Light meters for extremely low light?

maxxxx · 04-21-2014, 10:52 AM

Hi

I like to take pictures of the milky way together with some landscape in the foreground. To get good quality of the foreground it seems it's better to shoot the foreground separately and merge the sky and the foreground together later. When I do this I have no idea how to expose the foreground though. The camera meter doesn't work at these light levels and the eye is also not reliable.

Dies anybody know a light meter that works well in near darkness (like Death Valley for example)? I don't even necessarily need it to calculate exposure times , just a reliable measurement of the light level in lux would do so I can compare different shots and make adjustments.

Not a Number · 04-21-2014, 12:50 PM

The Gossen Luna meter series got their name (allegedly) for being sensitive enough to use under the light of the moon. I remember using my Luna-Pro-F to get the exposure times for a scene lit under a full moon. The manual give the low sensitivity as 0.125 footcandles (1.345488802 lux).

I'm sure current meters are just as sensitive if not more. Check the spec sheets.

**lmd91343** · 04-21-2014, 12:55 PM

My K20 camera will measure down EV 0. Probably the most popular meter, the Sekonic 308 measures done to EV 0 also. My old Canon with the Meter Booster head measures down to EV -3.5, which is darker than my LA back yard gets on a moonless night.

The old Gossen Luna-Pro (s) measures to EV -4. They can be found on EBay for $10 plus batteries.

That meter for many years was the low light champ. It takes the old mecury batteries, so you need to use the Wein cells or silver cells and find the offset (1/2 stop). You can buy a battery conversion kit at B&H for $23. Get the dirt cheap meter and buy two silver cells for a couple dollars each. For less than $20 you are good to go.

Remember it is a CDS meter. They have memories, so you need to meter for a few (5?) seconds to overcome the memory at low light levels.

The S variant has a slightly different dial and a black not grey case. It costs more.

stevebrot · 04-21-2014, 12:59 PM

Gossen Luna Pro SBC, -8 to +24 EV(100) and takes a modern battery.

I own the Gossen Luna Lux SBC, which has a more pedestrian range of -3 to +20 EV(100). It too takes a modern battery.

Steve

maxxxx · 04-21-2014, 01:05 PM

Originally posted by stevebrot

Gossen Luna Pro SBC, -8 to +24 EV(100) and takes a modern battery.

I own the Gossen Luna Lux, which has a more pedestrian range of -3 to +20 EV(100). It too takes a modern battery.

Steve

I am looking for an SBC or a Pro F on eBay right now. I hope it will go low enough for a moonless night. Death Valley without moon is pretty dark. You don't see a person 5 meters away from you.

Does anybody have experience with lux meters? Are there any on the market that are sensitive enough? I don't really need the exposure calculation.

---------- Post added 04-21-14 at 01:24 PM ----------

According to this Lux - Wikipedia, the free encyclopedia, a moonless night with clear sky is 0.002 lux. That's pretty low :-(

Not a Number · 04-21-2014, 04:29 PM

FWIW: The specs on the Luna Pro F in EV lists -3 to 15 EV at ISO 25.

maxxxx · 04-21-2014, 05:00 PM

Originally posted by Not a Number

FWIW: The specs on the Luna Pro F in EV lists -3 to 15 EV at ISO 25.

Do you know how these numbers can be translated into lux?

Not a Number · 04-21-2014, 05:55 PM

From the Luna Pro-F manual
0.125 to 32,000 foot candles

1 footcandle = 10.763910417 lux (unitconversion.org

1.345488802 to 344445.1333344 lux

The Luna Pro SBC low end would be 0.172222567 lux (0.016 footcandles). Lighting by the galactic core of the Milky Way is average 0.00244140625 lux (EV -11 to -9 @ ISO 100).

maxxxx · 04-21-2014, 06:38 PM

Originally posted by Not a Number

From the Luna Pro-F manual
0.125 to 32,000 foot candles

1 footcandle = 10.763910417 lux (unitconversion.org

1.345488802 to 344445.1333344 lux

The Luna Pro SBC low end would be 0.172222567 lux (0.016 footcandles). Lighting by the galactic core of the Milky Way is average 0.00244140625 lux (EV -11 to -9 @ ISO 100).

Thanks! Looks like this won't work. I wonder if there are any (affordable) lux meters in that range or I can build something.

Not a Number · 04-21-2014, 07:44 PM

You don't really need a meter if you use the EV values given for the lighting situations. There are plenty of charts around giving the f-stop and exposure time for given EVs.

Sources give the EV for moonless starlit scenes from -11 to -6 EV @ ISO 100. Sure that's a wide range but you can narrow it down depending on the scene and Bracket Like Hell (BLH). If you're shooting digital you can get almost instant feedback.

Lux meters seem cheap enough but I doubt the ones for sale on eBay and Amazon are sensitive or accurate at the light levels you are interested in. The more expensive ones have a range of 0 to 200,000 lux in four ranges (0-2000, 0-20000 etc.) with an accuracy of +/-5%. I suspect you'd need to spend hundreds of dollars on a meter to measure the light levels you are looking at.

I suppose you can buy one of the $10-40 meters and drive far away from big cities to see if it will even meter down to 4 decimal places and return it if it doesn't.

04-21-2014, 10:52 AM	#1
maxxxx Veteran Member Join Date: Nov 2013 Posts: 385	Light meters for extremely low light? Hi I like to take pictures of the milky way together with some landscape in the foreground. To get good quality of the foreground it seems it's better to shoot the foreground separately and merge the sky and the foreground together later. When I do this I have no idea how to expose the foreground though. The camera meter doesn't work at these light levels and the eye is also not reliable. Dies anybody know a light meter that works well in near darkness (like Death Valley for example)? I don't even necessarily need it to calculate exposure times , just a reliable measurement of the light level in lux would do so I can compare different shots and make adjustments.

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04-21-2014, 12:50 PM	#2
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	The Gossen Luna meter series got their name (allegedly) for being sensitive enough to use under the light of the moon. I remember using my Luna-Pro-F to get the exposure times for a scene lit under a full moon. The manual give the low sensitivity as 0.125 footcandles (1.345488802 lux). I'm sure current meters are just as sensitive if not more. Check the spec sheets.

04-21-2014, 12:55 PM	#3
lmd91343 Site Supporter Join Date: Jul 2009 Location: Los Angeles, CA USA Photos: Gallery \| Albums Posts: 1,027	My K20 camera will measure down EV 0. Probably the most popular meter, the Sekonic 308 measures done to EV 0 also. My old Canon with the Meter Booster head measures down to EV -3.5, which is darker than my LA back yard gets on a moonless night. The old Gossen Luna-Pro (s) measures to EV -4. They can be found on EBay for $10 plus batteries. That meter for many years was the low light champ. It takes the old mecury batteries, so you need to use the Wein cells or silver cells and find the offset (1/2 stop). You can buy a battery conversion kit at B&H for $23. Get the dirt cheap meter and buy two silver cells for a couple dollars each. For less than $20 you are good to go. Remember it is a CDS meter. They have memories, so you need to meter for a few (5?) seconds to overcome the memory at low light levels. The S variant has a slightly different dial and a black not grey case. It costs more.

04-21-2014, 12:59 PM	#4
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Gossen Luna Pro SBC, -8 to +24 EV(100) and takes a modern battery. I own the Gossen Luna Lux SBC, which has a more pedestrian range of -3 to +20 EV(100). It too takes a modern battery. Steve

04-21-2014, 01:05 PM	#5
maxxxx Veteran Member Join Date: Nov 2013 Posts: 385 Original Poster	Originally posted by stevebrot Gossen Luna Pro SBC, -8 to +24 EV(100) and takes a modern battery. I own the Gossen Luna Lux, which has a more pedestrian range of -3 to +20 EV(100). It too takes a modern battery. Steve I am looking for an SBC or a Pro F on eBay right now. I hope it will go low enough for a moonless night. Death Valley without moon is pretty dark. You don't see a person 5 meters away from you. Does anybody have experience with lux meters? Are there any on the market that are sensitive enough? I don't really need the exposure calculation. ---------- Post added 04-21-14 at 01:24 PM ---------- According to this Lux - Wikipedia, the free encyclopedia, a moonless night with clear sky is 0.002 lux. That's pretty low :-(

04-21-2014, 04:29 PM	#6
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	FWIW: The specs on the Luna Pro F in EV lists -3 to 15 EV at ISO 25.

04-21-2014, 05:00 PM	#7
maxxxx Veteran Member Join Date: Nov 2013 Posts: 385 Original Poster	Originally posted by Not a Number FWIW: The specs on the Luna Pro F in EV lists -3 to 15 EV at ISO 25. Do you know how these numbers can be translated into lux?

04-21-2014, 05:55 PM	#8
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	From the Luna Pro-F manual 0.125 to 32,000 foot candles 1 footcandle = 10.763910417 lux (unitconversion.org 1.345488802 to 344445.1333344 lux The Luna Pro SBC low end would be 0.172222567 lux (0.016 footcandles). Lighting by the galactic core of the Milky Way is average 0.00244140625 lux (EV -11 to -9 @ ISO 100).

04-21-2014, 06:38 PM	#9
maxxxx Veteran Member Join Date: Nov 2013 Posts: 385 Original Poster	Originally posted by Not a Number From the Luna Pro-F manual 0.125 to 32,000 foot candles 1 footcandle = 10.763910417 lux (unitconversion.org 1.345488802 to 344445.1333344 lux The Luna Pro SBC low end would be 0.172222567 lux (0.016 footcandles). Lighting by the galactic core of the Milky Way is average 0.00244140625 lux (EV -11 to -9 @ ISO 100). Thanks! Looks like this won't work. I wonder if there are any (affordable) lux meters in that range or I can build something.

04-21-2014, 07:44 PM	#10
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	You don't really need a meter if you use the EV values given for the lighting situations. There are plenty of charts around giving the f-stop and exposure time for given EVs. Sources give the EV for moonless starlit scenes from -11 to -6 EV @ ISO 100. Sure that's a wide range but you can narrow it down depending on the scene and Bracket Like Hell (BLH). If you're shooting digital you can get almost instant feedback. Lux meters seem cheap enough but I doubt the ones for sale on eBay and Amazon are sensitive or accurate at the light levels you are interested in. The more expensive ones have a range of 0 to 200,000 lux in four ranges (0-2000, 0-20000 etc.) with an accuracy of +/-5%. I suspect you'd need to spend hundreds of dollars on a meter to measure the light levels you are looking at. I suppose you can buy one of the $10-40 meters and drive far away from big cities to see if it will even meter down to 4 decimal places and return it if it doesn't.