Tutorials · Module 01 · Free
Depth of field simulator.See what your lens, aperture, distance and sensor do to a picture, before you take it.
Drag the camera around a real 3D subject. Every slider changes the picture the way it would on set, and every number under it is explained in plain English. Seven guided lessons walk you through it, and an AI coach sets it up for the shot you actually have.
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Drag to walk around · scroll to move closer or further · arrow keys tooDrag to walk around · pinch to move closer
Aperture blades (bokeh shape)
Wide open, every lens draws round discs. Stopped down, the blades show: more blades stay rounder.
Past about f/21 on this sensor, the tiny aperture itself softens the whole picture. See the Numbers tab.
01What depth of field is
A lens focuses on one distance. Everything else is blurred a little, or a lot.
Point a lens at a face three metres away and it draws that face sharp on the sensor. A lamp six metres away is drawn as a small disc instead of a point, because its light comes to a focus in front of the sensor and spreads out again before it lands. The further something is from the focus distance, the bigger its disc. Depth of field is the range of distances where those discs are still small enough to look like points. Background blur is how big the discs get for things well outside it. They are related, but they are not the same thing, and the simulator shows both.
02The levers
Five things change it. You control all five.
Aperture
The f-number. A smaller number is a bigger hole: less in focus, bigger blur discs. Each full stop (1.4, 2, 2.8, 4, 5.6, 8, 11, 16) roughly doubles or halves the blur. It also doubles or halves the light, which is the price.
Distance to the subject
Closer means less in focus, and it is a strong effect: halve the distance and the depth of field drops to about a quarter. Macro work has millimetres to play with. Step back for a group.
Focal length
At the same distance, a longer lens has much less depth of field. At the same framing (you step back), the depth of field is similar but the background blur is far bigger, because the long lens magnifies a narrow slice of the background.
Sensor size
A smaller sensor sees a smaller crop of the image, so the same lens frames tighter and you stand further back, which gives more depth of field. Multiply focal length and f-number by the crop factor to compare cameras honestly.
Distance to the background
The one that costs nothing. A wall half a metre behind the subject cannot blur; the same wall five metres back goes soft at the same settings. Before you buy a faster lens, find a deeper room.
What counts as sharp
The circle of confusion. A picture viewed small on a phone forgives more than a large print studied up close. The simulator lets you set the standard, and it changes the numbers without changing the picture.
03The circle of confusion
“Sharp” is a judgement, and here is the number behind it.
Depth of field tables all rest on one assumption: the largest blur disc that still looks like a point. The convention is the sensor diagonal divided by 1500, which assumes an 8 x 10 inch print viewed at arm's length. On full frame that is about 0.029mm, roughly four pixels on a 24 megapixel sensor, so “in focus” by the tables is not pixel sharp. Zoom to 100% and the depth of field is smaller than the chart says; post it to a phone feed and it is bigger.
| Sensor | Size (mm) | Crop | CoC |
|---|---|---|---|
| Medium format 54 x 40 | 53.4 × 40 | 0.65x | 0.0445 mm |
| Medium format 44 x 33 | 43.8 × 32.9 | 0.79x | 0.0365 mm |
| Full frame 36 x 24 | 36 × 24 | 1.00x | 0.0288 mm |
| APS-H 28 x 19 | 27.9 × 18.6 | 1.29x | 0.0224 mm |
| Super 35 cine 25 x 14 | 24.89 × 14 | 1.52x | 0.0190 mm |
| APS-C 23.5 x 15.6 | 23.5 × 15.6 | 1.53x | 0.0188 mm |
| APS-C Canon 22.3 x 14.9 | 22.3 × 14.9 | 1.61x | 0.0179 mm |
| Micro Four Thirds 17.3 x 13 | 17.3 × 13 | 2.00x | 0.0144 mm |
| 1 inch 13.2 x 8.8 | 13.2 × 8.8 | 2.73x | 0.0106 mm |
| Phone main 1/1.3 inch | 9.8 × 7.3 | 3.54x | 0.0081 mm |
| Phone 1/2 inch | 6.4 × 4.8 | 5.41x | 0.0053 mm |
| 1/2.3 inch 6.2 x 4.6 | 6.17 × 4.55 | 5.64x | 0.0051 mm |
04Hyperfocal distance
Focus here and everything to the horizon is sharp.
For every lens and aperture there is a focus distance where the far limit of the depth of field reaches infinity. That is the hyperfocal distance, and it has a bonus: focused there, the near limit is half that distance. A 24mm lens at f/8 on full frame has a hyperfocal distance of about 2.5m, so focusing at 2.5m makes 1.25m to infinity sharp. Focus at infinity instead and you throw away everything nearer than 2.5m. Real estate, landscapes and wide establishing shots use this.
| Lens | f/2.8 | f/5.6 | f/8 | f/11 | f/16 |
|---|---|---|---|---|---|
| 16mm | 3.2 m | 1.6 m | 1.1 m | 82.3 cm | 57.1 cm |
| 24mm | 7.2 m | 3.6 m | 2.5 m | 1.8 m | 1.3 m |
| 35mm | 15.2 m | 7.6 m | 5.3 m | 3.9 m | 2.7 m |
| 50mm | 31.0 m | 15.5 m | 10.9 m | 7.9 m | 5.5 m |
| 85mm | 89.5 m | 44.8 m | 31.4 m | 22.9 m | 15.7 m |
Crop sensors: divide by about the crop factor (the smaller circle of confusion and the shorter equivalent lens roughly cancel). The simulator gives the exact number for any sensor.
05Phone versus camera
Why a phone fakes it, and what “equivalent” means.
A phone's main camera is a 6.8mm f/1.8 lens on a sensor a quarter the width of full frame. For framing, that behaves like a 24mm lens; for blur, like 24mm at f/6.5. At a normal portrait distance it produces almost no background blur, so the phone measures depth with a second camera or a model and paints the blur in. To compare any two cameras, multiply both the focal length and the f-number by the crop factor. Same framing, same equivalent f-number: same picture.
| Camera | Lens | Full-frame equivalent | Background blur | In focus |
|---|---|---|---|---|
| Phone main camera | 6.8mm f/1.8 | 24mm f/6.4 | 0.1% | 4.2 m |
| 1 inch compact / drone | 9mm f/2.8 | 25mm f/7.6 | 0.1% | 6.2 m |
| Micro Four Thirds | 25mm f/1.8 | 50mm f/3.6 | 1.0% | 33.0 cm |
| APS-C | 35mm f/1.8 | 54mm f/2.8 | 1.5% | 21.8 cm |
| Full frame | 50mm f/1.8 | 50mm f/1.8 | 2.0% | 16.2 cm |
| Medium format 44 x 33 | 63mm f/2.8 | 50mm f/2.2 | 1.7% | 20.0 cm |
06Bokeh and diffraction
The shape of the blur, and the point where stopping down stops helping.
Bokeh
Bokeh is the character of the blur, not the amount. A point of light out of focus takes the shape of the aperture: round wide open, a polygon once the blades close in. More blades stay rounder. Bright points become solid discs, which is why string lights and street lamps are the classic bokeh background, and why the simulator's environments are full of them. Try the aperture blade setting in the Lens tab at f/4 against a lit background.
Diffraction
Light bends at the edge of a small hole. At f/16 and beyond, every point of light lands as a tiny soft disc, the Airy disc, whatever the focus. On full frame it passes the circle of confusion at about f/22; on a Micro Four Thirds sensor at about f/11; on a phone sensor at about f/4. Past that, more depth of field buys you a picture that is evenly soft everywhere. The Numbers tab shows both thresholds for your sensor and tells you which one is limiting the background.
07Starting points
Settings we reach for, by kind of shot.
Full-frame numbers. On APS-C use about two-thirds of the focal length; on Micro Four Thirds, half. Load any of them into the simulator with the Learn tab's coach.
| Shot | Start here | Why |
|---|---|---|
| Seated interview | 85mm, f/2.8, 2.5m, background 3m+ behind | Face crisp from nose to ears, the room a soft wash. Long lens flatters; f/2.8 forgives a lean forward. |
| Headshot | 85 to 135mm, f/2 to f/2.8, 1.5 to 2m | Eyes sharp, background gone. Focus on the nearer eye; at f/1.4 the ears go soft, which is fine. |
| Full-length portrait | 50 to 85mm, f/2.8 to f/4, 4 to 6m | Keep the whole person sharp. Walk the subject away from the wall for blur instead of opening up. |
| Group of five | 35 to 50mm, f/5.6 to f/8, 3 to 4m, one row | Depth of field has to cover the front and back row. Two rows: f/8 and focus on the front row's eyes. |
| Product on a table | 50 to 100mm macro, f/8 to f/11, 0.3 to 0.6m | Close focus kills depth of field; stop down. Focus stack if the whole product must be sharp. |
| Real estate room | 16 to 24mm, f/8, focus at the hyperfocal distance | Everything from the foreground chair to the window sharp. Tripod, since f/8 indoors means a slow shutter. |
| Speaker on stage | 70 to 200mm at 135+, f/4 to f/5.6, from the back | A speaker moves. f/4 gives half a metre of sharp zone at 10m so a step does not lose focus. |
| Wrestling, sports | 24 to 70 or 70 to 200, f/2.8 to f/4, fast shutter | Fast lenses for the shutter speed, not the blur. Continuous autofocus does the rest. |
| Landscape | 16 to 35mm, f/8 to f/11, hyperfocal | Past f/11, diffraction softens everything. f/8 and the right focus distance beats f/22 and guesswork. |
08The maths
For the curious: the formulas behind every number.
With focal length f, f-number N, focus distance s, circle of confusion c, all in millimetres:
- Hyperfocal distance H = f² ÷ (N × c) + f
- Near limit = s (H − f) ÷ (H + s − 2f)
- Far limit = s (H − f) ÷ (H − s), or infinity when s ≥ H
- Blur disc for something at distance x = (f² ÷ N) × |x − s| ÷ (x (s − f)), on the sensor
- Blur at infinity = f² ÷ (N (s − f))
- Magnification = f ÷ (s − f); frame height at the subject = sensor height ÷ magnification
- Airy disc (diffraction) = 2.44 × 0.00055 × N
- Equivalent focal length and f-number = the real ones × the crop factor
Thin-lens model, distances from the lens. Real lenses breathe a little as they focus and macro lenses stretch; close enough for every decision you will make on set.
Questions people ask
How do I get a blurry background?
Four levers, in order of cost: move the subject further from the background, get closer to the subject, use a longer lens at the same framing, and open the aperture (a smaller f-number). A phone cannot do much of the last two, which is why it fakes it in software.
Does a full-frame camera have less depth of field?
At the same framing and aperture, yes: a sensor 1.5x smaller needs a lens about one stop faster (f/2 instead of f/2.8) to match the blur. Multiply both the focal length and the f-number by the crop factor to compare: 35mm f/1.8 on APS-C looks like 52mm f/2.7 on full frame.
What is the hyperfocal distance?
The focus distance that puts everything from half that distance to infinity acceptably sharp. For a 24mm lens at f/8 on full frame it is about 2.5 metres (8 ft): focus there and 1.25 metres to the horizon is sharp. Landscape and real estate photographers live by it.
What is the circle of confusion?
The largest blur spot that still reads as a sharp point in the finished picture. It depends on the sensor size and on how big the picture is viewed, which is why depth of field is a judgement, not a hard line. Most calculators use the sensor diagonal divided by 1500: about 0.029mm on full frame.
Why is f/22 soft?
Diffraction. Light bends at the edges of a small hole, and at f/22 every point of light becomes a disc larger than a pixel. More is in the depth of field, but nothing is truly sharp. On full frame the trade starts to bite past about f/11; on a phone sensor past about f/4, which is why phones have fixed apertures.
Is background blur the same as depth of field?
No. Depth of field is the zone that counts as sharp. Background blur is how big the out-of-focus discs are for things outside that zone. A wide lens close up can have shallow depth of field and still a fairly sharp-looking background; a long lens from far away can have more depth of field and a creamier background. The simulator shows both numbers for that reason.
What f-stop should I use for a group photo?
f/5.6 to f/8 with a 35 to 50mm lens, one row if you can. For two rows focus on the front row's eyes at f/8. Check the in-focus range in the Numbers tab: it needs to cover the front and the back of the group with a little spare.
Does focal length change depth of field?
At the same framing (you step back with a longer lens), the depth of field is nearly the same, but the background blur is much bigger with the longer lens because it magnifies a narrower slice of the background. At the same distance, a longer lens has much less depth of field. Try the Focal length lesson in the simulator to see both.
Now the light.
Module 02 puts four lights around a face and lets you find the Rembrandt triangle yourself.