Light meter calibration

[macfred]

Can you say what difference(s) there will be between a meter that reads EV15 and one that reads EV14.7 and how those differences manifest itself ...

No differences for me but there might be other opinions

 

[ic-racer]

This!
--
Does anyone tried to calibrate that fat old sun ??

Again, I believe Steve B. offered up this reference. Jones and Codit argued that since the correct exposure for B&W Neg-Pos processes is determined by shadow exposure, the light from the sky, vs just the sun, is important. In fact they went to lengths to calculate the total light from the sky, as volume density of luminous energy (explained in the paper...50 pages).
This value, as might be expected, is somewhat unpredictable due to latitude, time of day, season and other atmospheric conditions. I think a 'standard candle' would be better calibration standard than the sun.

VOLUME 38, NUMBER 2 FEBRUARY, 1948
Sunlight and Skylight as Determinants of Photographic Exposure.a I. Luminous Density as Determined by Solar Altitude
and Atmospheric Conditions
LOYD A. JONES AND H. R. CONDIT
CommunicationNo. 1155 from the Kodak Research Laboratories,Eastman Kodak Company, Rochester,New York
(Received August 4, 1947)

 

[Nicholas Lindan]

Does anyone tried to calibrate that fat old sun ??

The "Solar Constant:" https://en.wikipedia.org/wiki/Solar_constant About 1.4kW/m^2 in space, 1kW on the earth's surface, and subject of lots of research and head scratching.

The sun isn't old and fat, it's rather young and middlin' small.

 

[Alan Edward Klein]

I use film to calibrate photographic light-meters.

The standard scene outside my house is shot in a series of stepped exposures around late morning on a sunny day where the light won't change for a while.

The film is developed immediately and the best negative, and my exposure notes, tells me the correct camera settings.

Then I go back into the same scene (the light hasn't changed), do my usual metering routine, and adjust the meter's film speed dial until the meter reads out the camera settings I already know are correct.

Calibration done.

The same approach can calibrate a light-meter when there is a developer change, film change, or filter change. I often find the adjusted light-meter's film speed dial is set to about half the ISO box speed.

None of the above is useful for calibrating meters for Luminance in units of Candelas per square meter,or Illuminance in units of Lux but those radiometric parameters tend not to have direct applications in simply taking and making photographs.

That seems OK. But I'm wondering., Aren't you adding in a variable to the light metering, the development process, that could throw it off a little?

 

[BrianShaw]

That seems OK. But I'm wondering., Aren't you adding in a variable to the light metering, the development process, that could throw it off a little?

That logic works both ways… development could potentially add another variable to a scientifically calibrated meter also. The negative (or transparency positive) is the immediate end goal. One needs to accept the fact that neither the meter or shutter/aperture or development may be “perfect”. As long as the sum of the photographic process steps result in an acceptable negative or transparency positive… life is great and a good composition will make photography great again.

 

[faberryman]

After you have calibrated your meter out to nine decimal places, you are still going to have to determine your exposure index and normal development time for each film and developer combination you use.

 

[ic-racer]

There could be a "technical" or "photo electronics" sub forum. One of the popular photography magazines of the 1970s had a regular column on "photo electronics."

 

[btaylor]

I think it is important not to confuse meter calibration with the practical photographic process. What the original post was about is largely an “academic” exercise - for knowledge. Unless a meter is way out of spec, none of this will make a practical difference in the field. There are too many variables.

I say this for two reasons:

1. Unless you are interested in the topic of exposure meter calibration, you don’t need to worry about it.

2. There is nothing wrong with being interested in such things, nor are artistry and technical knowledge mutually exclusive or inversely related. This is a false dichotomy frequently implied or sometimes outright stated by people, presumably to soothe (delude) themselves. I assume it makes them feel more arty.

Nicely put, Michael. One can deal with as much or as little of the technical as one likes. Some people get to where they want to go using a lot of the technical aspects of this medium, others do not. In the end, the final photograph doesn’t care one way or the other!

 

[ic-racer]

The final photograph always follows the laws of physics and chemistry.

 

[MattKing]

I think it is important not to confuse meter calibration with the practical photographic process.

There is a bit of overlap.
I regularly make use of a very rough form of meter calibration check - I mentally check readings against what Sunny 16 tells me.
It is a little bit like musical instruments - if you keep them in tune, and you use the same tuning for all the instruments that play together, they play together well.
For repeatable photographic results, it is really useful to at least understand generally the science behind meter calibration. And if you want to use meters more scientifically, learn and use the science.

 

[Stephen Benskin]

I think it is important not to confuse meter calibration with the practical photographic process. What the original post was about is largely an “academic” exercise - for knowledge. Unless a meter is way out of spec, none of this will make a practical difference in the field. There are too many variables.

I say this for two reasons:

1. Unless you are interested in the topic of exposure meter calibration, you don’t need to worry about it.

2. There is nothing wrong with being interested in such things, nor are artistry and technical knowledge mutually exclusive or inversely related. This is a false dichotomy frequently implied or sometimes outright stated by people, presumably to soothe (delude) themselves. I assume it makes them feel more arty.

Disingenuously conflating two subjects I believe is the logical fallacy of false equivalency. I used to get incredibly frustrated trying to discuss film speed while people would conflate it with exposure. While not completely separate, they are not the same.

 

[BrianShaw]

“Disingenuously”????

 

[Stephen Benskin]

“Disingenuously”????

disingenuously
adverb

1. in a way that is not sincere, especially when you pretend to know less about something than you really do.

How about "dishonestly?"

 

[BrianShaw]

disingenuously
adverb

1. in a way that is not sincere, especially when you pretend to know less about something than you really do.

How about "dishonestly?"

Lol… I know what the word means. But thanks for looking it up in case there might be questions. Are you using it generically or sayin that this discussion is dishonest. I find that a very odd word in this context. I’m not seeing dishonesty and welcome understanding if there is some that I’m just not seeing.

 

[Stephen Benskin]

Lol… I know what the word means. But thanks for looking it up in case there might be questions. Are you using it generically or sayin that this discussion is dishonest. I find that a very odd word in this context. I’m not seeing dishonesty and welcome understanding if there is some that I’m just not seeing.

You could have just said that in the first place. I'm saying that false equivalency (and logical fallacies in general) is a bad debating technique and does not lead to truth. I'm not accusing anyone.

 

[BrianShaw]

You could have just said that in the first place. I'm saying that false equivalency (and logical fallacies in general) is a bad debating technique and does not lead to truth. I'm not accusing anyone.

You could have not used that word and made your point perfectly clear in the first place.

Whether disingenuous or erroneous... I completely agree with you now. Thanks for engaging with me in clarification,

 

[Stephen Benskin]

You could have not used that word and made your point perfectly clear in the first place.

Whether disingenuous or erroneous... I completely agree with you now.

Agreed.

 

[macfred]

The sun isn't old and fat, it's rather young and middlin' small.

Oh, sorry ... I referred to this and took it at face value

 

[Alan Edward Klein]

That logic works both ways… development could potentially add another variable to a scientifically calibrated meter also. The negative (or transparency positive) is the immediate end goal. One needs to accept the fact that neither the meter or shutter/aperture or development may be “perfect”. As long as the sum of the photographic process steps result in an acceptable negative or transparency positive… life is great and a good composition will make photography great again.

But let's say you calibrate your meter to a development process that you change next month to a different developer. Do you recalibrate your meter all over again? Shouldn't the calibration of the meter stand on its own? Otherwise, you'd be changing the meter's calibration constantly depending on what development procedure you use.

 

[Sirius Glass]

That logic works both ways… development could potentially add another variable to a scientifically calibrated meter also. The negative (or transparency positive) is the immediate end goal. One needs to accept the fact that neither the meter or shutter/aperture or development may be “perfect”. As long as the sum of the photographic process steps result in an acceptable negative or transparency positive… life is great and a good composition will make photography great again.

If a change of developer changes the light meter reading/calibration, then there are bigger problems in that person's system.

 

[MattKing]

But let's say you calibrate your meter to a development process that you change next month to a different developer. Do you recalibrate your meter all over again?

That isn't meter calibration, it is process calibration.

 

[Chan Tran]

This!
--
Does anyone tried to calibrate that fat old sun ??

When you buy a calibrated light source you trust that it deliver the luminance that it's supposed to deliver. So the sund l is a calibrate light source and its light intensity is what it is.
(I am not serious about this OK)

 

[Chan Tran]

Can you say what difference(s) there will be between a meter that reads EV15 and one that reads EV14.7 and how those differences manifest itself themselves in terms of what effect on the negative that then translates into the prints i.e. will the two prints show noticeable differences?

Thank
pentaxuser

When you calibrate a micrometer, a ruler you don't ask whether the difference would make in building your house. You calibrate so that the micrometer is accurate to its specification. Meters have resolution of 1/3 stop or 1/10 stop and being accurate to better than 1/3 stop is to be expected. If m'y meter can't do that I rather guess at the exposure.

 

[pentaxuser]

Thanks Chan Tran. My curiosity was aroused as you seemed to make quite a point of Ralph's test of 15 EV and your own of 14.7 and I simply wondered if 0.3 EV made a real, practical difference.

Your reply has answered my curiosity

pentaxuser

 

[RalphLambrecht]

[QUOTE="RalphLambrecht, post: 2460147, mems
My check is EV14.7 ISO100. Which agrees with the Sunny 16 rule and yours does not.

that's only a difference of 1/3 stop and is usually lost in the rounding of the film speed to get to the shutter speed; Our methods are essentially the same.