In this case, a light meter that is suitable for both modes would need to know what kind of measurement it is doing in order to yield correct results. For instance, according to the manual of Gossen Sixtomat F2, the only thing that a user needs to do to change between modes is to move the white dome accordingly. I assume that internally, there are switches to determine the position of the dome for the meter's electronics to distinguish between modes.

Incident lightmetervsspot meter

A reflected metering tells you how much you need to compensate your exposure based on the specific subject you're shooting, because it may be backlit, or have a dark background, or have other specific conditions that make the scene lighting particular, unique, and well, not boring gray.

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incidentlight中文

GU1d0 is fitted with a MINI GU10 (or MR11) bulb, smaller than the normal GU10 bulb because of its 35 mm diameter and 46 mm height (socket included) that you can replace very easily by removing the silicone ring and rotating the bulb.

When you move the plastic dome, position the lightmeter in the place of the gray card, and point it toward the light, the plastic dome reflects some light, disperses some other light which does not enter the hole (B) and, as if it is well designed, will spill the equivalent of 18% of the light it received inside the hole into the sensor.

Here you will find detailed and analytical articles about the latest trends, technologies, and products in the field of lighting.

Reflectivelightmetering

In this method, the meter is pointed, not at the subject but in a direction that reads the light that is about to play on the subject. The method is called an “incident” light reading. Incident is old French for about to happen.

Incident light vstransmittedlight

A reflective light meter assumes a nominal reflectivity of the subject. But different objects and surfaces reflect light differently, including differing colors, which affect the light intensity entering the meter. Subjects darker than middle gray reflect less light, and thus will be metered (exposed) higher. Conversely, subjects brighter than middle gray will be metered darker. Smooth reflective surfaces, even dark ones, with specular light reflection will show up very bright. The meter doesn't know this.

Today, our cameras use sophisticated metering technology coupled with computer chip logic, all this and the experience of the photographer, get the job done.

Incident lightmeter app

Measuring incident light makes no assumptions about the subject, because it's not measuring the subject. It's measuring the environmental light falling on the subject.

Well, of course you're assuming equal lighting conditions, because that's the scene and light you're measuring. But no, you're not correct in assuming. By spot metering the gray card, your exposure settings will render the gray card as middle gray. That's it.

Now, when using an incident light meter, the meter should assume that the measured light is the same as that reflected by the subject. In order to provide a reading that will also render an 18% reflective object a middle gray tone in the photography, is it going to calculate that the measured incident light will be reflected by 18% by the subject, thus mulitplying the measured light intensity with 0.18 before treating it like a reflective light measurement?

Technical specifications: Kit for spotlight in different finishes Total diameter 44 mm Total height 76 mm Upper hole: M10x1 1 GU10 lamp holder with push-fit connectors Rated voltage: 250 V Rated current: 2kV Press-in terminals for cables 0.5 mm2:0.75 mm2 Certificazioni: EN60838-1:2017+A1

Incidentmetering

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Mini GU10 LED light bulb: Connection: Mini GU10 (MR11) Volts: 110-240V Energy class: F Light colour: 2700 K Watts: 3.2W Lumen output: 260 Lm Dimensions : D 34.5 mm ; H 46 mm Dimmable: NO

The first practical light meter was a thermometer. Researchers in England circa 1900’s, took temperature readings in sunlight and in shadow, a chart was consulted which returned the camera settings. Carts and tables gave hit or miss settings. The electric light meter arrived on the scene in the early 1930’s. These light meters averaged the scene’s brightness. Kodak laboratories discovered that one could take a close-up reading of a yellow film box. Seems this box, when properly exposed was rendered as a middle-gray tone on the finished film/print.

Reflected lightmetervs incident

You used the word "assume" quite a bit. Unfortunately, your assumptions about the assumptions made by the light meter are incorrect.

The diffusion dome itself reduces the incident light transmission to equal ~18% grey reflectance. The meter sensor inside simply reacts to the intensity of the light that falls on it, reflected or incident. I.e. there are no "switches" required and the sensor doesn't need to know what the operating state is. Use the meter wrong and it will give you bad information... it doesn't know or care.

I wasn't able to find any related information in web searches. Maybe my understanding is fundamentally wrong, in which case I ask you to help me out...

You are correct that the light meter is calibrated to 18% gray. But no, there is no "multiplication by .18" going on. Don't get hung up on the number 18% or 0.18. It's just a thing, a standard. Might as well call it "nominal gray", "middle gray", or even "arbitrary gray" for purposes of using the light meter.

You can make the dome bigger, smaller add more plastic, or remove the thickness of the dome so the right amount of light enters and gives you a consistent reading, either incident or reflected.

In other words, assuming equal lighting conditions and an 18% gray card as a subject, in order for an incident and a reflective light metering to yield equal exposure settings, am I correct in assuming that the only difference of both modes is that in incident mode, a light meter needs to account for an assumed reflection of 18%, but otherwise works the same way as in reflective mode?

I am struggling to understand what is going on inside the logic of an incident light meter in order to determine the exposure as opposed to a reflective light meter.

The theory of these methods, if you can figure out the exposure setting that will render one tone of the scene correct, the rest fall in line by law. Thus, rendering the 18% “middle gray” correct, provides the best basis for exposure.

The goal isn't to get an incident light meter and reflected meter to yield equal exposure settings. They are not interchangeable or "convertible" techniques.

An incident light meter essentially tells you "you're in Sunny 16 conditions", or "you're in indoor lighting conditions". It tells you the intensity of light, in EV.

Reflectedmetering

In other words, assuming equal lighting conditions and an 18% gray card as a subject, in order for an incident and a reflective light metering to yield equal exposure settings, am I correct in assuming that the only difference of both modes is that in incident mode, a light meter needs to account for an assumed reflection of 18%, but otherwise works the same way as in reflective mode?

GU1d0 has a hidden cable clamp which has an M10x1 thread at the top. This allows it to connect it to joints (like our Snodo), flexible tubes (like our Flex) or extensions.

You have a light source (L) and some rays hit your gray target (C). This absorbs some rays and reflects 18% of the light to the lightmeter which has a hole (B) and a sensor (A)

I understand that a reflective light meter assumes the measured spot to represent a middle gray tone, and accordingly displays exposure settings that will render the measured portion of the frame as a middle gray tone.

Written GU1d0 but pronounced GU1d0, it is a mini spotlight for directional LED light that allows you to illuminate with an approximately 260-lumen directional beam light the bedside table when reading, your child's homework (when he eventually decides to do it), in short, any point where you need a direct and circumscribed beam of light (of about 36°).

Let me add, Cine photographers (movie camera operators) relied almost exclusively on the incident method. Considering the cost expended on a Hollowood movie shoot, they were under pressure to get the exposure right the first time.

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This discovery led to the use of a target placard with an 18% reflective surface. We call this a “gray card”. The 18% gray card became a useful tool for exposure determination. An alternative to carrying a gray card was a translucent cover that mounted over the entrance of the light meter. This device furnished a light meter reading that matched a reflective 18% gray card reading.

You can get adaptor disks that will do the same thing for your camera making it suitable for making incidence readings. This is just one version.