Light meter calibration

ic-racer

Member
Joined
Feb 25, 2007
Messages
16,544
Location
USA
Format
Multi Format
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).
T
his 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.



 

Nicholas Lindan

Advertiser
Advertiser
Joined
Sep 2, 2006
Messages
4,243
Location
Cleveland, Ohio
Format
Multi Format
Joined
Aug 29, 2017
Messages
9,444
Location
New Jersey formerly NYC
Format
Multi Format
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

Member
Joined
Nov 30, 2005
Messages
16,521
Location
La-la-land
Format
Multi Format
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

Member
Joined
Jun 4, 2016
Messages
6,048
Location
Wherever
Format
Multi Format
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

Member
Joined
Feb 25, 2007
Messages
16,544
Location
USA
Format
Multi Format
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

Subscriber
Joined
Dec 28, 2010
Messages
2,252
Location
Los Angeles
Format
Large Format
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

Member
Joined
Feb 25, 2007
Messages
16,544
Location
USA
Format
Multi Format
The final photograph always follows the laws of physics and chemistry.
 

MattKing

Moderator
Moderator
Joined
Apr 24, 2005
Messages
52,873
Location
Delta, BC Canada
Format
Medium Format
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.
 
Joined
Jan 7, 2005
Messages
2,612
Location
Los Angeles
Format
4x5 Format

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

Member
Joined
Nov 30, 2005
Messages
16,521
Location
La-la-land
Format
Multi Format
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.
 
Joined
Jan 7, 2005
Messages
2,612
Location
Los Angeles
Format
4x5 Format

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.
 
Last edited:

BrianShaw

Member
Joined
Nov 30, 2005
Messages
16,521
Location
La-la-land
Format
Multi Format
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,
 
Joined
Aug 29, 2017
Messages
9,444
Location
New Jersey formerly NYC
Format
Multi Format
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

Subscriber
Joined
Jan 18, 2007
Messages
50,356
Location
Southern California
Format
Multi Format

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

MattKing

Moderator
Moderator
Joined
Apr 24, 2005
Messages
52,873
Location
Delta, BC Canada
Format
Medium Format
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

Subscriber
Joined
May 10, 2006
Messages
6,810
Location
Sachse, TX
Format
35mm
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

Subscriber
Joined
May 10, 2006
Messages
6,810
Location
Sachse, TX
Format
35mm

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

Member
Joined
May 9, 2005
Messages
19,934
Location
Daventry, No
Format
35mm
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

Subscriber
Joined
Sep 19, 2003
Messages
14,644
Location
K,Germany
Format
Medium Format
[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.
 
Cookies are required to use this site. You must accept them to continue using the site. Learn more…