What Is E-TTL?

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While taking shots on your Canon camera, you definitely need all the help you can get to capture images with great quality. A Speedlight flash system like an Ettl helps to regulate the amount of lighting for your shots. Yet, as it is with several camera terms, what is E-TTL?

What Is E-TTL?

An E-TTL, also known as the “Evaluative Through-The-Lens” is an autoflash exposure system on your camera that applies some information gotten through its lens to calculate the amount of lighting/exposure that your flash needs to produce for it to capture images with the appropriate brightness.

An image of Canon speedlite

The E-TTL autoflash system functions as a flash meter that helps to regulate and improve the exposure/brightness of your camera in ambient lighting. It makes up for your sensor’s inability to measure accurately the ambient light after it measures the pre-flash lighting and can easily make or break your image quality.

How Does the E-TTL System Work?

Now, after knowing that the E-TTL autoflash mode on your camera is an essential determinant of its ability to produce high-quality images in ambient light conditions, the next question to consider is “How Does the Ettl Work?”

Below is an overview of what takes place when we shoot in the E-TTL mode on your camera:

  1. A pre-flash is triggered whenever the shutter is pressed, and this occurs before the real photograph is taken.
  2. This pre-flash enables light to reflect off of the subject, which then travels through the lens and reaches the integrated light meter inside of the camera.
  3. The flash output is then calculated based on the readings from the sensors of the light meter, which measures the amount of available light.
  4. Using this reading, the camera is able to determine the necessary intensity of the main flash in order to attain the appropriate exposure.
  5. Then, when the shutter finally opens, the main flash fires at this previously determined level of intensity.

The E-TTL system relies on the presence of an autofocus point to illuminate your subject. In some cases, an autofocus point does not cover all the aspects of the subject where you want the flash exposure to reach.

The problem of inefficient autofocus is solved by the ETTL II autoflash mechanism solved using lens-to-subject distance. This mode of operation helps your camera narrow down its measurements using the factor discussed above.

Here’s a detailed overview of how this model works:

  1. When the shutter button is pressed, several sensors measure the current ambient light.
  2. After that, a pre-flash is also projected, which is likewise recorded by all the sensors in the system.
  3. To see how accurate each sensor is, the ambient and flash measurements are compared.
  4. The pre-flash meter readings from accepted areas are weighted and averaged, and then they are compared with the ambient light readings.
  5. This is used to figure out the main flash output and store it in memory for exposure.
  6. If the lens can tell distance, this information is used to figure out how close the subject is and if there are any areas that are very reflective compared to the background.
  7. With this information, the camera’s flash exposure can be made better and suitable for capturing difficult subjects in amber light.

What Are the Effects of the E-TTL on Your Images?

As we’ve said, the E-TTL of your camera can drastically improve or reduce the quality of the lighting of images taken with your camera. However, depending on the different shooting conditions, it can produce different effects on your images.

While using a direct on-camera flash, the E-TTL is capable of casting vivid, dark shadows behind your subjects. It can also produce a diffuse light with less image contrast while using an indirect bounce flash.

The Ettl also produces a vivid, dark, and high-contrast image when you shoot with side-lighting. Although the E-TTL system can display different effects on your images, depending on how you shoot,  it still maintains the same exposure level.

An image of Canon camera with lighting

What Are the Benefits of Using E-TTL?

Here are some of the upsides of using the E-TTL to regulate flash exposure:

  • Enables you to shoot with the proper flash system for specific lighting conditions
  • Improves your camera’s light sensors for better performance
  • Helps to capture quality images even in poor lighting conditions

Related Questions

Do All Cameras Use E-TTL?

Not all cameras use E-TTL, as this mechanism is only specific to Canon cameras. However, other camera models have their own through-the-lens systems that they use similar to the Ettl on canon.

Is the E-TTL the Same as TTLFlash?

Although they both help to regulate exposure, the E-TTL is not the same as a TTL flash. While the latter uses light reflected from the film to take readings, the former uses a Pre-flash system to set the flash exposure before capturing an image.


The E-TTL is an autoflash mechanism peculiar to canon cameras. It uses through-the-lens information to set the right exposure for your flash to capture stunning images even in amber lighting conditions. This mechanism can drastically affect the quality of your everyday shots.