Color temperature and Black and White film

Discussion in 'Large Format' started by neal_shields, Jul 26, 2002.

  1. I understand that different light meters read different parts of the
    spectrum, different films have different spectrical sensitivity
    curves, daylight and reflected light can be all over the temperature
    spectrum and color filters for altering contrast add yet another
    complication.

    A 79 year old friend of mine says that you should use a color
    temperature meter even for black and white photography. I need to
    take the time to go sit down with him and let him explain it further,
    but he still runs a business full time and you never know when you
    will get time to get into detail with him. He used to own the
    authorized Graflex service center locally, so he has seen a few
    cameras and photographers. I have found that he is usually right. (I
    may have mis-understood him, but I don't think so.)

    In the mean time I though I would see what you guys (and gals)
    thought about it. My question is: if all the factors stack up the
    wrong way, how far off do you think color temperature mis-matches
    can effect black and white film? In terms of overall exposure and
    contrast?

    Also, I always put the filter in front of my meter instead of using a
    filter factor, is that a bad habit?

    Neal
     
  2. I always thought a light meter sees only 18% gray, and not different parts of the spectrum. And as far as a color temperature meter is concerned, I can not see the relevance. My color temp meter (which I must admit, I haven't used in many a year, does nothing more than give a specific filtration to acheive either daylight or tungstun, depend on the film I'm using at the time.

    But the "Old Foxes" have alot they can teach the younger generations, so let him explain further, and hopefully you'll be able to pass it on to us.
     
  3. At 79; he probably remembers alot of usage of ortho B&W films; which are/were only blue sensitive...<br><br>Indoor portraits with 3400K Photofloods were the norm long ago.....The spectral output of a 3400K bulb peaks in the red portion ; and has little/low output in the blue region; which was the peak sensitivity to ortho films.....Thus a color temperature meter is standard equipment for hardcore B&W photographers.....<BR><BR>You might ask him whether he prefers a Kalart or a Hugo Meyer..
     
  4. In 1946; Verichrome roll film was ortho film; ie not red sensitive..Its speed was 100 in Daylight; and 50 in Tungsten....; These were also the same film speeds for Super Ortho Press in Film Packs....<BR><BR>In mixed lighting; a color temperature meter allowed one to get a better exposure...
     
  5. There were color temperature meters in 1946?
     
  6. For panchromatic B&W film, color temperature is almost NEVERa problem.
     
  7. I see what you mean...
    Suppose that you have 3 bell peppers a dark green, a red, a bright yellow and a gray card...you meter the gray card as reference and then meter those 3 peppers seperately...(under same lighting condition)...those 3 peppers will give 3 different reading... which one you choose?...well it depends on how you want to render the scene on film... I read a book about this but can't remember it now ... I will let you know if I ever find it... about a filter in front of the meter it's ok (similar to a filter in front of a 35mm camera lens), as long as the filter won't give glare which result in false reading....
     
  8. Taking a meter reading through a filter, instead of using filter factors, can be a bad idea, especially for some of the stronger filters like orange and red. If you were to look at the some of published filter factors on Kodak data sheets, you would see that they can vary quite a bit from film to film, and vary between tungsten and daylight for the same film. TMAX films in particular seem to have different filter factors than other films, which is not surprising since Kodak designed the film to record values as the human eye sees, rather than most other films that usually require a yellow filter for a "normal correction." If published filter factors can vary from film to film, how can a meter know which film you are using to make the proper reading?

    My own experience is that these published filter factors are merely estimates based on average locations. For example when shooting landscapes at altitudes above 7000 feet on a sunny day, I find that orange and red filters need a much higher filter factor than is usually the case at sea level. The relative humidity (and its affect on the sun’s visible wavelength) is probably the main reason for the differences. In theory a meter could measure these differences, but I am not sure how well conventional meters can do this, hence the recommendation for a color balance meter.

    I think it would be more useful and probably more practical to just conduct a series of film speed tests with different films and locations and then make the adjustment manually. This would adjust for any differences in film, filters, and location all at once. I have found that it is necessary to conduct two sets of tests, one in direct sunlight and one in shade, and then use judgment when making the exposure to account for how much shadow detail is needed in the negative.

    Here is quote from the Ilford data sheets on filter factors: "The exposure increase in daylight may vary with the angle of the sun and the time of day. In the late afternoon or the winter months, when daylight contains more red light, green and blue filters may need slightly more exposure than usual. Cameras with through-the-lens metering will usually adjust the exposure automatically when using filters. With some automatic exposure cameras, the correction given for deep red and orange filters can produce negatives under exposed by as much as 1 1/2 stops."
     
  9. A light meter sees 18% gray. The reading is gives is the exposure that would be necessary to render the object that was read, as 18% gray. So if you had 3 bell peppers like in the example above, AND a gray card for "reference", the reading from the gray card would be the correct reading. Especially in a situation where the objects in question were evenly lit.
     
  10. Mike Gudzinowicz has given some nice data on this on usenet
    and the pure silver mailing list. My computer was stolen last
    weekend, and I haven't restored my bookmarks yet, but he
    should be easy to find at google.groups.

    I seem to remember, for example, the Tmax sheet film has
    roughly the same speed for red, green and blue light but has
    different contrast indices. That is, the same exposure is
    required to lift the density above base+fog, but the increase from
    then on is different according to the colour of the light. Useful to
    know if you're photographing red peppers alone.
     
  11. Were talking here like black and white film has the same exposure laditude as Ektachrome. Even if you were able to nail that exposure to within a 1/4 stop of perfection, your developer is going to be either 2° warmer or colder than when you ran your tests, or your methode of agitation is going to be off by just a tad.

    Attain recorded information in your shadows, don't block up the highlights by overdeveloping and you'll be able to create a Fine Print in the darkroom.
     
  12. If you think about it, there is no such thing as white light, or grey light, in the spectrum. Our brain conveys the impression of grey or white light when our eyes detect a balance of red, green, and blue. Our eyes use "cones" to detect those three colors in bright light, and "rods", which are sensitive to all 3 colors, in dim light.

    Similarly, the sensors in a light meter are designed to read all the colors of the spectrum in a balanced way.. hopefully. Some are more balanced than others. Zone VI corrected meters are purportedly more balanced than other meters. None of them will be perfect, but a good one will be very balanced.

    Perhaps your friend was basically alluding to this whole issue, and warning you that meters are not perfect - that they do not always treat all colors "equally".
     
  13. It's not uncommon for B&W movie films to have different ratings for tungsten and daylight, since this is a fairly common issue for cinematographers, so I would suspect the old guy's not off his rocker. This difference is usually on the order of less than half a stop, and many people might just not notice a half stop in B&W, so maybe we don't worry about it too much, but if you're using the zone system and trying to push the film to its limits--getting maximum density in the highlights and keeping shadow detail with good contrast for the printing process--a half stop difference in exposure is quite visible on the negative.
     
  14. Cinematographers have used color temperature meters before WW2. Some of the early models had two variable pots......One would plug the unit in the AC or DC 110 volt wall; and adjust the first pot to normalize the output to say 90 volts; this took out the line voltage problem...Then the other knob was varied until the light Redness & color output of the bulb in the unit matched the color of the suroundings being viewing viewed. Then the Color Temperature of the second knob was read.

    The old color temperature "meter" that I payed with belonged to an old cinematographer who lived in Ventura county California. The meter was made in the 1920's or 1930's; and had the art deco look to it.

    The bulbs in these units have a nominal voltage in the 40 to 70 volt range. Thus with the normalized voltage reference of 90 volts to the pot; one can drive the lamp well above the brightness & redness of existing 3200K color lamps; 3400K Photoflood lamps; and roughly 2400 to 2850K household lamps....A dinky 15W household bulb will have a much lower color temperature than a 200W household bulb.

    Today this method of using a variable voltage hot wire is used to measure the temperature of hot iron ingots....;

    Cinematographers typically use higher end equipment in any given era; because the burn rate in dollars/hour is huge in a movie production..Using the proper tools gives them a better yield...To pay a grand or two for a proper meter is peanuts compared to reshooting a scene again..
     
  15. William Re "Were talking here like black and white film has the same exposure laditude as Ektachrome"<BR><BR>Black And White films such as Kodalith; Old Microfile; and High Contrast copy films have a MUCH narrower exposure than Ektachrome. The Special Kodak Copy films for photographing old photographs has a wider latitude; but still requires alot of care to get a good exposure on a difficult print.<BR><BR>
     
  16. In the sense that very reddish light (say sunset or a light bulb)
    makes the film see as if you have a reddish/yellowish gel on the
    light source an dthat if you have very blue-ish light source then
    your film will respond as if you have a blue filter then yes there is
    an interaction between B&W film and color temperature.<P>Most
    B&W films do not see all colors of the spectrum evenly, most are
    a bit more sensitive to blue light than to red -- this is why a blue
    sky burns out so that you have very seperation between a white
    cloud and a blue sky around it. Some films --the ISO 1600 and
    3200 films-- are actually designed for shooting under standard
    (2700K to 3200K) room lights , which are more reddish than
    daylight or electronic flash which is about 5500K. My source for
    this info is a Kodak tech rep.
     
  17. Kelly, who is currently using Kodalith; Old Microfile; and High Contrast copy films? Am I the only one using "modern films" like Ilford HP5+, Tri-X and Efke?
     
  18. This thread started out with the following statement:

    "A 79 year old friend of mine says that you should use a color temperature meter even for black and white photography."

    This was not a man saying that in order to get the best results from various specialty film, like those used in the Print industry, a color temperature meter would be useful, (that might be was he was alluding to though....Neal will have to meet with him again for more information) but rather a color meter should be used with b&w photography.

    OK, let's hear it, how many of you schlepp your color meter out in the field while shooting your black and white film?

    For that matter, color films certainly have various sensitivity levels, so how many of you alwaays carry a color meter when shooting in daylight? (Not a mixed light or pure tungsten, but pure daylight)

    From what Ihave been reading, I can only assume that there are quite a few out there who do.
     
  19. Neither meters nor film does have an even coverage of the color spectrum, so the idea of using a color temp. meter is not that bad. I guess that "modern" B/W material does have a straighter curve, but that it's still a curve and not a straight line.<br>
    As for meters, the same thing goes there. Several statements says that the meter "sees" 18% grey. I don't think that they "see" 18% grey, or any other gray for that matter. They simply read the light and give you a reading that will render an 18% grey. What they "see" is interesting though, as e.g. the Zone VI modified meter is supposed to be corrected for the fact that the color sensitivity curve for the meter cell differs from the curve of "normal" B/W film.
     
  20. I was the one who said a meter "sees" 18% gray or zoneV. Of course it can't see, it can only telluse how to expose our film so that with normal development proceedures an 18% grey will be made.
     
  21. I'm sorry if anyone feels that I picked upon choice of words. I did in fact use the very same word, as it is "good enough" as a metaphor and that everyone here understands what we mean. I still hope though that the point that I made came through.<br>
    As for filters in front of the meter, I prefer to take a straight meter value and then adjust the value with the filter factor. This is due to the fact of the meter having a different way of "seeing" the colors than film. This is especially important when it comes to red filters, where the difference is more pronounced than with the other colors of the spectrum.
     
  22. William; every bank check was photographed with microfilm cameras up to a few years ago....Kodalith is still used in process cameras; because of it high contrast in making maps...Graphics arts work is about 100% ortho work.......You thrust the 12x18 negative in the tray and watch the image develop....many times ones leaves the negative in longer or shorter because the exposure was not perfect......

    Professional copy films are used to make a QUALITY copy of an existing professional photo print; in which their is no negative still available...These negative films a have different shape of the toe, mid and highlight portions of their characteric curves; than Ilford HP5+, Tri-X and Efke....If you want to turn out Amateur looking copys of existing paper B&W prints; then by all means use the inferior films....The Professional copy films are designed to capture the tonal range of the existing print....Usage of Tri-X in a copying situation yields blocked up highlights and loss of shadow detail........

    When one is copying an valuable rare old map or photo; one cannot afford to ruin it....Many times the darn thing is in pieces; and must be pieced together to make a photo of it...The jig saw puzzle of map peices sometimes must covered with a giant piece of glass.....All the piece are curled like doritos....this is a royal pain...Tape is vorboten many times....The high wattage copy lights will even degrade the old maps...To focus and adjust the polarizing filters; yellow filters, etc we usually have the bulbs only at a fraction of their brightness..Many times with valuable originals stobes are not allowed; and only bulbs with a reduced brightness is allowed.....The map owner may want to be present so we dont ruin his valuable map......

    Thus when the bulbs are at some weird low voltage and alot redder than normal; the exposure gets alot more trial and error..........At say 1200 or 1500 Kelvin there is not much blue light output The Normal ASA of Kodalith is about 6 to 10 the two ratings are for different light sources......With the low Kelvin lighting ; the asa setting on ones meter must be adjusted lower..................We have a chart of Kodalith effective ASA for our incident light meter versus color temperature This is used to get a better first guess when the lights are not at full brightness.........This saves time and money......It takes time to load giant negatives; make the exposures by timing the lights; and develop it in the giant 30x40 trays........One can also change all the many many bulbs out; but this takes time to do; and also realign everything.......

    Typically films; and Sensors are naturally blue sensitive; modern films and sensors are doped to get a pseudo visible light response...Alot of the older sensors had compensating filters to give them a more broader response.........

    Color temperature meters are used in specialized types black and white work; but is ususally not important for panchromatic films used outdoors....

    I will throw away my color temperture meter for special B&W copy work; when everyone posts their VISA card numbers so I can charge the added scrap film and time....
     
  23. Cool down Kelly,

    who said that the origional comment, "you should use a color temperature meter even for black and white photography" had anything to do with copy work or pre-press. And the use of such films is going to be going the way of manual retouching, dupe slides and lead type, if it's not already out the door, and replaced by high end scans.

    You wanna tell me what my Visa number have to do with the question, how many people are actually using a color temperature meter when shooting black and white.
     
  24. Sorry Kelly, I enjoy a good discussion as much as the next guy, and my previous response was out of line, sorry.
     
  25. One interesting thing about color temperature is in black and white printing of photos on an enlarger. Our old Durst 5x7 enlarger had a point light source tungsten bulb; with a variable voltage control knob.

    Since most all black and white photographic materials are ortho **( because b&w papers are ortho) ; varying the voltage to the light source while Projecting back a negative would give screwy results with a enlarger exposure meter

    One could set the 210mm lenses aperture to F11; and then increase the bulbs brightness to make the meter read at say "10 seconds"

    With another less dense negative, one could decrease the bulbs brightness to make the meter read "10 seconds" exposure time for the print..

    The photopaper on the enlargers platen would both receieve the same amount of fractional footcandles; but the color temperature would be alot different...Because the color temperature was way different; the two examples above many times were off 2 to 3 times in exposure; because a low color temperture bulb has little blue light output..

    Since most all B&W photo papers for manual processing is ORTHO ; ie not red sensitive; the print exposure meter was goofy if ones enlargers light source varied in brightness...

    With our 210mm the best aperture was F11. Thus to adjust the print exposure one had only two variables. Either vary the light brightness or vary the exposure time.. Varying the exposure time only; with a fixed light brightness is the better way to go; there is less scrap test prints..( 30 years ago an expert Kodak photo rep sales guy recommended the variable bulb method to us to save paper; looking back he was ignorant of the color temperature problem with ortho films and papers)....The meter and variable bulb was better than a blind guess; but almost never on the money...

    With outside supplied too dense negatives; we used the meter alot more; and varied the light brightness just once for each negative printed. After about one or two test strips we got a good print.With high contrast ortho projection films; there is also a narrow exposure tolerance.

    Later we placed a constant voltage regulator on our black and white enlarger; and rarely used the variable brightness control. In printing many duplicate prints; a varying voltage may cause problems..A 3 to 5% voltage drop due to all the airconditioners being on causes the bulb to vary alot in brightness. The print density varies even more; because the bulb color temperature is also varying. We discovered this while printing some prints at the end of a hot day; and then finishing up the job the next morning. The mornings prints were alot darker; because of the higher voltage; brightness and color temperature; which gave the morning batch more blue light..
     
  26. William; no problem.

    Art summed it up that is almost never a problem the panchromatic films

    Many times someone that is almost 80 may have alot better memory of the old times; versus the current year. My belief is that the old guy is thinking of is speed graphic; film packs; and flashbulbs; and thinking of the 2 to 1 speed difference between daylight to tungsten film speeds. With some of the prewar household 15w and 25 watt bulbs used in houses; the speed difference was about 3 to 1 ..ie tungsten was 1/3 the weston speed.

    My prewar and early post war Kodak books cover this color temperature effect of film speed on ortho films in several paragraphs.

    The reason old people are really concerned about lights being left on; is that electrity was very expense back then.One of my 1920 electrical books goes into a house wired with a whopping THREE 6 amp 110 volt circuits! ; the electrical code was set to a maximum of 6 amps per circuit then .(that is where the magic 660 watts comes from on many older electrical sockets and items) The entire 1920 house electrical design has mostly one or two 10 or 15 watt bulbs per room; with a monster 25 watter in the living room! One 660 watt circuit was for the Kitchen.. The average price for electricity then was 10 cents per kilowatt hour in the early 1920's ; today here it is about 8.5 cents....Thus electricity in 1920 was real expense compared to ones wages..

    I have some 10 watt edison base bulbs in an ancient 8x10 contact printer...These bulbs are not all that white..; and probably have a rather low color temperature...

    When the bulb voltage is real real low; it is so red that it can be used almost as a safelight! ..
     
  27. This seems to have mutated into another 'why bother' thread. I'll
    confess that the people I know who really care about this effect
    with modern pictorial films are all astrophotographers who want
    to get the relative brightnesses of their stars correct, or at least,
    wrong by a known amount.

    That said, I think it is significant that a red filter will make a
    normally exposed scene look like you gave it N-1 development,
    even if you used the correct filter factor. With Tmax and its long
    straight line that's not a big deal, but with some of the more
    classic s-curve films you could end up with a very different tonal
    distribution to what you were aiming for. If you miss putting the
    highlights on the shoulder and compress the midtones too
    much, you are going to need a lot more darkroom wizardry to
    make a good print than if you had simply increased development
    a bit.
     
  28. Struan; <BR><BR>Maybe my longterm dealing with astrophography has me fired up about this thread!<BR><BR>
     

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