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Colour bleeding issue



 
 
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  #1  
Old September 9th 17, 11:12 AM posted to rec.photo.digital
Alfred Molon[_4_]
external usenet poster
 
Posts: 2,591
Default Colour bleeding issue

I call it "colour bleeding", but I'm not sure if it's the right term.

In this image (out of camera JPEG):
http://myolympus.org/document.php?id=20159

It's mostly in the upper right part, where the trees are against the sky
that in the border areas blue colour/tint spreads to the tree trunks,
branches and leaves.

This was taken with the UWA Laowa 7.5mm lens (= 15mm FF equiv.) and a
polariser filter.

I wonder if it's the polariser filter which causes this, because I
bought a cheap one (Hoya Slim Cirkular Polfilter 46mm):
https://www.amazon.de/dp/B00HF6FYDA/...740101_TE_item

for 16 Euro, while the polariser filter for the main lens (the 12-100)
cost around 100 Euro. And in fact the 12-100 with its polariser filter
is more resistant against backlighting issues.

Any comments?

Another question, I wonder if there is a simple way in postprocessing to
correct the image.
--
Alfred Molon

Olympus E-series DSLRs and micro 4/3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site
  #2  
Old September 9th 17, 11:14 AM posted to rec.photo.digital
Alfred Molon[_4_]
external usenet poster
 
Posts: 2,591
Default Colour bleeding issue

In article , Alfred Molon
says...
out of camera JPEG


Sorry, it's a processed RAW.
--
Alfred Molon

Olympus E-series DSLRs and micro 4/3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site
  #3  
Old September 9th 17, 12:43 PM posted to rec.photo.digital
Davoud
external usenet poster
 
Posts: 639
Default Colour bleeding issue

Alfred Molon:

I call it "colour bleeding", but I'm not sure if it's the right term.

In this image (out of camera JPEG):
http://myolympus.org/document.php?id=20159

It's mostly in the upper right part, where the trees are against the sky
that in the border areas blue colour/tint spreads to the tree trunks,
branches and leaves.


Looks to me like a kind of lens flare, very possibly caused by the
filter.

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm
  #4  
Old September 9th 17, 03:36 PM posted to rec.photo.digital
Savageduck[_3_]
external usenet poster
 
Posts: 16,487
Default Colour bleeding issue

On Sep 9, 2017, Alfred Molon wrote
(in . com):

I call it "colour bleeding", but I'm not sure if it's the right term.

In this image (out of camera JPEG):
http://myolympus.org/document.php?id=20159

It's mostly in the upper right part, where the trees are against the sky
that in the border areas blue colour/tint spreads to the tree trunks,
branches and leaves.

This was taken with the UWA Laowa 7.5mm lens (= 15mm FF equiv.) and a
polariser filter.

I wonder if it's the polariser filter which causes this, because I
bought a cheap one (Hoya Slim Cirkular Polfilter 46mm):
https://www.amazon.de/dp/B00HF6FYDA/...740101_TE_item

for 16 Euro, while the polariser filter for the main lens (the 12-100)
cost around 100 Euro. And in fact the 12-100 with its polariser filter
is more resistant against backlighting issues.

Any comments?

Another question, I wonder if there is a simple way in postprocessing to
correct the image.


You have a combination of issues with different causes.

I would start with the lens caused issues with Chromatic Aberration (CA) with
purple fringing visible at the contrasting edges of the leaves and branches
where higher contrast light filters through the vegitation. Depending on your
RAW processing software, you should be able to correct for CA and/or fringing
with software lens correction tools. Most good RAW software has a tool for
making this correction.

Then, where the Sun is bright there is some lens flare, but it is not as bad
as it could have been with a lens this wide. It is a factor, along with CA,
many ultra wide lenses are vulnerable to, especially budget lenses.
Unfortunately there is not much which can be done to correct flare in post
processing. However, using it deliberately can make for some interesting
compositions.

A check on the Photozone review of this lens shows some mild CA (which should
be easily corrected) and some issues with flare. They have this to say:
“Back-light scenes are a bit of a challenge for the little Laowa lens.
Ghostings and/or glare can be an issue at times.”
http://www.photozone.de/m43/1001-laowa75f2mft?start=1

I doubt that the Hoya CPF is the problem. However, CPFs are not at their best
when aimed dirrectly toward the Sun, and it might have exacerbated issues
inherent in the lens.

Other than that, I like your shot, and I think with a careful selection of
scene, you should get some interesting to great images out of that lens.

--

Regards,
Savageduck

  #5  
Old September 9th 17, 03:48 PM posted to rec.photo.digital
Alfred Molon[_4_]
external usenet poster
 
Posts: 2,591
Default Colour bleeding issue

In article .com,
Savageduck says...
It is a factor, along with CA,
many ultra wide lenses are vulnerable to, especially budget lenses.


Actually this lens (Laowa 7.5mm) is not exactly budget. It costs 500 USD
and it's quite sharp, but may have other weaknesses.

Maybe I need to do some tests of backlit scenes, with and without
filters.

I'm just wondering if a high quality filter (i.e. with the right
coatings) would have mitigated the issue a bit.
--
Alfred Molon

Olympus E-series DSLRs and micro 4/3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site
  #6  
Old September 9th 17, 05:29 PM posted to rec.photo.digital
Savageduck[_3_]
external usenet poster
 
Posts: 16,487
Default Colour bleeding issue

On Sep 9, 2017, Alfred Molon wrote
(in om):

In iganews.com,
Savageduck says...
It is a factor, along with CA,
many ultra wide lenses are vulnerable to, especially budget lenses.


Actually this lens (Laowa 7.5mm) is not exactly budget. It costs 500 USD
and it's quite sharp, but may have other weaknesses.


For an ultra-wide that is not particularly expensive, and compares with the
Rokinon/Samyung lenses. Each have problems once they go ultra-wide. There is
no denying that they can produce sharp results, one just has to be aware of
their weaknesses and limitations, and how best to utilize them when planning
your shots.

Maybe I need to do some tests of backlit scenes, with and without
filters.


Why not? You have to do a little experimenting so you can wring the best out
of your equipment.

I'm just wondering if a high quality filter (i.e. with the right
coatings) would have mitigated the issue a bit.


I don’t believe that the filter was a major factor in the problem, other
than proper use of the CPF. Hoya filters actually have several quality/price
levels, but have a good reputation. I have several of the Hoya NXT Cir-PL
filters, and a few of their IRND filters of various stop levels. When used
correctly they have not been an issue. For the most part a CPF works to best
effect when shooting at 90º to the Sun, not shooting into the Sun, or with
the Sun behind you. Also understand that a CPF can effect your exposure
settings as it acts as an ND filter.

http://www.manfrottoschoolofxcellence.com/2016/02/56124/
http://www.cambridgeincolour.com/tutorials/polarizing-filters.htm
--

Regards,
Savageduck

  #7  
Old September 9th 17, 06:06 PM posted to rec.photo.digital
me[_5_]
external usenet poster
 
Posts: 578
Default Colour bleeding issue

On Sat, 09 Sep 2017 07:36:24 -0700, Savageduck
wrote:

On Sep 9, 2017, Alfred Molon wrote
(in . com):

I call it "colour bleeding", but I'm not sure if it's the right term.

In this image (out of camera JPEG):
http://myolympus.org/document.php?id=20159

It's mostly in the upper right part, where the trees are against the sky
that in the border areas blue colour/tint spreads to the tree trunks,
branches and leaves.

This was taken with the UWA Laowa 7.5mm lens (= 15mm FF equiv.) and a
polariser filter.

I wonder if it's the polariser filter which causes this, because I
bought a cheap one (Hoya Slim Cirkular Polfilter 46mm):
https://www.amazon.de/dp/B00HF6FYDA/...740101_TE_item

for 16 Euro, while the polariser filter for the main lens (the 12-100)
cost around 100 Euro. And in fact the 12-100 with its polariser filter
is more resistant against backlighting issues.

Any comments?

Another question, I wonder if there is a simple way in postprocessing to
correct the image.


You have a combination of issues with different causes.

I would start with the lens caused issues with Chromatic Aberration (CA) with
purple fringing visible at the contrasting edges of the leaves and branches
where higher contrast light filters through the vegitation. Depending on your
RAW processing software, you should be able to correct for CA and/or fringing
with software lens correction tools. Most good RAW software has a tool for
making this correction.

Then, where the Sun is bright there is some lens flare, but it is not as bad
as it could have been with a lens this wide. It is a factor, along with CA,
many ultra wide lenses are vulnerable to, especially budget lenses.
Unfortunately there is not much which can be done to correct flare in post
processing. However, using it deliberately can make for some interesting
compositions.

A check on the Photozone review of this lens shows some mild CA (which should
be easily corrected) and some issues with flare. They have this to say:
Back-light scenes are a bit of a challenge for the little Laowa lens.
Ghostings and/or glare can be an issue at times.
http://www.photozone.de/m43/1001-laowa75f2mft?start=1

I doubt that the Hoya CPF is the problem. However, CPFs are not at their best
when aimed dirrectly toward the Sun, and it might have exacerbated issues
inherent in the lens.

Other than that, I like your shot, and I think with a careful selection of
scene, you should get some interesting to great images out of that lens.



A few additional issues. First there appears to be some clipping still
in the image in this area and it appears to have been shot suing auto
white balance, not sure if in the camera and/or in post processing.
Shooting trees in the shadows with blue sky in the background is
typically going to require some white balance tweaks in my experience
to eliminate a bluish tint in the shadows.

  #8  
Old September 9th 17, 08:28 PM posted to rec.photo.digital
Alfred Molon[_4_]
external usenet poster
 
Posts: 2,591
Default Colour bleeding issue

In article , me says...
A few additional issues. First there appears to be some clipping still
in the image in this area and it appears to have been shot suing auto
white balance, not sure if in the camera and/or in post processing.
Shooting trees in the shadows with blue sky in the background is
typically going to require some white balance tweaks in my experience
to eliminate a bluish tint in the shadows.


The camera was on AutoWB and measured 5500K, but in RAW conversion I
used 4900K. Can't remember why, looking again at the image I could also
have used 5500K. Probably using a warmer WB in RAW conversion would make
sense.
--
Alfred Molon

Olympus E-series DSLRs and micro 4/3 forum at
http://tech.groups.yahoo.com/group/MyOlympus/
http://myolympus.org/ photo sharing site
 




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