title: Get EXR image luminance
body: <p>As far as i know, I think to get an image.exr luminance we have to render the image in different exposure and gather them into one ?</p>
  <p>Here is my image made in Adobe which have different luminance from 0(left) to 10 (right) in exr extension.
  <a href="https://i.stack.imgur.com/N4A1u.png" rel="nofollow noreferrer">exr_to_png_forViewingPurpose</a></p>
  <p><strong>FIRST TEST :</strong></p>
  <p>so I tried ImageMagick with this command line from this <a href="https://stackoverflow.com/questions/58740992/splitting-openexr-into-different-exposure-images">link</a>:</p>
  <pre><code>magick .\img.exr -evaluate multiply 2 img1EV.png
  </code></pre>
  <p>So I did the same for +-2EV, and +-3EV but the negatif EV give me an empty image.</p>
  <p><strong>SECOND TEST :</strong></p>
  <p>I saw on this <a href="https://blender.stackexchange.com/q/46825">link</a> that use different exposure as 0.1, 0.2, 0.4 etc...
  I did the same with a sofware to get the same value of exposure as him.</p>
  <p>Next, I implemented a program in py to get the right luminance from a png (as suggested <a href="https://stackoverflow.com/a/56678483/17659599">here</a>).</p>
  <p>In the end with the first test, I have the same result for each image that have different exposure.
  For the second test, I do have different image but I don't know what to do with them after that.
  I don't know if it's the right way to do it, hope someone knows.</p>
  <p><a href="https://i.stack.imgur.com/3qA6J.png" rel="nofollow noreferrer">FirstTest Result</a>
  <a href="https://i.stack.imgur.com/jmzwS.png" rel="nofollow noreferrer">SecondTest Result</a></p>