Zone System & Reciprocity Failure

[Andrew Pell]

Hello all,

I've just moved up to LF from MF and have got to get used to the joys of non-TTL metering again. I have some idea on the workings and aims of the zone system bu t as I generally take architectural shots inside dark / dingy churches, I have t o compensate for reciprocity failure. I'm using B&W negative film, usually Delta 100. My problem is understanding whether the reciprocity correction makes any d ifference to the negative contrast and, if so, how to get around it. For example , I might have a 5 stop contrast range in a picture, I can meter for the highlig ht and put it on zone viii or meter for the shadows and put it on zone ii and ge t an equivalent zone v reading. (I suppose I should use the shadow reading to ge t to zone v reading rather than the highlight reading with respect to the "expos e for shadows, develop for highlights?") Do I then just add on the reciprocity c ompensation for this zone v reading or do I have to do something else?

Any help appreciated if you can understand the above. Thanks.

[Robert Haury]

A good starting point for you might be Using The View Camera by Steve Simmons. In it he has a table of reciprocity corrections and recommended development time adjustments. The way I've been doing it is to meter the shadows and place them in zone 3 then adjust dev. time according to the contrast range after adjusting for reciprocity. In other words I might reduce dev time by 5% for reciprocity then 15% for n-1. But as I am still a LF rookie my times are still being experimented with. Rob

[Andrew Pell]

Thanks Rob, it looks like I'll have to carry on with cutting the development time. I've used approx 10% less to date but that was with my Bronica and I knew the lenses were contrasty as well as the light via my previous metering technique (meter and expose for shadows and try to get the highlight detail back via development and split grade printing) which, overall, is trying to rescue high contrast negs. I need to get enough shots done to do a proper LF test instead of giving myself printing headaches.

[N Dhananjay]

Reciprocity will influence negative contrast. The reason is that the highlights are less affected by reciprocity failure than the shadows. Exposure, though is typically based on shadows to ensure adequate density in the shadows. However, what you place on Zone VII may not need any reeciprocity correction (or less than required in the shadows). The nett result is that what you place on Zone VII is actually higher on the scale. Typical advise given is to increase exposure by about a stop beyond 1 second exposures, by 2 stops beyond 10 seconds and by 3 stops beyond 100 seconds (these are just rules of thumb - its worth checking your film's data sheets). Corresponding changees to deevelopmeent are 10% less, 20% less and 30% less. Again, worth testing. Good luck. DJ

[John Hennessy]

I have a reciprocity table on a label on my lightmeter. It is for HP5+ to be developed in PMK and beginning at 8 seconds (which adjusts to 19" seconds) I deduct 5% of development time. That is, I deduct 5% after deciding which time (i.e., which zone) in which to place the highlights. The far end of the table is 4 minutes adjusted to 3 hours, 10 minute and minus 30% of development time.

Don't know what I'd do if I wanted to do N-3 (about 5 minutes I think) and also needed to deduct 30% of that time!? But I cannot think how an extremly high contrast scene would need such a long exposure anyway.

The bottom line is you do need to take both elements into account in turn. It is analogous to bellows factor plus a filter factor.

[Matt_1193]

Gentlemen;

Reciprocity failure is the breakdown in the linear relationship between aperture settings/film in regard to it's ability to record detail. Corrections for long exposures must be done IN THE CAMERA, by increasing exposures. Adjusting development will do nothing for a negative that is underexposed due to lack of correction in exposure.

[Lars Hagglund]

Matt, reciprocity also have an effect on the negative contrast. Because the shadows on the negative are hit by light of less intensity than the highlights, they are more affected by reciprocity failure. Thats why the contrast of the neg increase, and we need to shorten dev time to compensate

[Brian Ellis]

I have several generic reciprocity tables for all films other than T Max (T Max films have their own reciprocity tables since they are less affected by reciprocity failure than other films). These tables were taken from several sources (a workshop, a magazine article). I've been using them for several years with HP5+ film and they seem to work well. FWIW, these tables show the following effect of development on reciprocity failure: no change in developing time until the metered exposure is 15 seconds (resulting in a 27 second exposure to take reciprocity failure into account). If developed normally, the resulting negative will be the equivalent of N + 1/2 so you reduce development accordingly (unless, of course, you want N + 1/2 contrast in the negative). When the metered exposure is 30 seconds, the actual expsoure time is one minute and the resulting development will be the equivalent of N + 1 so again you reduce development time accordingly (unless you want N +1 contrast). If the metered time is 2 minutes, the actual time is 6 minutes and the resulting development will be N + 1 1/2. If the metered time is 4 minutes, the actual time will be 15 minutes znd the resulting develoment will produce the equivalent of N +2. If the metered time is 8 minutes the actual time will be 35 minutes and the resulting development will be the equivalent of N + 3. That's as high as my tables go. You exrapolate for times in between these times.

[Ken Burns]

Andrew:

Just because the increase in exposure necessary to compensate for reciprocity law failure in the shadow areas will cause an increase in the overall contrast of the negative does not necessarily mean that it will be necessary to reduce development times. As a matter of fact, I have found a number of situations where an increase in development time was called for because the increase in contrast was inadequate to provide adequate overall desity range in the negative. It is not unusal to find a dimly-lit scene that does not have an adequate brightness range to provide the wanted density range in the negative even after the increased negative contrast resulting from the compensation for reciprocity law failure.

Let me give you an example. Say you have found a dimly lit scene that has shadows that are placed on Zone III of the exposure scale. Let us also say that the highlight areas of the scene fall only on Zone V (this is not unusual since a lot of dimly lit scenes are also rather softly lit). Let us say (for purpose of example) that this Zone III placement indicates an exposure time of 1 second at whatever f/stop we have elected to use (we MUST expose correctly for the shadows since, if we don't get the detail there through exposure, we won't be able to get it there at all). If we are using a conventional type of B&W film, we would probably find it necessary to give 2 seconds of exposure in order to compensate for reciprocity law failure in the areas of the projected image that fall in Zone III or lower.

Now, let's take a look at what is going to happen in the areas of the projected image that will fall in Zone IV and higher because of our Zone III placement of a particular shadow area. Since these brighter areas of the scene are at least one stop brighter than the Zone III area, these areas would have indicated an exposure of 1/2 second or less if they had been placed in Zone III. Therefore, these higher- falling Zones will not suffer from as much reciprocity law failure. As a matter of fact, in this particular example, they will, for all practical purposes, suffer from no reciprocity law failure at all. When we give a 2-second exposure to our negative, the areas falling in Zone IV and higher will actually get a full 2 seconds worth of exposure while the areas in Zone III and lower will get only 1 second worth of exposure.

The result of this will be that the areas falling in Zone IV and higher will get 1 additional stop worth of exposure. This will cause these areas of the negative to gain about 1 stop worth of additional exposure and resultant density. In other words, the highlight areas of our scene that fell in Zone V will get moved up to Zone VI. We must now determine if this resulting Zone VI density is appropriate. If we feel that it is correct, then no compensation in developing time is necessary. If we feel that the highlights should fall higher than Zone VI, then we must increase our development time. If we feel that the highlights should be darker than Zone VI (possible, but unlikely), we would then (and only then) reduce our development.

This is only an example of a single situation where reduction in development times could be disasterous! There are, however, some situations that will absolutely require a reduction in development times. In those situations, failure to do so can also be disasterous! And there are situations that will require no compensation in development time at all. What all of this means is that each situation encountered must be analyzed individually and handled individually. There are no rules-of-thumb that apply to all situations.

[Andrew Pell]

Thanks for everybody's answers so far.

Brian: From the reciprocity corrections and contrast increase, I'd assume that if a 30sec metered exposure plus reciprocity gave an N+1 contrast level, developing at N-1 would bring the contrast back to normal? I have an Ilford data sheet and have calculated the reciprocity curve but never really used the contrast / time curves apart froma a blanket "knock a minute off to stop developing the highlights." (Also, is N+1 the same as producing a contrast equivalent to 1 grade higher on multigrade / varicontrast paper?)

Ken: I understand your reasoning about wanting to increase development times if you have a flat subject to create contrast, i.e. forcing tones to lie on more separated zones. The problems I normally encounter are trying to flatten the contrast in a scene. My scenarios usually involve the dimly lit church having a dark oak altar below a stained glass window (hopefully I'm taking pictures on an overcast day but it doesn't always work out like that and I have to try to stop the window burning out and still get the shadow detail on film as you say - if it isn't there, you can't print it in.

At the moment I'm using a roll film back on the camera. It looks like I'll have to go to sheet film for some trials as I can't afford some more backs to label each one for different development / contrast settings. I'll have to dig out the old grafmatic backs.

Andrew