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Incorrect exposure bias value #24

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Anasthase opened this issue Apr 2, 2017 · 1 comment
Open

Incorrect exposure bias value #24

Anasthase opened this issue Apr 2, 2017 · 1 comment

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@Anasthase
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Hello,

Attached are 2 files with non-zero exposure bias value. DSC_5644 is +0.3 EV and DSC02268 is -1.3EV. Easyexif reports 0 for both images.

In fact the exposure bias value is not read at all, as the expected format is 5, but the reported format is 10. I've tried to force-read the tag as format 5, but it crashed.

Thanks for your help.

dsc_5644
dsc02268
@asmaloney
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This is because ExposureBiasValue (or ExposureCompensation) is a signed rational which isn't handled properly.

A signed rational is format 10 and this code only handles formats 1-5.

Because of this, ShutterSpeedValue and ExposureBiasValue will not be correctly reported.

asmaloney added a commit to asmaloney/easyexif that referenced this issue Sep 10, 2018
@asmaloney
Handle signed rationals to fix ExposureBiasValue and ShutterSpeedValue
81267c3 
- signed rationals (format 10) are treated the same way as unsigned rationals (format 5)
- ShutterSpeedValue is an APEX value, so calculate and store the actual value

Fixes mayanklahiri#24
asmaloney added a commit to asmaloney/easyexif that referenced this issue Sep 10, 2018
@asmaloney
Handle signed rationals to fix ExposureBiasValue and ShutterSpeedValue
9d46abb 
Signed rationals (format 10) are treated the same way as unsigned rationals (format 5)

Fixes mayanklahiri#24
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@asmaloney @Anasthase