Gossen Luna Pro F Meter

[Dream Merchant]

Basically, we might have the EV set wrongly.

But is the EV moves, the shutter speed also moves!

We were doing this:

1) Meter zeroed without battery.
2) Put batt in, set to ISO 400.
3) Under my friend's calculations, and EV of about 7.2 should get us 1/40 and f/4.
4) Shutter speed is correct, and aperture is correct. But the EV now reads about 9.8 (estimate).


Does anyone know if the EV can be set, or calibrated without moving any other scale on the Gossen Luna Pro F? Or are we evel looking in the right direction?

http://www.butkus.org/chinon/flashes_meters/luna-pro_f/luna-pro_f.pdf

 

[denniskee]

hahaha, so fast u post liao ah?

ok, situation like this.

inside bk in marina square. lighting condition very similar to funan food court (the red sofa section). so for easy reference for newbies, i always advice them to use 4, 4, 4 rule, ie ISO400, 1/40sec, f4.

the histogram showed we r right on the spot. so using sunny16 rule as reference which is EV15, base on above setting, EV should be 1/3 stop over EV7.

DM's meter show correct settings, but problem is, it showed 1/2 stop over EV9.

we just did a test over phone, set the Meter to ISO100, f16, 1/125sec, it shows EV15.

 

[denniskee]

i just check with my polaris light meter, it also showed EV9.

sunny 16 rule :

ISO400, f16, 1/500sec = EV15

f16 to f4 = 4stop = 4EV

1/500sec to 1/40sec = 3 2/3 stop = 3.66EV

EV15 - 7.66EV = EV7.34

so where in the calculation did i go wrong?:dunno:

 

[catchlights]

I cracking my brain and don't have answer yet.....

will need more time to mediate...... :embrass:

 

[catchlights]

I did a test with my Sekonic meter and arrive the same result as yours. ISO 400, 1/30s, f4 and EV is at 7 something.

after searching for an answer, I think we have made some kind of mistake, here is the simple explanation of the mystery.

Exposure Value does directly tied to ISO, so when EV 15 is Sunny f16, if you change your ISO in your hand held meter to another value, IT DOES CHANGES the EV as well.

that is the reason why you are getting higher EV than it suppose to be, cos you meter is at ISO 400, I did a simple test with my meter again, when the reading is taken and EV is recorded, I change the ISO, the EV move along.

Hope this explanation is clear and your "Ah Gong" Gossen Luna Pro F meter has nothing wrong, still very accurate.

 

[denniskee]

I did a test with my Sekonic meter and arrive the same result as yours. ISO 400, 1/30s, f4 and EV is at 7 something.

after searching for an answer, I think we have made some kind of mistake, here is the simple explanation of the mystery.

Exposure Value does directly tied to ISO, so when EV 15 is Sunny f16, if you change your ISO in your hand held meter to another value, IT DOES CHANGES the EV as well.

that is the reason why you are getting higher EV than it suppose to be, cos you meter is at ISO 400, I did a simple test with my meter again, when the reading is taken and EV is recorded, I change the ISO, the EV move along.

Hope this explanation is clear and your "Ah Gong" Gossen Luna Pro F meter has nothing wrong, still very accurate.

i still dont understand :

looking at the Exposure Factor Relationship Chart B in THE ULTIMATE EXPOSURE COMPUTER, it shows EV reading "drops" 1 row with every single stop increase in ISO, which makes sense to me.
http://www.fredparker.com/ultexp1.htm#Light Intensity Chart

so which is correct? assuming i am prefer to use EV than reading from the usual aperture & shutter speed when using light meter, than i will be mis-lead right?

using EV, initially i thought after reading the Chart B, will be correct as since i will not get the "wrong" setting because i forget to change the iso setting of the light meter, which happpen to me in various occasion.

with EV reading, i thought, i can use various combi of iso, aperture & shutter speed to achieve the EV reading from the light meter. it is very easy to remember EV, ISO100, 1/125sec :

f16 = EV15
f2.8 = EV10 (just remember most pro-zoom lens for ff sensor are f2.8 max)

 

[karnage]

I have a copy of the Ultimate Exposure Computer in my wallet! =)

Anyways, I have my Sekonic with me at the office. I checked ISO400, 1/30, f4, it's EV9 leh. But I checked the UEC table, EV9 for ISO400 at f4 is 1/125. So which is right? I only have my FE2 with me at the moment, so I can't check histograms. Haha!

 

[denniskee]

i wrote to Gossen about this confusion, lets wait for their reply :\

Dear Sir

My friend & myself (photography hobbyist) recently run into a confusing situation regarding the reading we get from Gossen Luna Pro F Meter, a Polaris SPD100 & a Sekonic l-508 from measuring the lighting condition in a brightly lit fast food joint.

Though all our 3 light meters are not calibrated (being a hobbyist & not using them for commercial purposes), all 3 gave us these reading :

ISO400, 1/40sec, f4

This setting is correct as we shot a grey card (cardboard from a writing pad) with Canon 1DMKII & Canon Powershot G2, with the histogram showing a peak right in the centre.

Now comes the confusing part, when we change all 3 light meters to EV mode, they all showed EV9-9.5.

But we know that at the above setting, the correct EV should be 7.

As we are all members of a internet Photography Forum from Singapore, ClubSnap, we posted the question in search for a better understanding why this different.

http://www.clubsnap.com/forums/showthread.php?t=745530

We will all appreciate if you shed some light into our confusion either replying to my email or better still, help our members by replying to the above link.

We look forward to your kind assistant. Thank you in advance.

Sincerely
Dennis Kee

 

[zk-diq]

i just check with my polaris light meter, it also showed EV9.

sunny 16 rule :

ISO400, f16, 1/500sec = EV15

f16 to f4 = 4stop = 4EV

1/500sec to 1/40sec = 3 2/3 stop = 3.66EV

EV15 - 7.66EV = EV7.34

so where in the calculation did i go wrong?:dunno:

SORRY to interrupt,

EV15 = f16 1/125 sec = f11 1/250 etc.. the value is fixed no relation with luminosity or film speed.

ASA or DIN or ISO film speed is only a reference point, with the same light condition,
when Film speed / sensor sensitivity higher EV will be higher.

ie: ASA 100 in sunny day with hard shadow f16 1/125 = EV 15
ASA 200 same condition f16 1/250 = EV 16
ASA 400 f16 1/500 = EV 17

For your sunny 16, if you use 400 film/sensor speed your EV will be 17 = f16 1/500

 

[denniskee]

SORRY to interrupt,

EV15 = f16 1/125 sec = f11 1/250 etc.. the value is fixed no relation with luminosity or film speed.

ASA or DIN or ISO film speed is only a reference point, with the same light condition,
when Film speed / sensor sensitivity higher EV will be higher.

ie: ASA 100 in sunny day with hard shadow f16 1/125 = EV 15
ASA 200 same condition f16 1/250 = EV 16
ASA 400 f16 1/500 = EV 17

For your sunny 16, if you use 400 film/sensor speed your EV will be 17 = f16 1/500

er... nope

pls refer to the chart in the link i posted earlier

 

[denniskee]

Mr Gudrun Zeller from Gossen had replied me, but i dont understand what he is trying to explain as my english is not very goood.



Dear Mister Kee,

Please apologize the delay in answering your e-mail but we have checked with
our expert first. He made the same measurements and came to the following
results:

ISO 400, 1/40sec, f4 = EV 9 (correct)

ISO 100, 1/40sec, f4 = EV 7 (correct, too; and the two f-stops up to ISO 400
are also confirmed herewith)

Therefore we kindly ask you to check the ISO and to let us know if you get
the same results now.

Kind regards from Nuernberg,

GOSSEN Foto- und Lichtmesstechnik GmbH
i.A.Gudrun Zeller
Export Area Manager
Lina-Ammon-Strasse 22
D-90471 Nürnberg

Tel./Phone: D-(0)911-8602-181
Fax: D-(0)911-8602-142
e-mail: gudrun.zeller@gossen-photo.de
Website: www.gossen-photo.de

Social Siege/Amtsgericht Nürnberg HRB 15549
Managing Director/Geschäftsführer: Hans Arnold


I did a test with my Polaris SPD100 under similar lighting condition but set the ISO to 100, the reading I get :

ISO100, 1/13sec, f4 = EV7


But looking at his reply, at EV7 with ISO100, his reading is

ISO100, 1/40sec, f4

With refernece to the chart in the link I posted earlier, with the reading Mr Gudrun Zeller has, it should be 1/3 over EV9.


What I see here in his reply is reverse of what is stated in the chart,

ISO400, 1/40sec, f4 = EV7.33

ISO100, 1/40sec, f4 = EV9.33


Now I am not sure if :

1) He had understood my email
2) I dont understand his reply
3) the chart in the link is wrong
4) my understanding of EV conversion from the ISO, aperture & shutter speed is wrong.

Vey confuse


How should I reply him to seek further clarification on this issue?

 

[Dream Merchant]

Dennis,

I'm guessing ... the scale is sliding.

Which is why he said :

ISO 400, 1/40sec, f4 = EV 9 (correct)

ISO 100, 1/40sec, f4 = EV 7 (correct, too; and the two f-stops up to ISO 400 are also confirmed herewith)

and also agreeable with what Catchlights said earlier:

Exposure Value does directly tied to ISO, so when EV 15 is Sunny f16, if you change your ISO in your hand held meter to another value, IT DOES CHANGES the EV as well.

that is the reason why you are getting higher EV than it suppose to be, cos you meter is at ISO 400, I did a simple test with my meter again, when the reading is taken and EV is recorded, I change the ISO, the EV move along.

 

[denniskee]

i realize that too, so now what does that means?

1) the chart is wrong
2) my understanding of EV with respect to the function of ISO, aperture & shutter speed is wrong. so everytime we adjust the function, though the exposure remains the same (as in the photo doesnt over / under expose), the EV actually changes?


does that means that stating EV alone is not correct, ISO has to be stated too?

 

[zk-diq]

When footcandle = 8000 unit, film speed ISO = 100,
object with 18% reflectance will gain a correct exposure
with EV15.
When light condition is the same and film speed changes,

Fc=8000 unit, film=200 require EV16 setting.
Fc=8000 unit, film=400 require EV17 setting.
Fc=8000 unit, film=800 require EV18 setting.
Fc=8000 unit, film=50 require EV14 setting.

 

[denniskee]

When footcandle = 8000 unit, film speed ISO = 100,
object with 18% reflectance will gain a correct exposure
with EV15.
When light condition is the same and film speed changes,

Fc=8000 unit, film=200 require EV16 setting.
Fc=8000 unit, film=400 require EV17 setting.
Fc=8000 unit, film=800 require EV18 setting.
Fc=8000 unit, film=50 require EV14 setting.

i understand because the lighting didnt change in the room, the light intensity is absolute, regardless of camera setting. but we are adjusting the funstion of the 3 parameters. just like when we shoot outday on a bright day light.

ok, if a person measure the light intensity inside BK with any of the 3 meters i mentioned in EV reading & had set the ISO to 400, which in this case yields EV9, say we use this EV to set the aperture & shutter values with any of the possible combi stated in the chart, we result in 2 stop under.

i am going round and round, pls can someone explain in layman terms (as much as possible lar), is my above example wrong, if so, where did i go wrong, or is the chart wrong?

 

[denniskee]

Dennis,

I'm guessing ... the scale is sliding.

Which is why he said :


and also agreeable with what Catchlights said earlier:

if that is the case, do u mean using sunny 16 rule, the EV changes with respect to ISO even if we measure around noon time? looking at the Exposure Value Chart in the link, it has nothing to do with ISO setting.

i find this site makes sense to me, cause i can play with the 3 parameters to avheive correct exposure.

but if say we follow the explainations given here by fellow csers, how than, can i make use of the EV reading even if i know what ISO setting was used during measuement?

 

[Dream Merchant]

PM you.