Hi,
The high contrast of slide film is both its strength and weakness. It is very easy to lose detail on the highlights: everything that meters above Zone VII is rendered as pure white on most transparency material. I was curious to see if some this detail was recoverable--in other words, if the dynamic range of slide film could be increased somehow. This could be done by under-developing (pulling) the film.
Information on the topic is very scarce (I found one old youtube video and some vague treads on flickr). Ansel Adams itself in his book "The Negative" dedicated a short paragraph on reversal film, but he wrote the opposite of what I found. He states: <<If development modifications are possible, they will have their primary effect on the low values (higher densities).>>
Conversely, I found that, as with negative film, the highlight are restrained by under-developing the film. As an afterthought, this is not surprising because the first step of the E-6 process is the development of a negative silver image, that is then reversed. Therefore, the effect of changing development time is the same in both trasnparency and negative film (except for the different contrast of the two media, see below).
This is what I found in my first experiments. Please compare the two pictures below (both on 4x5 Velvia 50):
The two images were exposed as indicated above via the zone system, but they were then given different development. The picture with normal development has blown out highlights, and some areas looks too bright. The one that was underdeveloped by half stop shows significantly more details in the highlights. It's not a scientific 1:1 comparison, but I am confident in my metering and I know that without the reduced development, the image on the right would have been too harsh.
A change in development of half a stop makes quite a large impact to slide film, because its inherent high contrast, as opposed to negative film that has much wider dynamic range (most transparency material records no texture outside Zone II-III and Zone VII, as opposed to Zone II and Zone VIII++ for negative film).
I made a Youtube video to share my experience on this topic, going a little more in depth. Please let me know if you find something different.
I am sure that many people use these procedures of development control on a consistent basis, but I could not understand how it worked until I tried it out.
Some final thoughts and additional information:
Fuji recommends pulling up to 1/2 stop. So what I have done is not revolutionary. See the manual http://www.fujifilm.com/products/pro..._datasheet.pdf
The question is why it appears that there is more information in the highlights of Velvia 50 that what is retained after reversing the film, information that can be recovered when under-developing the film.
I think this is mostly due the color developer bath of the E-6 process: under-developing the film leaves more unreacted silver salts with which the colors can react to.
Unlike negative film chemistry, in which highly are optical density that linearly builds up with exposure leaving less and less Ag salts, the color developer in E-6 needs a certain amount of unreacted AgBr, a sort of threshold to have minimal density (i.e. texture in the highlights).
I am a chemist during the day and all this is just fun to think and thinker about for me. If then this reasoning leads to some (minor) artistic improvement of my images, and to some understainding by the readers--this is a nice added bonus.
I will post more test that compare the same image. Stay tuned if interested.
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