The only issue with that is, the old Sekonic reads more EV than the new Sekonic. There is 30 years difference between both
I still think that is because the dome gets old. You eyes don't see it but it transmit less light. I found that out on my Minolta meters. The 12.5 vs 14 is related only to the reflected meter. Both meter are Sekonic and thus should be calibrated to K12.5 while the Pentax should be calibrated to K14 and they all read the same. For the incident with the sphere the Sekonic calibrated with a C340 while some other brand like Minota is calibrated to C330.
Wouldn't it be best to just calibrate all three to the same known accurate reference source?
In theory, or in practice?
You may get better agreement if you will get a 12.5% gray card and meter off it in reflected light mode, and compare it to the incident light mode.
If you only have an 18% gray, the difference between 18 and 12.5 is expected and means that your meter agrees (if the difference can be accounted for by that much) and you should leave it alone. Treat it as OK if they differ by that much.
In practice. Calibrate one professionally and then adjust the other two to it.
In practice. Calibrate one professionally and then adjust the other two to it.
Where do you get a 12.5 % grey card?
Big thanks to Peter Woodford who did numerous tests and helped to identify behaviour of various light meters.
Hi all,
So I have 3 light meters;
When I measure reflective light, it all shows the same EV value, which is great.
- Sekonic L308X, incident and reflective light meter
- Sekonic L-28C, incident and reflective light meter
- Pentax Digital Spotmeter, reflective light meter
But when I measure incident light while the Lumispheres are on with both Sekonics, L308X measures 0.5 EV less than L-28C. Certainly, I can put the ISO value down on L-28C and be fine with it but wanted to understand why it would create this difference.
Cheers,
Fatih
Wouldn't it be best to just calibrate all three to the same known accurate reference source?
To start with, I have no idea how to calibrate both Sekonics and it might be above my skill set.
I guess the best course of action for the time being would be, shoot the gray card with the measured settings for each lightmeter and compare the result. At the end of the day, this is pretty much what we do with the film as well, shooting through a step wedge and see if our processing is correct.
Sometimes the dome got old (yellowed, cloudy, or less transparent) as the aged. It is the problem from the white plastic degeneration.
If the reading is 1/4 stop of less then I won't brother. Otherwise I would look for another dome and try
Where do you get a 12.5 % grey card?
To start with, I have no idea how to calibrate both Sekonics and it might be above my skill set.
I guess the best course of action for the time being would be, shoot the gray card with the measured settings for each lightmeter and compare the result. At the end of the day, this is pretty much what we do with the film as well, shooting through a step wedge and see if our processing is correct.
Calibrating the 308
I knew someone who had an L-28C2. There is a dial on the back that you can turn with a coin, to zero out the metre. Does the 28C have something similar?
You're supposed to cover your hand over the dome. If the needle does not go to zero, then the dial is turned so that the needle points to zero. I guess that is how that particular metre is calibrated. I would probably just use the 308. My L-588 is super easy to calibrate in the field.
You're supposed to cover your hand over the dome. If the needle does not go to zero, then the dial is turned so that the needle points to zero. I guess that is how that particular metre is calibrated. I would probably just use the 308. My L-588 is super easy to calibrate in the field.
Who does light meter calibration? How does one “adjust” other than noting the deviation?
In the given situation, wouldn’t it be just as good to take 2 exposures, one per each meter, and see if there is any practical difference?
The OP says he's getting a half-stop difference in readings. Assuming one's right, the others off half a stop. Of course, calibration won't help him if he's misusing the meters.
How do you calibrate the 2 meters the OP has (assuming you have the light standard)
No doubt; a very true statement about the improtance to correctly use meters, especially when of different designs. But don't assume that only one is off as both could be off.
Case in point: I happily used Weston meters in a vertical position until I compared the readings with a "better and more modern" meter. Then discoverred that the corrrect position fo using a Weson meter is in the horizontal postiion, and a map of the acceptance pattern proved that my "incorrect reading" were because of that. Using that specific Weston meter became much more in agreement with the "modern meter" when the erroneous use was corrected. Truth be told, though... the minor difference in exposure recommendation was rather insignificant to practical image making.
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