LensSimulator.photo: Interactive Lens, Bokeh & Depth of Field Simulator

What Lens Simulator does

• Side-by-side 3D portraits: keep the subject the same size, or walk closer and farther yourself
• Ray-tracing of lens profiles based on patent information from Nikon, Canon, Sony, Leica and Fujifilm: glass, bokeh, vignetting and focus breathing
• Live Optical X-Ray of the cross-section, the aperture stop, the ray path and the focusing groups
• Depth of field and perspective: camera distance, near and far limits, hyperfocal distance and background compression from f/0.95 to f/32
• 1-inch, Micro Four Thirds, APS-C, full frame, medium format and 4×5 / 8×10 large format

How the simulator is built

How to read the simulator

Choose a framing preset (Face, Headshot, Upper body, Full body) and the simulator moves the longer lens farther back so the person stays the same size in the frame. To test a tight room or minimum focus, drag Camera distance and walk forward or back yourself. Open Side view for the sharp zone in metres, or Optical X-Ray to watch the focusing elements move inside the barrel.

Ideal lens math vs. real patent ray-tracing

Each camera has two modes.

Ideal lens uses thin-lens math for the geometric effect of focal length, aperture and sensor size on background blur.

Real lens traces rays through the multi-element glass prescription from the optical patent. Compare it with an ideal lens at the same focal length and f-stop to see what the real optics do: cat's-eye bokeh toward the corners, spherical-aberration glow wide open, and focus breathing at close portrait distances. Production tolerances, coatings and aspherical molding texture are not modeled.

Choosing a portrait lens and the entrance pupil

Frame a person the same way and step back with a longer lens, and two things happen. The background looks larger and closer, and the entrance pupil (focal length ÷ f-number) sets how large distant blur circles are next to the subject. A 58mm f/0.95 (61 mm pupil) and an 85mm f/1.4 (60.7 mm pupil) blur a distant background by nearly the same amount, from completely different working distances and with a different background view.

DSLR, mirrorless and sensor formats

A DSLR and a mirrorless camera with the same sensor size frame a portrait the same way. What changes the picture is the sensor format and the optical design of the lens. A 56mm f/1.2 on APS-C frames like an 85mm on full frame, and matches the depth of field and background blur of a full-frame 85mm f/1.8.

Depth of field, bokeh and crop factor

Depth of field explains the sharp zone beside the picture. Bokeh draws the traced disc: cat’s eye, aperture blades and spherical aberration. Crop factor compares the same framing on APS-C, full frame and medium format. Lens compression shows why a longer lens makes the background look closer.

Compare two lenses

• 35mm vs 50mm: more of the place, or a slightly tighter view.
• 50mm vs 85mm: closer, with more surroundings, or farther back and a calmer background.
• 85mm vs 135mm: a classic portrait distance, or a longer one with stronger background blur.
• 50mm vs 200mm: a normal working distance against a long lens and a compressed background.
• 35mm vs 85mm: an environmental portrait against a short telephoto.
• 56mm APS-C vs 85mm full frame: a similar framing on a smaller sensor and on full frame, with different blur.
• 80mm medium format vs 85mm full frame: a closer view on the larger sensor, which still blurs the background more easily.

Real lens patent matchups

• Nikon Z 58mm f/0.95 S Noct vs. Nikon 58mm f/1.2 Noct-NIKKOR: the modern 17-element Z flagship against the classic 7-element F-mount Noct.
• Nikon Z 85mm f/1.2 S vs. Nikon Z 85mm f/1.8 S: how much extra background blur and character 1.2 stops buy at portrait distance.
• Canon RF 50mm F1.2 L USM vs. Sony FE 50mm F1.2 GM: flagship standard primes traced through their optical patents.
• Leica Noctilux-M 50mm f/0.95 ASPH. vs. Leica APO-Summicron-M 50mm f/2 ASPH.: extreme speed and character against clinical apochromatic correction.

All lens comparisons