Bokeh Simulator
See the blur before you shoot.

Bokeh describes the appearance of out-of-focus areas, including the shape of blurred highlights. Depth of field describes the distance range that appears acceptably sharp. A shallow depth of field can help separate your subject from the background, but it does not tell you whether the blur will look smooth or busy. This simulator compares blur amount and cat-eye effects; individual lenses can render bokeh differently.

Choose a subject, then adjust the sensor, focal length, aperture, and distances. Click Save as A, change a setting, and drag the A/B split to compare the saved setup on the left with the current one on the right. The summary explains the difference in background blur. You can also start with a comparison preset in the tips section. This is a tool for planning and learning about camera settings; it does not edit your uploaded photos.

Depth of field is the range in front of and behind the focus distance that appears acceptably sharp. The calculator shows the near and far limits below the total depth. With the default full-frame, 50mm, f/1.8 setup focused at 3 m (9.8 ft), that range is about 2.83–3.20 m: roughly 37 cm, or 14.5 inches, deep. Holding the lens and focus distance fixed, stopping down increases the range. Moving farther away with the same lens also increases it. Switching to a smaller sensor while matching framing and keeping the same f-number generally increases depth of field. Changing focal length while moving the camera to keep subject size usually changes the depth near the subject much less.

This simulator uses full frame as the reference and adjusts actual focal length to keep the subject the same size when you switch sensors. At the same f-number and distances, the smaller sensor uses a shorter lens and produces less visible background blur at the same display size. For distant subjects, Micro Four Thirds at f/1.8 gives roughly the depth of field and blur of full frame at f/3.6 with matched framing. That equivalence describes blur, not the exposure setting.

Keep subject size is on by default. As you change focal length, the camera moves to maintain the subject framing while the gap behind the subject stays the same. Stepping back with a longer lens changes perspective: the background appears larger relative to the subject, often called compression. Turn the switch off to zoom from a fixed position. Editing the subject distance or dragging the subject moves it between the fixed camera and background; the new subject size becomes the reference.

It is a way to compare framing across sensor sizes using a full-frame camera as the reference. The crop factor is 43.27 mm divided by the sensor diagonal. For distant subjects, actual focal length is approximately the equivalent focal length divided by that crop factor. At close range, this thin-lens model adjusts for image distance to match the subject size. You can enter the actual lens focal length directly. The preview uses a common 3:2 frame and diagonal-based scaling, so it does not reproduce every sensor aspect ratio exactly.

No. The iPhone option compares optical blur using an approximate 1/1.59-inch-type sensor modeled as 4:3, about 8.05 × 6.04 mm. These dimensions are an estimate, not a measurement of the device. Apple’s US technical specifications do not list the physical sensor dimensions. Computational blur added by Portrait mode is not simulated.

The calculator uses an ideal thin lens focused on the subject. It calculates the diameter of a defocused background point on the sensor. In the equation, f is actual focal length, N is the f-number, s is camera-to-subject distance, and z is camera-to-background distance. All lengths in the equation are in millimeters; distances are measured from the ideal lens principal plane. Reference: Foundations of Image Systems Engineering — Thin lenses

The acceptable circle of confusion is the blur threshold used to decide what appears sharp. Here it is the sensor diagonal divided by 1,500, or about 0.029 mm for full frame. It determines the reported depth of field, not the physical background blur diameter. Perceived sharpness also depends on viewing distance, output size, and eyesight.

The preview uses a 3D scene to show the positions of the subject, ground, and background. With Keep subject size on, changing focal length moves the camera, which changes perspective and how large the background appears. Turn it off to zoom from a fixed position. Some backgrounds use AI-generated images. The preview helps you compare settings; it does not reproduce an actual photograph exactly. Some devices or browsers may use a simplified image preview. Extreme distances and focal lengths can reveal the limits of image coverage and detail. Very strong blur is limited in the preview, while the numerical results remain uncapped.

It does not reproduce lens-specific bokeh, color fringing, loss of sharpness at very small apertures, exposure changes, or minimum focusing distances. It also simplifies the depth within the person and dog, the distances between objects in the background, and foreground blur overlapping the subject. Use it to compare how settings change the image, rather than to predict the exact look or compatibility of a specific lens.