Metering w/ Sekonic Twinmate - reading error?

[Waterman100]

This is very much a handheld-meter-newbie question... I just received a new Sekonic Twinmate, which is my first ever handheld light meter. I was wondering if someone could help to explain the following:

I wanted to see the difference in EV values between incident and reflected readings. So I used the wall (off-white color) of my office as target, pointed the meter at it, and got a reflected reading of EV 11. But then when I turned the meter around, I got only EV8 as an incident reading from the wall. BTW, I had used the correct lumisphere setting for both readings.

I did expect some differences, but I was surprised to see a 3-stop difference. Can someone shed light on this? As said, I'd never used a handheld light meter before, so I am not sure if it's my way of using it, or if the meter was faulty. How should I interpret the readings?

[Roger Hicks]

How far from the wall were you? And how close to the light source?

Bear in mind, too, that a incident light reading is an artificial highlight, i.e. a reading from the brightest highlight in which you want texture and detail -- NOT 'off-white'.

Cheers,

R.

[Waterman100]

I was about 5 feet from the wall.

Light source was fluorescent light from the ceiling, and some natural light (bec window blinds were lowered) from the window.

Does this help?

Originally Posted by Roger Hicks

How far from the wall were you? And how close to the light source?

Bear in mind, too, that a incident light reading is an artificial highlight, i.e. a reading from the brightest highlight in which you want texture and detail -- NOT 'off-white'.

Cheers,

R.

[stephan_cautaerts]

I think this is normal since the reflected light mode "sees" a white surface and gives you the exposure value for a neutral grey while the incident mode does not interfere with the color of the subject. You won't see this difference when performing the same exercise on a neutral grey surface.
This is also why a snowy landscape turns grey without exposure correction of about 2 stops.

Kind regards,

Stephan

[Landshark]

So you used the Lumisphere for incident only, correct?
There's no doubt the meter should read differently. A white wall will reflect much more light than a darker wall or incident reading. Reflected readings have to be interpreted, IE:when you want a subject to come out lighter you will have to give less exposure and darker subjects like shadow detail will need more. This will come with experience.
Try taking a picture of different color cards(poster board) and take a frame with NO adjustment of the reading.
Then, use the incident reading with the incident ball facing the camera and shoot again, with NO adjustment. You should find the negatives taken using the incident reading will be closer in density than the reflected.

[FrankS]

There is a slide-y thing on the front of the meter that needs to be adjusted for reflected and incident readings.

[Roger Hicks]

Originally Posted by Waterman100

I was about 5 feet from the wall.

Light source was fluorescent light from the ceiling, and some natural light (bec window blinds were lowered) from the window.

Does this help?

So you were probably closer to the light as well? Remember the inverse square law...

But the main point is that as Stephan says, you'd get the same reading with a grey mid-tone (ideally 14%, not 18, but the difference is not great).

I apologize for confusing matters earlier. Some meters have different indices for subects of different reflectivity (I'd just been writing about spot meters). With a very bright white wall under exactly the same illumination as the incident dome (same distance from the light), and using the same index, you'd expect a difference of about 2-1/2 stops (the wall reading brighter). With anything other than a very bright white wall under identical illumination, or a neutral grey card under the same illumination (where the readings should be very close), all bets are off.

Cheers,

R.

[Paul T.]

I might have misinderstood you... but did you point the meter in its incident mode (with the little plastic slider down( at the wall rather than at the light?

Point the meter at a white wall and you will get a reading a couple of stops over, as of course it will assume it's metering a gray scene.

[retro]

Seems right to me.

I have a TwinMate too and the "sphere" is very tiny. On incident
readings you have to be sure to angle the meter so the sphere is
not being blocked by your hand or the body of the meter.

It's a great little meter but I wish the sphere was bigger.

[taylan]

Originally Posted by retro

Seems right to me.

I have a TwinMate too and the "sphere" is very tiny. On incident
readings you have to be sure to angle the meter so the sphere is
not being blocked by your hand or the body of the meter.

It's a great little meter but I wish the sphere was bigger.

i agreed Bob. it is very small and useful especially in street photography. i think you must read something about incident and reflected light measuring. if you get it you can understand why it is reading different values. by the way your readings seems correct.