When Do The Lower Values Start To Develop ?

Discussion in 'Talk About Developing Film' started by Ian-Barber, Dec 14, 2016.

  1. Ian-Barber

    Ian-Barber Administrator Staff Member

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    If I have a scenario whereby I am using a single soft light on say a still life subject. The areas not receiving much light are obviously going to want a longer exposure for them to register on the film.

    Increasing the exposure for the shadows is in turn going to make the areas receiving the lions share of the light brighter and could even become too bright.

    In situations like this, I am assuming that reducing the development time would be one way to control the highlights.

    Back to my question
    If the normal development time is 9 minutes, reducing this by say 20% would give a development time of 7 minutes 20 seconds.
    Would this time be sufficient for the shadow areas to have been developed ?
     
  2. alexmuir

    alexmuir Member

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    I would think so. I think I'm correct in saying the shadows develop quickly, but highlights continue for much longer. 20% is the reduction I am using to control highlights in my night shots. It would be a good starting point. The alternative might be trying to reflect some light into the shadow areas to reduce the overall brightness ratio, and then you could use a shorter camera exposure.
    Alex
     
  3. Ian-Barber

    Ian-Barber Administrator Staff Member

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    Do you have a website showing your work Graham.
     
  4. Stephen Batey

    Stephen Batey Well-Known Member

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    Easily. See the example showing the effect of 3, 10 and 15 minutes development in Langford's book (photo sent via PM in October). The shadows don't do very much relatively speaking after 3 minutes, while the highlights get noticeably darker.

    You could also experiment with preflashing to reduce the latency of the film.
     
    Last edited: Dec 15, 2016
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  5. Alan9940

    Alan9940 Active Member

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    What most folks tend to forget is that reducing development time usually reduces film speed which impacts shadow values. Therefore, one tends to think that not enough development has been given due to weak shadows. i doubt that a 20% reduction would have any appreciable impact on film speed, but it's something to keep in mind. Testing is the only way to know for sure.
     
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  6. Ian-Barber

    Ian-Barber Administrator Staff Member

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    I forgot I still had these, thanks
     
  7. Stephen Batey

    Stephen Batey Well-Known Member

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    You might also find it informative (depending on how you view chemistry) to read chapter XI "The Kinetics of Development" in Mees' Theory of the Photographic Process p402 onwards, 1942 edition. I'm citing this edition as it's the pdf I posted a link to somewhere else on the forum as part of the photographic information I'd collected (it's in the "Books" section). This is the link, but space on my OneDrive is vanishing rapidly, and I may need to delete this whole section.
     
  8. Stephen Batey

    Stephen Batey Well-Known Member

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    How true is this actually? My understanding would be that, yes, reducing development does reduce shadow detail, but not by much; the most you can usually gain in shadow detail by developing to finality is only about one stop, and the loss from shorter development isn't much, as Michael Langford's illustrations show.

    Reducing development affects mainly the high densities, and therefore reduces the contrast; giving extra exposure with reduced development will therefore preferentially boost the shadows and the next effect is more shadow detail (due to increased exposure) without appreciable extra highlight density. The net effect being an easily printed negative with good shadow detail and reduced contrast which helps with a high subject brightness range.
     
  9. alexmuir

    alexmuir Member

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    I also wondered about this statement. I didn't think the film speed, or its sensitivity to light was governed by development time. You can alter the film speed set on your metering device, and expose for a longer or shorter period as a result, but I had understood that the speed determined by the manufacturer remains constant. When you deliberately reduce development time to control contrast, this is normally accompanied by an increased exposure to retain shadow detail, but I've never heard that described as altering the film speed. Does that description come from a particular text or writer?
    Alex.
     
  10. Alan9940

    Alan9940 Active Member

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    Stephen/Alex,

    Reduced development time does impact film speed; I've measured it on a densitometer. You are both correct, though, that a reduction or increase in development time does only minimally impact each of the respective ends of the curve. However, in my experience I've found that when a deep shadow value is teetering on the edge of retaining a bit of texture or dropping into total black I really want to know my anticipated film speed based on the development planned. A little bit off and my deep shadows are gone!

    I will admit, though, that much of this may relate more to older films of the past; back when things like N-2 and N-3 were possible. I haven't tested any of the modern films (T-grain and the like) because I haven't had access to a densitometer for years (though I have one on its way to me as I type this.)

    Alex - film speed is not necessarily constant. It is a rating based on controlled laboratory measurement. Do you really believe that an ISO 100 film is always 100? Trying storing a roll for 20 or so years, then test it for film speed. I'd be willing to bet it ain't 100!

    But, your statement saying "When you deliberately reduce development time to control contrast, this is normally accompanied by an increased exposure to retain shadow detail" is effectively an increase in film speed. Maybe we look at it differently, but we're saying the same thing.
     
  11. Stephen Batey

    Stephen Batey Well-Known Member

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    As far as I recall (I haven't double checked this in case my memory is at fault) the film speed is actually rather precisely defined in terms of the exposure needed to produce a specific density (I think something like 0.1) above base + fog when a specified developer, temperature, time and agitation are used to process the film. On this basis, a change of developer, agitation method etc. etc. could impact on the density produced, but the actual film speed wouldn't be affected, which is why pedants use EI for exposure index to specify what they set on the meter. And hence the need for testing film speed to see if your methods produce an acceptable result.

    Michael Langford's book does show that development times affect the shadow density, but not by much compared to the effect on the highlights. So yes, you might need to increase exposure if you severely curtail development compared to your normal time.

    Those with long memories will recall that in the early 1960s (1961/2 or thereabouts) film speeds doubled overnight when the standard was changed to remove a safety factor that had hitherto been built in. Smaller negative sizes had made minimum exposure more important, as excess exposure adversely affects sharpness and granularity.

    And those with even longer memories (or who have read up on history :D) will recall that Kodak originally set their film speeds by making the best possible print for a whole series of exposures and then basing it on the minimum exposure in the series that was noticeably better than the one with less exposure. Cutting it as fine as possible, in other words. This method did have the advantage of being a "real world" value, based on the end result of a print in the hand.

    I haven't looked around to see if I can find any densitometer measurements showing the effect of development time for a constant exposure; but given that shutter speeds and apertures may not be accurate, and given the question of shutter efficiency where a between lens shutter can have a wide variation anyway of effective exposures based on the aperture set, I wonder how large the development time variable is in relation to these other variables.

    Sorry Ian I'm going way off topic.
     
  12. David M

    David M Member

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    It seems that we are debating the expression "film speed".
    A reasonable person might suppose that you'd judge the speed of a film in the way you judge the doneness of a steak; you'd see what happened in the middle of the steak. Then, in an exact parallel with N+ and N- development, you could predict how to cook rare, medium and completely ruined steaks. (Would Zone V = medium?) We might even draw parallels with the heat of the pan and the brightness of the incoming light. A really dedicated cook might have different times for different frying pans. Vegetarians might like substitute lentils and have boiling-times for tooth-cracking, really really nice and mushy. Enough metaphors.
    Photography doesn't do this. Film speed is determined in a way that's convenient for film testers and members of the Densitometer Appreciation Society. They scrutinise the bottom left-hand corner of a graph and measure a suspiciously round number, up from the bottom. It's not a practical system out in the field. (Or in the kitchen, where the chef doesn't want to know what will make the steak slightly lukewarm.)
    What we do know is that reducing development reduces negative density and it's difficult to see how we can distinguish this from reduced "film speed". It might more proper to talk about a reduced Personal EI. In the field, we'd just click the meter around a third- or a half-stop if we visualised N-minus development.
    We will all have discovered that it can be difficult to print from very faint traces on the negative, and still get the rest of the print right in the darkroom. On screen we have more resources to rescue those faint traces.(Image > Adjustments > Highlight/Shadow, for instance. Magic, used sparingly)
    To return to the original paragraph of the original post... If this is a still life, artificially lit, then the answer is clearly to adjust the lighting. I'm not an expert, but I've found that a piece of white card, propped up close, but just out of frame, can often rescue a too-dark shadow. Even a small mirror can be used with care. If there's space, a card can be placed right underneath the lens (or hung from it) to lift all the darker parts that the lens can see. You'd need to experiment with the size, angle and tilt of the card, but that might be the fun of it all anyway.
     
    Last edited: Mar 3, 2017
  13. Stephen Batey

    Stephen Batey Well-Known Member

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    It might be truer to say that we can never, except in very exceptional circumstances, get the film's actual rated speed except by accident. As soon as we step away from the specified developer, temperature, agitiation method and so on we've stepped away from any hope of actually achieving the rated speed, defined in terms of base+fog+density. Whether the effect is to give what could be interpreted as a higher or lower speed is another matter; it would still be an EI rather than a rigourously defined ISO rating.

    Reducing development time is like using a proportional reducer - it affects the highlights more than the shadows. If you overexpose enough, you'll compensate for reduced development in terms of average density; and if you give enough extra exposure you'll lift the shadow areas without the highlights blocking.

    Of course, you could use a proportional reducer after the fact...
     
  14. David M

    David M Member

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    Yes indeed. Film speed is determined under extraordinary conditions and I understand that it's done that way to provide a constant reference across all films.
    I've seen a suggestion that there are two possible approaches, both valid: one is the 0.1 above fog that we are familiar with and the other is to measure where a tangent at a particular slope touches the toe of the curve. I forget what the slope is, but one can see the logic of doing it this way. (Or I think I can – it's a long time since I wrote the word tangent.) Many photographers seem to use the expression "speed" rather loosely, and using personal exposure index might seem just a teeny bit pretentious, but it's what they usually mean. It seems to me that what we are after is printable density, rather than merely detectable density.
    I hadn't thought of reducer as a sort of mirror image of developer but it's a very nice point.
    I think my own point (if there was one) was that when looking at images, we are mostly looking at the mid-tones, where the main subject interest usually lies. On that basis, it would seem logical to define film's reaction to light at Zone Five, under repeatable and controlled conditions of course. A few picky fuddy-duddies (like me and, if I may presume, you) worry about shadow detail and the delicacy of the highlight tones, but we are the exception. I am not suggesting that this should be done and I haven't done it myself, but I do suggest that it seems reasonable. A goodly number of photographers already discuss exposure in terms of meter-reading-minus- or -plus a number of stops. That would translate into Zone Five plus/minus the number of stops.
    I do wonder about the kind of obsession with precise negative density that you can find on the American LF format. I don't want to snatch away their toys, but I do wonder what it has to do with expressive image making.
    I came across one post where someone had got the camera, got the lens, the tripod, the holders, meter, cloth and no doubt the boots and was asking for advice on how to meter so he could exactly hit that magic 0.1 over base-plus fog before he actually ventured out and took some pictures. This did look like a whole herd of carts before horses. Perhaps fortunately, I haven't kept the reference.
    This is turning into a novel. I'd better stop.
     

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