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spot metering confusion


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#1 dee

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Posted 04 August 2005 - 06:56 PM

hello everyone,

I used to do still photography a lot, and just recently got dragged into motion picture, which i find more fascinating and confusing at the same time.

anyhow, i'll jump straight to the point.

still films has a lot less latitude that film for sure. it is only +2 stops to get white with detail and -2 stops to get black with detail. outside those 5 stops exposure latitude, you will get nothing but pure black or white without detail.

so, if I am using a spot meter to measure a white with detail object --let's say, a fabric--, i spot it, and overexpose it by 2 stops so it is +2 exposure which is white with detail.

I'm sure it works the same way with motion picture film, but the problem is it has more latitude! maybe 3/4 stops over expose to take it to white ith detail. so it raises the question: should I overexpose it by 3/4 stops to get white with detail?

Then i made a little test with my gray card and meter. I spot both the gray side and the white side, and the meter told me 2 stops difference.. OMG i'm confused, so this raises another question: does the meter I have only calibrated for still photography purposes? because if I'm using a motion picture film, it should show more than 2 stops exposure difference, right?

I don't know if you guys are following me this far.

the only purpose i ask this is spot metering maybe crucial sometimes, especially when you want an EXACT tonality for a reflection on specular object --e.g. a black car--

help...
Dee
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#2 oscar jimenez

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Posted 04 August 2005 - 08:53 PM

Hi, a meter is calibrated for exposure, wether still or motion picture film. <i f you are shootind slides, shure they are more contrasty, near more in the textural range of zone system that is z 3 to z 8, and may be related to the exposure time in seconds. <motion film is negative, and may be suited for working on the dynanic range of zone system that is z 2 to z 9 or even 10. But regardless of medium, a metering is a metering, keep in mind that normal real time recording in film being 24 fps, would be equivalent to 1/50 of a second. and for other speeds at 180 degree shutter, you can use this formulae 1/ 2x FPS so therefore, if you have your cam running at 24 fps, then 1/2x24 fps= 1/48th of a second. And yes, the spot meter will always tell you 2 stops or over when reading withe or neutral gray, the meter doesnt know what it is, it is just telling you that is taking that value to zone 5. Wether gray, black or withe, you decide your placement in the scale.
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#3 Chris Keth

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Posted 04 August 2005 - 09:40 PM

hello everyone,

I used to do still photography a lot, and just recently got dragged into motion picture, which i find more fascinating and confusing at the same time.

anyhow, i'll jump straight to the point.

still films has a lot less latitude that film for sure. it is only +2 stops to get white with detail and -2 stops to get black with detail. outside those 5 stops exposure latitude, you will get nothing but pure black or white without detail.

so, if I am using a spot meter to measure a white with detail object --let's say, a fabric--, i spot it, and overexpose it by 2 stops so it is +2 exposure which is white with detail.

I'm sure it works the same way with motion picture film, but the problem is it has more latitude! maybe 3/4 stops over expose to take it to white ith detail. so it raises the question: should I overexpose it by 3/4 stops to get white with detail?

Then i made a little test with my gray card and meter. I spot both the gray side and the white side, and the meter told me 2 stops difference.. OMG i'm confused, so this raises another question: does the meter I have only calibrated for still photography purposes? because if I'm using a motion picture film, it should show more than 2 stops exposure difference, right?

I don't know if you guys are following me this far.

the only purpose i ask this is spot metering maybe crucial sometimes, especially when you want an EXACT tonality for a reflection on specular object --e.g. a black car--

help...
Dee

<{POST_SNAPBACK}>


Your exposure ideas seem about right for black and white reversal, have you never shot negative film before? Still film and motion picture film are essentially the same thing, except for some differences in the base and certain lubricants that exist on motion film that still film lacks. There's not a fundamental difference in emulsions, really. Get some color negative still film and see what I mean. You can easily get a 10 stop range from paper-base-white to the paper's D-Max black, if not more in some cases.
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#4 dee

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Posted 05 August 2005 - 09:17 PM

Hi all,

thanks for the advice!!
spot meter brings everything to zone 5..that's what i have to remember.. shoot.. i forgot the very basic of it..
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#5 dee

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Posted 05 August 2005 - 09:22 PM

Your exposure ideas seem about right for black and white reversal, have you never shot negative film before? Still film and motion picture film are essentially the same thing, except for some differences in the base and certain lubricants that exist on motion film that still film lacks. There's not a fundamental difference in emulsions, really. Get some color negative still film and see what I mean. You can easily get a 10 stop range from paper-base-white to the paper's D-Max black, if not more in some cases.

<{POST_SNAPBACK}>


hmmm interesting comment....
I have used some BnW film, some negatives, as well as some slides..
I'm still pretty positive that even still negative has a more limited exposure range, about 5 stops for the final print or file.
the first time I shot motion picture film, i did not realize that it has such a great latitute; I shot it with still film ratio. of course everything turned out damn flat.

I did a little grey card test with all the film i've used and motion picture film is the craziest...
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#6 oscar jimenez

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Posted 06 August 2005 - 11:24 AM

I guess it all depends on the kind of imagery your after, a good test should be with even lightning, to take shots of a gray card for zone 5 and take it up to 10 and zone 2 also, try to do this with a calibrated color chart, such as mcbeth or kodak color chart, color reflectance and rendering may be a little tricky at first, after some practice youll learn to identify by eye the place that every color should properly 'fall' /normally / in your scale, unless you want something different, but that comes after experiencing. i do like to use slide film for tests, i learn to be more careful on exposure and light control. iI love slide contrast.
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#7 Greg Gross

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Posted 08 August 2005 - 11:49 AM

Hello Dee,

Why don't you do some film tests to check your results? I assume you'll be
looking at 200 ASA, 500ASA. You could do some film tests and even change
your rated ASA to see what results you get. What will you do some day if no
spotmeter or spectra 4 is available. If you ever come across a book entitled
"Reflections" check out the section on film tests. I'm not sure if you are just
talking about b&w or b&w and color also? You can use color zone system also.
Generally you want to overexpose color film a little. I am an independent film-
maker at the age of 57 years. I am not an expert,have been a long time pro-
fessional photographer and medical professional. I will always consider my-
self a student cinematographer as I'm continually learning. Remember if you
change the lens you are using,change camera,change lab,then all of your zone
tests become invalid. The things to keep in mind are 1.light source,2.light in-
tensity,3.light quality. Try holding your hands in the light you are using and
look at the apperance of the light on your skin. Try to remember and visualize
the lights that you set. Pretty soon you will have a catalog of light in your mind.
You can then call these situations up and visualize the look you wish to achieve.
Lets say that your key light is 30ft. away from your actor and its a 5K light. If
you set the light 18ft. away from your actor the light will be more intense. If
you set the light 40ft away from your actor the light will be less intense. Hope
I have stimulated your thinking a little bit. Suppose you have a sheet behind
the camera with two 2K's and this is your fill light. Then we are filling shadows
created by the 5K key. Then you want to visualize and catalog in your mind the
look of this lighting. Happy shooting Dee!


Greg Gross
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#8 Manu Anand

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Posted 08 August 2005 - 02:37 PM

the only purpose i ask this is spot metering maybe crucial sometimes, especially when you want an EXACT tonality for a reflection on specular object --e.g. a black car--

help...
Dee

<{POST_SNAPBACK}>


Hello Dee

Dont Forget to check the calibration of your spot meter.. Reflected meters contrary to popular beleif are not calibrated for 18 % gray.

Sekonics i think are calibrated for 12.5 %....
Spectras i think are the only ones calibrated at 18% but i may be wrong.

While shooting slides this half a stop difference matters a lot ..but not so much while shooting negatives..

But since you said "Exact tonality" check your meter calibration and make the appropriate adjustment.

Manu Anand
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#9 Manu Anand

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Posted 08 August 2005 - 02:51 PM

For some reason i was unable to edit my last message

but heres a link that explains this better

12.3 %

Manu Anand
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#10 dee

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Posted 11 August 2005 - 03:36 PM

thanks..
i will do a test... and..

I heard that it's not that the meter is not calibrated to 18% grey.. but the actual middle grey is not 18%.. it's about 13% ?
I'm not sure.. but that has not really brought me any problem so far... maybe 1/3 of a stop on EI?
I usually do an EI test to any film i'm going to shoot anyway..so my meter should be calibrated to it.
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#11 orgjava

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Posted 19 August 2005 - 11:14 PM

hi..all

i'm interesting with this topic (how to use spotmeter corectly) is it true when we use spot meter for reading w'll get corectly color reproduction..?

help
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#12 Paul Bruening

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Posted 21 August 2005 - 01:24 PM

Hey orgjava,

All meters except a color meter only read the intensity of light, whether it be in luxes, footcandles, or an f-stop read-out. Only a color meter can assess color. Most folks just learn and manage their color by knowing the kelvins of their lights,taking into consideration the color of reflecting surfaces, and some basics of how the sun changes color through the day. Sloppy as that sounds, it has served DP's since the advent of color film. Minolta makes a dynamite color meter for around $850.00. I'd love to have one. But, frankly, I've done just fine without it, so far.
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#13 Paul Bruening

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Posted 21 August 2005 - 01:30 PM

... as far as the calibration thing: I've seen five guys stand together and get as much as 3.5 stops variation between their meters. It's funny to see them look up at each other trying to decide who's meter is the most acurate. There's that "oh, crap" moment on all their faces that just tickles me.
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Aerial Filmworks

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