Depth of field
- Near limit
- Far limit
- Depth of field
- Hyperfocal distance
- In front of focus
- Behind focus
- At the hyperfocal distance, sharp from
Depth of field table
Formulas
H = f2 / (N c) + f Hyperfocal distance.
Dnear = s(H − f) / (H + s − 2f) Near limit.
Dfar = s(H − f) / (H − s) Far limit, infinite once s reaches H.
c = d / 1500 Circle of confusion from the format diagonal d: 0.029 mm for full frame.
f focal length, N f-number, c circle of confusion, s focus distance measured from the lens. Thin-lens model; at macro distances, lens asymmetry makes real lenses differ.
Sources: J. Conrad, Depth of Field in Depth, equations 6, 7 and 11, written here in terms of H; the d/1500 criterion from Circle of confusion; sensor sizes from Image sensor format and 120 film.
Exposure
Shutter speed as 1/250, 0.5, 4, 2m30s or 1:30.
Equivalent exposures
Formulas
EV = log2(N2 / t) Exposure value of a pair of settings.
EVS = EV100 + log2(S / 100) The settings that suit a light level at ISO S.
t = N2 / 2EVS Shutter time for a light level.
N f-number, t exposure time in seconds, S ISO speed. One EV is one stop.
Sources: Exposure value (Wikipedia, CC BY-SA 4.0), including its table of light levels taken from the ANSI PH2.7-1973 and PH2.7-1986 exposure guides; stop scales from F-number.
ND filter
As 1/250, 0.5, 4 or 2m30s.
On the lens
No filter on the lens.
Exposure with filters
- Reduction
- Light through
- Optical density
00:00.0
Filter for a set time
Formulas
t′ = t × 2stops Exposure time behind the filters.
stops = log2 k = d / log102 From the filter factor k or the optical density d. Stacked filters add their stops and densities and multiply their factors.
Filters are named by factor (ND8 passes 1/8 of the light) or by density (ND 0.9). ND1000 is density 3.0 and is counted as 10 stops, a factor of 1024.
Source: Neutral-density filter.
Night sky
The declination in the frame closest to the celestial equator; 0° when unsure.
- NPF rule
- NPF rule, full form
- 500 rule
Formulas
t = (35N + 30p) / f NPF rule.
t = k(16.9N + 0.10f + 13.7p) / (f cos δ) NPF rule, full form.
t = 500 / (f × crop factor) 500 rule.
p = √(sensor area / pixel count) Pixel pitch from the resolution.
t longest exposure in seconds before stars trail on a fixed tripod, N f-number, p pixel pitch in µm, f focal length in mm, δ declination, k from 1 for point stars to 3 for slightly elongated ones.
Sources: the NPF rule is by Frédéric Michaud of the Société Astronomique du Havre, 2010: La règle NPF. The 500 rule as given by W. Fulton, Star trail calculator; crop factor from Crop factor.
Time-lapse
As 2h, 1h30m, 45m, 1:30:00 or 3d.
Shots
- Clip length
- Speed-up
- Storage
- Card holds
- Card lasts
- Exposure per shot
Formulas
shots = shooting time / interval
clip length = shots / frame rate
speed-up = interval × frame rate
exposure = shutter angle / 360° × interval 180° gives the motion blur of a normal film shutter.
Storage uses 1 GB = 1000 MB.
Source: Time-lapse photography.
Print size
Print size
Formulas
print size = pixels / ppi 1 in = 2.54 cm.
pixels = print size × ppi
eye limit = 1 / (d × tan 1′) Pixels per inch that 20/20 vision resolves at distance d in inches.
20/20 vision resolves two points one minute of arc apart. The paper turns to match the image.
Sources: Pixel density, Visual acuity, ISO 216 paper sizes, Photo print sizes.
Crop factor
Same framing and depth of field
- Crop factor
- Equivalent focal length
- Equivalent aperture
Angle of view
- Horizontal
- Vertical
- Diagonal
Formulas
crop factor = dref / d Ratio of the format diagonals.
feq = f × crop factor Same angle of view.
Neq = N × crop factor Same depth of field at the same framing, for subjects far away compared with the focal length.
α = 2 arctan(d / 2f) Angle of view across dimension d, focused at infinity.
The f-number sets the exposure, so f/2 gives the same exposure on every format.
Sources: Crop factor, Angle of view, J. Conrad, Depth of Field in Depth, equation 76.
Keyboard
- 1 to 7
- Switch calculator
- [ ]
- Aperture a third of a stop wider or narrower
- ← →
- Turn the focused ring
- Home End
- Turn the focused ring to its stop
- H
- Focus at the hyperfocal distance
- U
- Switch meters and feet