Night photography and processing

[Onestepbeyond70]

I read somewhere that you should underdevelop bw film when shooting
with long exposure, as a rule of thumb. Is that correct?
Where does it come from?

Thanks!

[Bjorn Nilsson]

This is due to what is called "Reciprocity failure" which affect the different zones of the long exposure shot different. So the shadows (z2-4), will be more affected than the highlights (z6-8) by reciprocity (failure). This means that if you have to correct say a 10 sec exposure to 1 minute, the 1 min exposure is just enough to get the shadow detail you want them as the film needs a certain amount of light to "wake up" before they even start to register light. The highlights in the same example will get that wake-up exposure in much shorter time (as they are highlights...) so they will wind up being somewhat overexposed. Thus you have to compensate this highlight overexposure by shortening the development by e.g. 20% or so.
As the reciprocity failure is different for every film, you have to look at the data for the film(s) you are using. In general modern films are better, i.e. suffers less from reciprocity failure. Among the best are the TMax films and possibly also the Delta films from Ilford. The very best current B/W film when it comes to long exposure times is supposed to be Fuji Acros.

I'm sure someone else can give a more technical description of this if needed, but I recon that this will do for starters.

//Björn

[Vlad Soare]

Also, at night the subject is very likely to be more contrasty than usual. If you expose for the street/sidewalk/by-passers/cars/etc. and develop normally, all lights will probably look like blurry, shapeless blobs. The details in brightly lit shop windows can be lost, too. That's one more reason to go easy on the development.

[CG]

At night it is hard to overexpose, but it can be easy to overdevelop. If you meter the well lit areas, or go by a consistent set of guidelines you will do fine.

www.fredparker.com/ultexp1.htm offers a good set of guides to low and ultra low light photography.

If you are willing to invest the time to shoot at various exposure indexes, and develop various times, you can find the "look" that suits your intended outcome.

[Mattg]

Also consider the use of a tanning and compensating developer with Pyro or Catechol in it. One of the problems of urban night photography is the light sources tend to blow out and also effect the area immediately around them so they end up looking like blobs. A tanning developer can help minimise this effect. Choosing a film with lesser reciprocity failure can also improve things, although each different film has a different look (I don't like Acros but others do)

If you want to try a more common developer then divided D-23 with Tmax 400 can do a good job and the short development time also seems to help sharpen up the light sources a little. To get much compensating effect from divided D23 it's important to minimise the agitation in the second bath.

[Vlad Soare]

Here's an example of picture taken at night, where the lights have been kept under control. OK, I agree it's not something to write home about, but it's all I have at this time.
Unfortunately at this size it's not so obvious, but the lightbulbs were recorded as individual points, rather than as overlapping blobs. Also, if you look at the traffic light on the bottom right side, just above the light trails left by cars, you see that it's well defined, and the red light doesn't leak into the surroundings. Even the reflection of the red light on the inner side of the light shade is clearly defined.

The exposure was 56 seconds at f/8 on Fomapan 100. The actual reading was 8 seconds.
Had I developed normally, the lights would have blown out and leaked into the surrounding areas. I know, because I made that mistake many times.



Stand developing in R09 1+160. I agitated for one minute, then let it stand for two hours. The high dilution and the lack of agitation gave this compensating effect.
This is a straight print, at the normal contrast setting (all filter dials set to zero), on Fomaspeed Variant. I scanned the print, not the negative.