Editing Multi-exposure HDR capture (section)

== Benefits ==
One aim of HDR is to present a similar range of [[luminance]] to that experienced through the human [[visual system]]. The human eye, through non-linear response, [[Adaptation (eye)|adaptation]] of the [[Iris (anatomy)|iris]], and other methods, adjusts constantly to a broad range of luminance present in the environment. The brain continuously interprets this information so that a viewer can see in a wide range of light conditions.
{|class="wikitable unsortable floatright"
|+ Dynamic ranges of common devices
|-
! Device
! Stops
! Contrast ratio
|- style="background-color:#DDF;"
| colspan="4" | Single exposure
|-
| Human eye: close objects
| {{0}}7.5
| {{0|00}}150...200
|-
| Human eye: 4° angular separation
| 13
| {{0}}8000...10000
|-
| Human eye (static)
| 10...14&nbsp;<ref>{{cite web |url= http://www.cambridgeincolour.com/tutorials/dynamic-range.htm |title=Dynamic Range in Digital Photography |work=Cambridge in Colour |editor-first=Sean |editor-last=McHugh |date=2005 |access-date=December 30, 2010}}</ref>
| {{0}}1000...15000
|-
| Negative film ([[List of motion picture film stocks#VISION3 color negative (ECN-2 process 2007–present)|Kodak VISION3]])
| 13&nbsp;<ref>{{cite web |url= http://motion.kodak.com/motion/About/The_Storyboard/17788/index.htm |title=Dynamic Range}}{{dead link|date=November 2017 |bot=InternetArchiveBot |fix-attempted=yes}}<!--Tried manually searching around for it, too. No dice.--></ref>
| {{0}}8000
|-
| 1/1.7" camera ([[Nikon Coolpix]] P340)
| 11.9&nbsp;<ref name="DXOMark" />
| {{0}}3800
|-
| 1" camera ([[Canon PowerShot G7 X]])
| 12.7&nbsp;<ref name="DXOMark" />
| {{0}}6600
|-
| Four-thirds DSLR camera ([[Panasonic Lumix DC-GH5]])
| 13.0&nbsp;<ref name="DXOMark" />
| {{0}}8200
|-
| APS DSLR camera ([[Nikon D7200]])
| 14.6&nbsp;<ref name="DXOMark">{{cite web |url= http://www.dxomark.com/Cameras/Camera-Sensor-Ratings/%28type%29/usecase_landscape |title=Camera Sensor Ratings |work=DxOMark |date=2015 |publisher=[[DxO Labs]] |access-date=February 2, 2015}}</ref>
| 24800
|-
| Full-frame DSLR camera ([[Nikon D810]])
| 14.8&nbsp;<ref name="DXOMark" />
| 28500 <!-- Calculated from formula: Contrast Ratio = 2^(Dynamic Range) -->
|- style="background-color:#DDF;"
|}

Most cameras are limited to a much narrower range of exposure values within a single image, due to the dynamic range of the capturing medium. With a limited dynamic range, tonal differences can be captured only within a certain range of brightness. Outside of this range, no details can be distinguished: when the tone being captured exceeds the range in bright areas, these tones appear as pure white, and when the tone being captured does not meet the minimum threshold, these tones appear as pure black. Images captured with non-HDR cameras that have a limited exposure range (low dynamic range, LDR), may lose detail in highlights or [[Shadow#Photography|shadows]].

Modern [[CMOS]] [[image sensor]]s have improved dynamic range and can often capture a wider range of tones in a single exposure<ref name=":2" /> reducing the need to perform multi-exposure HDR. Color film negatives and slides consist of multiple film layers that respond to light differently. Original film (especially negatives versus transparencies or slides) feature a very high dynamic range (in the order of 8 for negatives and 4 to 4.5 for positive transparencies).

Multi-exposure HDR is used in photography and also in extreme dynamic range applications such as welding or automotive work. In security cameras the term "wide dynamic range" is used instead of HDR.

=== {{anchor|Ghosting}}Limitations ===
[[File:Hdr capture golf swing ghost effect.jpg|thumb|upright=1.8|This composited multi-exposure HDR capture shows the correct exposure for both the shaded grass and the bright sky, but the fast-moving golf swing led to a "ghost" club.]]
[[File:HDR ghosting from motion - playground - HDR on.jpg|thumb|HDR ghosting from spinning carousel]]
A fast-moving subject, or camera movement between the multiple exposures, will generate a "ghost" effect or a staggered-blur strobe effect due to the merged images not being identical. Unless the subject is static and the camera mounted on a tripod there may be a tradeoff between extended dynamic range and sharpness. Sudden changes in the lighting conditions (strobed LED light) can also interfere with the desired results, by producing one or more HDR layers that do have the luminosity expected by an automated HDR system, though one might still be able to produce a reasonable HDR image manually in software by rearranging the image layers to merge in order of their actual luminosity.

Because of the nonlinearity of some sensors image artifacts can be common.

Camera characteristics such as [[Gamma correction|gamma curves]], sensor resolution, noise, [[Photometry (optics)|photometric]] calibration and [[color calibration]] affect resulting high-dynamic-range images.<ref>{{cite book|last1=Sá|first1=Asla M.|url=https://books.google.com/books?id=mDsFgWPhWWYC|title=High Dynamic Range|last2=Carvalho|first2=Paulo Cezar|last3=Velho|first3=Luiz|date=2007|publisher=Focal Press|isbn=978-1-59829-562-7|page=11}}</ref>