1 stop difference

Discussion in 'Exposure Discussion' started by Ken, Mar 24, 2003.

  1. Ken

    Ken Member

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    Greetings,
    My Gossen Luna pro F, compared with the meter in my Canon F1N, indicates an exposure one stop less than that of the Canon. Incident, reflected, shadow or highlight, it is dfferent. I have compensated for the difference when making the exposure, I'm just wondering if this is unusual.
    Regards.
    Ken
     
  2. Eric Rose

    Eric Rose Subscriber

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    I just finished posting something about this last week. You might want to check it out. Essentially the Gossen is a Euro meter and they are balanced for 5500 degree Kelvin whereas the Canon being a Japanese meter is balanced for 3200 degrees Kelvin. The difference works out to exactly 1 stop. I see the same thing between my Gossen and my Pentax spotmeter.

    It is my theory that this is percisely why so many people de-rate their asa on most B&W films as they find using the Japanese model the exposures are over by 1 stop. Personally I trust my Gossen and adjust my Pentax to compensate for the error.

    Eric
     
  3. Mark in SD

    Mark in SD Member

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    Interesting. I'm assuming the meter in my Nikon N80 is balanced for 3200K as well.

    So, the question is, which is the "correct" or "best" meter reading? Wouldn't that depend on what the film is balanced for? I seem to recall that "natural" light is in the 6500k range (it may have been even lower, I don't remember exactly).
     
  4. Donald Miller

    Donald Miller Member

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    The measurements of degrees Kelvin are measurements of color temperature and not measurements of light intensity. The color of a northward exposure to blue sky is normally acknowledged as being 5500 K. Thus daylight color film is balanced for this color temperature.

    Tungsten film which is color balanced for a warmer light source (more yellow) will render a daylight exposure as excessively blue. The higher the degrees Kelvin the colder the light source and conversely the warmer temperatures are lower in degrees Kelvin.

    I do not believe the measurement of color temperature that a meter is calibrated for will cause a measurement of differing amounts of light intensity.

    Light meters, even the best of them, are prone to differing measurements and are influenced by such things as internal and external flare and the sensitivity of the photocell to IR and UV emissions. That is why green pine trees very often are a lower negative density (in a black and white film) then what a meter reading would indicate (the amount of IR emission).

    This is further complicated in black and white film by the sensitivity of the film emulsion toward red in the case of panchromatic materials and blue in the case of othochromatic materials. I think that it is important to gain experience with a particular meter and learn it's characteristics. From this knowledge, one is able to meter a scene more accurately and in conformity with the materials used.
     
  5. Eric Rose

    Eric Rose Subscriber

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    most slide films are balanced for around 5500 I think. for the most part so is B&W films as they seem to take an extra stop to expose them when under tungsten lights. It's not so much which is right or wrong, it's a matter of testing to see what works with your setup. It's my opinion this is why so many people fiddle with their asa's. When you combine this fudge factor with trying to understand the zone system it's no wonder people get all confused.

    The test data that is out there shows that how a meter is color balanced also determines it's sensitivity to illumination. Think of it as a band pass filter.

    I do agree that if you take 10 meters and compare them side by side you will probably get 10 different readings. However the error should only be within 1/2 stop either way. Moreover, if you did a plot of Euro meters compared to Japanese meters you will see the graph will show a 1 stop spread on average between the two, deviations normalized.
     
  6. avandesande

    avandesande Member

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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Ken @ Mar 24 2003, 11:02 AM)</td></tr><tr><td id='QUOTE'> Greetings,
    My Gossen Luna pro F, compared with the meter in my Canon F1N, indicates an exposure one stop less than that of the Canon. Incident, reflected, shadow or highlight, it is dfferent. I have compensated for the difference when making the exposure, I'm just wondering if this is unusual.
    Regards.
    Ken </td></tr></table><span class='postcolor'>
    I am not sure about this but both the meter and the camera can (and should) be calibrated.
    I know that this is routine with spotmeters.
     
  7. Mark in SD

    Mark in SD Member

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    OK. I think I've got this.

    So, the Japanese Meters (like the one in my N80), will be balanced for 3200K. European meters will be balanced for 5500K. Natural lighting tends to be about 5500K. So, given the same picture, it looks like the European meters will read about 1 stop less exposure than the Japanese meters (it was never stated directly which way the difference was to I've inferred it from otehr comments).

    Basically correct?

    Now, why the difference? I did notice when I was working in a photo lab that the oriental customers almost universally preferred their prints lighter by 1-2 stops than I would have preferred. Could that be it?
     
  8. Ed Sukach

    Ed Sukach Member

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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (Mark in SD @ Mar 24 2003, 02:17 PM)</td></tr><tr><td id='QUOTE'>So, given the same picture, it looks like the European meters will read about 1 stop less exposure than the Japanese meters (it was never stated directly which way the difference was to I've inferred it from otehr comments).

    Basically correct?</td></tr></table><span class='postcolor'>
    I've Been following this .... I have two meters now, a Gossen Ultra Pro and the internal meter in my Olympus OM 4.

    Both agree with each other - near as I can tell, dead-on.

    Must be me. I seem to be eternally the "odd one". I don't subtract 10% - 15% of time in the JOBO processor - and now my Japanese and German meters agree with each other.

    I have *no* idea why they should be different. I've worked with some sophisticated light-measuring equipment - Cascade Photomultiplier based systems ... and there was *no* bias - as far as color temperature goes. Couldn't be, where light energy at discrete frquencies was being measured. I *suppose* one could deliberately introduce filters to create a bias, a' la Fred Picker - but for a meter that is intended for *universal* use - why would you?

    Is everyone SURE of that 3200K - 5500K difference? - Or are we looking at a calibration problem?

    --- Uh ... tell me we're NOT trying to verify sophisticated light meters by the "Sunny 16 Rule" ...
     
  9. Donald Miller

    Donald Miller Member

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    I think that I will go back to doing what Edward W. did...not using a meter at all. I understand that he made most of his images without the impediment of such extraneous and untrustworthy devices. Probably would be a big boost to my photography. Learn to trust my eyes. Work with the materials and learn to know them and what they are capable of. I have heard that if he had relied on a meter to make his "Church at Hornitas" he would have underexposed the image by at least 3 stops...go figure!!!!
     
  10. David Hall

    David Hall Member

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    Donald,

    Your comment above about light color and light intensity not being related...wasn't the whole idea behind the Zone VI modified meter that Any Old Pentax Spotmeter's readings were off because it didn't do a good enough job measuring the color of light?

    And to those who use both Gossen and Pentax...which do you prefer? I have looked at the Gossens and they seem harder to use, especially for zone system thinking. True?

    dgh
     
  11. Eric Rose

    Eric Rose Subscriber

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    I love both of them. As I've said I will use the Gossen with the dome for quick and dirty readings, or when using chromes, but use the Pentax when I find the need to get anal. The Pentax I adjust so it reads a grey card at the same reading as my Gossen. Once that is done I meter shadows, highlights, middle tones, cleveage whatever it takes. Apply the suitable high velocity fudge factor and then take my shot.

    Actually before I got back into all this LF stuff I very rarely used a meter at all for B&W. After 30+ years doing this stuff you kind of get the hang of it. That's another reason why I like to keep things simple. One type of film (well maybe two), one type of paper ( well one brand anyway) and one type of developer. Ok so I tried Pyro tonight, but I haven't contact printed the negs yet.

    Eric
     
  12. Ken

    Ken Member

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    Greetings,
    Well, I had no idea this would be the result of my query though I have been pleasantly enlightened! The Canon negs seem to be a bit overexposed when compared to the negatives made using the exposure indicated by the Gossen. Knowing there is a difference I can make the adjustments. I prefer a 'thicker' negative be it 35mm or otherwise. My goal is to eventually be able to make exposures without a meter, but for now, the meter is there to build the foundation in the brain. I strictly shoot B+W 400. Color is of no interest to me. I have messed with the Zone system as a way to learn about exposure and development and have found what works best for me so the real critical measurements are of no real concern. Expose for the highlights.
    Many thanks.
    Ken
     
  13. Ed Sukach

    Ed Sukach Member

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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (David Hall @ Mar 24 2003, 08:42 PM)</td></tr><tr><td id='QUOTE'>...wasn't the whole idea behind the Zone VI modified meter that Any Old Pentax Spotmeter's readings were off because it didn't do a good enough job measuring the color of light?
    </td></tr></table><span class='postcolor'>
    I think that you'll find that the Zone VI modifications were intended to match the sensitivity curves of black and white film. Color was a factor, but it is not entirely accurate to say that the Honeywell meter was "off" because it "did not read color correctly".

    I always thought that that the Zone IV mods were nit-picking, but there are those among us who are perfectionists.

    I've progressed t the point where I take the information from the exposure meter as "useful information" and use it as a base for the final settings.
    In all truth, the jury is still out over whether or my "Kentucky Windage" is a good idea. Sometimes it works ... other times .... well, it is a useful "experiment".
     
  14. Donald Miller

    Donald Miller Member

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    </span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (David Hall @ Mar 24 2003, 11:42 PM)</td></tr><tr><td id='QUOTE'> Donald,

    Your comment above about light color and light intensity not being related...wasn't the whole idea behind the Zone VI modified meter that Any Old Pentax Spotmeter's readings were off because it didn't do a good enough job measuring the color of light?

    And to those who use both Gossen and Pentax...which do you prefer? I have looked at the Gossens and they seem harder to use, especially for zone system thinking. True?

    dgh </td></tr></table><span class='postcolor'>
    While I have no experience with the Gossen meter, it to all appearances seems to be more difficult for my use in Zone system usage. The Zone VI modifications orginated from the recognition that light meters (even the best of them did a marginal job of accurately metering a scene for black and white zone system photography) The modifications consisted of several internal changes. Among those were improved internal baffling to reduce the effects of both internal and external flare (effects of nearby bright sources). A couple of filters to eliminate or reduce the effects of UV and IR radiation (IR being the more problematic) and filter packs to bring the meter sensitivity into agreement with the sensitivity of panchromatic black and white emulsions. The effects of these modifications can be determined by metering (with both a modified and unmodified meter) green pine trees and also a green and a red surface. By exposing the film in accordance with the meter reading and then developing the film in the same manner the resulting prints will be the determiner of the effects of the modifications. These modifications really had no bearing (from Zone VI advertisements) on the meters sensitivity to a given color temperature of light. Color temperature really is an entirely different parameter then light intensity.
     
  15. Tom Duffy

    Tom Duffy Member

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    As usual, I have nothing constructive to offer, so I figured I would just throw a monkey wrench into the "color temperature" argument. (We all do what we can.)

    A photography instructor, who taught for years at the Maine Photographic workshops, told me that Canon had decided that "average scenes" were not really 18% gray, but 10% gray (I assume that's darker than 18%) and adjusted their meters accordingly. If true, that would also account for a one stop difference in meter readings. Of course it might also be t-stops vs. f stops <g>...
     
  16. lee

    lee Member

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    more monkey motion:
    There are calibrations for 18% gray and if I recall correctly (IIRC) 36% gray. Maybe that is the difference? Quien sabe?

    lee\c
     
  17. Eric Rose

    Eric Rose Subscriber

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    It's all academic really. Once you have done your testing you should have everything nailed down for the film/devloper/paper combinations you use. It doesn't really matter if my meter reads the same as yours etc. It only matters that I know how mine reacts to various lighting situations and I can apply the appropriate adjustments to the "suggested" exposure to obtain my pre-visualized image in the darkroom. I prefer not to trip over the roots so I can at least get to the forest, so I can photograph the tree.