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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 12 Jul 2018 (Thursday) 01:19
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Light metering question for New York guys

 
Wilt
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Jul 13, 2018 16:08 |  #16

Wilt wrote in post #18662077 (external link)
1/4000, f/2.0 + 0.9EV @ 13:30hr PDT, Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk

Proving my point about too much variability to jump to any valid conclusion,
Measured at 14:05 PDT: 1/4000, f/2.0 + 0.8EV , Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk


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Left ­ Handed ­ Brisket
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Jul 13, 2018 16:17 |  #17

13 degrees farther south and less sun?!?! How can it be!?!?!

:D

http://www.hko.gov.hk …du06nature/ele_​srad_e.htm (external link)

Temp differences are largely based in the torch example in that link and hours of daylight each day. Absorption is only a big difference maker at the extreme latitudes and when ground level pollution is significant. Scattered light is scattered everywhere so any light that is scattered is at least in part scattered back to the point of measurement.

Wilt, you forgot the most important part of Lambert's law, the Beer!

http://pages.mtu.edu …/transmission_l​ecture.pdf (external link)

No, I did not read that, but browsing it will give a good idea of the factors other than angle/lat that impact radiation hitting the earth.

Speaking of beer, it's after 5:00 here.

Cheers all.


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Wilt
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Jul 13, 2018 16:23 |  #18

Left Handed Brisket wrote in post #18662092 (external link)
13 degrees farther south and less sun?!?! How can it be!?!?!

:D

You noticed that oddity in the two data samples, did you?!


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Wilt
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Jul 13, 2018 16:26 |  #19

Wilt wrote in post #18662089 (external link)
Proving my point about too much variability to jump to any valid conclusion,
Measured at 14:05 PDT: 1/4000, f/2.0 + 0.8EV , Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk

Sample 3: 1/4000, f/2.0 + 0.9EV @ 14:25hr PDT, Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk

The sun apparently got brighter 20 minutes later in the afternoon..closer to sunset?!


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Left ­ Handed ­ Brisket
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Jul 13, 2018 16:27 |  #20

Wilt wrote in post #18662093 (external link)
You noticed that oddity in the two data samples, did you?!

Indeed.

I wish it wasn't mostly cloudy here or I'd grab my beer and step outside with my meter.


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ZoranC
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Jul 13, 2018 22:46 |  #21

Alveric wrote in post #18661970 (external link)
I get 1/5000 sec. @ 50° 26' N.

Thank you! Looks like you are only person in this thread that didn't feel the need to show how wise he is.




  
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John ­ Sheehy
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Jul 14, 2018 10:01 |  #22

Wilt wrote in post #18661923 (external link)
Pointless! Unless you measure at the same time of year, there can be variances. And on a given day, there may be more/less water vapor or smoke in the air to dispell light. And unless you use the SAME meter in both places, you cannot account for differences in individual meter calibration!

There is also color-specific concerns. The illumination also varies in color balance, even at different latitudes in the same air quality. The green channel in a Bayer digital camera is what is of concern in exposure index, because the green channel is always more sensitive in a Bayer camera, and is what is in the most immediate danger of clipping. The green channel is what the camera targets for ISO exposure index, and the red and blue channels just fall where they do, almost always with less signal in the sensor, under the color filters.

So, a highly green-weighted value of sun strength is actually the most precise for Bayer camera concerns regarding "ISO" and "exposure".

It is a pity that cameras don't do more to guide us in RAW-relevant exposure; as I said in another post in this thread, people are wishing for lower ISO, have them in their cameras, under the hood, and don't use them. Most of the newest cameras are capable of ISO exposure indices down to 64 (Canon) or to 44 or less, at base ISO! What a camera with a saturation-based base ISO of 44 doesn't have is extended highlight headroom, like negative film. It does as well as slide film, though, when you are in control of exposure vs RAW file and don't need headroom insurance.




  
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Left ­ Handed ­ Brisket
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Jul 14, 2018 10:06 |  #23

@ 10:27am 35.7N

Sun's highest point will be 75.91 @ 1:26


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ZoranC
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Jul 14, 2018 13:35 |  #24

Left Handed Brisket wrote in post #18662516 (external link)
@ 10:27am 35.7N

Sun's highest point will be 75.91 @ 1:26
thumbnail
Hosted photo: posted by Left Handed Brisket in
./showthread.php?p=186​62516&i=i104572719
forum: Flash and Studio Lighting

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Hosted photo: posted by Left Handed Brisket in
./showthread.php?p=186​62516&i=i247803604
forum: Flash and Studio Lighting

Thank you for your readout, but Uwharrie National Forrest (where you seem to be) is not that much north from Los Angeles.

BTW, which app is that, please?




  
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Left ­ Handed ­ Brisket
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Jul 14, 2018 14:19 |  #25

ZoranC wrote in post #18662647 (external link)
Yet another attempt at evading the point. This is becoming very predictable. Have you ever considered career in politics? Not that you are good at evading but vast majority of politicians is not any better at it than you either. As in: They are very bad at it.

Actually, you are avoiding the point being made by most of us. That is, a moderately higher latitude resulting in the sun's lower maximum angle of elevation relative to the subject is not worth worrying about. It is arguably the least important factor to consider.

My 2:00 reading was 1/4000 2.8 +0.1

Sun elevation 73.9

25 degrees higher than this morning, but I was also standing near a bright wall of my house rather than out in a field as I was this morning.




 :p


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ZoranC
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Jul 14, 2018 14:21 |  #26

Wilt wrote in post #18662670 (external link)
First post with meter reading was from Canada. With over 12 degrees of Latitude difference from N. California, the result was LESS light at the closer-to-Equator location?! It does not matter that NEITHER Canada nor Belmont are 'at NYC' per your original request for a meter reading at NYC...you got three readings from two locations and NONE of them agreed. Here is a 4th reading

Sample 4: 1/4000, f/2.8 @ 11:57hr PDT, Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk

Four readings, only two of which match, using the same meter. Proving my point about variability of readings even from a single meter.

Just maybe, the fact that one reading of four matches the one taken by LHB might prove 'not appreciable difference' in intensity at two positions two degrees of latitude apart.
But then reading #1apparently proves that the clearer air in Canada makes for a brighter reading than two in California, in spite of it being farther from the equator.
Just WHAT has anyone 'proven' with any 'facts', and why is it necessary to be so abrasive with your responses to reported observations???

1. Only thing this is proving is that three different observers all at practically same distance from equator are getting practically same readout. No surprises there.

2. We have just one data from up north and don't know much about that data. Besides, there is a reason why I said New York (as in city metropolitan area).

3. If you are getting noticeable difference between your readouts you need to double check your meter and/or metering technique. Practically all of my readouts with L858D over one hour period are identical (max difference for few that are not is 0.1EV).

4. When somebody is abrasive toward me first I tend to give them back dose of their own medicine. Why you seem to be surprised that is the result? Or you just can't handle your own medicine.




  
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Jul 14, 2018 14:38 |  #27

The bickering and personal attacks need to stop.

Re-read the rules and abide by them.

Thanks,

T.D.
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Wilt
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Post edited over 1 year ago by Wilt.
     
Jul 14, 2018 15:35 |  #28

I had reported four observations


  1. 1/4000 f/ 2.0 + 0.9EV Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk(yesterday)
  2. 1/4000 f/2.0 + 0.8EV Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk (yesterday)
  3. 1/4000 f/2.0 + 0.9EV Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk(yesterdau)
  4. 1/4000 f/2.8 Latitude 37° 31' N measured with Minolta Autometer Vf with flat disk (today)


All four were LESS light than as measured in Canada at Latitude 50, and only test 4 equalled Los Angeles (Latitude 35).
I reported only observations, and commented that none of them exhibited enough 'consistency' to draw any conclusion about measurements at one latitude vs. another. Scientific method. That is all, no intended bickering on my part.

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Jul 14, 2018 16:42 |  #29

I think many have already pointed out that local variations, such as atmospheric variations and such will render any measurement inaccurate, but I found this (external link) while web surfing. It pretty much give you every mathematical equation one could ask for to calculate all different types of radiation falling an any square meter of the planet.


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Jul 14, 2018 16:52 |  #30
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ZoranC, have you tried shooting some frames at Sunny 16? How's that working for you down there?

I'm curious because when I was a wee bit farther north of my present location, in May, Sunny 16 was giving me photos that were a bit underexposed. But in my home town Sunny 16 gives me a perfect exposure.

I've also found that when I take meter readings (dome out) in full sun (Sunny 16 conditions) the meter completely agrees with the Sunny 16 rule. (Again, this in my home town, Regina, SK.)

For those concerned with the insolation values and their oscillations, please keep in mind that it's not only the time of the day, but also the time of the year: the perpendicularity of the sun rays varies by location as the Earth tilts away from the sun in the present season.


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Light metering question for New York guys
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