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Open EXR - wrong gamma & brightness

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    Open EXR - wrong gamma & brightness

    Hi! I'm very pleased to see that Irfanview supports the OpenEXR, as I use it a lot. However, there are a few issues with the plugin when loading 32 bit images: it seems to load the wrong gamma and the wrong brightness. Here are a few screenshots:

    1. This is how it's in irfanview

    2. This is photoshop (again, wrong, it loads with a gamma of 1.0)

    3. This is fusion (correct gamma of 2.2)

    You can see that there are differences between #1 and #2, while #3 is the correct one. I'd be very pleased if Irfanview would go at least as far as photoshop (messing up the gamma only), but it would be perfect if it loaded them with all the correct settings.

    Thank you!
    Attached Files
    Last edited by Rockin; 18.08.2009, 09:33 AM.

    The EXR plug-in has been updated after version 4.67 with a new formula for the transfer function. Since there are many varieties of EXR files with different word lengths and gamma, EXR users, please check if there are any regressions and tell Irfan Skiljan about them while has this stuff fresh in memory.

    The most common format containing half-precision float16 pixels with linear 1.0 gamma should now be corrected to gamma 2.2 on loading.

    A typical EXR file should contain values in linear format and should get gamma applied for display. Without it, the contrast should be extremely high and average brightness low. If you have files with gamma 2.2 baked in, perhaps show them to Irfan, so that he can output them straight. This post mentions a flag, but calls it "linear gamma".


    The test images on the OpenEXR site now look close to their reference renderings. The blacks are slightly brighter in IrfanView because a gamma of 2.2 is applied instead of the sRGB transfer curve for simplicity and to undo the gamma that is often applied on saving.

    Last edited by j7n; 01.05.2024, 11:57 AM.