The incident light meter has a semicircular head and a flat head that can be replaced. So when should I use a semicircular head and when should I use a flat head? Why

There is a slight problem with the question. Just remove the first two characters.

The two words removed are almost the question and the answer. But it’s wrong to put it on the first two words.

:-)

The light meter has a semicircular head and a flat head that can be replaced. So when should a semicircular head be used and when should a flat head be used?

The milky white hemispherical cover is used to measure the incident light;

Remove the milky white hemispherical cover to expose the flat photometric window inside, which is used to measure the incident light. Reflecting light.

Most handheld light meters now can be used for both purposes.

It can measure both incident light and reflected light.

Most modern cameras have built-in TTL metering.

In fact, what is measured is reflected light.

Light shines on the object, reflects into the lens, and reaches the photometric element.

There is a problem with the reflectivity of objects.

Common textbooks will definitely talk about extreme examples of shooting snow and coal.

Incidence metering is not affected by the reflection of the object surface. It directly measures the illuminance of the light hitting the subject.

When the incident light meter is working, the meter head (white hemispherical head) is facing the light source, and the light meter should be close to the position of the subject to be measured.

When the reflective light meter is working, the meter head (flat head) is pointed directly at the subject where the light is to be measured, as close as possible, but do not let the light meter or your body block the light.

There are also some light meters with lenses, which are just telephoto lenses with a small angle to facilitate the measurement of reflected light from subjects that are inconvenient to get close to.

Supplement:

Yes, your original method of using the light meter was wrong.

The white hemisphere should be facing the light source, because you are receiving the light from the light source, that is, incident type.

Why add this white ball cover? Just take into account the diffuse reflection of light.

Generally, the main light is basically on the same side as the camera,

So it is almost the same if you use a white dome to face the camera.

But in theory it should be pointed at the light source.

"Reflected light metering may be affected by the direct exposure of the contour light behind the object."

So we must find ways to overcome interference, block what should be blocked, and expose what should not be blocked. of.

If you cannot avoid it, the causing light should be turned off.

Strictly speaking, studio light metering should be measured one lamp at a time.

Afterwards, adjust them one by one according to the conditions of each lamp and the key is your needs.

When photographing a model, you don’t just measure the face, you measure at least three points at the top, middle and bottom.

Of course, whether the values ??of these three points should be consistent depends on how you design them. .

The readings of the light meter are for your reference, and they are not meant to be taken using the exposure combination that represents the number.

For example, if you want to take a backlit silhouette, where should you meter the light?

Test the face facing the camera? If you take pictures and adjust according to the readings obtained in this way, you should get a portrait with normal exposure, and the silhouette effect will be gone.

So, the light meter is an auxiliary tool and must be used flexibly in actual use.