Canon 6d, sensitivity 200, aperture 18, why does the depth of field appear when I shoot an object less than 1 m?

There are several factors that can affect the background blur (shallow depth of field) of a photo.

1, the longer the actual focal length (not the equivalent focal length) of the lens, the more obvious the blur.

2. The larger the aperture, the more obvious the blur.

3. The greater the ratio of background distance to subject distance, the more obvious the blur is. Especially when shooting macro, background blur is almost inevitable.

You just narrowed the aperture to get a larger depth of field, but close-range photography (near macro) inevitably has a shallow depth of field. As shown in the macro photo below, focusing on the slug's eyes, the left leg is obviously blurred.

90mmF/6.3