In this fourth installment to this series, I have selected a series of photographs that I made with long exposures on three film stocks to share in the context of a discussion of film reciprocity departure and the use of filters in color film photography. Although I had originally intended to include a discussion of exposure corrections for close-ups in Part IV, in the interest of brevity I decided to defer this topic to a final Part V to this series. Of note, reciprocity departure and filtration in color film photography are complex and interesting topics. This article is not meant to be a comprehensive treatment of both topics, but rather an introduction that I may expand upon in future articles.
In order to understand the meaning of reciprocity departure, one must first understand what reciprocity itself means. Reciprocity is the basic law of exposure that governs the relationship between the intensity of light reaching the film plane (as determined by the subject brightness and aperture) and the length of the exposure (as determined by the shutter speed) in producing a given response, or exposure density, on the film.
For example, to maintain the same exposure density at a given light intensity for a given film, allowing more light through the entrance pupil of the lens (i.e., a wider aperture) requires a proportionate decrease in the length of the exposure (i.e., a faster shutter speed). Thus, doubling the light intensity on the film coupled with a full stop increase in the shutter speed results in no change in the exposure density. Analogously, a given result on film that is achieved at f/4 and 1/60 seconds is equivalent to the effect that is achieved at f/2.8 at 1/125 seconds – under the same scene luminance.
The converse holds true: allowing less light through the entrance pupil of the lens (i.e., a smaller aperture) requires a proportionate increase in the length of the exposure (i.e., a slower shutter speed) to create the same density on the film. Thus, a full stop decrease in the size of the aperture requires a full stop decrease in the shutter speed to create the same result.
For the beginning photographer, the law of reciprocity can be summarized as follows: you can achieve the same exposure by inversely and proportionally varying both the quantity of light exposing the film and the duration of the exposure. Simple enough.
The law of reciprocity is valid for both black and white and color film over a broad range of exposures for many different film stocks.
But … at very low light levels requiring longer exposures (i.e., seconds) and at very high light levels requiring very short exposures (i.e., 1/10,000 sec), the reciprocal relationship between the total amount of light intensity striking the film and the duration of the exposure in creating a given density on the film breaks down. Restricting this effect to the scenario involving very low light levels and long exposures (the predominant type applicable to general photography), what happens is that a given film stock becomes less responsive to the available photos of light that is not accounted for by the usual aperture-shutter speed relationship. At very low light levels, a longer exposure than that predicted by the law of reciprocity and indicated by a light meter is now required to achieve the same effect. This phenomenon is called “reciprocity failure” or “reciprocity departure”. As Ansel Adams describes in his book, “The Negative”, the breakdown of reciprocity is not a failure per se but more of an effect, or behavior, of film at the extremes of exposure. Although a full description of reciprocity departure is beyond the scope of this article, the salient concept is that for a given film stock at very low light levels beyond a given shutter speed (typically > 1 sec), the film behaves as if it has an slower ISO; to compensate, the photographer must lend additional exposure beyond what the light meter indicates for the measured luminance.
But wait … there’s more! With color film at low light levels and long exposures, the individual emulsions that are sensitive to the different wavelengths of light react differently and can result in color shifts on the negative or slide. Yikes!
So, the immediate practical questions become: how much additional exposure should the photographer impart for a given film at this extreme? And how should the photographer handle the potential for color shifts on color film? Fortunately, some (but not all) film manufacturers supply data sheets for their film stocks that include recommendations for reciprocity departure correction and color correction. However, some of these recommendations are either limited or not entirely accurate, which unfairly places the burden (in my humble opinion) of determining the appropriate reciprocity departure compensation on the individual photographer.
Some of the data sheets that are supplied by film manufacturers explicitly recommend that for critical work photographers should perform their own tests to determine the appropriate reciprocity correction. The good news for modern day film photographers is that over the years many experienced and professional photographers have worked out the reciprocity corrections for many film stocks, which is a tremendous help. Further, there are a few reasonably good applications for cell phones and tablets that are on the market for calculating reciprocity correction. An important caveat here is how one photographer corrects for reciprocity departure for a given film stock may differ from how other photographers do it, depending on their individual empiric results, lighting conditions, and visualization process.
Common low light scenarios where correction for reciprocity departure is mandatory are early sunrise; late sunset; night time exposures; day time exposures with slow speed film and the need for small apertures for expanded depth of field; the use of high density lens filters (e.g., black and white contrast, neutral density, color correction); and close-up and macro exposures where exposure density is lost at the film plane (much more on this in Part V). In large format photography, in particular, the need for reciprocity compensation is commonplace (especially for landscapes and close-ups) where small apertures (f/22 to f/64) and long exposures are the rule, not the exception.
So, with this background set forth let’s delve into a typical scenario involving reciprocity departure correction for long film exposures. Within the renowned Balboa Park in San Diego, California, there are a plethora of gardens, trees, flowers, and exotic succulent plants to admire and photograph. Among my personal favorite subjects at this park is this iconic fig tree with its enormous and visually stunning root system.
The structure and intricate pattern of the roots, their textures and fine detail, and interplay of light and shadows make this a delightful subject to explore. On two separate days (sunset and sunrise), I took several exposures of this tree at varying perspectives, angles, and lenses. Using my composing card to help study and select a composition, I chose the perspective in the iPhone scout shot above, roughly 8 feet away. To frame this perspective, I chose a “normal” lens in the 4×5 format. Due to the low intensity lighting at this time, intuitively I understood that my exposure was going to be long, and thus, compensation for reciprocity departure would be a necessity.
To create a strong visual effect and mood, I desired to keep the pockets of deep shadows between the large roots near the top of the frame very dark (Zone 0 to Zone I) yet preserve detail in the shadows in the foreground. After carefully studying the scene, I decided to meter the shadows indicated by the “red circle” in the above iPhone image and place those low values in Zone IV. As I do with all of my exposures, I apply the Zone System to determine my exposure and film development.
In general, if the photographer desires to preserve optimum shadow detail in the scene with panchromatic black and white film (sensitive to all wavelengths of visible light), then it is best to avoid the use of red, orange, and yellow filters for contrast. Since these filters block blue light (red filters >> orange > yellow), which is predominantly responsible for illuminating shadows via sky light, they actually decrease shadow detail, or “close” shadows. Hence, these filters must be used with caution. Alternatively, the photographer may choose to use an orthochromatic film (sensitive to blue-green light but blind to red light) to capture more shadow detail, or to soften or “open” up shadows. Using a blue filter with panchromatic film to simulate an orthochromatic response is another option. The applications of panchromatic vs orthochromatic film emulsions are a potentially good topic for a future article.
For my camera and lens, I chose the Ikeda Anba 4×5 (one of the lightest view cameras ever made) and the compact and light weight Nikkor-W 150mm f/5.6, respectively. This lens provides an angle of view that is similar to that seen with a 40mm lens in the 35mm format. For film, I chose Ilford Delta 100 (a panchromatic film), with an exposure index of 80. Based on a photographer’s personal experience and objectives for given photograph, it is not uncommon to rate the ISO lower than the box speed in order to obtain more shadow detail during the exposure, especially if he/she intends to reduce development of the film to reduce the contrast range on the negative. I used no filters. After applying movements to the view camera to control the plane of focus and the shape of the perspective, I stopped down the aperture to f/16 to control depth of field. On my meter, I dialed ISO 80 into the ISO dial of my Pentax Digital Spot Meter.
As I had described previously in Part I and Part II and which merits reinforcement for the beginning photographer, since a spot light meter automatically renders an exposure value that lies within Zone V (“middle gray”) regardless of the scene’s illumination, the photographer must override this meter reading in order to place that exposure value in the desired Zone (unless, of course, Zone V is desired).
Since I wanted my shadow detail and tonality to fall on Zone IV at this metered spot, I rotated the EV dial to Zone IV (indicating 1 stop less exposure) and read off the shutter speed (4 seconds). For Ilford Delta 100, Ilford recommends the following:
“Making long exposures for exposures between 1/2 and 1/10,000 second, no adjustments are needed for reciprocity law failure. When exposures longer than 1/2 second are given, 100 DELTA Professional along with other films, needs to be given more exposure than indicated by a meter. Use the graph to calculate the increased exposure time which should be given once the measured time is known.”
Although it would seem that the graph Ilford provides is helpful and trustworthy, it turns out that this curve is inaccurate. For the adjusted shutter speed for numerous black and white films, I heavily rely on reciprocity departure tables that have been kindly provided by the impeccable work of Howard Bond in his article, “Black and White Reciprocity Departure Revisited“. At a shutter speed of 4 seconds, the adjusted shutter speed is approximately 5 seconds (+⅓ additional stop).
Another important consequence of reciprocity departure that the photographer must take into account during the development of the film is that during the long exposure the responses of the film to the low and high values in the scene are not equal. The low values are disproportionately underexposed compared to the high values. So, when the film is developed normally, the highlights will become more prominent than otherwise predicted, leading to potentially excessive contrast on the negative. Therefore, based on the scene’s intensity of the high values, the photographer may choose to reduce the development time accordingly to lower the density of the high values (and thus compress the overall contrast range) on the negative, a concept known as negative contraction. On the other hand, the photographer may choose to lend normal development to the film, as he/she may desire a high contrast negative. For this scene, I desired high contrast. The potentially increased density of the high values on the roots of the tree that may result from exposure compensation for reciprocity departure was precisely what I wanted, so I requested “normal” development from my lab technician. I also made a duplicate exposure destined for N+1 development (extended development of the film) to raise the density of the high values (and thus expand the overall contrast range) on the negative, also known as negative expansion.
Upon examination of the negative on the light table, the overall exposure (with reciprocity departure accounted for) looked very good. The negative had ample shadow detail and tonality where I desired them. There was strong contrast and adequate sharpness. I personally scanned the negative on the Epson V850 Pro. I made no post-processing adjustments, not even sharpening (all film and modern lenses are sharp enough). I cropped the image to a 4:3 aspect ratio. Overall, I think the final image faithfully represented the structure and mood of the scene as I had visualized it in my mind: strong contrast replete with fine detail and texture for the viewer to visually explore. If I had chosen the originally metered shutter speed of 4 seconds (⅓ stop less exposure), then the desired shadow detail would have been inadequate, in my mind.
The next photograph is of the same subject but with a slightly wider angle of view, the same perspective (same subject distance), and a different lens on a different format.
Although this wider angle of view shows the pillars from the wooden bridge (upper middle right) that provide some degree of scale to this subject, it also shows evidence of the disheartening problem of vandalism of our city, state, and national park systems. The following crop of the upper middle right of the previous photo reveals the willful, senseless, and cruel acts of damage to the tree’s roots. Sadly, the opposite face of the tree is terribly scarred with more carving from vandals. As a nature lover who respects and supports conservation, it makes me angry and heartbroken to see such disrespectful and criminal acts being perpetrated by those who have no regard for nature conservation or public/private property.
Moving on to another example of reciprocity departure correction, I chose the following sunset photo to share and discuss. Ever since I started my photography exploits six years ago, I continue to gravitate to sunrises and sunsets as subjects. The visual beauty, aesthetics, and psychological effects of these scenes resonate deeply with me. I made this photograph along coastal San Diego at the “second sunset”. With this type of scene, my goal is to capture the quintessence of the intersection of light, land, and sea. Vibrant colors, high contrast, and visual and emotional impact are the attributes that I wish to create on my final print. From an aesthetic standpoint, conveying what you are seeing and feeling at the time that you open the shutter and inviting your viewer into that scene with a print can be a rewarding experience as an artist.
A potentially critical step in the visualization process involves what Ansel Adams refers to in his books as the “conscious departure from reality”. That is, after the photographer studies the scene before his/her eyes and reconciles the reality of it with what he visualizes on the print, he may take decisive action to adjust and/or manipulate the exposure (and downstream development and printing manipulations) so that the final print conveys what he saw in his mind and felt in his heart at the time of the exposure. You can read here and here the classic story behind this step in visualization.
To achieve my goals with this sunset scene, I chose Fujichrome Velvia 50 slide, or transparency, film. As I discussed in Part I, Velvia 50 is a high saturation, high contrast, vibrant, and incredibly 3-dimensional and sharp color film that has been a popular tool for landscape photographers for over 25 years. Due to these attributes, Velvia 50 is one of my personal favorite films.
Due to the combination of low light intensity, slow speed film, lens filters, and a small aperture, the need for a long exposure and compensation for reciprocity departure were evident. Under low light conditions, I often rate the exposure index of Velvia 50 at ISO 40 (occasionally at 32). For color film (both slide and negative), adding to the complexity in long exposures is the potential for color shifts, which have been described in the literature and by experienced photographers as varying from green to cyan. Personally, I have yet to see these color shifts with Velvia 50, but I have seen these with Portra 400, for example, with exposures approaching 20 seconds or more. Film manufacturers recommend in their data sheets to use color correction filters (i.e., magenta filters) to counteract green shifts in the exposure (more on these below).
In order to craft my calculated departure from reality to create this photograph, I used two tools of the trade: strong color conversion filters, the 85C, and the FLW filters. The beginning film photographer may ask: why these filters? Traditionally, the 85C filter has been used to help match, or balance, the color temperature of daylight illumination to the color temperature of tungsten balanced film (i.e., white balance), but it can also be used creatively as a strong warming filter with daylight balanced film. With sunsets and sunrises, the 85C can powerfully (and beautifully) accentuate the crimson in skies. The FLW filter, on the other hand, has been used traditionally to balance the color temperature of warm white fluorescent lighting with the color temperature of daylight balanced film; however, the FLW can also be used creatively to impart magenta to a scene using daylight balanced film. Aesthetically and technically, I used these filters to create the image that I had visualized in my mind and to convey the emotion that I felt at that time.
The 85C and the FLW filters carry exposure factors of +⅔ and +1⅓ stops, respectively, meaning that their density causes light loss at the filter plane by these amounts, which must be manually accounted for during the exposure when using an external light meter, as I did in this photograph.
For my camera and lens, I chose my Mamiya 7II and its accompanying 43mm f/4.5 L lens, which provides an angle of view that is similar to that seen with a 21mm lens in the 35mm format. This particular camera system lends itself well to long exposures; because it is a rangefinder system (no mirror) with leaf shutter lenses, these mechanical designs significantly reduce the risk of sharpness-robbing vibrations that are more common with mirrors and focal plane shutters in SLR camera systems.
Although the Mamiya 7II has a functional (and excellent) spot meter, I prefer to use an external hand held spot meter for my exposures. On my meter, I dialed into the ISO dial my rated exposure index for Velvia 50 (EI 40) as well as the filter factors (+⅔ and +1⅓ stops). I closed the aperture down to f/11. As I describe in Part I, due to the tight dynamic range and poor exposure latitude of slide film, I (nearly) always expose for the high values. I chose to meter the strong high values in the center of the frame and place those on Zone VII. With slide film, placement of the high values of interest above Zone VII (even by a half stop) would not be wise, as highlight detail starts to significantly degrade above that point. Again, since spot light meters by default yield an exposure value that automatically lies in Zone V, I rotated the EV dial to indicate two additional stops of exposure (i.e., Zone VII). The meter gave a shutter speed of 8 seconds.
With Velvia 50, Fuji recommends correcting for reciprocity departure for any exposure of ≥ 4 seconds. Based on Fuji’s published recommendations on its data sheet, the experience of other photographers using this film, and my own experience, the reciprocity departure compensation gives an adjusted shutter speed of 12 seconds (+½ additional stop). For a critical shot on slide film, many photographers might well opt to bracket the main exposure with an exposure at (+/-) ⅓ stop or even (+/-) ½ stop.
Upon viewing the transparency on the light table, the exposure turned out exactly as I had envisioned it. The colors were rich and vibrant. The film recorded excellent detail and texture in the strong highlights. In an uncanny manner, the light table / light box transports you to the scene again to re-experience the emotion . . . I personally scanned the slide, made no conventional post-processing adjustments, and cropped the image to a 4:3 aspect ratio. The overall exposure, as determined by the reciprocity departure correction, was on target. In my mind, if I had made this exposure at the original metered shutter speed of 8 seconds (½ stop less), the photo would have been underexposed; yet that is a matter of subjective taste. An exposure that appears “right” for one photographer might well be interpreted differently by another. Perhaps, one of my fellow photographers would have added an additional ⅓ to ½ stop to this main exposure for reciprocity (shutter speed 15-18 seconds instead of 12 seconds). Or ½ stop less? Much like the art of composition, compensation for film reciprocity departure can be individualized according to the photographer’s own experience, lighting conditions, and his/her vision for the final print. It is not uncommon for a film photographer to personally craft his own reciprocity table for a given film based on different lighting conditions and his own rated exposure index for the film.
From a technical and aesthetic standpoint, the beginning film photographer might ask: was it necessary to use an 85C filter for a warming effect? No, of course not. Could I not have been equally satisfied if I had used a weaker warming filter, or satisfied if I had used no filters at all? Certainly, if I had desired and visualized less vibrant colors, or less warmth in the sky, perhaps I would have used a weaker warming filter. And herein lies the beauty of the art of photography: in the end, you have to go with your intuition and what suits your style and your unique process of visualization to achieve the effects that you desire as an artist. The “conscious departure from reality”– or not. It all depends on what the photographer and artist wishes to accomplish.
For this next photo at glorious Torrey Pines State Natural Reserve in San Diego, CA, I chose color negative film with a relatively weaker warming filter, the 81A, along with a polarizer. Since most of my subjects that I photograph on Kodak Ektar 100 are scenics, I typically will have at least an 81A filter on my lenses to impart modest warmth to the scene and to remove ghastly blue casts within the shadows. Since I scan my negatives and print digitally instead of the traditional way with an optical enlarger and color filter packs, I often use light balancing filters (e.g., 81A, 81B, 82A) and occasionally color correction filters, to help achieve the desired color balance during the exposure. In contrast to a much stronger color conversion filter, which balances the color temperature of light to the color temperature of the film, a light balancing filter is a weaker filter that is designed for creating warming (or cooling) effects during the exposure. For example, the 81A filter, which blocks blue light, can be used to remove blue casts in shadows and under overcast skies or to remove blue casts from an electronic flash unit. Color correction filters (e.g., magenta, cyan) are specialized filters that modify primary colors to achieve a normal color balance in the scene; for example, a CC magenta filter can be used to help balance color in a scene that is illuminated by fluorescent lamps (which tend to create an unsavory green cast ), or to neutralize the cyan/green shifts during long exposures with color film.
For this sunset photo, I visualized a less vibrant and more natural rendition to the colors, as that was congruent with my mood at the time. The 81A filter, as opposed to the stronger 85C, helped me create this rendition. In contrast to the previous sunset exposure on Velvia, I did not pursue a “conscious departure from reality” in my visualization for this photograph. Of note, since the density of the 81A is less than that of the 85C, the former carries a filter factor of +⅓ stop compared to +⅔ stop for the latter.
Although Kodak continues to do a phenomenal job in producing and maintaining on the market this vibrant, sharp, and 3-dimensional color negative film for photographers to enjoy, its recommendation for reciprocity departure correction for Ektar 100 leaves much to be desired. Here is what Kodak recommends for Ektar:
“Adjustments for Long and Short Exposures: No filter correction or exposure compensation is required for exposures from 1⁄10,000 second to 1 second. For critical applications with longer exposure times, make tests under your conditions.”
Well, that is not very helpful, is it? Fortunately, many experienced photographers have done formal testing of this film and kindly shared their results. Personally, I use this very good table for reciprocity departure for Ektar 100.
Returning to the photo, after metering the shadows and placing them on the desired Zone, the meter gave a shutter speed of 4 sec, which when adjusted for reciprocity departure yields a shutter speed of approximately 6 seconds (+⅔ additional stop). After studying the negative and subsequent scan, the image was, to my eyes, a faithful representation of what I saw and felt at the time. The image appeared natural with warm (yet not over the top) colors. The exposure and development were nominal. The shadow detail and high value rendition appeared as I had visualized them, and the long exposure provided a subtle and pleasing sense of movement of the clouds. With regards to reciprocity departure compensation, if I had chosen the metered shutter speed of 4 seconds instead of 6 seconds, certainly my shadow detail in the canyons would have suffered. On the other hand, if I had chosen a full extra stop for reciprocity departure compensation (8 seconds), the exposure would still have been excellent, although I would likely have considered reduced development of the film to bring the strong high values in the clouds under control.
Given the generous exposure latitude and beautiful highlight rendition of negative film, as long as the skilled photographer leans on the side of modest overexposure in order to preserve shadow detail, then the final image should turn out just fine. From an aesthetic standpoint, perhaps some of my fellow photographers would have been happy using no color correction filters with this scene; others might have chosen a stronger filter (e.g., 81B, 81C) for more warmth. For the beginning film photographer who may be struggling with the decision to use filters with color negative film, take a deep breath and relax.
Remember, color correction filters are simply tools in the visualization process. As with many other aspects of general photography, my best recommendation is to experiment and discover for yourself what works for your photography and helps to consummate your own visualization process.
Reciprocity departure has been and always will be a routine way of life for the film photographer. Once in command of the rationale for this effect and its compensation during both the exposure and subsequent film development, making long exposure photographs under low light conditions becomes second nature. The salient points are (1) that the photographer be cognizant of when to account for reciprocity departure and (2) that by its very nature compensation for this effect creates high contrast on the negative or slide. If the photographer does not account for reciprocity departure, then the negative will be underexposed (gasp!) with loss of potentially desired shadow detail and a ruined photograph. And if the development of the film is not appropriately reduced (if applicable) for a given scene, then the negative or slide may contain more contrast than originally visualized.
Recommendations from film manufacturers (where applicable) and the empiric work of our colleagues on when and how much to correct for reciprocity departure are instrumental, yet not the final word. Reciprocity departure correction need not be 100% systematic for all scenes and lighting conditions. How a given photographer chooses to correct for it during the exposure and if/when to reduce development of the film to control contrast afterwards are individual decisions that should be predicated on his/her own experience and objectives for a given scene. There is no right or wrong. In future contributions to Photography Life, I envision sharing more photographs made with other popular film stocks (e.g., Tri-X, HP5 Plus, Portra 400) in the context of reciprocity departure.
Filtration in color film photography (slide and negative film) in the visualization process is likewise predicated on individual aesthetic and technical preferences. From a technical standpoint, filtration with slide film has traditionally been viewed as more critical than it is with color negative film. With color negative film, many photographers choose to ignore filters altogether and defer color correction until the printing stage (traditional optical printing workflow) or the scanning stage (digital workflow). Philosophically and technically, I prefer to achieve correct color balance (and avoid undesirable blue casts) as much as possible during the exposure. Aesthetically, filtration can be an effective creative tool in the visualization process. Again, whatever approach works well for you, roll with it. And whatever result that looks and feels right for you *is* right. That is the embodiment of the art of photography, in my humble opinion. My recommendation: experiment . . . discover . . . take good field notes . . . and have fun with it!
I hope you have enjoyed this fourth article on Visualization and Film Photography. Special thanks to Northcoast Photographic Services for providing the film development services for these photographs (great job as always, Scott!). In the final Part V to this series, I will discuss the rationale and technical considerations for exposure compensation in close-up and macro film photography along with concluding remarks. Please, stay tuned.
- “Black and White Reciprocity Departure Revisited”. Howard Bond. Photo Techniques Magazine.
- “The Negative: The Ansel Adams Photography Series 2”. Ansel Adams.
- “The The Zone System Revisted Part I”. Popular Photography Magazine. Ansel Adams.
- “The The Zone System Revisted Part II”. Popular Photography Magazine. Ansel Adams.
- “Color Photography: A Working Manual”. Henry Horenstein.
- “Photography and Digital Imaging“. Marvin Rosen and David Devries.
- “Gimme A Break”. Popular Photography Magazine. Russel Hart.
- “Zone VI Workshop”. Fred Picker.
- “Beyond The Zone System”. Phil Davis.
- “Scanning Tips”. Kenneth Lee Gallery
- “View Camera Magazine”
- “Principles of View Camera Focus”. Harold Merklinger.
- “View Camera Focus and Depth of Field: Part I”. Harold Merklinger.
- “Technical Books on Photography”. Harold Merklinger.
- “Check List for View Camera Users”. Howard Bond.