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I was wondering what is the dynamic range of an HDR photo if the bracketing was set at 2EV? (in F-stops)

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  • \$\begingroup\$ Real or perceived? \$\endgroup\$
    – xenoid
    Commented Jan 27, 2020 at 16:06
  • \$\begingroup\$ Real dynamic range \$\endgroup\$
    – Tornado 77
    Commented Jan 27, 2020 at 16:12
  • \$\begingroup\$ HDR will extend the effective dynamic range of a camera (assuming that it is processed properly). So, to answer this, you need to specify the dynamic range of the camera without HDR. A typical camera might have 12 or 14 stops of dynamic range. Shooting a +/- 2 stop HDR will extend it by 4 stops. \$\endgroup\$
    – Mattman944
    Commented Jan 27, 2020 at 16:12
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    \$\begingroup\$ @Mattman944 That also depends on how many bracketed shots are taken. e.g. my 7DII can shoot up to 7 shots, which, at +/- 2EV could cover the base dynamic range + 12 additional stops... \$\endgroup\$
    – twalberg
    Commented Jan 27, 2020 at 16:19
  • \$\begingroup\$ What is the dynamic range of the scene? If there's only four or five stops between the brightest and dimmest things in the scene, it doesn't matter how much you bracket, you've still only got a four or five stop photo. \$\endgroup\$
    – Michael C
    Commented Jan 28, 2020 at 3:53

4 Answers 4

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HDR does not extend the dynamic range of a photo. It compresses the extended dynamic range into the same dynamic range limits (display/print reproducibility).

Technically dynamic range is the difference between min/max; i.e. contrast. That is always the same (black and white) as limited by the display medium.

Tonality is the measure of the number of tones that fall w/in the min/max values. Which is why HDR is also referred to as "tone mapping;" because it rewrites the values to fall w/in the min/max.

There are also limitations as to the file format and gamma curve applied. i.e. an 8bit jpeg w/ 2.2 gamma curve can show about 12 stops of tonality; whereas a 14bit encoded raw file with a 1.0 gamma applied can show 14 stops of tonality.

And then there are the limits of the camera in use, as well as the scene being recorded. I.e. how much dynamic range and tonality was actually recorded in each image, and how many images are being combined/compressed?

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  • \$\begingroup\$ tone mapping is what you do to an hdr picture to display it. it's not the same. \$\endgroup\$
    – ths
    Commented Jan 27, 2020 at 22:45
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    \$\begingroup\$ 32bit is the working/processing format (8bit/color + alpha), but that result must be tone mapped to output a viewable image (typically as an 8bit jpeg or 16bit tiff)... it is integral to having "a photo." \$\endgroup\$
    – Steven Kersting
    Commented Jan 28, 2020 at 0:15
  • \$\begingroup\$ displaying a hdr photo on a device that is not able to display that much dynamic range and having a hdr photo are 2 different things. so i have to agree with @ths \$\endgroup\$
    – Horitsu
    Commented Jan 28, 2020 at 6:33
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    \$\begingroup\$ @Horitsu Please share with us what current technology is capable of displaying a 32-bit floating point light map? It's not a photo until one can look at it. \$\endgroup\$
    – Michael C
    Commented Jan 28, 2020 at 9:50
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    \$\begingroup\$ @Horitsu If you can not see it, it is not a photo. It may be a latent image on undeveloped film, or it may be a data file. But it is not a photo. \$\endgroup\$
    – Michael C
    Commented Jan 29, 2020 at 23:51
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I don't believe you understand the question you're asking, but that's OK.

I'm assuming you've taken some guesses here about daylight range of 13 'stops', the eye's visible range, and wondered how an HDR photo with a +2 'stop' of intensity would work.

Well... if you think in 'stops' (for photos) then it becomes pretty easy- it's 15 stops. If you go +2, you get 17 stops.

Film is pretty forgiving but I believe 13 stops was pretty easy to do with good processing, and if you worked hard you might get slightly better.

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I agree with @J.Hirsch answer. If you have an additional bracketing +2EV you have 2 stops more range than the previous one.

But you need to take into account that an HDR Image must be saved in a special format, normally a floating-point file format, then the file itself has now space to hold a lot more dynamic range, but if it is used or not is beyond the point.

If the second image you capture has the same information you already captured with the previous image, you probably will not get any additional information.

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The real dynamic range is limited by the number of bits in the image format (and whatever the display can accurately show), one EV for each bit. So you have a 8EV dynamic range.

The perceived dynamic range will be 4EV bigger, if the processing is done right.

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  • \$\begingroup\$ You only need 1bit/EV when linearly encoded (i.e. raw files). When converted with a gamma curve applied you can encode much more; I.e. approx 12 stops in an 8bit, 2.2 gamma jpeg. \$\endgroup\$
    – Steven Kersting
    Commented Jan 27, 2020 at 19:17
  • \$\begingroup\$ you do typically not use an 8 bit integer format for hdr images. a 32 bit floating point format can record virtually infinite DR. \$\endgroup\$
    – ths
    Commented Jan 27, 2020 at 22:47
  • \$\begingroup\$ @ths And nothing we currently have is capable of actually displaying that 32-bit floating point file, so it's not really an image at that point. \$\endgroup\$
    – Michael C
    Commented Jan 28, 2020 at 3:56
  • \$\begingroup\$ @MichaelC of course we have. that the viewer software will have to map the image to the displayable range is inevitable, but not different from printing an JPEG on paper with its much lower DR. the Q was about the DR of the HDR file, not how it is represented on any display medium. \$\endgroup\$
    – ths
    Commented Jan 28, 2020 at 15:44
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    \$\begingroup\$ @ths, the question was about an HDR photo, not what is in the file... Take that a step farther; how is it even possible to know what DR is actually described within the file itself? I suppose if you have an accurate measurement of the DR/tonality the scene contained originally, and if it exceeded the capability of the camera, and you also know the accurate DR/tonality capability of the camera at the ISO used; then maybe you could calculate it. Or maybe if you have the ability to do a byte level read of the proprietary file format... but all of that is pretty useless until it is a photo. \$\endgroup\$
    – Steven Kersting
    Commented Jan 28, 2020 at 18:59

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