Color waves

[Golden Lasky]

I've got these things on my scans which are kinda hard to explain.
They look like when you throw a pebble in the water only waves are all
different colors.

I don't see anything on the glass or the photos so what is that and
how do I get rid of it?

Golden

 

[CSM1]

I've got these things on my scans which are kinda hard to explain.
They look like when you throw a pebble in the water only waves are all
different colors.

I don't see anything on the glass or the photos so what is that and
how do I get rid of it?

Golden

If you are scanning magazines, what you are seeing is called moiré.
Definition:
Having a wavy or rippled surface pattern

You use the Descreen function of your scanner to get rid of it.

Here is an explanation:
http://www.scantips.com/basics06.html

 

[Golden Lasky]

If you are scanning magazines, what you are seeing is called moiré.
Definition:
Having a wavy or rippled surface pattern

No I'm not scanning magazines. These are just regular photos. The
waves are only in certain places but when I move the photo and rescan
sometimes they move to another place but not always. It's really
weird.

Golden

 

[Bart van der Wolf]

I've got these things on my scans which are kinda hard to explain.
They look like when you throw a pebble in the water only waves are
all
different colors.

I don't see anything on the glass or the photos so what is that and
how do I get rid of it?

They could be "Newton rings", hard to say for sure without an example.
If it is Newton rings you are looking at, they can be totally
prevented by putting a spacer between film and glass. The colors are
caused by interference between the light and the sub-micron thin layer
of air between two smooth surfaces.

Bart

 

[Don]

No I'm not scanning magazines. These are just regular photos. The
waves are only in certain places but when I move the photo and rescan
sometimes they move to another place but not always. It's really
weird.

If you're scanning glossy photos those are so-called "Newton's rings".
It's light bouncing off of the photograph's surface and canceling out
certain frequencies. Another symptom is a gray ameba-like splotch in
the middle of the rings where the photo literally sticks to the glass.

I've been wrestling with this for a while and if you check the
archives I wrote a message about my workaround less than a week ago.

Basically, you need to keep the photo as flat as possible (I use
double-sided tape to affix it to a piece of Plexiglas) and have it
just a tad above the glass (I put pieces of cardboard around the photo
to lift the Plexiglas).

The problem is you lose some contrast that way but this can be fixed
in postprocessing. (Also, if you have a "contact" scanner like Canon
LIDE series they only focus on the glass surface).

Don.

 

[Golden Lasky]

If it is Newton rings you are looking at, they can be totally
prevented by putting a spacer between film and glass.

I'm scanning photos not film but what do you mean by a spacer? Can I
use that on photographs too?

Golden

 

[Golden Lasky]

If you're scanning glossy photos those are so-called "Newton's rings".
It's light bouncing off of the photograph's surface and canceling out
certain frequencies. Another symptom is a gray ameba-like splotch in
the middle of the rings where the photo literally sticks to the glass.

Yeah now that you mentioned it I see it! I thought that was just dirt
on the picture.

Basically, you need to keep the photo as flat as possible (I use
double-sided tape to affix it to a piece of Plexiglas) and have it
just a tad above the glass (I put pieces of cardboard around the photo
to lift the Plexiglas).

That looks very complicated. Is there maybe an easier way?

Golden

 

[Bart van der Wolf]

I'm scanning photos not film but what do you mean by a spacer?
Can I use that on photographs too?

Sure, but it may be harder to prevent a picture from sagging in the
middle than film. You can use e.g. a piece of thin cardboard and cut
out the area you want to scan and position the sandwich of border and
picture in the scanner platen. You can also make a more flexible
solution with two "L" shaped spacers, but it will be hard to align
everything.
Another solution is by non-permanent mounting of the picture to a
rigid background and use something at the corners to create some space
with the glass.

Bart

 

[wim wiskerke]

Yeah now that you mentioned it I see it! I thought that was just dirt
on the picture.


That looks very complicated. Is there maybe an easier way?

Yes, use scanning oil or scanning fluid. It is used on drum scanners.
Basically any oily fluid will do, but some will damage your originals.
Clear mineral oil, like lamp oil, is ok.
If you have a lot of scanning to do, consider buying Kami Scanner
Mounting Fluid. It leaves no trace:

It's a very thin volatile substance similar to
film cleaner, with kind of a citrus scent. Because it's thin, it flows
very well, without any of the small bubbles you sometimes get with mineral
oil. In addition, because it is a volatile compound, it evaporates very
quickly with almost no residue.

Btw does anybody know a seller of Kami who sells it per *1* bottle?
(In the US.)

regards, wim

 

[Don]

That looks very complicated. Is there maybe an easier way?

I don't know of any other way. I figured this out myself. Perhaps
someone else can chime in?

Don.

 

[Golden Lasky]

Sure, but it may be harder to prevent a picture from sagging in the
middle than film. You can use e.g. a piece of thin cardboard and cut
out the area you want to scan and position the sandwich of border and

picture in the scanner platen. You can also make a more flexible
solution with two "L" shaped spacers, but it will be hard to align
everything.
Another solution is by non-permanent mounting of the picture to a
rigid background and use something at the corners to create some space
with the glass.

Bart

OK that's like what Don said. A big thank you to everyone!

Golden

 

[Don]

Yes, use scanning oil or scanning fluid. It is used on drum scanners.
Basically any oily fluid will do, but some will damage your originals.
Clear mineral oil, like lamp oil, is ok.
If you have a lot of scanning to do, consider buying Kami Scanner
Mounting Fluid. It leaves no trace:

That's really interesting!!! (Too late for me, though, because I only
have 26 pics left so I'll just continue with my Plexiglas/cardboard
"method".)

BTW, doesn't the oil make the image stick to the scanner glass?

What I'm getting at is this: First time I noticed the effect was when
lifting the scanner lid one day in a darkened room. I saw small
"holes" in the photo with white scanner light shining through - which
surprised me because the photo was pristine.

On closer inspection there were no holes, of course, but wherever the
glossy photo stuck to the glass is where the photo became
"transparent" giving the appearance of the light shining through.

Placing a finger on the back of the photo an dragging the finger
around generated a very neat "pixie dust" effect as the glossy surface
stuck and then let go of the scanner glass.

The problem is all these places where the photo sticks result in a
gray splotch in the scan. So my question is wouldn't the oil do the
same?

Don.

 

[wim wiskerke]

That's really interesting!!! (Too late for me, though, because I only
have 26 pics left so I'll just continue with my Plexiglas/cardboard
"method".)

BTW, doesn't the oil make the image stick to the scanner glass?

Yes that is the purpose of the procedure.

What I'm getting at is this: First time I noticed the effect was when
lifting the scanner lid one day in a darkened room. I saw small
"holes" in the photo with white scanner light shining through - which
surprised me because the photo was pristine.

On closer inspection there were no holes, of course, but wherever the
glossy photo stuck to the glass is where the photo became
"transparent" giving the appearance of the light shining through.

Placing a finger on the back of the photo an dragging the finger
around generated a very neat "pixie dust" effect as the glossy surface
stuck and then let go of the scanner glass.

The problem is all these places where the photo sticks result in a
gray splotch in the scan. So my question is wouldn't the oil do the
same?

Do a search on <newton's rings>, this is really very very basic
photography knowledge.
http://scienceworld.wolfram.com/physics/NewtonsRings.html
http://physics.kenyon.edu/EarlyApparatus/Optics/Newtons_Rings/Newtons_Rings.html
http://van.hep.uiuc.edu/van/qa/section/Light_and_Sound/Diffraction/20021028002405.htm
The oil or gel will eliminate air between the surfaces of the glass
and the picture. Thus eliminating newton rings.

regards, wim

 

[Don]

Do a search on <newton's rings>, this is really very very basic
photography knowledge.
http://scienceworld.wolfram.com/physics/NewtonsRings.html
http://physics.kenyon.edu/EarlyApparatus/Optics/Newtons_Rings/Newtons_Rings.html
http://van.hep.uiuc.edu/van/qa/section/Light_and_Sound/Diffraction/20021028002405.htm
The oil or gel will eliminate air between the surfaces of the glass
and the picture. Thus eliminating newton rings.

Yes, I am clear on Newton's rings. What I was wondering about is the
"gray splotch" effect and I haven't seen any references to this (I
still have to chase up your links, though...).

Unlike rings which only eliminate certain frequencies (hence the
different colored rings), the "gray splotch" totally obscures image
data.

Of course, it may just be a special case of the rings i.e., in the
areas where the photo actually sticks to the glass all color
components are cancelled proportionally resulting in near-total loss
of image data which is manifested as this gray artifact.

But if that's the case, then why doesn't the same thing happen when
the oil makes the photo stick to the glass?

Don.

 

[wim wiskerke]

Yes, I am clear on Newton's rings. What I was wondering about is the
"gray splotch" effect and I haven't seen any references to this (I
still have to chase up your links, though...).

Unlike rings which only eliminate certain frequencies (hence the
different colored rings), the "gray splotch" totally obscures image
data.

You can observe the same with a picture behind glass in a frame.

Of course, it may just be a special case of the rings i.e., in the
areas where the photo actually sticks to the glass all color
components are cancelled proportionally resulting in near-total loss
of image data which is manifested as this gray artifact.

It is not a special case, but a normal case of Newton's rings afaik.
;-)

But if that's the case, then why doesn't the same thing happen when
the oil makes the photo stick to the glass?

Because there is no air there are no surface/air transitions.

regards, wim

 

[Brooks Moses]

Yes, I am clear on Newton's rings. What I was wondering about is the
"gray splotch" effect and I haven't seen any references to this (I
still have to chase up your links, though...).

Unlike rings which only eliminate certain frequencies (hence the
different colored rings), the "gray splotch" totally obscures image
data.

I think what's happening there is that, when you lose the air gap, the
direct glass-to-emulsion transition you get is nearly completely
reflective due to the optical indices of the two materials. (It's been
long enough since I've had any optics classes that I don't remember any
useful details to explain beyond that, though.)

[...]

But if that's the case, then why doesn't the same thing happen when
the oil makes the photo stick to the glass?

The oil doesn't make the photo stick to the glass in an optical sense,
though; it prevents it -- since it's too thick to get squeezed out like
air, there's always a thin layer of oil between the glass and the film
emulsion. Thus, instead of the glass-to-emulsion transition, you have a
glass-to-oil transition, followed by an oil-to-emulsion transition. The
resulting pair of transitions do not have the same reflective
characteristics as a direct glass-to-emulsion transition.

- Brooks

 

[Don]

[...]

But if that's the case, then why doesn't the same thing happen when
the oil makes the photo stick to the glass?

The oil doesn't make the photo stick to the glass in an optical sense,
though; it prevents it -- since it's too thick to get squeezed out like
air, there's always a thin layer of oil between the glass and the film
emulsion. Thus, instead of the glass-to-emulsion transition, you have a
glass-to-oil transition, followed by an oil-to-emulsion transition. The
resulting pair of transitions do not have the same reflective
characteristics as a direct glass-to-emulsion transition.

I see! That makes sense.

Thanks both, Brooks and Wim!

Don.