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Spot Removal - preview bug?

John Doe
Hi!

Yesterday I was confronted with a strange behavior using the spot removal tool.

Here's a detail from the original picture as displayed by Capture One:
https://dl.dropboxusercontent.com/u/23809758/CO-bug/original.jpg

I wanted to remove the two white threads, so I used the spot removal tool and the fit-sized preview in CO showed me this:
https://dl.dropboxusercontent.com/u/23809758/CO-bug/spotremoval-fit.jpg

Not perfect but good enough, I thought. Let's export this to JPEG. Damn! Here's how it appeared in the Finder:
https://dl.dropboxusercontent.com/u/23809758/CO-bug/spotremoval-jpegoutput.jpg

So I went back to CO to investigate, and found out that while the fit-sized preview was OK, those two dark stains show up if I zoom in:
https://dl.dropboxusercontent.com/u/23809758/CO-bug/spotremoval-zoom.jpg

Looks somewhat like a bug to me. A double bug even:
1/ Why is the preview different between "sized to fit" and "zoomed in"?
2/ Why did the spot removal tool create those horrible stains?
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Kommentare

9 Kommentare

Datum Stimmen
  • Permanently deleted user
    As an fyi... I have seen this also. I have started to bounce out to PS for spotting because of this.

    Alan
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  • John Doe
    I've just filed a bug report, #212679.
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  • RichardT
    I hadn't noticed this before because I had only ever used the Remove Spot tool to remove dark spots from light backgrounds (e.g. sky).

    I just tried on the windows version to remove a light spot from a dark background. In this case the dark patch appeared when I zoomed into 50% and then disappeared when I zoomed back out to 33%. It also appeared in exported JPEGs at 100% and with long edge of 1024px.

    Richard
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  • John Doe
    Thx Alan and Richard, you both confirm there's probably a bug there.
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  • SFA
    The Spot and Dust fixes are for rather specific purposes although they may be used more widely with some success.

    For the particular challenge presented I would have thought these days the better C1 tool would be a Heal layer correction.

    What result does that give?


    Grant
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  • John Doe
    Not available in Capture One Express, AFAIK.

    However it doesn't explain the first bug (difference in previews with two different zooms).
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  • SFA
    [quote="John Doe" wrote:
    Not available in Capture One Express, AFAIK.


    Good point!

    [quote="John Doe" wrote:

    However it doesn't explain the first bug (difference in previews with two different zooms).


    That is true.

    One of the problems with zooming and resolution is that at everything less than 100% data is being binned. Sometime quite a lot of data and in some colour and texture situations the decisions about what to bin and by how much an be challenging if consistency across zoom levels is paramount.

    That said this example is slightly odd in the way it presents.

    I have yet to find anything similar amongst my images with which to experiment.

    What happens if you make the selected area smaller and perhaps use two spots to cover the blemish?

    I would guess that the area to be "fixed" is more or less equally balanced between the lighter and darker shade of the man colour plus a few other bits. the proportion of each may just flip between the two shades as the area changes in size and pixels are included and excluded. As the spot tool and the dust version are mainly try to blend against primary colours (and the main use of the spot probably relates to spots on the sensor (relatively contiguous sky being a prime example) or skin in a portrait (again a relatively contiguous colour range) it may not be a best fit for the darker areas you have need to fix.

    Or it could simply be an error.

    It will be interesting to hear what support say.


    Grant
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  • RichardT
    [quote="SFA" wrote:
    What happens if you make the selected area smaller and perhaps use two spots to cover the blemish?


    It created two small dark patches, instead of one larger one.

    I then clicked several times with the Spot Removal tool randomly on a dark brown carpet. When I zoomed in, each one showed as a darker patch, even where there was no light coloured blemish to be removed.
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  • SFA
    [quote="RichardT" wrote:
    [quote="SFA" wrote:
    What happens if you make the selected area smaller and perhaps use two spots to cover the blemish?


    It created two small dark patches, instead of one larger one.

    I then clicked several times with the Spot Removal tool randomly on a dark brown carpet. When I zoomed in, each one showed as a darker patch, even where there was no light coloured blemish to be removed.


    I don't think there is much intent within the code to try to analyse what it is we might be trying to remove, other than by some assessment of the data under the spot.

    I played around with a photo of a fox. The results varied quite a lot depending on which part of the fox's fur I was trying to adjust and how big the "spot" was. The proportions of the different colours under the spot area clearly influenced the result but equally clearly there are other factors involved.

    The will be some times when "the magic" needs to be found elsewhere or to be summoned up differently.


    Grant
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