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I am editing photos of the total solar eclipse 2019. I configured my Canon Rebel T6s to aperture priority and fixed ISO 100. I used bracketing +/-2/3. However, some pictures have identical shutter values (as recorded in the exif metadata accessed in RawTherapee).

For example
Pic1 = 1/15 shutter, 100 iso, 0.00 ECV
Pic2 = 1/25 shutter, 100 iso, -0.67 ECV
Pic3 = 1/25 shutter, 100 iso, +0.67 ECV (<-- should have slower shutter than 1/15)

How can pics 2 and 3 have the same shutter value yet have different ECV? What am I missing?

NOTE: some of my pictures did work as expected. Any idea why some did not?

Thanks!

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    \$\begingroup\$ What’s happening with the aperture settings? \$\endgroup\$
    – Eric S
    Commented Jul 25, 2019 at 2:29
  • \$\begingroup\$ @Xiota Generally (maybe always), when Canon cameras bracket exposure, all of the bracketed frames are based on a single meter reading before the first exposure. The exposure values for all of the bracketed frames are"locked in" at that time. That's why the exposure lock indicator is lit until the full sequence has been recorded. \$\endgroup\$
    – Michael C
    Commented Jul 25, 2019 at 4:33
  • \$\begingroup\$ What lens are you using? If a zoom, at what focal length? \$\endgroup\$
    – Michael C
    Commented Jul 25, 2019 at 5:36
  • \$\begingroup\$ Thanks for clarifying and reading my question. I am using a telescope (f=1000mm) and a T-mount. So, the camera does not recognize the lens attached. Exif says FNumber=0.0 and ApertureValue=0.0. \$\endgroup\$
    – AeroMac
    Commented Jul 25, 2019 at 14:54
  • \$\begingroup\$ Using the scope is fine (I do this regularly). Also, when bracketing, the camera should not change the aperture (since that alters the depth of field). It will normally bracket by changing exposure times. I would have expected your 3rd pic to use 1/10th sec. Not sure why the shutter time is the not longer. \$\endgroup\$
    – Tim Campbell
    Commented Jul 25, 2019 at 15:57

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