The Correct ISO Value When Doing Photography

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The correct ISO value:

The ISO value describes the light sensitivity of the image sensor. In the past in analog photography in difficult lighting conditions you inserted a film with higher ISO sensitivity, today in digital photography it is possible to change the ISO sensitivity of the image sensor simply by pressing a button.


If the lighting conditions become so difficult that, even with the aperture open, a blur-free exposure by hand is no longer possible, because the exposure time is too long for an adequately exposed picture, you have the option of increasing the light sensitivity via the ISO value increase. An ISO value of 100 is often set by default, but this is often too low in difficult lighting conditions.

In order to take a blur-free picture with the same exposure and aperture settings, it is necessary to set the ISO value to a value of 200, 400 or higher. With a shutter speed of 20 minutes and ISO 100, for example, you only need 10 minutes shutter speed with the same aperture setting with ISO 200, with ISO 400 only 5 minutes and with ISO 800 only 2.5 minutes. Doubling the ISO value therefore halves the shutter speed. If you increase the sensor sensitivity, the so-called image noise and interference in the image signal also increase. Image noise becomes visible in the form of grit or clumps of color and the performance of the sensor also decreases. This means that high contrasts can no longer be managed so well and colors appear a bit paler.

Since your camera is only attached to a tripod for night photography and most photos are taken using the remote release in order to keep any camera shake as low as possible, it does not always make sense to increase the ISO sensitivity above a value of 100. The exposure time is then a little longer, but the noise behavior and sensor errors are as low as possible. Thus the image quality of the finished photo is better than with higher ISO values.

Nevertheless, you can take advantage of the ISO sensitivity of your image sensor for night photography by increasing it to find the right image section in the dark. In this case, set the ISO value to a very high value. Now you only need to expose relatively briefly, even in the dark, in order to align your camera with the correct image section. Once you have found it, set it back to ISO 100, as this ensures the best image quality.

It is best to always take photos in the lowest ISO value. But there are also subjects for which a higher ISO value makes sense. The basic setting should, however, be low in order to avoid image noise.

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