Editing Exposure value (section)

==Tabulated exposure values==

An exposure meter may not always be available, and using a meter to determine exposure for some scenes with unusual lighting distribution may be difficult.<ref>Appendix C of ANSI PH3.49-1971 noted this possibility "when the background luminance within the field is radically different from the subject luminance", and further stated "In this kind of scene, a meter reading of the integrated luminance (''B''<sub>a</sub>) of the whole scene may not lead to the best picture."</ref> However, natural light, as well as many scenes with artificial lighting, is predictable, so that exposure often can be determined with reasonable accuracy from tabulated values.

[[File:Exposure_Value_Scale_Visualized_as_Circles.png|thumb|300px|right|Visualization of lighting conditions and corresponding exposure values, where the area of each circle is proportional to the amount of light in the scene. Note that each level includes the full area inside the circle, not merely the ring.]]

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:{| class="wikitable" style="padding: 0.1em 0.5em; text-align: left"
|+<span id="Table2">Table 2</span>. Exposure values (ISO 100) for various lighting conditions<ref>
    Exposure values in Table 2 are taken from ANSI exposure
    guides [[#CITEREFANSI PH2.7-1973|PH2.7-1973]] and
    [[#CITEREFANSI PH2.7-1986|PH2.7-1986]]; where the two guides differ, ranges of values have been given or extended.
    The ANSI guides were derived from studies by [[Loyd A. Jones]] and H.R. Condit, described in
    [[#CITEREFJonesCondit1941|Jones and Condit (1941)]],
    [[#CITEREFJonesCondit1948|Jones and Condit (1948)]], and
    [[#CITEREFJonesCondit1949|Jones and Condit (1949)]].</ref>
|-
! Lighting condition || EV<sub>100</sub>
|-
! colspan="2" | Daylight
|-
|  | Light sand or snow in full or slightly hazy sunlight (distinct shadows)<sup>a</sup>
| style="text-align: center;" | 16
|-
|  | Typical scene in full or slightly hazy sunlight (distinct shadows)<sup>a, b</sup>
| style="text-align: center;" | 15
|-
|  | Typical scene in hazy sunlight (soft shadows)
| style="text-align: center;" | 14
|-
|  | Typical scene, cloudy bright (no shadows)
| style="text-align: center;" | 13
|-
|  | Typical scene, heavy overcast
| style="text-align: center;" | 12
|-
|  | Areas in open shade, clear sunlight
| style="text-align: center;" | 12
|-
! colspan="2" | Outdoor, natural light
|-
| colspan="2"  | Rainbows
|-
| style="padding: 0.1em 1.5em;" | Clear sky background
| style="text-align: center;" | 15
|-
| style="padding: 0.1em 1.5em;" | Cloudy sky background
| style="text-align: center;" | 14
|-
| colspan="2"  | Sunsets and skylines
|-
| style="padding: 0.1em 1.5em;" | Just before sunset
| style="text-align: center;" | 12&ndash;14
|-
| style="padding: 0.1em 1.5em;" | At sunset
| style="text-align: center;" | 12
|-
| style="padding: 0.1em 1.5em;" | Just after sunset
| style="text-align: center;" | 9&ndash;11
|-
| colspan="2"  | The Moon,<sup>c</sup> [[altitude (astronomy)|altitude]] > 40°
|-
| style="padding: 0.1em 1.5em;" | Full
| style="text-align: center;" | 15
|-
| style="padding: 0.1em 1.5em;" | Gibbous
| style="text-align: center;" | 14
|-
| style="padding: 0.1em 1.5em;" | Quarter
| style="text-align: center;" | 13
|-
| style="padding: 0.1em 1.5em;" | Crescent
| style="text-align: center;" | 12
|-
| style="padding: 0.1em 1.5em;" | [[Lunar eclipse|Blood]]
| style="text-align: center;" | 0 to 3<ref>See exposure parameters at pictures in subcategories of [[c:Category:21st century lunar eclipses|21st century lunar eclipses]] in Commons.</ref>
|-
| colspan="2"  | Moonlight, Moon altitude > 40°
|-
| style="padding: 0.1em 1.5em;" | Full
| style="text-align: center;" | &minus;3 to &minus;2
|-
| style="padding: 0.1em 1.5em;" | Gibbous
| style="text-align: center;" | &minus;4
|-
| style="padding: 0.1em 1.5em;" | Quarter
| style="text-align: center;" | &minus;6
|-
| colspan="2"  | Aurora borealis and australis
|-
| style="padding: 0.1em 1.5em;" | Bright
| style="text-align: center;" | &minus;4 to &minus;3
|-
| style="padding: 0.1em 1.5em;" | Medium
| style="text-align: center;" | &minus;6 to &minus;5
|-
|  | Milky Way galactic center
| style="text-align: center;" | &minus;11 to &minus;9
|-
! colspan="2" | Outdoor, artificial light
|-
|  | Neon and other bright signs
| style="text-align: center;" | 9&ndash;10
|-
|  | Night sports
| style="text-align: center;" | 9
|-
|  | Fires and burning buildings
| style="text-align: center;" | 9
|-
|  | Bright street scenes
| style="text-align: center;" | 8
|-
|  | Night street scenes and window displays
| style="text-align: center;" | 7&ndash;8
|-
|  | Night vehicle traffic
| style="text-align: center;" | 5
|-
|  | Fairs and amusement parks
| style="text-align: center;" | 7
|-
|  | Christmas tree lights
| style="text-align: center;" | 4&ndash;5
|-
|  | Floodlit buildings, monuments, and fountains
| style="text-align: center;" | 3&ndash;5
|-
|  | Distant views of lighted buildings
| style="text-align: center;" | 2
|-
! colspan="2" | Indoor, artificial light
|-
|  | Galleries
| style="text-align: center;" | 8&ndash;11
|-
|  | Sports events, stage shows, and the like
| style="text-align: center;" | 8&ndash;9
|-
|  | Circuses, floodlit
| style="text-align: center;" | 8
|-
|  | Ice shows, floodlit
| style="text-align: center;" | 9
|-
|  | Offices and work areas
| style="text-align: center;" | 7&ndash;8
|-
|  | Home interiors
| style="text-align: center;" | 5&ndash;7
|-
|  | Christmas tree lights
| style="text-align: center;" | 4&ndash;5
|}

<ol type="a">
<li>Values for direct sunlight apply between approximately two hours after sunrise and two hours before sunset, and assume front lighting. As a rough general rule, decrease EV by 1 for side lighting, and decrease EV by 2 for back lighting.</li>
<li>This is approximately the value given by the [[sunny 16]] rule.</li>
<li>These values are appropriate for pictures of the Moon taken at night with a long lens or telescope, and will render the Moon as a medium tone. They will not, in general, be suitable for landscape pictures that include the Moon. In a landscape photograph, the Moon typically is near the horizon, where its luminance changes considerably with [[altitude (astronomy)|altitude]]. Moreover, a landscape photograph usually must take account of the sky and foreground as well as the Moon. Consequently, it is nearly impossible to give a single correct exposure value for such a situation.</li>
</ol>

Exposure values in Table 2 are reasonable general guidelines, but they should be used with caution. For simplicity, they are rounded to the nearest integer, and they omit numerous considerations described in the ANSI exposure guides from which they are derived. Moreover, they take no account of color shifts or [[reciprocity (photography)|reciprocity]] failure. Proper use of tabulated exposure values is explained in detail in the ANSI exposure guide, [[#CITEREFANSI PH2.7-1986|ANSI PH2.7-1986]].

The exposure values in Table 2 are for ISO 100 speed ("EV<sub>100</sub>"). For a different ISO speed <math>S</math>, increase the exposure values (decrease the exposures) by the number of exposure steps by which that speed is greater than ISO 100, formally

:<math>\mathrm{EV}_{S} = \mathrm{EV}_{100} + \log_2 \frac {S} {100} \,.</math>

For example, ISO 400 speed is two steps greater than ISO 100:

:<math>\mathrm{EV}_{400} = \mathrm{EV}_{100} + \log_2 \frac {400} {100}
= \mathrm{EV}_{100} + 2 \,.</math>

To photograph outdoor night sports with an ISO 400&ndash;speed imaging medium, search Table 2 for "Night sports" (which has an EV of 9 for ISO 100), and add 2 to get {{nowrap|1=EV<sub>400</sub>&nbsp;=&nbsp;11}}.

For lower ISO speed, decrease the exposure values (increase the exposures) by the number of exposure steps by which the speed is less than ISO 100. For example, ISO 50 speed is one step less than ISO 100:

:<math>\mathrm{EV}_{50} = \mathrm{EV}_{100} + \log_2 \frac {50} {100}
= \mathrm{EV}_{100} - 1 \,.</math>

To photograph a rainbow against a cloudy sky with an ISO 50&ndash;speed imaging medium, search Table 2 for "Rainbows-Cloudy sky background" (which has an EV of 14), and subtract 1 to get {{nowrap|1=EV<sub>50</sub>&nbsp;=&nbsp;13}}.

The equation for correcting for ISO speed can also be solved for EV<sub>100</sub>:

:<math>\mathrm{EV}_{100} = \mathrm{EV}_{S} - \log_2 \frac {S} {100} \,.</math>

For example, using ISO 400 film and setting the camera for EV 11 allows shooting night sports at a light level of EV<sub>100</sub> = 9, in agreement with the example done the other way around above. An online calculator that implemented this calculation was available at [http://www.dpreview.com dpreview.com].<ref name=dpreview>[http://www.dpreview.com/glossary/exposure/exposure Exposure at dpreview.com] {{webarchive |url=https://web.archive.org/web/20131112083840/http://www.dpreview.com/glossary/exposure/exposure |date=November 12, 2013 }}</ref>