Aperture

Definition

The opening of a lens is the ratio of the Focal length distance and b>Diameter of the aperture (N = F / D). The diaphragm being the mechanical element which reduces the opening between the lens and the sensor.

N is a number without units, commonly denoted F / # where # is the aperture diameter of the diaphragm.

Change the aperture is to act on:

Brightness

Mechanically, the more the diaphragm is closed, the less light enters the housing.

Depth of field

The higher the aperture open, the smaller the region of space in which the subject is in focus.

Optical aberrations

The higher the aperture open, the more you will see the optical defects due to the lens.

For more information, please visit Wikipedia

Digital Camera Modes

Full Automatic

In this mode, the camera controls all parameters in order to offer you the best possible configuration. But this configuration is not done to make long exposures, so this mode will be totally useless to Light Painting.

Program Mode

On Program Mode (P for Nikion & Canon ), lthe camera calculates the exposure speed and perfect opening through its specific algorithms. However you have control over the other parameters, particularly the ISO sensitivity.

Shutter Priority Mode

On Shutter Priority Mode (S for Nikon | Tv for Canon), you set the exposure time, the device then determines the aperture according to the illumination.

Aperture Priority Mode

In Aperture Priority Mode (A for Nikon | Av for Canon), it's the opposite, you set the aperture and this is the device that determines the exposure time depending on the brightness.

Fully Manual Mode

In this mode (M for Nikon & Canon ), you take control over all critical parameters. The camera controls more than nothing, he runs. It's up to you to find the best configuration. This is the best mode for long exposures and therefore the one to use for Light Painting.

Depth of field

The depth of field is the area of space in which the subject must be so that it is in focus.

The size of the area depends on the distance of focus, the aperture and the size of the sensor. Control of depth of field allows to highlight a subject. Higher the depth of field is, the more the subject is integrated in its environment. By contrast, over the depth of field is small, the more the subject is isolated. The foreground and backgrounds are then more or less blurred.

Use the aperture to make Light Painting

When we perform long exposure photography, we mostly use low diaphragm openings, even very low. This is explained by the need to reduce the amount of light that reaches the sensor. This specificity of Light Painting allows to have a large depth of field, which may prove handy.

This is generally one of the settings who give best results.

But the use of the aperture allows to also consider much more!

Decrease brightness

When working in a bright environment, the lower ISO is not enough! To achieve an long enough exposure time, two solutions exist, reduce the aperture or use filters. Reduce the aperture is usually the most effective solution.

Supprimer les parasites

Reducing the aperture attenuates parasitic effects (blur and halos) that appear around the drawings when working in dark environments. These effects, totally normal, not always very beautiful and often pollute the readability of drawings.

Depth of field

Any photographer knows, nothing like a very small aperture for maximum depth of field. When making Light Painting, we mostly work with a viewing angle as wide as possible, or with a wide angle lens, in order to make the most of this space, it is better that everything is as net as possible.

The scene

Choose a place where light does not fail, indoors and outdoors. Please note, not too much light!

Scope

After installing the scene, do some scoping tests to see the configurations proposed by your camera. To do this, put your camera in automatic mode and made some pictures. This test will be interesting for comparisons with next pictures.

Exposure time

We will try to take a picture with an exposure time of 5 seconds. It's very short, but it should give us enough time to do few drawings! So set your camera to an exposure of 5 seconds.

ISO sensitivity

Minimize the ISO sensitivity of the device, ideally, a dSLR can go down to ISO 100.

Aperture

Now ISO and exposure time are set, it remains to find the right opening to get a photo with the exposure (brightness) that will be comparable to those of our tests in automatic mode. To do this, go to the lowest aperture and increase step by step until you have a correct result.

LightPainting Tutorial - Aperture Test F/25 - ISO 100 - 5s Exposure

F/22

F/20

F/18

F/16

F/14

F/13

F/11

F/10

By observing the results, we quickly noticed what settings best match. Here, aperture F / 25 and F / 18 clearly seem best suited. Other openings give too bright image.

 Trick

Much of the modern SLR cameras offer tools to facilitate manual or semi-automatic setup. In particular, a contrast gauge that calculates in real time the brightness "theoretical" of the picture depending on the chosen settings. These functions are available for all exposure times, provided it is fixed. Feel free to use it to save time.

Shoot it!!!

In the first photo, we chose the aperture of F / 20, which seemed to be the best compromise for the image, the light from the lamp is saturated, but still net.

LightPainting Tutorial - Light painting with Ambiant Light F/20 - ISO 100 - 5s Exposure

For the second photo, we chose the aperture of F / 25 which makes a little darker image, however the light of the lamp is not saturated and allow expressing the color.

LightPainting Tutorial - Light painting with Ambiant Light F/25 - ISO 100 - 5s Exposure