W ND's. Never seems to happen in overcast conditions, and less so with longer FL's even in bright conditions. Anybody else ever notice this?
Best educated guess, the severe curvature of the WA lens coupled with yet another glass surface of the ND filter affects some type of artifact or distortion as it exits yet again a dramatic optical formula to cover a large area of film. Years ago I noticed the shots I made with WA lens didn't hold the detail that a longer lens could when the subject matter was nearly the same final size. Particularily since the perfection of the Minimal Agitation technique this anomally IMHO leads me to almost never use a WA lens for my work. My seat of the pants 2 cents !!

[Drew Wiley]

Long exposure contrast is not that simple. You have to test specifically. Different films differ in this respect, and even the same emulsion has different contrast responses to significantly different color filters at long exposures. Even how long "long" means is a factor. So is the film developer.

[John Layton]

Another important aspect that I might add to this discussion is the extent to which subject tonal values can be transient for the duration of a given exposure.

Take crashing surf, for example - where one might interpret the nearly white churn of bubbly water over rocks as highlight values and attempt to place them as such, only to find that those "highlights" are transient...whereas the white, bubbly water present in a waterfall can indeed be accurately placed as it will generally continue to remain in place for the duration of a long exposure.

Another "transient" situation can occur when light changes generally during an exposure - such as fleeting sunlight, or working at dusk in an area where ambient light fades relatively quickly after the sun sets...presenting a moving target of values, requiring continuous recalculation for the duration of an exposure. This happens fairly often in my case when working just after the sun sets in the desert southwest.

At any rate...I typically find the "science" involved in calculating long exposure times to be inexact at best - which I think is a good thing as I am always kept on my toes!