Author Topic: Measuring reflected light using an incident light meter  (Read 7401 times)

Zang

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Hello everyone,

I wonder if anyone know a trick to measure reflected light just like cameras do, using an incident light meter?

Cheers,
Zang

Akira

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Re: Measuring reflected light using an incident light meter
« Reply #1 on: June 20, 2019, 03:15:00 »
An obvious answer should be, yes, a dedicated light meter.  Spot meters or light meters with the adapters the enable them to meter reflected light.

Nowadays, I guess there are smartphone apps to meter utilizing the integrated camera.  I'm not sure of their accuracy, though.
"The eye is blind if the mind is absent." - Confucius

"Limitation is inspiration." - Akira

Zang

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Re: Measuring reflected light using an incident light meter
« Reply #2 on: June 20, 2019, 05:40:50 »
I do have a light meter but it has incident metering only. I wonder If and how I can make an adapter to make it meter the reflected light :)

Cheers,
Zang

Ann

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Re: Measuring reflected light using an incident light meter
« Reply #3 on: June 20, 2019, 06:19:02 »
Adapters for measuring reflected light for some meters are available — including some Sekonic ones.
(B&H, among others, sell them.)

The reason most people use a meter is for taking Incident Light readings which are particularly helpful when balancing several light sources; or for gauging the correct exposure for difficult subjects like the proverbial white-dog-in-the-snow or black-cat-in -a-coal-cellar.


Birna Rørslett

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Re: Measuring reflected light using an incident light meter
« Reply #4 on: June 20, 2019, 07:30:34 »
If one is going to the trouble of using a separate light meter, measuring *incident* light is vastly more useful and informative than what is reflected. If the latter is deemed necessary, using a spot meter probably is the better approach.

In all situations whether incident or reflected light is measured, an evaluation of what the reading entails in terms of exposure is mandatory.

armando_m

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Re: Measuring reflected light using an incident light meter
« Reply #5 on: June 20, 2019, 15:34:45 »
For reflected light why not just use the camera light meter ?
Armando Morales
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Hugh_3170

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Re: Measuring reflected light using an incident light meter
« Reply #6 on: June 20, 2019, 18:20:07 »
There are various diffusers and discs that can be attached to the lens of camera to turn it into an incident meter.

Here is one:   https://www.expodisc.com/pages/expodisc-2-0-instructions

At a pinch, a thin polystyrene sheet or even a polystyrene coffe cup can be pressed into service  - as a starting point for those that are experimentally inclined.
Hugh Gunn

Zang

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Re: Measuring reflected light using an incident light meter
« Reply #7 on: June 21, 2019, 01:14:17 »
For reflected light why not just use the camera light meter ?

I plan to use some combination of lens and adapter that does not support the camera metering :)

Zang

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Re: Measuring reflected light using an incident light meter
« Reply #8 on: June 21, 2019, 01:16:10 »
There are various diffusers and discs that can be attached to the lens of camera to turn it into an incident meter.

Here is one:   https://www.expodisc.com/pages/expodisc-2-0-instructions

At a pinch, a thin polystyrene sheet or even a polystyrene coffe cup can be pressed into service  - as a starting point for those that are experimentally inclined.

Hmm, I plan to turn my incident light meter to a reflected one, not my camera :) Thanks anyway.

Matthew Currie

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Re: Measuring reflected light using an incident light meter
« Reply #9 on: June 21, 2019, 04:46:30 »
Is this a digital camera?

I ask because I've found that most hand held reflected light meters are pretty imprecise, since they don't "see" exactly what the camera's sensor does, and as a result, unless one is in an urgent situation where there's only an opportunity for one shot, the usual way to do it in a digital camera would be to take a guess and then use the camera's histogram to adjust it.

Cameras like the D3200 do not meter at all with manual lenses and adapters, and I always found that was the simplest way to do it, as the wide view of a hand held meter rarely matches the view of the camera anyway.


Hugh_3170

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Re: Measuring reflected light using an incident light meter
« Reply #10 on: June 21, 2019, 07:00:05 »
All of which is why I prefer the Expodisc approach and using the digital camera with its inbuilt meter; the last points (camera view) being something that few meters can emulate.

Is this a digital camera?

I ask because I've found that most hand held reflected light meters are pretty imprecise, since they don't "see" exactly what the camera's sensor does, and as a result, unless one is in an urgent situation where there's only an opportunity for one shot, the usual way to do it in a digital camera would be to take a guess and then use the camera's histogram to adjust it.

Cameras like the D3200 do not meter at all with manual lenses and adapters, and I always found that was the simplest way to do it, as the wide view of a hand held meter rarely matches the view of the camera anyway.
Hugh Gunn

pluton

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Re: Measuring reflected light using an incident light meter
« Reply #11 on: June 21, 2019, 07:22:22 »
There is no way to make incident meter read as a reflected light meter, UNLESS the incident meter was designed to do both jobs, such as my Minolta (now Kenko) Auto Meter IV.  It is intended as primarily an incident unit, but the sphere can be swapped out for a black disc with a square hole in it, which is said to give a nominal 30-40º reflected field of view to the meter. Spectra and Gossen have made these dual types;  Sekonic may have them also.
With a bit of experience, reflected exposure for common types of scenes can be fairly accurately guessed using a straight incident meter as a rough guide. One must take over thinking from the hands of the machine, so to speak.
Birna's suggestion about the usefulness of the spot meter among reflected meters is is right on.
Keith B., Santa Monica, CA, USA

Zang

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Re: Measuring reflected light using an incident light meter
« Reply #12 on: June 21, 2019, 16:36:20 »
There is no way to make incident meter read as a reflected light meter, UNLESS the incident meter was designed to do both jobs, such as my Minolta (now Kenko) Auto Meter IV.  It is intended as primarily an incident unit, but the sphere can be swapped out for a black disc with a square hole in it, which is said to give a nominal 30-40º reflected field of view to the meter. Spectra and Gossen have made these dual types;  Sekonic may have them also.
With a bit of experience, reflected exposure for common types of scenes can be fairly accurately guessed using a straight incident meter as a rough guide. One must take over thinking from the hands of the machine, so to speak.
Birna's suggestion about the usefulness of the spot meter among reflected meters is is right on.

Konica-Minolta Auto Meter IV is the one I have. Brand new in box unused for 15 years :) I do not have the adapter so I guess it was not included, but I can try 3-D print it.

Ann

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Re: Measuring reflected light using an incident light meter
« Reply #13 on: June 21, 2019, 18:35:24 »
Birna's comment about "interpreting" what the meter is indicating is so important.

You need to understand that the meter's recommendation will produce a 12% Grey.

Do you actually want grey Snow or a grey Black Cat?

The object from which you take a metered measurement (whether by the Spot or the Reflected Light method) will affect the recommended exposure setting: the photographer still has to interpret what the meter (whether in a camera or in his hand) is telling him.

If you Spot meter from a human face, remember to adjust for the skin-colour.
Spot meter a White object and then expose by +3.00 EV.
Green grass can stand-in for the traditional Grey Card with a Reflected Light meter.

However, an Incident Light meter simply measures the light that is actually hitting the subject (regardless of what that subject is) so you have a standard from which you can adjust your camera settings to achieve the results which you want to achieve.

Back-lit object (without any fill-in lighting)?
Do you want a silhouette against a colourful background; or do you want a detailed subject against a blown-out background?

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I did a quick google and a reflected-light converter for your Minolta is being sold on eBay for $20.

https://www.ebay.com/itm/Konica-Minolta-40-Degree-Reflected-Light-Attachment-8038700/183666529829?hash=item2ac360d625:g:cUUAAOSwqLlcVeEn



pluton

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Re: Measuring reflected light using an incident light meter
« Reply #14 on: June 21, 2019, 19:07:33 »
Same...for the Kenko, which may or may not fit... at B&H for a bit more:https://www.bhphotovideo.com/c/product/552281-REG/Kenko_KFM400_KFM400_Reflected_Light_Attachment_for.html
Keith B., Santa Monica, CA, USA