On the effect of shutter speed on image contrast for R5 Monobath film-development

[Lenrick]

Disclaimer: If you are looking for a well-throughout, well-executed and well-analyzed test done according to industry standards written in industry jargon, I’m afraid you have to look elsewhere.

I wanted to test if it was possible to increase or decrease the contrast in New55 Atomic-X film developed in New55 R5 Monobath. I’m not sure what I can do with agitation or time emerged in liquid, but now I tested exposure time. I took two exposures of a still life setup, one with short exposure time and one with long exposure time and compared the negatives.

The two exposures were done back to back on the same equipment and in the same lighting condition (no filters). My incident-light meter read EV 9 which gave me the two exposures as:
1) f/5.6 and 1/15 s
2) f/64 and 8 s, which I compensated to 50 s due to reciprocity.
But I really messed up the second (the long) exposure since 8 s should be adjusted to about 37-38 s according to the reciprocity information provided by New55. My bad, but I think we can still get some information from this test. But remember the long exposure is overexposed compared to the short exposure. The negatives were developed simultaneously in the same tank, and later scanned in an old Agfa Duoscan T2500.

Figure 1 is a photo of the scene captured on my iPhone, the gray floor is quite close to a gray card. The statue made of gypsum and is positioned on a sheet of A3 typing paper.



Figure 2 shows the TIF-scans of the negatives seen as they were exported from scanner, a RAW format would probably be better but I think this is ok for now.

Fig2.pdf

As you can see in Figure 2, the development is in uneven over the negatives (there is a “pouring-pattern”), and since the negatives were places in the tank face to face different parts of the two negative have been hit by the pouring liquid. I use a Combi Plan tank, which is not suited for R5 Monbath unless you can plunge the film directly into the open tank in total darkness (as recommended by New55). I don’t have total darkness anywhere outside my changing bag so I’m limited to using the narrow ports. The pixel intensity line plots show that the bright side of the nose is saturated in both exposures and the floor boards have very different intensity in the two images. I’m not sure how much the scanner is to blame for the saturation; perhaps a better scanner can penetrate the dense parts of the negatives. You can also see that the non-exposed areas of the negatives (the areas hidden in the film holder grooves) are completely black while there is some intensity in the very dark areas between the floor boards.

Now in hindsight I realize that it is almost pointless to compare images with such different depth of field. There is almost no texture in the floor boards in the short exposure image but plenty of texture in the floor boards in the long exposure images. I should of course use neutral-density filter to adjust the exposure time. I should also have found a better subject with both dark and bright regions.

In Figure 2 I have also marked four small areas of interest in the two images. “SE” is short for short exposure and “LE” for long exposure. The pixel intensity valued for the eight areas are:

___SE | LE
1: 220 | 225
2: 108 | 145
3: 027 | 057
4: 015 | 006


The histograms can be seen in Figure 3.

Fig3.pdf

The area with the highest intensity while still having some texture (position 1 in both images) are very close in intensity (a difference of only 5 units), even though one image is overexposed. The two mid-gray areas (position 2 and 3) have both increased with about 30-40 units due to the overexposure in the long exposure. The very dark shadow (between the floor boards in position 4), actually have lower intensity in the overexposed image. This is, however, most likely due to the increased depth of field in the overexposed image. The floor board gaps are smeared into gray goo in the short exposure image while being clear and distinct in the long exposure image.


It is hard to say how the long exposure time affected the contrast, but it seems the contrast increased quite a bit in the darker areas while still maintaining acceptable in the brighter areas. It seems that the very bright areas are affected much less by overexposure than the darker areas. Is this finding true for all overexposed negatives developed in R5 Monobath, independent of exposure time (shutter speed)?

Now I would like to find a better subject and capture 3 images and with the aid of neutral-density filters keep the aperture constant.
1) One image at normal exposure and short exposure time
2) One image at normal exposure and long exposure
3) One overexposed image at short exposure time

Questions, suggestions or other feedback?

[ic-racer]

Exposure time does not affect film contrast unless the time is very short, like 1/10,000 or less or very long, like 10 seconds or more. If you discover something, let us know. If you only want to expose only a portion of the tonal range of you scene, then you can under-expose to remove the unwanted low values. This will give you a low contrast negative with no shadow detail. Common jargon for that technique is 'push processing.'


Make note of the sections "Family of Curves" and "Exposure Latitude"
http://motion.kodak.com/KodakGCG/upl...y_workbook.pdf

[Ken Lee]

Exposure time does not affect film contrast unless the time is very short, like 1/10,000 or less or very long, like 10 seconds or more.

What happens to contrast at those extremes please ?

[Jody_S]

Any exposure done under conditions of reciprocity failure will necessarily have a different contrast than one done in 'normal' conditions (which results in over-exposing the highlights, and under-exposing the shadows). No matter the film, but obviously worse with some films that are notoriously bad for reciprocity failure.

Simple logic: if you meter a scene and discover the highlights require a 2s correction for RF, and the shadows require 10m correction. You meter for a midtone and end up adding 12s to your metered time. You have over-exposed the highlights by 10s, and under-exposed the shadows by 9m48s (for neutral grey). This will mean your scene with 5 stops between shadows and highlights will be exposed so as to have 8 stops.

[Ted R]

There is a lot to learn about photography. I learned a lot by reading books from Kodak, Ilford and technical books written for black and white photographers. There are important and fundamental principals involved. Perhaps some study of the basic texts on the meaning of film density, the purpose and effects of development changes, and the concept of exposure variables would be appropriate? Look for technical books on black and white photography. Here is one suggestion http://www.amazon.com/Negative-Ansel...sel+adams+book

[Ken Lee]

Any exposure done under conditions of reciprocity failure will necessarily have a different contrast than one done in 'normal' conditions (which results in over-exposing the highlights, and under-exposing the shadows). No matter the film, but obviously worse with some films that are notoriously bad for reciprocity failure.

Simple logic: if you meter a scene and discover the highlights require a 2s correction for RF, and the shadows require 10m correction. You meter for a midtone and end up adding 12s to your metered time. You have over-exposed the highlights by 10s, and under-exposed the shadows by 9m48s (for neutral grey). This will mean your scene with 5 stops between shadows and highlights will be exposed so as to have 8 stops.

I never thought about it that way.

It's common practice to meter and expose for the shadows - and to determine compensation for reciprocity failure after determining exposure.

Your analysis exposes a flaw in that approach: how do we solve the problem ?

I use development by inspection, so perhaps during development I am compensating unknowingly - but I rarely adjust development by more than +/- 1.

[koraks]

You solve it by contraction: decrease the EI and develop shorter to decrease contrast. Af the same time, this makes the reciprocity issue bigger. It then follows that at some point, you run out of options to deal with the situation and you have to resort to other measures - open up the aperture and/or use different film.

[Michael R]

I never thought about it that way.

It's common practice to meter and expose for the shadows - and to determine compensation for reciprocity failure after determining exposure.

Your analysis exposes a flaw in that approach: how do we solve the problem ?

I use development by inspection, so perhaps during development I am compensating unknowingly - but I rarely adjust development by more than +/- 1.

It is to some extent an unavoidable problem when we make long exposure reciprocity adjustments based on the metered exposure time rather than actual subject luminances. It's a shortcoming of typical reciprocity tables/graphs. Long exposures generally cause an increase in contrast (a consequence of reciprocity failure to begin with). However current films perform quite a bit better than older films.

In practice it doesn't work out too badly for a few reasons. 1) Since most Zone System users apply reciprocity adjustments to their Zone III metered exposures, the contrast effect is typically minimal throughout the normal "textural" range. Instead the reciprocity effects are confined mostly to the lowest light levels (ie below Zone III). For an example of this, refer to Howard Bond's reciprocity tests. Since he was targeting a constant Zone III for his exposure adjustment factors, he found there was virtually no minus development adjustment required. 2) Flare counteracts the effects of reciprocity failure. 3) The effects of (1) and (2) combine with other slop in the process so that we don't notice. We compensate unknowingly in printing/editing. When it comes to making negatives, we don't have quite the control and precision we think we do, no matter how much testing, calibrating and fiddling we do. Fortunately it doesn't matter because there is enough latitude in the process and materials that we can work around these inaccuracies (usually without realizing it) and make great prints.

Now, I don't think any of this explains anything in the original post, but it is an interesting question nonetheless. It highlights the fact that low light/long exposure reciprocity failure depends on the intensity of light hitting the film, not the exposure time per se.

[David Schaller]

I never thought about it that way.

It's common practice to meter and expose for the shadows - and to determine compensation for reciprocity failure after determining exposure.

Your analysis exposes a flaw in that approach: how do we solve the problem ?

I use development by inspection, so perhaps during development I am compensating unknowingly - but I rarely adjust development by more than +/- 1.

I'm with Jody. I do it, when I remember(!), by metering for the shadow, and applying the reciprocity correction right away, to place the shadow. So, for example, if the meter says the shadow is EV 8 at a film speed of 100, and my aperture is f32, it would be 4 seconds so to compensate that would be 8 seconds. Then I divide the corrected time by 4 to place the shadow in zone III, and my exposure is 2 seconds. Then I see where the highlight fell, and apply N- whatever is necessary. So in many situations I am doing fairly big N minuses to tame the highlights, and to have adequate shadow exposure. If it's more than N-3, I'll place the shadow in Zone IV, since there will be a loss of film speed with reduced development.

Of course these are different ways of talking about the same phenomena. Really this has turned into a discussion of compensating for reciprocity failure, especially when the shadows and the highlights are on opposite sides of 1 second.

[koraks]

> It highlights the fact that low light/long exposure reciprocity failure depends on the intensity of light hitting the film, not the exposure time per se.
Isn't it a matter of what happens at the toe of the film curve? Threshold sensitivity and the non-linear bit at the start of the curve?