Bad quality when downsizing image (posterization)

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5 comments

  • Dave R
    It is possible to embed images in the post using the Img button but they do have to be downsized a lot (660 pixle wide)to fit the board window. That said I looked at your images and they all looked alright to me. That does not mean they are, downsizing is notorious for introducing artefacts unless the correct algorithm is used.

    Just by chance I had CO open at the same time as viewing your post and it just happened to be showing some Irish Graveyard pictures I took in May 2016. I think this is the cross in your picture taken from the opposite direction

    https://bglkcq.ch.files.1drv.com/y4mPe94sK8SCoMvLG_vzQ9UhXNqrqkArHE5XiAvMo5BGk896CdA50uk46Vx0r46MP6IEkTMj0BJvAj_8U_X4Zrx2C7bJ1pFWwuSiSngnBV7iL34f1xfS2YC0Wmf_Khy0o8MGUw05WlGdgoPA3jE0gaG_d4nlbJFUXjjurAcYXSViBxvIAPkEFvOhKGfsDppKGiivQRXabi9kH8cfSrV_kWZZw?width=660&height=440&cropmode=none
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  • NNN636795052773784921
    Hi David, you are spot on. It is Corcomroe Abbey, not far from Galway, Ireland.
    For me the degradation when downsizing to web size is unacceptable. I have created another image to illustrate the posterization in the sky. The only difference between left and right is that on the left side the image is downscaled to 1500 pixel and on the right side it is downscaled to 1505 pixel, which is good quality.
    https://www.dropbox.com/s/vnfhwz5g1rr5e7p/CO-Error.jpg?raw=1
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  • BeO
    I don't have Fuji files, but 2 thouhgts came to my mind
    1. can you try to restart C1 and try again? Or even the computer?
    2. go to Edit / preferences and disable OPENCL ( set to "never") to see if the graphics card hardware acceleration has to do something with it. (In case hardware acceleration is currently ON)

    Regards
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  • Dave R
    NNN636795052773784921 wrote:
    Hi David, you are spot on. It is Corcomroe Abbey, not far from Galway, Ireland.
    For me the degradation when downsizing to web size is unacceptable. I have created another image to illustrate the posterization in the sky. The only difference between left and right is that on the left side the image is downscaled to 1500 pixel and on the right side it is downscaled to 1505 pixel, which is good quality.
    https://www.dropbox.com/s/vnfhwz5g1rr5e7p/CO-Error.jpg?raw=1

    The artefacts are quite clear and distinct in this pair of pictures. I have seen that type of mottling before and am racking my brain to remember where and the cause. If I remember I will add another reply.

    Dave
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  • NNN636795052773784921
    @BeO: I restarted everything and disabled OpenCL, no change. Thanks anyway for the hint.
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