darkening around the edges
Brian Cluff
Brian at Snaptek.com
Wed Mar 23 19:51:00 MST 2016
Just keep in mind that the book on linuxtopia, grokking the gimp, is 16 years old. I'm sure there are plenty of good examples, but the gimp has changed significantly since then, so you might have to do a little searching for features that have moved.
Brian Cluff
On March 23, 2016 7:12:40 PM MST, Michael <bmike1 at gmail.com> wrote:
>I think I'll spend a day (week?) reading the Linuxtopia book.
>
>On Wed, Mar 23, 2016 at 4:13 PM, Brian Cluff <brian at snaptek.com> wrote:
>
>> Here's some specifics of the blend modes.
>> https://en.wikipedia.org/wiki/Blend_modes
>>
>>
>http://www.linuxtopia.org/online_books/graphics_tools/gimp_advanced_guide/gimp_guide_node55_002.html
>>
>> For your example pictures, screen will over brighten the darker areas
>of
>> your picture, so dodge produces a better result. In a different
>picture,
>> screen could be the better choice.
>>
>> Brian
>>
>> On 03/23/2016 12:56 PM, Michael wrote:
>>
>>> please, what is the difference between the two modes?
>>>
>>> On Wed, Mar 23, 2016 at 2:35 PM, Brian Cluff <brian at snaptek.com
>>> <mailto:brian at snaptek.com>> wrote:
>>>
>>> Oops, use the Dodge layer mode instead of screen. You'll get
>better
>>> results.
>>>
>>> Brian
>>>
>>>
>>> On 03/23/2016 11:22 AM, Brian Cluff wrote:
>>>
>>> > On 03/23/2016 04:49 AM, Michael wrote:
>>> > Thanks Brian. I am putty in your hands!
>>>
>>> I get the bounces from the PLUG mailing list, so I got your
>>> images even
>>> though they were too big for the queue... nobody else did
>>> though, so my
>>> answer will be the only one based off your image.
>>>
>>> Anyway, looking at your pictures, it appears that the
>darkened
>>> edges
>>> aren't due to fading over time rather they are caused by
>what
>>> appear to
>>> be a flash going off that lit the center of the image more
>than
>>> the
>>> edges. This can also be caused of lower quality lenses
>giving you
>>> darkened edges in what is called a vignette.
>>>
>>> If you want to try and reduce/eliminate it, in gimp you
>would add
>>> a
>>> layer above your picture, but before you do that, if you
>have the
>>> option, go to Image -> Precision and set it to 16 ot 32 bit,
>so
>>> that you
>>> have more color data to work with. Unfortunately you'll
>only
>>> have that
>>> option if you are running the development version of GIMP,
>but
>>> it will
>>> still work OK if you can't do that setting. Next use the
>>> gradient tool,
>>> changing the gradient type to radial, and make a gradient
>that
>>> goes from
>>> black in the center fading to white at the corners. (draw
>the
>>> gradient
>>> from the center to one of the corners).
>>>
>>> Then set your new gradient layer's mode to "screen".
>>>
>>> At this point the effect will probably be too strong, so you
>>> will need
>>> to play with the opacity till it looks better and you can
>also
>>> play with
>>> the color curves moving the line on the lower left back and
>>> forth across
>>> the bottom to adjust the shape of the gradient till it
>better
>>> matches
>>> the vignette in your image. You can change the gradients
>layer
>>> mode
>>> back to normal to get an idea of what the color curve
>adjustment
>>> is
>>> doing to the gradient.
>>>
>>> Brian Cluff
>>>
>>> On 03/22/2016 06:42 PM, Brian Cluff wrote:
>>>
>>> Can you send an example so that I can see what you mean
>by
>>> "darkened
>>> around the edges"?
>>>
>>> I'll see if I can easily correct it and then send
>>> instructions on what I
>>> did.
>>>
>>> Brian Cluff
>>>
>>> On 03/22/2016 04:18 PM, Michael wrote:
>>>
>>> how does one use a transparent layer? is it only for
>>> drawing things on?
>>> I have some old pictures that have darkened around
>the
>>> edges. How I
>>> think I can fix it is to duplicate the layer then
>>> lighten the exposure
>>> value on the lower image, then paint black and
>uncover
>>> the lighter image
>>> over the section that has darkened. How do I do this
>>> with gradients and
>>> Darktable?
>>>
>>> --
>>> :-)~MIKE~(-:
>>>
>>>
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