What causes this blotching?


Dan Margulis
 

I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their surroundings, almost as if a drop of water had fallen on the lens. But the effect is so subtle that it can only be seen in an otherwise very smooth area, normally the sky. And often it still can't be seen unless the area has been stressed, which unfortunately the PPW tends to do.

There's no sweat cloning the defects out, but I would be interested in knowing how it comes about. Is it a sensor issue? I've seen it in my own shots but more commonly in the work of very fine photographers using top-of-the-line equipment. And like I said, the problem seems to be a growing one.

An example of what I'm talking about is in the Sunrise folder in our Photos section that many of us have recently worked on. If the link below doesn't work, it's my own version, the one with the -dm suffix. I boosted the sky quite a bit and the defects are evident. Why are they in the file in the first place?

http://groups.yahoo.com/group/colortheory/photos/album/734361103/pic/1620921285/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc

Dan Margulis


David Lawrence
 

--- In colortheory@..., Dan Margulis <DMargulis@...> wrote:

I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their surroundings, almost as if a drop of water had fallen on the lens. But the effect is so subtle that it can only be seen in an otherwise very smooth area, normally the sky. And often it still can't be seen unless the area has been stressed, which unfortunately the PPW tends to do.
Dan Margulis
Dan,

That is sensor dust inside the camera. A photogs nightmare. Modern cameras use ultrasonic sound to shake them off of the sensor on startup and shutdown, but some persist. They have to be cleaned professionally in most cases.

David Lawrence
PixelPurfect.com


Alessandro
 

Hi Dan
the spot are caused by the dust on the sensor, umidity and grease.
Photographers must clean the sensor.


Alessandro Anglisani


To: colortheory@...
From: DMargulis@...
Date: Wed, 6 Mar 2013 08:19:27 -0800
Subject: [colortheory] What causes this blotching?


























I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.



The capture contains circular or oval areas slightly darker than their surroundings, almost as if a drop of water had fallen on the lens. But the effect is so subtle that it can only be seen in an otherwise very smooth area, normally the sky. And often it still can't be seen unless the area has been stressed, which unfortunately the PPW tends to do.



There's no sweat cloning the defects out, but I would be interested in knowing how it comes about. Is it a sensor issue? I've seen it in my own shots but more commonly in the work of very fine photographers using top-of-the-line equipment. And like I said, the problem seems to be a growing one.



An example of what I'm talking about is in the Sunrise folder in our Photos section that many of us have recently worked on. If the link below doesn't work, it's my own version, the one with the -dm suffix. I boosted the sky quite a bit and the defects are evident. Why are they in the file in the first place?



http://groups.yahoo.com/group/colortheory/photos/album/734361103/pic/1620921285/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc



Dan Margulis














[Non-text portions of this message have been removed]


David Preutz
 

Hello All
This looks very much as through it's a drying mark from a sensor clean. Nigh on impossible to detect with the naked eye & almost as impossible even when you look down the throat of the camera with one of those specially made lupe things. I don't go near the sensors on my Nikons, preferring to pay the 'experts' to do it. Check the cleanliness & if it ain't right, get them to keep going until it is.I do get them on my P45+ regardless of whose cleaning solutions I use.
Never used to get them on my Tri-X or Provia - and still don't.

--- In colortheory@..., Dan Margulis <DMargulis@...> wrote:

I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their surroundings, almost as if a drop of water had fallen on the lens. But the effect is so subtle that it can only be seen in an otherwise very smooth area, normally the sky. And often it still can't be seen unless the area has been stressed, which unfortunately the PPW tends to do.


Calvin Jones
 

The cause is dust on the sensor (or on the low-pass filter covering the sensor in most cases). It's one of the banes of digital photographers who use smaller apertures to increase DOF.

Calvin

On Mar 6, 2013, at 11:19 AM, Dan Margulis <DMargulis@...> wrote:

I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their surroundings, almost as if a drop of water had fallen on the lens. But the effect is so subtle that it can only be seen in an otherwise very smooth area, normally the sky. And often it still can't be seen unless the area has been stressed, which unfortunately the PPW tends to do.

There's no sweat cloning the defects out, but I would be interested in knowing how it comes about. Is it a sensor issue? I've seen it in my own shots but more commonly in the work of very fine photographers using top-of-the-line equipment. And like I said, the problem seems to be a growing one.

An example of what I'm talking about is in the Sunrise folder in our Photos section that many of us have recently worked on. If the link below doesn't work, it's my own version, the one with the -dm suffix. I boosted the sky quite a bit and the defects are evident. Why are they in the file in the first place?

http://groups.yahoo.com/group/colortheory/photos/album/734361103/pic/1620921285/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc

Dan Margulis




Campo Weijerman
 

On Wed, Mar 6, 2013 at 5:19 PM, Dan Margulis <DMargulis@...> wrote:


An example of what I'm talking about is in the Sunrise folder in our
Photos section that many of us have recently worked on. If the link below
doesn't work, it's my own version, the one with the -dm suffix. I boosted
the sky quite a bit and the defects are evident. Why are they in the file
in the first place?


http://groups.yahoo.com/group/colortheory/photos/album/734361103/pic/1620921285/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc
Those are most likely dust specs that enter the camera usually when
changing lenses (in case of DSLR).
Some of the dust ends up on the sensor which is why most recent models
feature a shake mechanism.
The shake mechanism helps somewhat but I still find it necessary to inspect
and clean the sensor on a regular basis. Indeed, applying big contrast
boosts brings out the speckles more clearly.

Hth,
--
Campo Weijerman


berdov
 

I assume it is dust. It is present on all photos in one of my cameras, even
though I cleaned it many times. One example is at
http://www.bfcollection.net/errordocs/20121010177_dust_Tomar.jpg

My new, now 6 months old camera produces brilliant clean images, but even
there I am starting to notice light spots.

Boris Feldblyum
www.bfcollection.net

On Wed, Mar 6, 2013 at 11:19 AM, Dan Margulis <DMargulis@...> wrote:

**


I have a question for photographers about what causes a certain kind of
defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their
surroundings, almost as if a drop of water had fallen on the lens. But the
effect is so subtle that it can only be seen in an otherwise very smooth
area, normally the sky. And often it still can't be seen unless the area
has been stressed, which unfortunately the PPW tends to do.

There's no sweat cloning the defects out, but I would be interested in
knowing how it comes about. Is it a sensor issue? I've seen it in my own
shots but more commonly in the work of very fine photographers using
top-of-the-line equipment. And like I said, the problem seems to be a
growing one.

An example of what I'm talking about is in the Sunrise folder in our
Photos section that many of us have recently worked on. If the link below
doesn't work, it's my own version, the one with the -dm suffix. I boosted
the sky quite a bit and the defects are evident. Why are they in the file
in the first place?


http://groups.yahoo.com/group/colortheory/photos/album/734361103/pic/1620921285/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc

Dan Margulis


[Non-text portions of this message have been removed]


pmarr@...
 

Almost certainly sensor dust. You can see the most prominent one (upper right) in the original. Auto sensor cleaning helps but there's always some left. Generally they are most prominent at small apertures. I frequently shoot at f16 - f32 and they're a bear to eliminate from any uniform light background.

Paul Marriner

On 06/03/2013 12:19 PM, Dan Margulis wrote:
I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their surroundings, almost as if a drop of water had fallen on the lens. But the effect is so subtle that it can only be seen in an otherwise very smooth area, normally the sky. And often it still can't be seen unless the area has been stressed, which unfortunately the PPW tends to do.

There's no sweat cloning the defects out, but I would be interested in knowing how it comes about. Is it a sensor issue? I've seen it in my own shots but more commonly in the work of very fine photographers using top-of-the-line equipment. And like I said, the problem seems to be a growing one.

An example of what I'm talking about is in the Sunrise folder in our Photos section that many of us have recently worked on. If the link below doesn't work, it's my own version, the one with the -dm suffix. I boosted the sky quite a bit and the defects are evident. Why are they in the file in the first place?

http://groups.yahoo.com/group/colortheory/photos/album/734361103/pic/1620921285/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc

Dan Margulis

------------------------------------

Yahoo! Groups Links



Mark Morgan <mark@...>
 

Dust spots. I have seen this problem when I fail to clean the sensor often
enough. Some of my older cameras, which lack the auto sensor cleaning
function are more problematic.

I recently did an art gallery exhibition job for the artist and failed to
check the sensor first. The gallery, with walls of evenly lit neutral grey,
made the images to much trouble to clean up - it was quicker to retake them.



Mark Morgan

-----Original Message-----
From: colortheory@... [mailto:colortheory@...] On
Behalf Of Dan Margulis
Sent: Wednesday, March 06, 2013 11:19 AM
To: colortheory@...
Subject: [colortheory] What causes this blotching?

I have a question for photographers about what causes a certain kind of
defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their
surroundings, almost as if a drop of watejob for a r had fallen on the lens.
But the effect is so subtle that it can only be seen in an otherwise very
smooth area, normally the sky. And often it still can't be seen unless the
area has been stressed, which unfortunately the PPW tends to do.

There's no sweat cloning the defects out, but I would be interested in
knowing how it comes about. Is it a sensor issue? I've seen it in my own
shots but more commonly in the work of very fine photographers using
top-of-the-line equipment. And like I said, the problem seems to be a
growing one.

An example of what I'm talking about is in the Sunrise folder in our Photos
section that many of us have recently worked on. If the link below doesn't
work, it's my own version, the one with the -dm suffix. I boosted the sky
quite a bit and the defects are evident. Why are they in the file in the
first place?

http://groups.yahoo.com/group/colortheory/photos/album/734361103/pic/1620921
285/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc

Dan Margulis


Marco Diodato
 

Hi Dan,
this kind of blotches is due to some dust on the sensor surface, usually
the dust reach the sensor while changing the lens on a DSLR. This is the
most common situation.

It could be also a very little drop of grease (on the sensor again) if the
camera has got issues regardindg the shutter.

It could also be dust on the lens (or worst, IN the lens), not on the front
lens of the objective but on the bottom lens, the one that screws in the
mount of the camera body.

Best regards,
MD

--
Marco M Diodato
marco.diodato@...
+39 347 15 95 677
via Valpantena, 73 - 37142 Verona
P.IVA 03890370236
C.F. DDTMCM83C01L781M
Comunicazione visiva - Graphic design - Consulenza - Formazione
Adobe Certified Expert | Photoshop
Adobe Certified Instructor | Photoshop
www.cygnusdesign.eu
www.marcodiodato.com


jimbean wcc
 

hello dan,

I have not seen your example... sounds to me that you are discussing dust on a camera sensor.. mostly out-of-focus, soft...low contrast-no detail... if you could view consecutively created images, you would see those spots in the same location on each image...


my best guess.

regards, jim bean


Chris Corich
 

As many have already said, it's sensor dust; as paul says below, it's usually a small (large f-stop numeric value) aperture. One other factor is a longer focal length. I've not experimented in depth, but it's absolutely horrible on a shot taken at 400mm vs a wide angle shot at the same aperture. The example was taken at 50mm (75mm equivalent) at f/9.0.

When I'm cleaning my sensors (after one road trip where i didn't, and spent days futzing with dust spots), I check it by overexposing clear blue sky at 400mm f/32.


Chris Corich

--- In colortheory@..., Paul <pmarr@...> wrote:

Almost certainly sensor dust. You can see the most prominent one (upper
right) in the original. Auto sensor cleaning helps but there's always
some left. Generally they are most prominent at small apertures. I
frequently shoot at f16 - f32 and they're a bear to eliminate from any
uniform light background.

Paul Marriner

On 06/03/2013 12:19 PM, Dan Margulis wrote:
I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.


Nick Tresidder
 

To add to the comments, if you really want to see how dirty your sensor is, stop down to say f16 and do a slow shutter speed pan across a fairly plain background, the resulting motion blur will separate the background from the spots and reveal the full horror of what is on your sensor.

Nick Tresidder


RK Beautyseen <ron@...>
 

Dan

Count me in; I'd say it's dust on the sensor. I would also agree with some who've said that the self cleaning
functions of most modern cameras help, but do not eliminate, the eventual need for manual sensor cleaning.
Those of us who change lenses "in the real world" as opposed to a clean room in a microchip factory are going
to get dust where it's not wanted.

Contrary to some opinions expressed, I think it's possible to clean your own sensors. I recommend:

1. LED lupe to examine the sensor before and after.
2. Battery powered brush.
3. If necessary, swabs with the special cleaning fluid for spots that won't come off with brush only.
4. Careful technique; follow the directions of the manufacturers *exactly.*

This will cost upwards of $100-$150 but it's the price of doing business in the digital age. You'll get your
money back in the time saved.

Sincerely,
Ron Kelly

On 03-06-2013, at 9:19 AM, Dan Margulis wrote:

I have a question for photographers about what causes a certain kind of defect


munkiboy
 

Hi All,

Just to confirm it was my durty old lens and the the spots are usually dust but in this case it came from visiting the seaside previously and what I think happened was that wetness from the salty air entered the lens and then dried leaving tiny bits of salt behind.

This was visible in the lens as white specs from the "wrong" end. It's difficult to fix lenses that have this problem so I picked up a new one instead. There is a strange liquid that people use to clean mobile phones that somehow dries instantly (or doesn't wet things) and that can be used to clean inside a lens I believe.

As others mentioned it's often dust on the sensor which is pretty easy to clean and should be part of a frequent routine for photographers.

The specks on the photos are usually easy to fix with the spot removal tool in ACR or that thing that looks like a sticking plaster in Photoshop (spot healing brush - just checked).

In the Nikon software - I don't use - you can take a "dust off reference photo" of a white board and it maps where the specks are and then automagically removes them from your images.

For more difficult ones you can usually clone them out.

I am a little embarrassed by my dirty photo but I did give you the uncleaned RAWs.

My friend took a bunch of pics once and the silhouette of a bug could be seen in most of them, yes it was inside the camera when the lens was attached.

All the best,

-andy blundell

--- In colortheory@..., Dan Margulis <DMargulis@...> wrote:

I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their surroundings, almost as if a drop of water had fallen on the lens. But the effect is so subtle that it can only be seen in an otherwise very smooth area, normally the sky. And often it still can't be seen unless the area has been stressed, which unfortunately the PPW tends to do.


Dan Margulis


Campo Weijerman
 

On Wed, Mar 6, 2013 at 8:14 PM, Nick <parnell.studio@...> wrote:

To add to the comments, if you really want to see how dirty your sensor
is, stop down to say f16 and do a slow shutter speed pan across a fairly
plain background, the resulting motion blur will separate the background
from the spots and reveal the full horror of what is on your sensor.
Actually, the more evenly lit this background is, the better you'll be able
to see the dust. Even a computer monitor will do as a subject, as long as
you add a bit of motion blur. Ideally, the resulting histogram will occupy
only 10 - 20%. Now open the image and apply auto levels or a steep curve.
If all you see is some faint blotches don't worry because they don't
represent real problems. If you do see some real bad cases, apply the
procedure just mentioned by Ron Kelly.
Regards,
--
Campo Weijerman


dlruckus
 

Hello Dan.
The effect actually looks to me as if it is coming from the camera lens rather than dust on the sensor. If one enhances the contrast significantly in the sky area and looks at 100% or better you can see that the blotches all have ,arguably, the same shape and there is a multiplicity of them of different densities making up the image.Your water drop on the lens is a pretty decent analogy I think.
I suspect it is a circle of confusion effect(similar to mirror lens doughnut highlights). What within or on the lens might be causing it is hard to say except that it appears at first glance to be an irregular shape so is more likely to be something to do with coatings or element cement etc or even an uneven flare effect from the lens or hood mechanics.
I still work primarily with film and can attest to the ease of bringing out extremely subtle defects with stressing an image.It's the bane of my existence and ranges from film and coating striations and defects to surface scratches and pressure marks from machine processing or the camera transport itself. Added to that are the defects generated by film scanners.

Best,
Duane Ruck

--- In colortheory@..., Dan Margulis <DMargulis@...> wrote:

I have a question for photographers about what causes a certain kind of defect that I am seeing more and more of.

The capture contains circular or oval areas slightly darker than their surroundings, almost as if a drop of water had fallen on the lens. But the effect is so subtle that it can only be seen in an otherwise very smooth area, normally the sky. And often it still can't be seen unless the area has been stressed, which unfortunately the PPW tends to do.

There's no sweat cloning the defects out, but I would be interested in knowing how it comes about. Is it a sensor issue? I've seen it in my own shots but more commonly in the work of very fine photographers using top-of-the-line equipment. And like I said, the problem seems to be a growing one.

An example of what I'm talking about is in the Sunrise folder in our Photos section that many of us have recently worked on. If the link below doesn't work, it's my own version, the one with the -dm suffix. I boosted the sky quite a bit and the defects are evident. Why are they in the file in the first place?

http://groups.yahoo.com/group/colortheory/photos/album/734361103/pic/1620921285/view?picmode=large&mode=tn&order=ordinal&start=1&dir=asc

Dan Margulis


Hector Davila
 

I'm surprised in this digital age photographers are still
having...'dust problems'. Dust was the biggest enemy of photographers in
the past. It created a 'spotting industry'.
With all that dust in the air, how could you print from a negative?
Cleaning negatives and lenses is like having an OCD problem.

I don't know how 'color photos' before the digital age of computers
were....color corrected.

Hector Davila

On 3/6/2013 11:14 AM, Nick wrote:

To add to the comments, if you really want to see how dirty your
sensor is, stop down to say f16 and do a slow shutter speed pan across
a fairly plain background, the resulting motion blur will separate the
background from the spots and reveal the full horror of what is on
your sensor.

Nick Tresidder


Chuck Gierhart <chuck.gierhart@...>
 

Prints were nothing compared to slides. You had to hit the exposure within ½
stop and know your craft well enough that you could color correct with
filters as you shot.



No, I don’t miss those days J



Chuck Gierhart



From: colortheory@... [mailto:colortheory@...] On
Behalf Of Hector_APR
Sent: Thursday, March 07, 2013 4:31 PM
To: colortheory@...
Subject: Re: [colortheory] What causes this blotching?
Importance: High





I'm surprised in this digital age photographers are still
having...'dust problems'. Dust was the biggest enemy of photographers in
the past. It created a 'spotting industry'.
With all that dust in the air, how could you print from a negative?
Cleaning negatives and lenses is like having an OCD problem.

I don't know how 'color photos' before the digital age of computers
were....color corrected.

Hector Davila

On 3/6/2013 11:14 AM, Nick wrote:

To add to the comments, if you really want to see how dirty your
sensor is, stop down to say f16 and do a slow shutter speed pan across
a fairly plain background, the resulting motion blur will separate the
background from the spots and reveal the full horror of what is on
your sensor.

Nick Tresidder

[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]


john c.
 

A good custom lab technician could look at a negative and tell within seconds what corrections it would need without even having to make a print and be nearly spot on over 90 percent of the time. It's a lost art now but it's nice to finally get the appreciation we deserved, albeit a decade or two after the fact! :-)

-----Original Message-----
From: Hector_APR
With all that dust in the air, how could you print from a negative?
Cleaning negatives and lenses is like having an OCD problem.

I don't know how 'color photos' before the digital age of computers
were....color corrected.