How To Generate Bright and Clear Shooting

By increasing the ISO speed, this will increase the camera's sensitivity to light (photosensitivity), so you can capture bright shots with a glimmer of light. If you raise the ISO speed and fire the flash at the same time in the telephoto shot, the flash will be able to reach a longer distance. Sufficient brightness can also be obtained easily if the flash intensity is weak. Here I will explain the effects that can be gained from combining high speed ISO with flash photography.

Capturing the Face of a Model Model

After placing the emitter flash unit at a greater distance from the subject, the light will spread to a wider area, and therefore will weaken the irradiation on the subject. In this case, you can raise the ISO speed to increase photosensitivity (photo sensitivity) of the camera. By doing so, you can gain sufficient brightness, even if the intensity of the flash light is weakened. In this example, I
set the ISO speed to 800 and the exposure compensation to + 2EV to capture the glowing faces of both models on the stage in brightness. To prevent the subject from being blurred due to subject movement, I set shooting mode to Shutter-priority AE, then set the shutter speed to 1/200 sec.

Suggestion
Use a higher ISO speed to compensate for weak light due to longer distances 

Select Shutter-priority AE mode to prevent the subject from becoming blurred.

Shooting Conditions

The camera's distance from the model is only about 5m. The stage is surrounded by rails so it is impossible for me to move closer to them. At ISO 100, a considerable amount of light is required to obtain sufficient brightness from this distance. In fact, a brighter atmosphere would be preferred.

Catch the Wild Bird in Clear Colors from a Long Distance

To reproduce this wild bird color clearly in a dimly lit forest, I take advantage of flash, and reduce the flash exposure compensation to -0.3EV to prevent strong flashes from damaging the natural environment. Nevertheless, the camera's distance from the model is only about 10m. So, I set the ISO speed to 1000. By improving camera photosensitivity while keeping the flash intensity low, I can reproduce the bird color in the distance in bright and clear color tones.

Shooting Conditions
The atmosphere of tropical forest is dim, after rain. I climbed a not-so-high hill to catch a quetzal bird shot (Pharomachrus Mocinno) perched on a tree branch at its eye level. Reproduces clear colors This will be difficult if only rely on high ISO speed.