Most people know that full-frame cameras have larger sensors and better image quality. However, when photographing aircraft, the APS-C focal length offers more advantages. Deciding which model to use is indeed a headache. Let’s take the Canon 5D4 and 7D2 as examples to see the differences in Depth of Field (DoF) between full-frame and APS-C bodies.

For example, photographing an object 100 meters away: When using the 7D2 with a 200mm focal length and aperture f/7.1, You can see the Depth of Field is 75 meters.

To photograph the same object with the 5D4 requires a 320mm focal length, Therefore, the Depth of Field is only 43 meters, much shallower than the 7D2!!

To achieve equivalent Depth of Field, the aperture needs to be stopped down to f/11, At this point, the Depth of Field is 71 meters, basically the same as the 7D2. However, with a smaller aperture, the amount of incoming light is obviously reduced, When shooting in low light, you have to increase the ISO to get sufficient brightness, This in turn has a major impact on image quality.

So, when a large Depth of Field is required, it seems best not to blindly insist on using full-frame. Conversely, if you want background blur (bokeh), full-frame is still better. In short, understand the characteristics of your gear and choose the most suitable equipment based on the subject and purpose of the shoot—that is the right approach.

If the subject is further away, the impact on Depth of Field diminishes. For example, shooting at 500 meters with the 7D2, aperture f/4.5, the Depth of Field is near infinity, Using the 5D4, aperture set to f/6.3, the Depth of Field is 6 km, basically the same.

What if the distance is 1000 meters? With the 7D2, aperture f/4.5, Depth of Field is infinite, With the 5D4, aperture f/4.5, Depth of Field is infinite, It seems that at long distances, the Depth of Field difference between full-frame and APS-C is negligible.