How to use a 18% Grey Card with Reflected LIGHT Meter.

Discussion in 'Lighting Equipment' started by miss.annette_leigh_haynes, Dec 27, 2017.

  1. How to use a 18% Grey Card with Reflected LIGHT Meter. 35mm Manual Camera 80mm-200mm f`1:4.5 Outdoors, Ariz. Bright Sun.
    Do I put Grey Card in front of Meter? Is this good for color or B&W only Never did this before
     
  2. Unfortunately there is no 'quick and dirty' way to (properly) use it
    I assume you want to use it with a film camera (?)

    Then to begin with, how to meter the light depends on what type of film you use:
    - negative film - > does not work well when (heavily) under exposed (muddy shadows, grainy images)- > meter for the shadows (which will result in a somewhat over exposed film)
    - positive/slide film -> does not do well when (extrememly) over exposed => burnt out, irretrevable (sorry if spelled wrong, not a native English speaker) high lights -> expose for the high lights (which will result in a somewhat under exposed film)

    In real life that isn't as strict as it sounds, both negative and positive film have a certain margin within which under and over exposure can be dealt with (similar to the 'Dynamic Range' of modern digital camera's)
    Note: In my observation/experience, Nikon/Sony sensors behave much like slide fim and can better handle under exposure the Cnon sensors, which give better results when over exposed somewhat

    The best way (if you have enough time, eg when shooting a landscape, or product) is to take a reading for the hightlights, and a separate one for the shadows. and caculate the 'best' balance between to bet the 'proper' exposure
    In a real world situation that means
    a) to begin with, place your gray card in such way at a small distance in from of the meter that it fills major part of the metering field of the metering cell of the light meter
    (That metering field varies between meter and meter, and brand and brand, more on that eg here
    Gossen Lunasix3 System exposure meter user manual, instruction booklet )
    b) Aim the card in the direction of the (main) light, eg the sun, take a reading with the light meter and write the result down.
    c) Then take a second reading with the grey card turned away from the main light (sun), i.e. toward the shadow side of your subject.
    d) Then compare the two readings, and calculate an average between the two, keeping in mind what film you use.

    Example;
    Landscape :
    - sunny side (in the picture eg top of the trees) 100ASA f16 1/500th
    - shadow side (in the shadow under the canopy of the trees) f4 1/250
    In order to avoid camera shake you decide to shoot at 1/500th
    In order to be able tocompare both readings, your readings first have to have the same starting point(s) so they can be compared directy one with the other
    Both readings are at 100ASA, but one at 1/500, the 2nd at 1/250th
    To be able to make the direct comparison, recalculate the readings as if based on the same starting data
    in other words convert the reading at 1/250th as if based on 1/500th

    As 1/500th is half the time of 1/250th , so the aperture found at 1/250th will have to be opened 1 stop to
    maintain the same exposure (get the same amount of light to properly expose the film) when using 1/500th
    So f4 at 1/250th becomes f2.8 at 1/500th

    Difference between the two readings now is f16 for the sunny side and f2.8 for the shadows
    = 5 stops (f16-f11-f8-f5.6-f4-f2.8)
    Ideally f5.6 (at 1/500th) would be the perfect average
    However, when shooting negative film, better over expose a bit (maybe f4.5), and similarly with positive film, underexpose a bit (maybe f7.2?)
    although there unfortunately is no rule of fist you can apply on whatever brand of film (of the same type) you use.

    That the reason why in the 'old' days Polaroid was so extensively used: to get an indication what result the final exposure would give and maybe, based on experience with the specific film used and result wanted, maybe make small modifications in the exposure settings.
    And, especiallly when shooting subjects which could be left standing in the same position under the same lighting conditions. like product or landscape, a series of shots would be taken with slightly modidfied exposure settings would be taken to have a number of shots to select the 'best' one amongst them (similar to the 'bracketing' option many modern digital camera's offer)

    Unlike digital sensors from the same brand for the same camera, each specific type of film (not only positive or negative, but also brand, high vs low ASA, and depending on the age and batch number, even within the same brand , sensitivity and type of film) has it own charateristics.
    A film is made in batches, made at possibly different times (you eg can see that by comparing the expration date on the film boxes) and in the time between its manufacturing and expiration date will 'ripen' (much like chees or wine) and develop a specific charateristic/look
    This means a (very) specific type film manufactured in eg 2011 will risk giving completely different 'results/colors' then the 'same' film manufactured only last year
    That eg was the reason why in the past (in particular) product photographers would test a certain film,, and when the liked the result, buy a large stock of the same btach they would then put in the refrigurator to be sure to have the same film (and get the same results) for the coming months (or even years)
    And yes, when that private stock ran out, a new series of test would have to be made with a new fim, and a new stock would have to be bought and put in the freezer

    So IMO using a grey card is not an option for 'quick and dirty' shooting, eg when shooting an event or casual portraits
    An alternative in those situations would be to rely on the camera's TTL metering, or when using a hand held meter work in Incident mode
    The latter metering method in real world situation means
    - stand in the postion of the subject,
    - place the white dome over the metering cell,
    - aim the light meter in the direction where you will be standing with the camera
    - Similar to using the grey card take a reading on the 'sunny' side and a different one on the 'shadows' (quick and dirty: take a reading with the dome aimed at the 'camera' allowing the sun to hit it, and a 2nd one shielding the dome from beingg directly hit by the sun with one hand)
    - calculate an average (keeping in mind what type of film you use

    As far as your question on clor and b/w is concerned, he grey card is/was originally intended for 'just' metering the light, both for b/w of color
    But contrary to the modern time abuse of it for that purpose, it never was intended for color calibration
    Back in the film shooting days, one would for that purpose add a color chart like eg the X Rite color checker Classic Card (Kodak had its own, I still have my Agfa one) in one picture, to be able to find the 'correct' color (settings on the enlarger) when making a/the final print
    After all, unlike what many modern 'purists' think and claim, similar to modern digital post processing, back in the film shooting days a lot of tinkering was done in the darkroom to get the 'perfect' prints (although nothing resembing the degree of unnatural cloning, pasting and layering that can unfortunately too often be seen many modern digital images)

    Personally, although I have several Gossen meters lying around I bought in the 80's and used extensively in those days, I hardly ever use them anymore nowadays.
    II find the Matrix TTL metering on my Nikon DSLR's quite reliable most of the time especially when shooting under constantly changing lighting conditions
    In my 35+ year experience in photography, under those circumstances 100% perfect metering is never possible, neither with a camera's TTL metering or with a handheld light meter all the time, an occasional failure is a simple fact of life
    As a safeguard, I always have Control Image option turned on so I from the corner of my eye can get an impression what the picture looks like exposure wise (and possbily make some modifications on the fly) immediately after I take it without interrupting the shoot for 'chimping'
    I only use the 'flash' option when I shoot with strobes in the studio to be able to exactly determine the contrast between the different lights used
     
    Last edited: Dec 28, 2017
  3. You use the 18% gray card with the reflective light meter to simulate a reading from an incident light meter. Putting the card at the subject, face straight on to the camera to simulate a reading with a flat diffuser on the incident light. This is good for flat subject like copying a painting. Outdoor and with 3 dimensional subjects tilt the card up a bit toward the light to simulate a reading of an incident light meter with the sphere receptor.
     
  4. SCL

    SCL

    Excerpts from the instructions for kodak's gray cards:
    1. if the camera/ light meter is facing he subject, place the card about 6 inches away from the meter in the same light as the subject so there are no shadows on it and aim the card about 10-30 degrees skewed between the angle of the subject and the main light. The readings should be manually adjusted as follows:
    - For subjects with normal reflectance, increase exposure by 1/2 stop;
    - For light subjects use the indicated exposure, for very light subjects decrease exposure by 1/2 stop
    - For dark to very dark subjects increase indicated exposure by 1-1 1/2 stops
    2. Bracket exposures
    3. The instructions are much more detailed, but this should give you the basics. The instructions go on to explain how to use the white side of the card in low light situations. This is why I really prefer to use an incident light meter in most circumstances. Of course, with B&W film latitude, in my opinion, you can just use the meter reading directly and make the minor adjustments in the post processing printing process.
     
  5. Ok not enough information Camera Nikon F standard Prism Film Kodak plus 200 ASA
    Gossen Luna Pro F Light Meter also Gold Crest Photo-Cell No Battery. And indoors without Flash
    Hope this helps.
     
  6. Indoors Nikon f=1:2.8 Lens
     
  7. Indoors Nikon f=1:2.8 Lens
     

  8. Paul, I've been involved with extensive testing of several specific Kodak pro color neg films - VPSII, VPSIII, and Portra 160NC - over the years, and virtually never found any significant changes. No "ripening" effects at all, and any difference between emulsions was a rarity. These were well-controlled sensitometric tests with MANY test wedges over a range of different emulsions

    I used to buy in to these same explanations until actually doing the tests. (After this I never trusted any of the magazines again, with respect to anything they said about film variability or processing.)

    I think it's likely that amateur films will have more variation between emulsions, etc., but I don't know for sure.

    Of course, this doesn't really have much to do with metering.
     
  9. "Do I put Grey Card in front of Meter?"

    - Yes, that's all that's needed.

    Simply put the grey card where the subject is and take a reflected reading from it. The card needs to fill the field of the meter, which usually means putting the meter about a foot away from the card, while not shadowing it obviously.

    It's a lot easier to use the incident mode of your meter, if it has one.
     
  10. Hi, there's been a lot said about how to do the metering. One thing that I'll add is that you will more than likely have problems with indoor lighting and the color film. Modern color neg films are color balanced film for "daylight," and most of the indoor lighting does not meet this. There is no single simple answer to this, aside from either using flash or making test exposures ahead of time. (Since your meter has an 'F' in the name it can probably take flash readings, but I don't know details.)

    An experienced pro should understand the characteristics of the existing (indoor) light sources, and be able to judge how to deal with them. (This might be using a color balancing filter on the camera lens, etc.)
     
  11. The 18% is the reflectance of an average scene, and the assumption in making reflected light meters.

    You want the card to have similar lighting to the subject, and for the meter area not to be larger than the card.
     
  12. I see the Lunar Pro F has an incident dome. Why not just use that and forget the grey card?
    Grey cards can be subject to fading or getting dirty over time.

    Or you can use two fresh sheets of white copier paper and adjust the exposure by +2.5 EV. - Why two sheets of paper? Because most copier paper is semi-translucent and using a double sheet gives a reflectance closer to 100%.
     
  13. Copier paper rarely exceed 90% reflectance.
     
  14. Redo_Joe
    I see the Lunar Pro F has an incident dome. Why not just use that and forget the Grey card?
    Grey cards can be subject to fading or getting dirty over time.
    Would a Variable Angle Attachment for the Luna Pro F help or would that be a waist of Money?
     
  15. miss.annette_leigh_haynes said:
    Ok not enough information Camera Nikon F standard Prism Film Kodak plus 200 ASA
    Gossen Luna Pro F Light Meter also Gold Crest Photo-Cell No Battery. And indoors without Flash
    Hope this helps
    .

    Indoors Nikon f=1:2.8 Lens

    I'm a bit at a loss here
    The choice/type of camera, lens and brand of lightmeter is completely irrelevant for the (correct) use using a lightmeter in reflective mode with a grey card
    (I have a F2 with standard, non meter, prism, and Lunasix F lightmeter myself so am not unfamilair with your equipment)

    Whatever the type camera (35mm, medium format, large format), the meter will in all cases, independent of the camera used, register/meter the amount of light reflected by the grey card into the metering cell of the lightmeter, and, based on the ISO, gives a range of shutterspeed/aperture combinations which could be used to give a properly exposed image. one of which would then have then picked, and then dialed in on the/whatever camera and lens used

    Note : For simplicity sake I won't go into the extra calculations which would have to be madet when using
    bellows on eg a large format camera, or the reprocity factor that comes into account with extreme long exposure times

    However based on the technical info given so far, I can already say that given the relative low ISO of the film (Kodak Plus X ISO 125 pushed to ISO 200?), and the 'slowness' of the lens (f2.8) used, ypu will no matter have a hard time getting a well exposed image when shooting indoors, in particular when you want to use a shutterspeed fast enough to shoot handheld.

    That even will become worse if you are shooting indoors with just 'standard' livingroom lights, or Christmas lights.
    The light under those conditions is 'dim' at best, and for hand held shooting require a film of at least ISO 400 (better ISO 800) and a faster lens (ideally f1.4) to be able to use a shutterspeed of 1/60th or faster
    And I'm not even talking about the contrast between the highlights and shadows you would run into under such conditions

    I think you best explain what the issue is you ran into so far, possibly with an example of a failed shot if you have made any so far
     
    Last edited: Dec 29, 2017
  16. Dear Confused let me try and clear things up for you and others!
    The reason for this post was there was so much talk about Grey cards I wanted to see if it would help my pictures and would be worth spending the money for them my Pictures are coming out good haven’t shot any in about a year trying out new Film Kodak Plus 200 I have only shot about 5 want to put this Film to the test I have 4 more rolls to go.
    Rodeo_Joe said
    (-- I see the Lunar Pro F has an incident dome. Why not just use that and forget the Grey card?
    Grey cards can be subject to fading or getting dirty over time.-- )
    Question would a Variable Angle Attachment for the Luna Pro F help or would that be a waist of Money?
     
  17. I'm with Joe, use an incident reading and forget about the grey card. If you want a reflected, or spot, reading, use an app like Pocket Light Meter for your phone. I use it and is pretty close to my Sekonic L758DR.
     
  18. "Copier paper rarely exceed 90% reflectance."

    - Where do you get that information from Bebu? Because I'm pretty sure you're wrong, but it doesn't really matter anyway, since it's a 10% error at most, and photographically insignificant. It would be comparable to a grey card having 16.2% reflectance instead of 18% - an error of all of 1/8th of a stop.

    "Would a Variable Angle Attachment for the Luna Pro F help or would that be a waist of Money?"

    If such a device exists, it won't help at all. Just push the incident dome across the sensor of your Lunar Pro and point it back towards the camera from the subject position. No need for a grey card at all, unless you're trying to do sensitometry testing on your film.
     
    Last edited: Dec 31, 2017
  19. Agreed. If one has an incident meter, it seems pointless to use reflected readings off a gray card.
     
  20. I agree that it probably doesn't make too much difference, but BeBu's right - probably about 85 or 86% reflectance for "white" paper.


    BeBu's post #3 gives one specific situation where a gray card is preferable, at least when lacking a flat diffuser for an incident meter. When setting up the lighting for flat copy work a gray card reacts in exactly the same way as the copy subject, so this is preferable to the typically incident meter with a dome over the sensor. Other than this sort of situation I'd also tend to use an incident meter, but knowing that incident readings are not infallible.
     

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