Photography calculators

Viewpoint’s Tools tab opens on ten field calculators: depth of field, hyperfocal distance, long exposure, exposure, star trails, spot stars, timelapse, panorama, subject distance and focal match. They’re all on-device and work offline: no signal needed at the trailhead, and no account needed to use them.

All ten are free. Depth of Field, Hyperfocal, Exposure, Long Exposure, Star Trails, Spot Stars, Timelapse, Panorama, Subject Distance and Focal Match open straight from the Tools tab on every plan. Within a calculator you get the whole tool: nothing inside one is locked behind a different plan.

On a Max plan the app opens on the Conditions tab, and Tools is the next tab along; on Free and Pro it opens on Tools, with a Today card showing the sun and moon times for where you are, then your calculators.

How every calculator works

All ten share one layout, so once you’ve used one you know the rest:

• The answer comes first, at the top, with a small diagram that redraws as you change the inputs. Diagrams are schematic: they show how the numbers relate (where the sharp zone sits, how a filter stretches a shutter time, how far the sky turns), not a simulation of what your photo will look like. If an input doesn’t make sense, the answer and its diagram step aside and ask you to check your inputs rather than showing a wrong number.
• Inputs sit below the answer. Camera settings (aperture, shutter, ISO, ND strength) start as a list of presets, so you pick instead of typing; choose Custom… when your value isn’t on the list and type it in. Sensor choices cover Full frame, Medium format, APS-C, APS-C (Canon) and Micro 4/3. Focal length is the actual focal length printed on the lens: the calculator applies the sensor’s crop for you.
• Results follow your settings. Distances show in feet or metres to match the unit you’ve chosen, and aperture and shutter lists step in full, half or third stops, whichever you prefer.
• “How to use this” is a collapsed section on every calculator with what it’s for, what to do with the answer, and a worked example. This page is the long form of the same explanations.

Try them free, right now, in your browser — the same engine the app runs, no install and no sign-up. Each is a taste of what the app does in the field, where you also get the depth-of-field overlay, the sun/moon/Milky-Way planner, and GPS auto-stamping.

New to photography? Terms like aperture, f-number, stop, focal length, and crop factor are all explained in plain language in Photography basics — skim it once and everything below clicks into place. Each section here keeps the wording as plain as it can, then points you there for the deeper definition.

Depth of field

Depth of field is how much of your scene is sharp, front to back — the zone around whatever you focused on that still looks crisp, with everything nearer or farther melting into blur. A portrait with a creamy, blurred background has a shallow depth of field; a landscape sharp from the flowers at your feet to the peak on the horizon has a deep one. Knowing which you’ll get — before you’re standing there in the field — is the difference between the shot you wanted and the one you settled for.

Three things set it, and it helps to feel how each one pulls:

• Aperture (the f-number). A wider opening (smaller number, like f/2.8) puts less in focus; a smaller opening (bigger number, like f/11) puts more in focus. This is the lever most people reach for first.
• Focal length. A longer lens (a 600 mm telephoto) gives less in focus; a shorter lens (a 24 mm wide-angle) gives more.
• How far you are from your subject. The closer you stand, the less is in focus; step back and the sharp zone deepens. (Sensor size matters too — smaller sensors give more depth of field, which is why phone photos rarely blur the background.)

The part that surprises people: a longer, “faster” lens can leave less in focus, not more. Say a bird is sitting 30 m away. A 600 mm at f/2.8 — the expensive, fast choice — gives you a razor-thin sharp zone: get the eye pin-sharp and the far wing is already soft. A humbler 400 mm at f/4, from the same Location, keeps noticeably more of the bird sharp, because the shorter focal length and the narrower aperture both work in your favour. “Longer and faster” is the right call when you want to isolate a subject against melted-away surroundings — but when you want the whole subject sharp, it can be exactly the wrong lens to bring. That trade is the reason to check before you pack the bag.

So the calculator answers two real questions: “with the lens I have, how much will be in focus at this distance?” and “which lens and aperture should I bring for the shot I’m planning?” A still subject you can stop down and hold sharp; an action subject often pins you near wide-open, and the depth of field is whatever it is — better to know going in.

Inputs: sensor, focal length, aperture and subject distance. The answer is the Near and Far limits and the Total depth, with “Sharp to infinity” when the far limit runs off to the horizon. Keep your important details between Near and Far, and check a magnified test shot: acceptable sharpness depends on how large the picture is viewed. Near and Far are measured from the camera.

Compare is a section of the Depth of Field calculator, not a separate tool: set one subject distance, enter two lens-and-aperture setups side by side, and see which keeps more of the scene sharp and by how much. That settles the “you brought the wrong lens” question before you leave the house.

Technique. When no single aperture can hold a close foreground and the horizon both sharp, focus-stack — a few frames at different focus distances, blended in post — instead of stopping so far down that diffraction softens everything (past about f/11 on full frame the lens loses more sharpness to diffraction than it gains in depth).

Gear. Tripod (the frames must align for the blend).

Hyperfocal

The single focus distance that keeps everything from half that distance out to infinity acceptably sharp. It’s the classic landscape move for front-to-back sharpness: focus at the hyperfocal distance and the whole scene from the mid-foreground to the horizon falls within the depth of field. H = f² / (N · c) + f, where f is the focal length, N the f-number, and c the sensor’s circle of confusion. Shorter lenses and smaller apertures pull the hyperfocal distance nearer, so more of the scene is sharp — which is why a wide angle at f/11 holds everything from a metre out to the horizon.

Inputs: sensor, focal length and aperture. The answer is the hyperfocal distance, with the sharp range it gives (from about half that distance to infinity). Focus at the calculated distance itself, not a third of the way into the scene: the sharp range already begins at roughly half that distance.

Technique. Focus on something at the calculated distance, then check a magnified test shot that your nearest important detail falls inside the sharp range. Focusing at infinity wastes half your depth of field behind the subject.

Gear. Tripod for the slower shutter.

Long exposure

Your new shutter speed after screwing on an ND filter. Each stop of ND halves the light, so it doubles the exposure time: t = base × 2^stops. Inputs: your un-filtered base shutter (seconds or a fraction like 1/125) and the ND strength in stops, not the filter factor. You get the timed exposure to set on the camera (or on a remote for anything past 30 s). Handy for smoothing water, blurring cloud, or dropping a daylight exposure into multi-second territory. On a digital sensor a stop is a stop however long the frame — the real limits on minutes-long exposures are sensor heat and battery, not the math.

Technique. Compose, focus, and meter without the filter first — a 10-stop is far too dark to meter or focus through, and that un-filtered shutter is the base the calculator multiplies. Then fit the filter, switch to manual focus so it can’t hunt, and trip the shutter on a remote or the 2-second timer. No ND? Take a burst of normal exposures and median-stack them in post — water and cloud smooth out, much like one long frame, while the static scene stays sharp. Enter the filter strength in stops, not the ND factor, and check the histogram as the light changes.

Gear. Tripod, remote or 2-second timer, ND filter (or the burst-and-stack workaround).

Spot stars

The longest exposure before stars trail — before the Earth’s rotation (about 15°/hour) turns pinpoints into streaks. The 500 rule is the quick estimate: 500 / (focal × crop). The NPF rule is more accurate because it accounts for your aperture and how tightly your sensor samples detail: NPF = (35·N + 30·p) / f, where N is the aperture, p the pixel pitch in microns, and f the focal length. High-resolution sensors and fast lenses show trailing sooner, so NPF usually gives a shorter time than the 500 rule. Use the shorter (safer) of the two, then raise ISO to get the exposure — and recover the cleanliness by stacking, below.

Inputs: sensor, focal length, aperture and your sensor’s full resolution. Both limits are shown, and the shorter one is the one to start from; zoom in on a test frame and shorten the shutter if stars trail. A longer focal length shortens both limits, and the estimates assume an untracked camera: star position and viewing size matter.

Technique. Keep the exact same framing for every frame, then stack several (median or average) to beat down the high-ISO noise — noise is random and partly cancels, so a handful of frames gives a clean Milky Way without trailing. Don’t nudge the camera between frames or they won’t align.

Gear. Tripod, a fast wide lens.

Star trails

The opposite goal: let the stars streak. This plans how many frames you need for the trails you want and how long to shoot. The sky turns about 15° an hour (one full turn per sidereal day), so rotation = 15.04° × hours. Duration and rotation are coupled both ways: set the total duration (quick presets for 30 minutes, 1, 2 and 6 hours, or type your own up to one full turn of the sky) and read the sky rotation, or set the rotation you want and read the time it needs. Choose a frame length (30 seconds is a good start) and the calculator gives the frame count; for example, 2 hours at 30 s per frame is 240 frames and about 30° of sky rotation.

Looking toward lets you pick North or South. The trail diagram circles the north celestial pole (Polaris) and turns counter-clockwise in the north, and circles the south celestial pole and turns clockwise in the south; the numbers stay the same. The diagram is a schematic view toward the pole, not a simulation of your framing. An optional, collapsed Advanced · individual star control takes a star’s declination and gives that one star’s trail length (star arc = rotation × cos(declination)): a star on the celestial equator traces the full rotation, one at either pole barely moves, which is why trails curve around the pole.

Star trails are a stacked sequence of frames, never one long exposure. One 3–6 hour exposure blows out the sky, and a single bump ruins everything. Shoot continuous frames in manual mode with interval shooting and the shortest gap your camera allows (so the trails stay unbroken), lock focus and white balance, turn long-exposure noise reduction off, and stack the frames afterwards in a stacking app. Over two hours, watch battery, card space and sensor heat; in damp air, a dew heater or lens warmer helps.

Gear. Sturdy tripod that doesn’t shift between frames, intervalometer.

Timelapse

Turns a shoot plan into numbers: the frame count, the final clip length and a rough storage estimate. Inputs: the event length, your shooting interval, the playback frame rate (quick picks for common rates) and your photo file size. A small timeline shows the event as a bar with one tick per frame, and the clip beneath it on the same scale, plus how many times faster than real time the clip plays. Use it the other way too: under Wanted clip, enter the clip length you’re after and it tells you the interval to shoot every. frames = event ÷ interval, clip = frames ÷ fps. Match the interval to how fast the scene moves: 1–2 s for fast clouds or a busy street, 5–10 s for a sunset, 20–30 s+ for stars.

Technique. Shoot in manual exposure, and lock white balance too, so brightness and colour don’t flicker frame to frame. For a sunset-to-night “holy grail” timelapse the light changes by many stops, so ramp the exposure gradually (a few clicks of ISO or shutter spread over many frames) rather than letting auto-exposure pump.

Gear. Tripod, intervalometer.

Exposure

The exposure value (EV) of an aperture / shutter / ISO combination — a single number for “how much light”, which makes it easy to compare two settings or judge a scene. EV = log₂(N² / t) + log₂(ISO / 100), where N is the aperture and t the shutter in seconds. Inputs: aperture, shutter and ISO from a frame you know is well exposed, then a new aperture and/or new ISO; the answer is the equivalent shutter that keeps the same brightness. Two settings with the same EV give the same brightness, so you can trade aperture for shutter for ISO with confidence: going from f/8 to f/16 at the same ISO makes the shutter four times longer. Motion blur, depth of field and noise change along the way, and this assumes the scene light stays the same. It is not a light meter. As a feel for the scale at ISO 100: bright sun sits near EV 15, an overcast day near EV 12, a moonlit landscape down around EV −3.

Technique. Expose to the right — push the histogram as bright as you can without clipping the highlights — for the cleanest shadows, then pull it back in post. Watch the highlight blinkies and the per-channel (RGB) histogram, not just the overall one: a single channel (often red in a sunset) can blow out while the combined histogram still looks safe. Shoot RAW for the most recovery room.

Panorama

How many frames cover your sweep, and how far to turn between them, so the set stitches cleanly. Inputs: sensor, whether the camera is held in landscape or portrait, the actual focal length, the sweep you want to cover and the overlap your stitching software asks for. The results are Frames, Frame width (one frame’s field of view) and Step: the calculator works out the frame width, then the step (the turn between frames), the new coverage each frame adds after overlap: step = frameFOV × (1 − overlap). The first frame covers its whole width on its own, so a sweep no wider than one frame is a single frame, and each further frame adds one step: frames = 1 + ⌈(sweep − frameFOV) ÷ step⌉. A full 360° circle closes on itself, so the last frame has to overlap the first just like every other pair: frames = ⌈360 ÷ step⌉. For example, 24 mm on full frame in landscape (a 73.7° frame) at 30 % overlap turns 51.6° each time: 180° needs 4 frames, 60° needs just 1, and a full circle needs 7. Portrait frames are narrower along the sweep, so they need more frames; leave 20–30% overlap so the stitcher has something to match on, and shoot a touch wider than you think, because you’ll crop the ragged edges later.

Technique. Lock exposure and white balance to manual (and manual focus too) so the sky doesn’t step in brightness or colour between frames. Level the tripod: a tilted pano loses a lot to the crop. Rotate around the lens’s nodal point so near and far don’t shift against each other (parallax), or the stitcher can’t register them.

Gear. Tripod, a level, ideally a nodal-point pano head.

Subject distance

How far to stand so a subject of a known real height fills the frame, or, the other way round, which lens frames it from where you want to stand. Inputs: sensor, landscape or portrait, the subject’s real height and the actual focal length. The answer is the distance at which the subject fills the frame height. Enter a wanted distance and it gives the focal length for that distance instead. Example: a 1.8 m person at 50 mm on full frame in landscape fills the frame height from 3.75 m; to stand 10 m away instead, a 133 mm lens does it. It’s useful for wildlife (how far back for a deer to fill the frame) and for planning a shot before you’re on location. Frame fill lowers the fill to leave headroom around the subject. Portrait frames are taller, so you can stand closer.

Focal match

The focal length on one camera body that frames the same view as a focal length on another, for when you switch between bodies with different sensors. Inputs: the source body, its actual focal length and the target body; Swap bodies goes the other way. f₂ = f₁ × crop(source) ÷ crop(target). For example, 50 mm on full frame matches about 33 mm on APS-C. The result also shows the source frame’s horizontal field of view. Crop factors are rounded, so the other body’s angle can differ by a few percent. Use it to pack the right lens, or to reproduce a framing you liked on a different body.

Related

• Photography basics — plain-language glossary of every term used above.
• Getting started
• AR Celestial Scout
• Sun, Moon & Milky Way