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What's about b7w film stock?


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#1 Alex Fuchs

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Posted 11 May 2005 - 03:53 AM

Maybe my question is stupid, but is b/w-film stock sensibilized for tungsten or daylight? What's about the colour temperature? Do I use daylight/tungsten-filters?
Greetings Alex
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#2 Kevin Zanit

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Posted 11 May 2005 - 04:10 AM

B&W films are somewhat more sensitive to blue light. Thus when shooting outside (or with daylight as a source) one should rate the stock (as suggested by Kodak) faster than when it is in tungsten.

I have used this property to my advantage when I was shooting some B&W tungsten interiors. I needed a little extra stop from one of my units so I switched it to a daylight balanced source (specifically from tungsten Kino to daylight).

Filters for color work do not react in the same way as in b&w. Filtration in b&w is an art form. Do a search, and also look at some photography books that discuss b&w work. For example, a dark red filter will render blue skies nearly black, and with very distinguished clouds.


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#3 Alex Fuchs

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Posted 11 May 2005 - 04:30 AM

Thanks Kevin,

but what is with 85-Filters or 80 Filters. I don't need them when I shot b&w film stock, am I right?
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#4 Mike Williamson

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Posted 11 May 2005 - 07:38 AM

No, you won't need the 85 or 80 filters, just follow the two different speed ratings on the can: one for tungsten, one for daylight. Black and white stocks are faster in daylight because, as Kevin mentions, they are slightly more sensitive to the blue end of the spectrum.

Remember that the film is going to take all the color you put in front of the lens and turn it into varying shades of grey. You can't balance color that's not being reproduced.
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#5 L K Keerthi Basu

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Posted 11 May 2005 - 11:53 AM

Dear friend,

As others told, color films contain color couplers which are reponsible for the reproduction of color in film. So the color temperature and conversion filters are needed for the balancing for particular emulsion. When it is a black and white emulsion only picture negative and some sound negatives are panchromatic so that they are sensitive to all colors of the visible spectrum. The sensitivity of the any black and white emulsion is extended by the addtion of sensitisers to the silver halides. So there is no need to put a conversion filters for the black and white emulsions. Color temperature does not play a vital role in the B/W photography. But filters like RED, YELLOW AND ORANGE will increase darkness in the SKY and look very dramatic this reproduction depend upon the density of the filter used.
http://www.wolfes.co...ilters/B&W.html
http://www.ephotozin...e.cfm?recid=284

L.K.Keerthibasu
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#6 John Pytlak RIP

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Posted 11 May 2005 - 12:22 PM

Maybe my question is stupid, but is b/w-film stock sensibilized for  tungsten or daylight? What's about the colour temperature? Do I use daylight/tungsten-filters?
Greetings Alex

<{POST_SNAPBACK}>


As others have noted, a "Panchromatic" B&W film is sensitive to the entire visible spectrum, but typically does have a bit more sensitivity in the blue-green portion of the spectrum, so it usually is about 1/3 stop faster for blue-rich daylight or arc sources than red-rich tungsten lighting.


No correction filter is needed, but colored filters can be used to enhance certain colors (e.g., a red filter will really accentuate white clouds against a cyan sky).

Here is the spectral sensitivity of a typical B&W panchromatic film:

Posted Image
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#7 Alex Fuchs

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Posted 11 May 2005 - 03:34 PM

Thank you guys, but there is still one thing what I don't understand. E.g. I have here a cartridge of a KODAK plus-X reversal film 7276 (standard S8 film stock). On the box is the notice:
daylight (with filter) EI32/16
tungsten (without filter): EI40/17.
In my eyes it means, that this stock is slower by daylight or am I wrong? And what sort of filter they are talking about? Maybe somebody (maybe Mr. Pytlak) can explain it to me. (Sorry for my bad english!)
Greetings Alex
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#8 John Pytlak RIP

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Posted 11 May 2005 - 03:49 PM

Thank you guys, but there is still one thing what I don't understand.  E.g. I have here a cartridge of a KODAK plus-X reversal film 7276 (standard S8 film stock). On the box is the notice:
daylight (with filter) EI32/16
tungsten (without filter): EI40/17.
In my eyes it means, that this stock is slower by daylight or am I wrong? And what sort of filter they are talking about? Maybe somebody (maybe Mr. Pytlak) can explain it to me. (Sorry for my bad english!)
Greetings Alex

<{POST_SNAPBACK}>


Here is the techical data for EASTMAN Plus-X Reversal Film 7276 posted on the Kodak website:

http://www.kodak.com....4.8.12.4&lc=en

Exposure Index/DIN
Daylight-50/18

Tungsten (3200 K)-40/17

Use these exposure indexes with incident- or reflected-light exposure meters and cameras marked for ISO or ASA speeds or exposure indexes.

These indexes apply for meter readings of average subjects made from the camera position or for readings made from a gray card of 18-percent reflectance held close to and in front of the subject. For unusually light- or dark-colored subjects, decrease or increase the exposure indicated by the meter accordingly.

When exposing this film in manually operated super 8 cameras (through a KODAK WRATTEN Gelatin Filter No. 85), the effective speed is lowered to 32 for daylight.

In automatic cameras, because of the cartridge speed-and-filter notching system, the film will be exposed as follows:

Daylight (with filter)-25/15

Tungsten (without filter)-40/17
The film latitude will provide satisfactory results at these exposure levels.



The SMPTE Standard for Super-8 cartridge notching to communicate film EI and fiter only allows certain combinations.
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#9 Alex Fuchs

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Posted 11 May 2005 - 04:07 PM

Dear Mr. Pytlak,
thak you for the fast answer. Now I got it. But there is one more question (it has nothing to do with film stock but I want to know):
How does interior super8mm lightmeters work? There is quite a difference to my referenced external lightmeter? I keep in mind, that there is a reason, why the super8mm lightmeters-apperature row only seems to be so but I can not remind where I read it? Maybe you can help me.
Thanks a 1000 times
Alex
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#10 David Mullen ASC

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Posted 11 May 2005 - 05:44 PM

The meter in the camera would be a reflective meter (like a spot meter but probably not so narrow) -- your external meter is either an incident meter or a spot meter.

The internal meter, being reflective, is affected by scene brightness, just like the meter in a video camera -- so it can be fooled, like when panning past a bright window, which is why it's always good to be in manual exposure mode.

You can use a gray card and zoom in on it if you want to get more accurate readings under controlled lighting rather than an average reading.

The only question is how your camera's meter knows what ASA value you want to use; most Super-8 cameras read a notch on the side of the cassette that corresponds to some preset values like 40 ASA or 160 ASA. I don't know how many values there are or if all cameras can adjust for all of them. I think some high-end Super-8 cameras allowed you to select the ASA value on a dial.

I found the meter of my old Sankyo XL camera to be fairly reliable, by the way. I usually zoomed in on what I wanted to be correctly exposed, got the reading, and adjusted the exposure manually from there to compensate if necessary (for light or dark-toned subjects.)

The simplest thing is to shoot some tests and see if the results look accurately exposed, and compare your camera's reading to your own external meter.
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#11 Alex Fuchs

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Posted 12 May 2005 - 04:19 AM

Thanks a lot David,
by the way: I'm not so long on the board here, but you, Mr. Pytlak, Kevin and a lot of other dudes are so kindly in answering questions from a lot of unexperienced dudes like me. I would say thank you a 1000 times for that, dudes.
It's not High Definition but High Niveau :-)
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#12 serge

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Posted 31 August 2005 - 02:06 PM

Thank you guys, but there is still one thing what I don't understand.  E.g. I have here a cartridge of a KODAK plus-X reversal film 7276 (standard S8 film stock). On the box is the notice:
daylight (with filter) EI32/16
tungsten (without filter): EI40/17.
In my eyes it means, that this stock is slower by daylight or am I wrong? And what sort of filter they are talking about? Maybe somebody (maybe Mr. Pytlak) can explain it to me. (Sorry for my bad english!)
Greetings Alex

<{POST_SNAPBACK}>



It may be much too late to come in with this posting, but I have come upon this thread and wanted to clarify my confusion. The originator of this thread seems to be talking about super 8 PLUS-X Reversal Film 7276. This posting may well belong in the super 8 section of this forum, but if any of the pros should want to answer it here, it would be most kind of them. PLUS-X Reversal Film 7276 is rated: Daylight-50/18 Tungsten (3200 K)-40/17

this information is here:

http://www.kodak.com....12.4&lc=en#H05

Plus-X film is said to be balanced for daylight, and the filter notch (actually, the absence of notch) in the cartridge removes the 85A filter found in most super8 cameras. The change in the film speed between daylight and tungsten seems to be not a function of the filter, but of the light itself. If B&W film is more sensitive to the blue end of the spectrum, then it makes sense that in daylight it would be slightly faster than in tungsten (nothing to do with filters). The technical data sheet for this film goes on to say that if the film is exposed in daylight with an 85 filter, the film speed will drop to ASA 32. This goes for manual cameras, where the filter is set manually, that is the cartidge will not remove or set the filter automatically. Am I right in my understanding of the mechanics so far?

And why would you want to shoot daylight balanced B&W film in daylight with a color correction filter?

Also, why does Kodak have a different film stock (Plus-X 7265) listed in their super-8 portfolio?
http://www.kodak.com....4.10.4.4&lc=en

Now, I would like to extend my musing into color reversal films:

Both Kodachrome and Ektachrome super 8 film stocks are said to be balanced for tungsten. They are rated:

Kodachrome ASA 40/25

Ektachrome ASA 125/80

This means, I gather, that in tungsten lighting they will have their respective speeds 40 and 125 without a color correction filter in place. However, the filter notch on the cartridge (for both films) leaves the color correction filter in place. Why? Perhaps people at Kodak assume that the amateur filmmaker will not be using these films under studio lights, but outdoors. In manual cameras this, of course, does not matter; but in automatic cameras the film is set to be used outdoors, in daylight. Then, with the filter in place, the respective ratings are: Kodachrome 25 and Ektachrome 80.

So now, it seems that the Daylight/Tungsten rating difference in color reversal films is a mechanical matter -- filter takes away some of the light. but in B&W films, the difference in the rating is a chemical matter -- the film chemicals are more sensitive to the blue end of the spectrum -- nothing to do with filters.

Please let me know if all or any of this is correct. I must apologize for the article length of this posting, or for its possible misplacement in the forum subsections. But the strange vagueness with which exposure index for super 8 film is handled on various forums, and the effort i expended in puzzling out these matters for myself, prompted me to submit this overweight posting.

regards

s

Edited by serge, 31 August 2005 - 02:08 PM.

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#13 John Pytlak RIP

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Posted 31 August 2005 - 03:10 PM

The technical data for 7276 gave a speed of EI-50 for daylight, and EI-40 for tungsten illumination:

http://www.kodak.com....4.8.12.4&lc=en

So for this panchromatic film, the film is slightly more sensitive in daylight.

No correction filter is normally needed for color temperature differences.

The cartridge notching is per the specifications in standard SMPTE 166.

Many Super-8 consumer cameras had a slot where when the tungsten light was inserted, the orange filter was moved out of the optical path. They assumed if the slot was empty, the camera was being used in daylight.
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