Many photo viewers, when they see my very clear drop photos, first ask what shutter speed (shutter speed) the photo was taken with, and when I say the shutter speed is 1 second, they are quite surprised. They seem to be right in this surprise, because technically a shutter speed of 1 second means exposing the photo quite long. Actually, the movement should not freeze, but blur.

Well, cameras now support a very high shutter speed of 1/8000, one might ask why we don't take advantage of it.

Of course, photographers take advantage of this. In sports competitions or shooting moving objects, clear photos can be obtained if there is enough light and lens apertures allow it, or by using features such as high ISO values.

However, in the studio environment, it is not possible to take a clear drop photograph with a shutter speed of 1/8000 and a lens aperture of 2.8.

We can list the reasons for this as follows.

We're shooting close-ups and our lens aperture has to be pretty low for adequate depth of field, at least f/18

We cannot constantly illuminate the environment with light, at that point the drop motion will be blurry anyway.

If we say to use flash, when we exceed 1/200 shutter speed, photo blackening will occur.

Even if we overcome this problem by using the HSS etc (high speed sync) feature supported by modern cameras, 1/8000 f18 exposure values ​​in the studio environment will require 3-4 flashes running at full power.

Here we stand and say this. On the contrary, we use low-power flashes to freeze the droplet motion. We will examine this in more detail in the article.

Now, first of all, let's examine the characteristics of the flash light in general.

Of course, today, as in every subject, flash technologies are also developing and these advanced technologies are getting cheaper.

Basically, there are two types of flash. Flashes that we call overhead flashes that can be attached to cameras and studio flashes that can be used independently. Overhead flashes can also be used independently today. However, these two main groups are separated in terms of light powers and functions.

How flashlight and camera work in sync

Figure 1-2


Flash machine sync
In this case, the sensor is exposed by the flash light during the entire curtain movement.
In the image above, on the left, there is the shutter system found in many modern DSLR cameras. The curtain system consists of two leaves. First act and second act. As soon as you press the shutter button, the first curtain opens and the second curtain starts to close in line with the selected shutter speed.

Cameras can synchronize with flashes at shutter speeds of up to 1/250-1/320, and they help the photograph to be fully exposed. As seen in Figure 1-2 above. Normally, when flashes are used with a shutter speed higher than their fixed sync speed, the photo will be darkened due to insufficient exposure. Figure-3

Figure-3


Systems that allow us to shoot at a higher shutter speed than the fixed synchronous speeds are also used. These technical features, which we can generalize as high speed sync, are called HSS (High Speed ​​Sync), Hypersync, High-Sync.

While Hypersync, High-Sync systems have a very close technique to each other, HSS works with a very different technique. However, since HSS exposes with many bursts like a stroscopic flash, it reduces the current flash power considerably and consumes a lot of energy.

The other two techniques synchronize the start and end of flashing by detecting the shutter speed, regardless of the shutter speed. Therefore, there is no power drop and they consume less energy.

But regardless of the shutter speed of the camera, the flash light has a time. This term is included in the literature as “duration”.

Flash manufacturers use two basic ranges of measurement for this time. T 0.5 and T1

Figure-4


As you can see in Figure 4, the T0.5 value is the time the flash intensity is above 50% of its maximum brightness. The T01 value is the time during which the flash intensity is above 10% of its maximum brightness. Therefore, the T0.1 value is a much more accurate assessment of the actual flash duration. However, many flash manufacturers highlight T0.5 flash times as they create higher motion freeze time.

The two images to the side use two different patterns of flash and show the effect of flash duration on a moving object, it was a bicycle wheel spinning at serious speed. In the top image, the flash duration t0.5 (as measured on the Sekonic L-858D-U) is 1/353 second, which is quite slow. Bicycle wheel becomes blurry due to slow flash time. In the bottom image, the flash duration t0.5 was 1/5.350 seconds, which is a pretty fast flash duration and hence the wheel is frozen. Let's mention here that the flashes are fired with full power.

Compared to the bicycle wheel speed and size above, it is used to increase the duration of these flashes to freeze the movement of the forms formed by the collision of two water drops on a millisecond basis. This increase is achieved by reducing the power of the flashes. Compared to studio flashes, peak flashes have a higher duration (in a sense, freeze motion) at low power.

Below is the table showing this comparison Figure 5