Evaluating scene contrast

Discussion in 'B&W: Film, Paper, Chemistry' started by Rick Jones, Feb 16, 2007.

  1. Rick Jones

    Rick Jones Member

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    While much has been written and discussed about tailoring negatives to scene contrast through speed and +/- development tests much less seems to be written about how one actually goes about evaluating scene contrast. After all, if we misinterpret the scenes actual contrast much of our testing would seem to be wasted. Those using matrix metering and one average development time need not be concerned. But those adjusting E.I.'s and development time must make these judgments at the time of exposure. Exactly how do you go about evaluate scene contrast? Give me some ideas of how to get better at it.
     
  2. mcfactor

    mcfactor Member

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    The way i do it is to take spot-meter-readings of objects with different values in a scene. Then I decide what zone i want each to be, or rather, what zone i want my object (or area) of focus to be, and calculate where everything else falls. If the disparity between zones is too great, e.g., my subject is Zone V but the shadows fall on Zone I, there is too much contrast. In other words, I try to use the zone system. And I shoot a lot, as much as possible.
     
  3. Donald Miller

    Donald Miller Member

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    There are several ways to evaluate scene contrast. If using the Zone System one would normally meter the shadows and the highlights of the scene or subject with a spot meter which would measure the reflective values. For instance if the shadow meters at an EV 6 and the highlights EV 12 then one could place the EV 6 exposure on a zone III which would be two stops less exposure than the meter indicates for this luminance. That would indicate that the high values would fall on a Zone X and would require a N minus one or two development (depending on the high value subject matter and desired tonal rendition). Zone VIII would be the highest tonal value that would have texture apparent in the tone. Zone IX would have no texture present but would be marginally below Zone X tonality (which is typically considered to be paper base white). Alternatively one could place the low values on Zone II (three stops less exposure than the meter indicates) and the high values would then fall on Zone IX and may not require any reduced development. This may be true if the low values do not require the detail desired in the first example and if the highlights are specular in nature.

    If one were using an incident meter and BTZS methodology, then one would meter the shadow values with the dome pointed toward the camera lens. Next a high value reading would be taken (again with the dome pointed toward the camera lens). The low reading EV would next be subtracted from the high value EV and the resulting difference would be added to 5 to arrive at a SBR for the subject or scene. For instance if you have a high reading of EV 12 and a low reading of EV 8 that would leave you a net difference of 4and when added to five would be a SBR 9. Since SBR 7 is considered to be a normal range that would indicate a reduced development to accomodate the extended contrast of the scene.

    While it may initially appear that the Zone System provides for more creative latitude in shadow value placement, it should be noted that both systems allow for this creative latitude.
     
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  4. reellis67

    reellis67 Subscriber

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    I use the less detailed 'Expose for the shadows - develop for the highlights" method and to get an idea of how much to adjust I look at the shadows cast by the light. I adjust based on the strength of the shadows cast by objects in the scene, which admitedly requires a bit of experience to really fine tune, but works quite well for me without the need for a lot of gear I can't afford.

    I put together a simple article explaining how I judge light conditions on my personal web site in the articles section. My method is not for those who like to have ultimate control over everything, so be warned ahead of time...

    - Randy
     
  5. juan

    juan Subscriber

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    What the previous posters have said is correct, and this is an area where hard work is needed. There are no magic formulas - proper exposure (combined with development and printing) is simply something that comes only through lots of practice. I strongly recommend writing down your exposures as you make your negatives, and writing down your development. You learn from the knowledge you gain through trial, and particularly, error.
    juan
     
  6. Pinholemaster

    Pinholemaster Member

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    Experience and knowing your film and developer combo.

    Me, I simply use an incident meter for 90% of the time, with a spot meter when the light is really tough.

    Friends don't let friends use 'Matrix' metering. Grin. Or as the wise old someone said "A meter in the hand is worth two in the camera."
     
  7. MurrayMinchin

    MurrayMinchin Membership Council Council

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    Don't forget local contrast while considering the scenes over-all contrast. Sometimes you're better off dodging, burning and/or masking later, rather than squishing all the middle values together and sucking the life out of your main subject.

    Murray
     
  8. haryanto

    haryanto Member

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    I use pentax zone six modified, i spot meter the scene that include in my frame, first is the main object, I put it in the zone that I want, then I start to meter the others, if highlight more or less than zone VIII I will use N+ or -, but I'll measures the impact of N+- process to the zone of my main object, readjust, and then I start to check the shadow, if it's get adequate detail then done.

    I think that I'm not capturing the scene but I want to make a photograph with tonality that I want (as my visualisations at that time, so far it's work for me
     
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  9. Jean Noire

    Jean Noire Member

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    I think that the high values in your example would fall on Z IX.
    Regards
    John
     
  10. Allen Friday

    Allen Friday Member

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    Here's what I did to learn metering:

    Pick a scene close to home that you can go back to time and time again. It doesn't have to be anything special, the light just has to be extreme for minus development or flat for plus development. The scene I picked for minus development was a woodland with my white car parked in a sunny spot. Make one exposure based on your in camera reading (matrix metering) to give you a baseline and develop normally. Then look carefully at the shadows and decide how much detail you want to appear in the print. In my case it was a tree trunk. Meter that area and use it as your second exposure, marking development to make your highlights fall in the proper place. Then make two additional exposures, one reading a darker area of the shadows ( a tree trunk in shadow) and then one reading a lighter area of the scene. Mark each with the proper development to control the highlights. Keep notes.

    Go to the darkroom and print each negative at your standard printing time and make straight prints. Compare the prints to 1) what your visualization was and 2) take the prints out to the scene and compare them to the actual scene in the same light.

    The shadows will tell you which exposure works best for you. If your highlights are off, you can use the same exposure and adjust development on the later sheets.

    The problem in metering shadows is that there are dark shadows and light shadows. Which one do you pick? The only way to decide is to try both and see which looks better in the final print. The same goes for highlights.
     
  11. Donald Miller

    Donald Miller Member

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    John,

    You are correct. Thanks for pointing this out.

    Best,
    Don
     
  12. Roger Hicks

    Roger Hicks Member

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    Dear Rick,

    There are essentially three options.

    The only way to measure it directly is to take highlight and shadow readings with a spot meter. The I.R.E. '1' and '10' indices, 5 stops apart, are a useful tool for this.

    Second, you can infer it from other readings, especially BTZS incident light readings. These do not and cannot give direct readings, but are arguably more useful for getting consistent negatives under the great majority of circumstances, especially with short brightness ranges.

    Third, you can eyeball it. A bright, clear, sunny day with deep, dark shadows will typically have a brightness range 1 to 2 stops greater than 'average', while most of the weather in the UK is hard put to reach 'average' (allow a stop less) and misty weather can drop to 4 stops less or worse. 'Double lighting' (e.g. an interior with dark corners and sunlight streaming through a window) is the hardest to judge, and the one that will repay spot metering most.

    Ultimately, most people learn to trust the Mk. I eyeball plus experience plus whatever metering method they are happiest with. Anything else -- Zone System, BTZS, any other formalized or informal testing system -- is only a step (or a series of steps) on the way.

    Cheers,

    R.
     
  13. Jean Noire

    Jean Noire Member

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    Yes, I initially had a problem with this when I began to apply the ZS. The advice of "meter the shadows and place them on ZIII or IV" confused me because the shadows may have a SBR as well. I found the only way around this was to evaluate the whole scene to be photographed, make a decision as to the darkest tone I wanted with detail in my final print and then do the same for the highlight. The difference then gave my overall SBR and then any further changes in development applied if neccessary. It did take a little practise to asses the scene though.

    Regards
    John
     
  14. Jean Noire

    Jean Noire Member

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    "then do the same for the highlight."
    For the lightest tone that I want with detail of course.
    John
     
  15. Donald Miller

    Donald Miller Member

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    Do you think that this is a measureable difference in the way that the Zone System approaches things ie...in a more subjective way than BTZS?

    It would seem to me that if one is approaching this with the supposed greater precision of a spot meter (as some would lead us to believe) that "visualization" would give a practitioner of the Zone System the precision to very precisely place zones and hence print tonal representations. Am I understanding you to say that it isn't necessarily so?

    Thanks for your response to this.
     
  16. Jean Noire

    Jean Noire Member

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    No, all I am saying is that when a scene is viewed then decisions have to be made as to what is considered as important i.e the areas that require detail in brightest highlight and deepest shadow in the final print. I believe that use of the ZS is a means to facilitate this. It may be the case that detail is only required in one area, then you have to decide what you want to do with the rest of the scene in the final image. I find that this removes confusion as to what to meter in shadow and highlight.

    Best wishes
    John
     
  17. Roger Hicks

    Roger Hicks Member

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    Dear Don,

    Surely 'less subjective'. Where you place shadow detail is always a matter of choice. The ZS gives you that choice. BTZS, if I understand it correctly, does not give you that choice because it does not measure shadow detail directly, but infers it from a hghlight (incident) reading.

    BTZS should, on theoretical grounds, give more consistent negatives if the SBR is 5 stops or below under shadow lighting (the SBR under full light, if both shadow and full light, is another matter). The original ZS will work better with really tricky subjects under 'double lighting' such as sunlight streaming through a church window when you also want details in the roof beams.

    Cheers,

    R.
     
  18. Jean Noire

    Jean Noire Member

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    Hi Donald,
    I have given a little more thought to your question and would like to add:-

    I have not felt the need to familiarise myself with BTZS and cannot therefore give views about comparisons involving it.

    "It would seem to me that if one is approaching this with the supposed greater precision of a spot meter (as some would lead us to believe) that "visualization" would give a practitioner of the Zone System the precision to very precisely place zones and hence print tonal representations. Am I understanding you to say that it isn't necessarily so?"

    I am not sure how I came to give you the impression that I thought the precise placement of subject tones on the print value scale using ZS methods could be uncertain. I was actually trying to show that it is, IMHO, as accurate as it needs to be.

    I trust that that this has helped clarify my position in the previous posting.

    I also note that you have said elsewhere that you used the zone system for a number of years and have now switched to BTZS. Is the question you have posed above been bourne out in your experience? i.e that you have obtained more accurate placements of tones by following BTZS in favour to ZS.

    Regards
    John
     
  19. NikoSperi

    NikoSperi Member

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    Not to nit-pick, but in your example, EV12 would be zone IX, not X.

    Not a BTZS practitioner, but I find it somewhat surprising that a scene metered with five stops of range (EV8-EV12) would call for N- development. Would that be a result of the incident readings as opposed to spot readings?

    EDIT: And if I had read Page 2 of this thread before yacking... I would have seen everything I just asked has been answered! Apologies. :rolleyes:
     
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  20. Donald Miller

    Donald Miller Member

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    Hello John,

    There are strengths and weaknesses in each methodology. There are also
    distinct differences in both methods. The greatest difference, as I observe it, is this. In Zone System procedure, one concerns themselves with visualization of tonal representations before exposure. This engages the photographer into the decision making about exposure...and consequent development of the negative in a different way than BTZS does. Taking license with the example given earlier, one could decide, for instance, that the shadow placement (deepest shadow) could be a zone II or a higher exposure placement. The high values would fall where they will and development would then be determined.

    In BTZS there is no reference to zones as such. One determines, first and foremost, the characteristics of the desired print medium. From that the next step is to determine and produce negatives that are capable of being printed on that medium. The print material characteristics are expressed in terms of the exposure scale of the material and this is then accomodated in the density range of the negative. Most BTZS practitioners use an incident meter whereas Zone System practitioners use a spot meter as their meter of choice.

    Tonal representation in a print is another matter entirely, it would have seemed to me, as a Zone System practitioner, that the tonal representations on a print would have been ideally equally separated by equidistant measurable density differentiations, that I found was not the case. The reason is, as I am sure that you know that the characteristics of film and of paper are not linear in their application. While visualization can provide some guidance in making a photograph, it, I have found was best realized by making actual tonal scale swatches that I carried with me when I practiced the System.

    To answer your question as I inferred it to be, if I had not felt one system superior to the other, I would not now be using it.

    I hope that this has answered your question. Best of luck in your photography.