l-308s underexposing by 1/3 stop

hi everyone, i just got an anniversary edition green sekonic l-308s yesterday and i started to play with it in different light. i shoot with a 5DmII and i noticed that the readings from the l-308s seems to be underexposing by 1/3 stop. i read that even the l-358 needs to be calibrated but in this case my l-308s cannot. did i get a dud? should i just make the compensation in camera knowning my l-308s is 1/3 under? or is this some kind of user error. how can i verify that its not me?

wasabean wrote in post #13990977
hi everyone, i just got an anniversary edition green sekonic l-308s yesterday and i started to play with it in different light. i shoot with a 5DmII and i noticed that the readings from the l-308s seems to be underexposing by 1/3 stop. i read that even the l-358 needs to be calibrated but in this case my l-308s cannot. did i get a dud? should i just make the compensation in camera knowning my l-308s is 1/3 under? or is this some kind of user error. how can i verify that its not me?

1/3 of a stop is not very much.

How are you determining that your meter is 1/3 of a stop off?

If you are using the camera's meter as the standard, how do you know the camera is not 1/3 of a stop off.

I personally have no idea, but in order to determine a correct calibration you need a standard that is viable.

Enjoy! Lon

yeah, 1/3 isn't very much, but i expected an external light meter to be spot on since thats the only purpose it serves. anyway, i guess i'm not performing these tests under any controlled environment nor with any measurements tools, but just reading the histogram tells me the image i'm taking is slightly off when i use the sekonic values. i guess a more accurate test would to meter off a gray card to see.

Before you accuse the L308 of being '1/3 stop off', aim your camera at an 18% gray card and compare that reading with your L308. I know that if I aim my Canon camera at the 18% gray card, or I aim my Minolta spotmeter at the 18% gray card, both readings match my Minolta Autometer V incident reading.

Keep in mind that shooting per 18% gray card will NOT be the same exposure as shooting ETTR according to your histogram!

As metered

looks like i'll have to buy myself a gray card. i will mainly be using the sekonic for 35mm and MF cameras and not so much with digital.

wasabean wrote in post #13991105
yeah, 1/3 isn't very much, but i expected an external light meter to be spot on since thats the only purpose it serves. anyway, i guess i'm not performing these tests under any controlled environment nor with any measurements tools, but just reading the histogram tells me the image i'm taking is slightly off when i use the sekonic values. i guess a more accurate test would to meter off a gray card to see.

But again, how do you know that it is 1/3 of a stop off?

What "standard" are you using to draw this conclusion.

If it is your camera's meter, why are you assuming the camera is correct and the meter is not?

It could just as easily be that the meter is "spot on" and the camera is off.

Again, I do not know what is accurate, but you must establish something as a reference that is indeed a standard.

Now if your meter was 4 stops off you could be reasonable sure, but since 1/3 of a stop is so small why do you think it is the meter?

Enjoy! Lon

maybe i explained it incorrectly, what i shouldve said was "my camera and l-308s doesnt seem to agree with each other by 1/3 stops." i set my camera to spot meter and metered off the same subject as the l-308s and it's not in agreement.

wasabean wrote in post #13993042
maybe i explained it incorrectly, what i shouldve said was "my camera and l-308s doesnt seem to agree with each other by 1/3 stops." i set my camera to spot meter and metered off the same subject as the l-308s and it's not in agreement.

Take you camera off "spot meter".

The Sekonic meter is not a "spot meter".

Set you cameras metering to meter the largest area possible. This will more closely match the metering mode of the Sekonic meter

Find some large evenly surface like a wall.

Meter this with you camera, and the Sekonic meter set to reflective mode. Point the camera and the Sekonic meter at the same location on the wall.

Report you findings.

Enjoy! Lon

The first time I calibrated light meters and camera shutters was way back in the film days, and we started by creating a setup that included a Kodak gray card as well as a step wedge.

Today you have a much easier way to calibrate meters and camera shutters; Lightroom and an X-Rite color checker.

Put the passport flat on the side walk and meter it in evaluative with it mostly filling the frame. Now take an incident light reading by placing the meter on the pass port.

Now take the image of the Passport into Lightroom and read the white and black squares. White square should read 93% and the black about 13%. I've found that a strong tone curve is best.

Adjust the exposure slider up or down until you get the proper % for the white square.
Now you know how far off your camera meter is from proper exposure. It can't be calibrated except with EC. Your exposure meter, if not adjustable, reading should also be compared to proper exposure.

Back in the day, we put a piece of masking tape on the meter or lens board with the compensation from baseline. So, if meter is + half a stop and shutter was - half a stop, we set the camera for whatever the meter read. If another shutter was + half a stop with the same meter we had to compensate a whole stop.

Oh, and 1/3 stop is a rounding error.

thank you dmward, you might be correct. i changed the stop increments from .3 to .5 on both the camera and l-308s and the histograms look correct.

flashzebra, i was using the lightmeter on incident mode (lumisphere covering the sensor), the reflective mode on the lightmeter throws the values all over the place depending on which angle you point it and where you point it so it was hard to get a constant reading.

i guess i'm still learning how to accurately use this new tool.

wasabean wrote in post #13994302
thank you dmward, you might be correct. i changed the stop increments from .3 to .5 on both the camera and l-308s and the histograms look correct.

flashzebra, i was using the lightmeter on incident mode (lumisphere covering the sensor), the reflective mode on the lightmeter throws the values all over the place depending on which angle you point it and where you point it so it was hard to get a constant reading.

i guess i'm still learning how to accurately use this new tool.

Did you accomplish the exact test I suggested?

The test I suggest mitigates the issues you indicate in this post.

Regarding:
"i guess i'm still learning how to accurately use this new tool."

My suggestion is not one to help you use your flash meter in a general manner, but to specifically address the basic issue of this thread, to determine if your Sekonic meter and you camera provide the same exposure advise.

Enjoy! Lon

@flashzebra i just did the test, i set my flashmeter to reflective mode and camera to evaluative (largest area possible) pointed both at my wall and both read ISO100, 1/125, f2.0

however, when i set the lightmeter to incident mode, the meter reads ISO100, 1/125, f1.2

wasabean wrote in post #13995041
@flashzebra i just did the test, i set my flashmeter to reflective mode and camera to evaluative (largest area possible) pointed both at my wall and both read ISO100, 1/125, f2.0

however, when i set the lightmeter to incident mode, the meter reads ISO100, 1/125, f1.2

Well, if your wall was light in color, it will fool a meter to give LESS exposure than it truly needs, whereas the incident meter would not be similarly fooled by the wall. That is why several of us have referred to pointing a reflected light meter at an 18% gray target.

@wilt yea you are correct, when the photo is taken with the matching values, the white wall is more or less middle gray. so that means the incident mode from the meter is correct, f/1.2 should be correct.

wasabean wrote in post #13995041
@flashzebra i just did the test, i set my flashmeter to reflective mode and camera to evaluative (largest area possible) pointed both at my wall and both read ISO100, 1/125, f2.0

however, when i set the lightmeter to incident mode, the meter reads ISO100, 1/125, f1.2

Well if they both read the same thing using roughly the same metering methodology they are either BOTH correct or BOTH incorrect (by the excat same amount). The Sekonic meter is NOT "underexposing by 1/3 stop". Your metering methodology switch is causing the metering differences.

Enjoy! LOn