stability of 'sunny 16'

markjwyatt · Jan 31, 2022

Craig said:
Look on Ebay for a PX625or RC-53 battery. They are Russian made mercury cells and work perfectly in the older Gossen meters that need the1.35 voltage batteries. Work well in old Canon F-1's as well. Seller's name is Elkhartsix in St Petersburg, Russia.

I could use some. Not sure if they will get through customs.

The Wein cells are finicky. I wanted to test my original Luna Pro (call it #1), but the Wein cell was dead. So I popped the two out of the one that read eV 16 (call it #2), and dropped them in. On the #2, before removing teh batteries, batter y check brough the needle more than halfway through the red zone (indicating battery was good). In #1 , the same batteries were barely into the lowest part of the red zone, and the meter read eV 14. I swapped the batteries back to #2 and could not get even near the red zone. I swapped back to #1 and it was the same. I tried a couple more times, let the batteries sitting with the cover open, etc. I ordered more Wein cells, ad just put the cover back on #1, checked it and it was still far from the red zone. I came back 2-3 hours later and checked it and it is over half on the red zone! Just like on #2 originally. The Wein cells clearly take time to create a circuit.

markjwyatt · Jan 31, 2022

VTLD said:
Why bother? Voltage reducing adapter is one time purchase, some 20 bucks, then off one goes to silver oxides.

If you can find them. I do see Kanto brand from Japan, hey are $30-40 each.

Deleted member 88956 · Jan 31, 2022

markjwyatt said:
If you can find them.

All over the place, search eBay, PX 625 battery adapter. I now have the ones from Thailand, work great. His prices are now up a bit but still a one timer.

Craig · Jan 31, 2022

markjwyatt said:
I could use some. Not sure if they will get through customs.

They came through Canadian customs no problem. They were sent in a small padded envelope. The nice thing about them is they are the original type of cell the meter was designed to work with, and they do last a long time.

The seller who has a listing on eBay right now isn't the same one I bought the batteries from, so can't comment on him

markjwyatt · Jan 31, 2022

VTLD said:
All over the place, search eBay, PX 625 battery adapter. I now have the ones from Thailand, work great. His prices are now up a bit but still a one timer.

Thanks. They drop the voltage properly?

Deleted member 88956 · Jan 31, 2022

markjwyatt said:
Thanks. They drop the voltage properly?

Yes they do. This is an old trick with diode in the circuit that does that. All of these are basically the same. There is someone making them in UK, just double the cost.

grain elevator · Jan 31, 2022

markjwyatt said:
Luna Pro (recent acquisition) 16* (EDIT- checked zero, it is off. Adjust, but no more working Wein cells...)

The Luna Pro can be adjusted to work with silver cells without adapter. At least mine could. Just sayin.

wiltw · Jan 31, 2022

VTLD said:
All over the place, search eBay, PX 625 battery adapter. I now have the ones from Thailand, work great. His prices are now up a bit but still a one timer.

The link describes the right characteristics,

"MR-9 PX625 PX13 battery adapter for vintage film cameras and exposure meters.
Use of 386 / SR43W Silver Oxide battery (1.55 V) to convert voltage
to be equal to obsolete MR-9 PX625 PX13 Mercury battery (1.35V)."

While the linked to item appears to be is what it says it is, BUYER BEWARE...There are other, 'MR9 imposter' physical size adapters, that do NOT voltage conversions, but rely upon the air cell to provide 1.35V...and they continuously exhaust themselves once the air seal is removed. You can identify the imposters by the hole visible in the flat side of the adapter, which allows air into the air cell.
{MODERATORS CLARIFICATION added in bold}

markjwyatt · Feb 2, 2022

Got all batteries working and zero adjusted:

Chino Hills, CA (southern California, inland). Was cloudy yesterday, looks clear at this time.
34 N
ISO 100

LunaPro SBC: 14.5
Both Luna Pros: 15

Sirius Glass · Feb 2, 2022

markjwyatt said:
Got all batteries working and zero adjusted:

LunaPro SBC: 14.5
Both Luna Pros: 15

Again what is the ISO setting? ISO 100? I get higher EVs but I use ISO 400. It would be much simpler to express the ISO, f/stop and shutter speed or use the Sunny 16 as a basis of the discussion.

markjwyatt · Feb 2, 2022

Sirius Glass said:
Again what is the ISO setting? ISO 100? I get higher EVs but I use ISO 400. It would be much simpler to express the ISO, f/stop and shutter speed or use the Sunny 16 as a basis of the discussion.

Good point. I followed the standard of the thread which is ISO 100. Added the info as well as location info (I was implicitly referring back to my original post).

RalphLambrecht · Feb 2, 2022

mgb74 said:
I assume you need a clear, sunny day with the sun unobstructed by clouds. But does time of day have an impact?

not between 10am and 3pm(it's very stable during that time).

Deleted member 88956 · Feb 2, 2022

RalphLambrecht said:
not between 10am and 3pm(it's very stable during that time).

No idea where your information is coming from. It cannot be the case year round or at every latitude, and I am not talking beyond 60 degrees. Too much of generalisation in that statement. Would help if you could reference sources.

Sirius Glass · Feb 2, 2022

RalphLambrecht said:
not between 10am and 3pm(it's very stable during that time).

During the day from 0900 to 1500 hours as long as clouds or rain does not come in.

markjwyatt · Feb 2, 2022

Sirius Glass said:
During the day from 0900 to 1500 hours as long as clouds or rain does not come in.

I suspect X hours after sunset and Y hours before sunset may be more accurate (and say between +/- 40 Latitude)

Another way might be clear skies and the sun between 30 deg and 150 deg of the horizon...

Deleted member 88956 · Feb 2, 2022

There are so many variables throughout the day, even on days that appear as "clear skies" there is no universal fixed value. All it is, is an approximation, the reason Sunny 16 works only when it does. But it mostly works because of film latitude, not because it is so constant. Light is scattered to a degree on any day, but on some days much more so without appearing to be.

Sun peaks for about 2 hours around its upper transit (1 hour before and after), but that is not all. Depending on time of year, the change will not be much for longer, and on those wintery dates it could be relatively similar enough for 4-6 hours. Those who travel the world between both 75 degree latitudes can tell without measuring things are vastly different on a sunny day, and I am not referring to temperatures felt. So again, time of year AND latitude have effect.

The problem with calling it between 10-15 hundred hours is also exacerbated by time zone in any given area, so referencing to actual sun altitude is more precise in that respect.

grain elevator · Feb 3, 2022

VTLD said:
But it mostly works because of film latitude, not because it is so constant.

Latitude is why everything works. A necessary, but insufficient condition for everything to work, to be precise. For example driving only works because roads are a little wider than the vehicles we drive on them.
Sorry, you're right, I just couldn't help getting philosophical. Or engeneerical, I guess. They call it tolerance.

tokam · Feb 3, 2022

Sirius Glass said:
Again what is the ISO setting? ISO 100? I get higher EVs but I use ISO 400. It would be much simpler to express the ISO, f/stop and shutter speed or use the Sunny 16 as a basis of the discussion.

markjwyatt said:
Good point. I followed the standard of the thread which is ISO 100. Added the info as well as location info (I was implicitly referring back to my original post).

I just checked on my Profisix, (Luna Pro SBC) and at 100 ISO, EV15 is 1/125 sec at f16. No need to take a reading - just set film speed and adjust dial to EV 15 and read off the exposure details.

RalphLambrecht · Feb 3, 2022

Sirius Glass said:
During the day from 0900 to 1500 hours as long as clouds or rain does not come in.

agreed!

Helge · Feb 3, 2022

VTLD said:
Why bother? Voltage reducing adapter is one time purchase, some 20 bucks, then off one goes to silver oxides.

Because they are opportunistically priced. Buying four easily runs into $200 equivalent. Probably more with "postage".
That is a lot for batteries, especially something that isn't even batteries.
For some that might be a "bite the bullet", "rip the bandaid off", over once and for all thing.
But really, if you have just three cameras and a Gossen that takes two of the damn things, then you quickly run into a shuffle game and a "where is the camera that I need to borrow the adapter from now‽".
Irritating and unnecessary.
We need more competition in the voltage reducing adapters.
As is now, there is seemingly only one.
Half the price would probably be realistic without compromising quality.

Sirius Glass · Feb 3, 2022

VTLD said:
There are so many variables throughout the day, even on days that appear as "clear skies" there is no universal fixed value. All it is, is an approximation, the reason Sunny 16 works only when it does. But it mostly works because of film latitude, not because it is so constant. Light is scattered to a degree on any day, but on some days much more so without appearing to be.

Sun peaks for about 2 hours around its upper transit (1 hour before and after), but that is not all. Depending on time of year, the change will not be much for longer, and on those wintery dates it could be relatively similar enough for 4-6 hours. Those who travel the world between both 75 degree latitudes can tell without measuring things are vastly different on a sunny day, and I am not referring to temperatures felt. So again, time of year AND latitude have effect.

The problem with calling it between 10-15 hundred hours is also exacerbated by time zone in any given area, so referencing to actual sun altitude is more precise in that respect.

grain elevator said:
Latitude is why everything works. A necessary, but insufficient condition for everything to work, to be precise. For example driving only works because roads are a little wider than the vehicles we drive on them.
Sorry, you're right, I just couldn't help getting philosophical. Or engineerical, I guess. They call it tolerance.

Basically Sunny 16 works as long as one is able to see and evaluate when the sky is clear enough for a sunny day [distinct shadows], partly cloudy day[distinct shadows and indistinct shadows] and overcast [no shadows]. Frankly if one cannot determine those 3 or 4 states then probably photography is not a good vocation or hobby and one should take up embroidery, quilt making or basket weaving.

reddesert · Feb 3, 2022

tokam said:
I just checked on my Profisix, (Luna Pro SBC) and at 100 ISO, EV15 is 1/125 sec at f16. No need to take a reading - just set film speed and adjust dial to EV 15 and read off the exposure details.

EV 15 is always 1/125 at f/16, at any ISO. Try it on your meter dial and see. This is because exposure value EV only specifies an exposure, not a light value. In order to specify an amount of light you need to give both the EV and the ISO.

For the purposes of this thread, to measure the amount of light in a sunny scene, people need to say what ISO they are using when they give a shutter speed and f-stop from a meter reading.

RalphLambrecht · Feb 3, 2022

reddesert said:
EV 15 is always 1/125 at f/16, at any ISO. Try it on your meter dial and see. This is because exposure value EV only specifies an exposure, not a light value. In order to specify an amount of light you need to give both the EV and the ISO.

For the purposes of this thread, to measure the amount of light in a sunny scene, people need to say

what ISO they are using when they give a shutter speed and f-stop from a meter reading.

little known but true fact.

markjwyatt · Feb 4, 2022

reddesert said:
EV 15 is always 1/125 at f/16, at any ISO. Try it on your meter dial and see. This is because exposure value EV only specifies an exposure, not a light value.

True, but if you take an incident reading pointed at the sun at ISO 400 on clear day with no obstructions, you will read eV 17. That is still sunny 16. If you know any two (eV, ISO, aperture, shutter speed) and assume sunny 16 rule, you can figure out the others. So ISO and eV are enough to verify sunny 16. ISO 100 and eV 15 are pretty concise.

reddesert said:
Try it on your meter dial and see. This is because exposure value EV only specifies an exposure, not a light value. In order to specify an amount of light you need to give both the EV and the ISO.

For the purposes of this thread, to measure the amount of light in a sunny scene, people need to say what ISO they are using when they give a shutter speed and f-stop from a meter reading.

Not true. If I were to meter incident at ISO 400, I would read close to eV 17 (or f16 1/500 or close to that for instance). eV is an exposure, but is linked to ISO for a given level of light.

For purposes of this thread, we are reporting that the conditions we are metering under are sunny 16, and then we use an ISO setting on a meter (and a specified measurement technique- incident, point at sun) and measured eV to verify the rule. The rule is observation based, but the meter supplies evidence that it is correct.

If I metered at ISO 400 and reported ISO 15, I would discredit the rule. If I report eV17 or close, I confirm it, but I deviated from the form of the experiment (but we would all still agree the rule was confirmed, because we know the rule about eVs and stops/speeds and can convert it.

Look at the BACK of your meter- likely there is a table converting eV at ISO (for SBC it is ISO 50) to Lux in candles and/or foot-candles (or some other measure of light intensity); a light level. f-stop and shutter speed are not needed to establish light intensity level. "sunny 16" is a light intensity level in theory.

wiltw · Feb 4, 2022

[QUOTE="markjwyatt]
Not true.
[/QUOTE]

^ EV changes with ISO value under the same light
Using a Minolta Spotmeter F, I am sitting in my family room with constant source of artificial light, targeting a 18% gray card...

With ISO 250, 1/250 the EV measurement is 6.2
With ISO 500, 1/500 the EV measurement is 7.2
With ISO 2000, 1/200 the EV measurement is 9.2

Using Minolta Autometer Vf with incident hemisphere

With ISO 250, 1/250 the EV measurement is 6.8
With ISO 500, 1/500 the EV measurement is 7.8
With ISO 2000, 1/2000 the EV measurement is 9.8

stability of 'sunny 16'

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Deleted member 88956

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