Why does burning and dodging work?

Does silver emulsion paper not have a toe and shoulder. At what point can
one no longer burn in an image?

In article yUE4d.82177$%S.77379@pd7tw2no,
"Alan Smithee" wrote:

Does silver emulsion paper not have a toe and shoulder. At what point can
one no longer burn in an image?

Lets just say that above a density of 1.25 it becomes more and more
problematic. Especially if the negative unintentionally lacks mid tone
values. Most films will acquire density up to and including 3.0

Papers at best have a dynamic (usable) range of 1.0 at around grade 2.

The interesting thing though, is that your negative's exposure, as long
as its fairly even and within the contrast range of the paper should
print fairly normally even if it was maxed out at 3.0 of course
your enlarging time might be measured in hours.

--
LF Website @ http://members.verizon.net/~gregoryblank

"To announce that there must be no criticism of the President,
or that we are to stand by the President, right or wrong,
is not only unpatriotic and servile, but is morally treasonable
to the American public."--Theodore Roosevelt, May 7, 1918

In article yUE4d.82177$%S.77379@pd7tw2no,
"Alan Smithee" wrote:

Does silver emulsion paper not have a toe and shoulder. At what point can
one no longer burn in an image?

Lets just say that above a density of 1.25 it becomes more and more
problematic. Especially if the negative unintentionally lacks mid tone
values. Most films will acquire density up to and including 3.0

Papers at best have a dynamic (usable) range of 1.0 at around grade 2.

The interesting thing though, is that your negative's exposure, as long
as its fairly even and within the contrast range of the paper should
print fairly normally even if it was maxed out at 3.0 of course
your enlarging time might be measured in hours.

--
LF Website @ http://members.verizon.net/~gregoryblank

"To announce that there must be no criticism of the President,
or that we are to stand by the President, right or wrong,
is not only unpatriotic and servile, but is morally treasonable
to the American public."--Theodore Roosevelt, May 7, 1918

"Alan Smithee" wrote in message
news:yUE4d.82177$%S.77379@pd7tw2no...
Does silver emulsion paper not have a toe and shoulder. At what point can
one no longer burn in an image?

It certainly has a toe and a shoulder. That is, there's a limit to how
white or how black you can make something.

However, film sometimes covers a greater density range than paper can
respond to. Thus, by burning or dodging part of a picture, you can bring it
into the paper's range.

"Alan Smithee" wrote in message
news:yUE4d.82177$%S.77379@pd7tw2no...
Does silver emulsion paper not have a toe and shoulder. At
what point can
one no longer burn in an image?

Really to add to Gregory Blank's answer.
Yes, paper emulsions do have a sholder and toe. Of course,
the shoulder is the shadows and the toe is the highlights.
Long toe papers are made for printing film with high
contrast highlights. For instance, some Ilford papers have a
long toe for controlling contrast on films like T-Max, which
can record very dense highlights. On a normal negative these
papers can look flat even when the negative contrast is
correct for the paper.
On shadow side the limitation is the maximum visible
density of the paper. I use the term visible here because
paper emulsions will produce densities beyond those which
are visible on a reflection print. You can prove this by
illuminating a print from the back. Very often you will see
detail in areas of the shadows which look blank by
reflection. Maximum black is limited by the incident light
on a reflection print and by surface scattering. The
greatest range is on glossy paper. The more matte or
textured the surface the more light is scattered from the
surface effectively lightening the shadows and reducing
their contrast.
Burning works on highlights because the film may have
densities that are too high to produce a printable exposure.
Increasing the exposure of these areas increases the detail
in the highlight
Dodging holds back some of the expoure lighening some
area that is too dark. This can be a shadow or a mid-gray
area one wants to lighten. Of course, burning can be used in
the same way, that is to darken gray areas that are too
light. Very elaborate burning and dodging can be done with
masks. One old method of masking is to retouch the negative
using pencil. Another old method is work up the surface of
ground glass using pencil and then binding the ground glass
to the negative. It is also possible to use cut-out masks.
This was common in mass produced contact printing but can be
used in enlarging when the area to be burned or dodged is
complex or large.
Burning and dodging does not affect the image contrast.
If you are using variable contrast paper another technique
becomes available, namely selective printing using different
filters. The ability to print different areas with different
contrast can yield images that are not possible from simple
burning and dodging although they can be produced by
contrast masking.
To answer the question directly, one can no longer burn
in an image when there is no detail on the negative or where
the paper has reached maximum black and will not respond to
further exposure.
Most modern films have tremendous overexpsoure latitude
meaning also that they can record a very wide range of
brightness. Since most modern films do not shoulder off
until they reach very high densities one can nearly always
gain some detail in otherwise blank highlights by extended
burning. It may be a pain to do but works.

--
---
Richard Knoppow
Los Angeles, CA, USA

"Alan Smithee" wrote in message
news:yUE4d.82177$%S.77379@pd7tw2no...
Does silver emulsion paper not have a toe and shoulder. At
what point can
one no longer burn in an image?

Really to add to Gregory Blank's answer.
Yes, paper emulsions do have a sholder and toe. Of course,
the shoulder is the shadows and the toe is the highlights.
Long toe papers are made for printing film with high
contrast highlights. For instance, some Ilford papers have a
long toe for controlling contrast on films like T-Max, which
can record very dense highlights. On a normal negative these
papers can look flat even when the negative contrast is
correct for the paper.
On shadow side the limitation is the maximum visible
density of the paper. I use the term visible here because
paper emulsions will produce densities beyond those which
are visible on a reflection print. You can prove this by
illuminating a print from the back. Very often you will see
detail in areas of the shadows which look blank by
reflection. Maximum black is limited by the incident light
on a reflection print and by surface scattering. The
greatest range is on glossy paper. The more matte or
textured the surface the more light is scattered from the
surface effectively lightening the shadows and reducing
their contrast.
Burning works on highlights because the film may have
densities that are too high to produce a printable exposure.
Increasing the exposure of these areas increases the detail
in the highlight
Dodging holds back some of the expoure lighening some
area that is too dark. This can be a shadow or a mid-gray
area one wants to lighten. Of course, burning can be used in
the same way, that is to darken gray areas that are too
light. Very elaborate burning and dodging can be done with
masks. One old method of masking is to retouch the negative
using pencil. Another old method is work up the surface of
ground glass using pencil and then binding the ground glass
to the negative. It is also possible to use cut-out masks.
This was common in mass produced contact printing but can be
used in enlarging when the area to be burned or dodged is
complex or large.
Burning and dodging does not affect the image contrast.
If you are using variable contrast paper another technique
becomes available, namely selective printing using different
filters. The ability to print different areas with different
contrast can yield images that are not possible from simple
burning and dodging although they can be produced by
contrast masking.
To answer the question directly, one can no longer burn
in an image when there is no detail on the negative or where
the paper has reached maximum black and will not respond to
further exposure.
Most modern films have tremendous overexpsoure latitude
meaning also that they can record a very wide range of
brightness. Since most modern films do not shoulder off
until they reach very high densities one can nearly always
gain some detail in otherwise blank highlights by extended
burning. It may be a pain to do but works.

--
---
Richard Knoppow
Los Angeles, CA, USA