Improved T-Max 400

On Oct 28, 9:23 pm, (Thor Lancelot Simon) wrote:
In article . com,

UC wrote:

No, I test the materials I use.

Do you? Because you referred to a H&D curve you had, purportedly,
generated yourself, but then when I challenged you to post it, you said
to look at the published Kodak curve (which does not appear to show
anything like the effect you originally claimed). So. Let's see some of
this data from the testing you supposedly do of the materials you supposedly
use.

I never said I generated any H&D curve myself. The curve that Kodak
publishes supports what I say about the film. If you don't understand
that, too bad. Tri-X shoulders off in teh highlight region. T-Max 400
does not. It's that simple. For outdoor work, a curve like that of Tri-
X is preferable.


Oh, I forgot, you just like to hang around here and _talk_ about all the
photography you do. One wouldn't expect less from a famous Usenet kook,
I suppose.

Famous? Hardly.

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to
be abandoned or transcended, there is no problem." - Noam Chomsky

On Oct 28, 9:23 pm, (Thor Lancelot Simon) wrote:
In article . com,

UC wrote:

No, I test the materials I use.

Do you? Because you referred to a H&D curve you had, purportedly,
generated yourself, but then when I challenged you to post it, you said
to look at the published Kodak curve (which does not appear to show
anything like the effect you originally claimed). So. Let's see some of
this data from the testing you supposedly do of the materials you supposedly
use.

Oh, I forgot, you just like to hang around here and _talk_ about all the
photography you do. One wouldn't expect less from a famous Usenet kook,
I suppose.

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to
be abandoned or transcended, there is no problem." - Noam Chomsky

I said I had tested the films. I did not say I generated H&D curves.
You need special equipment for that.

Here is the curve for TMY:

http://www.kodak.com/global/en/profe...002_0507ac.gif

Here is the curve for Tri-X Pan:

http://www.kodak.com/global/en/profe...009_0490ac.gif

Do you see the difference?

In article . com,
UC wrote:
On Oct 28, 9:23 pm, (Thor Lancelot Simon) wrote:

Oh, I forgot, you just like to hang around here and _talk_ about all the
photography you do. One wouldn't expect less from a famous Usenet kook,
I suppose.

I said I had tested the films. I did not say I generated H&D curves.
You need special equipment for that.

Special equipment like, oh, I don't know, a densitometer? Heck, you
could get a perfectly functional one from eBay for about $100, if you
only need it for monochrome transmission sensiometry.

And to think, you like to throw around one-liners about how others have
"clearly never done critical testing of materials". I guess now I get it:
your "critical testing of materials" doesn't actually involve sensiometry
per se (it can't, since you evidently don't own the basic tools for the
job). Instead, you shoot some film and decide if you, personally, can
get the results you like without changing your technique any. If not, you
pop over here and spew some more about how the materials in question are
useless for everyone, all the time.

You really don't get it about why most people consider you a kook, do you?

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to
be abandoned or transcended, there is no problem." - Noam Chomsky

"UC" wrote in message
ups.com...
On Oct 28, 9:23 pm, (Thor Lancelot Simon)
wrote:
In article
. com,

UC wrote:

No, I test the materials I use.

Do you? Because you referred to a H&D curve you had,
purportedly,
generated yourself, but then when I challenged you to
post it, you said
to look at the published Kodak curve (which does not
appear to show
anything like the effect you originally claimed). So.
Let's see some of
this data from the testing you supposedly do of the
materials you supposedly
use.

Oh, I forgot, you just like to hang around here and
_talk_ about all the
photography you do. One wouldn't expect less from a
famous Usenet kook,
I suppose.

--
Thor Lancelot Simon


"The inconsistency is startling, though admittedly, if
consistency is to
be abandoned or transcended, there is no
- Noam Chomsky

I said I had tested the films. I did not say I generated
H&D curves.
You need special equipment for that.

Here is the curve for TMY:

http://www.kodak.com/global/en/profe...002_0507ac.gif

Here is the curve for Tri-X Pan:

http://www.kodak.com/global/en/profe...009_0490ac.gif

Do you see the difference?

The curves are quite interesting. Kodak does not appear
to smooth their film curves, otherwise there would not be
the slight uneveness exhibited by several of them including
those for 400T-Max above. Neither of these curves shows
much shouldering, it would appear that both films are
capable of considerably greater density than the log 3.0
shown as a maximum on the curves. The question is how much
the contrast is falling off at high exposures and high
densities. Note that the curves show a large range of
contrast indeces. What shouldering there is seems partly
dependent on the degree of development as one would expect.
Also note that the range of exposure is quite wide. Assuming
the minimum usable gradient is somwehere around log -2.5 the
arithmetical range is around 1:400 or a bit less than nine
stops. If we assume an average scene brightness range of a
little less than this both films are pretty linear. For the
most part highlight compression in both B&W and color is due
to the limitations of the printing medium and method of
illumination, that is reflected light. Transparencies can be
illuminated at levels much exceeding the ambient so can
reproduce very bright highlights, reflection prints do not
have this advantage unless illuminated in a light box and
printed especially for that purpose. In general reflection
prints have more shadow detail than can be seen by reflected
light but highlight detail is compressed because the print
is made to make the mid-tones right by reflected light. One
can usualy see some additional shadow detail in a print by
looking at it with transmitted light. A print can have a
range similar to a transparency if its illuminated by extra
bright light in a light box and printed to the right
contrast and density for the purpose.
The point is that film is seldom responsible for lack of
highlight detail. The eye generaly judges the "correctness"
of tone rendition by the reproduction of mid gray values. In
some cases there will be more detail in both shadows and
highlights than can be accomodated on a reflection print if
the contrast and overall density is chosen to meet this
criterion.
Getting valid characteristic curves for film is not
trivial. The method used by manuacturers uses a special
device for exposing called a sensitometer. This gives a
known and controlled exposure and uses a method suited to
the end use of the film. Processing must be done precisely
to eliminate as many errors as possible and the resulting
film is read on a densitometer, again matched to the use of
the film.
It is quite possible to get useful curves by simpler
means but they will include variables other than the
emulsion. Sometimes this is desirable, for instance, testing
in a camera will yield a curve showing the effects of flare
_in that camera_.
In any case, the developer will also have some effect on
the curve shape and presence or lack of a shoulder because
the maximum density possible with a given emulsion will vary
with the developer. For instance, active developers like
T-Max and Microphen (which is similar) will yield quite high
maximum densities, generally higher than can be used in
practice.


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

On 2007-10-29, UC wrote:
On Oct 28, 9:23 pm, (Thor Lancelot Simon) wrote:
In article . com,

UC wrote:

No, I test the materials I use.

Do you? Because you referred to a H&D curve you had, purportedly,
generated yourself, but then when I challenged you to post it, you said
to look at the published Kodak curve (which does not appear to show
anything like the effect you originally claimed). So. Let's see some of
this data from the testing you supposedly do of the materials you supposedly
use.

I never said I generated any H&D curve myself. The curve that Kodak
publishes supports what I say about the film. If you don't understand
that, too bad. Tri-X shoulders off in teh highlight region. T-Max 400
does not. It's that simple. For outdoor work, a curve like that of Tri-
X is preferable.

When I look at Kodak's graph for Tri-X 4164, I get only a hint of a
shoulder, and that begins at a density of 2 or more (depending on how
you develop it). Most photographers I know of would never want printable
highlights as dense as that. They either want them to go pure white,
or they adjust the contrast (if possible) in the field or in the
darkroom.

And furthermore, depending on how you develop it, the toe
starts at a density of 1 (though more likely, at a density of 0.7.


Oh, I forgot, you just like to hang around here and _talk_ about all the
photography you do. One wouldn't expect less from a famous Usenet kook,
I suppose.

Famous? Hardly.

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to
be abandoned or transcended, there is no problem." - Noam Chomsky




--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 18:40:01 up 6 days, 10:58, 5 users, load average: 5.17, 4.72, 5.01

Richard Knoppow wrote:

Assuming
the minimum usable gradient is somwehere around log -2.5

I had been under the impression that the Jones
point for a 200 old ASA film was at log -2.9.

I'm not really reliable at math, so I'd be glad
if someone would show me if I've gone wrong.

If the old ASA speed definition is:

old ASA speed = 1/(4xE)

then E = 1/(4x old ASA)

E = 1/(4 x 200)
E = 1/800
Log (E) = -2.903



the
arithmetical range is around 1:400 or a bit less than nine
stops.

The curve probably would continue as reasonably linear
a fair bit to the right of what is shown on the graph,
so the actual range of the film is pretty huge.

The slight bend at the right of the tri-x graph might
have some effect on tone reproduction, if you actually
gave the film that much exposure, but it hardly looks
like a major departure from linearity.

Peter.
--

"Peter Irwin" wrote in message
...
Richard Knoppow wrote:

Assuming
the minimum usable gradient is somwehere around log -2.5

I had been under the impression that the Jones
point for a 200 old ASA film was at log -2.9.

I'm not really reliable at math, so I'd be glad
if someone would show me if I've gone wrong.

If the old ASA speed definition is:

old ASA speed = 1/(4xE)

then E = 1/(4x old ASA)

E = 1/(4 x 200)
E = 1/800
Log (E) = -2.903


I think you are refering to log exposure. I am going to
have to research this because I don't remember if the
ASA/Jones method used the same units (lux seconds) as are
currently used. In any case, the Jones method was based on
an exposure giving a minimum toe gradient of 1.3rd of the
overall straight line gradient. I think the ASA standard
required a contrast index about the same as the current ISO
standard, that is, approximately right for contact printing
or diffusion enlarging. I just looked at the Kodak curves on
their web site and estimated there the log exposure
intercepted the toe. In any case, moving a little one way or
another would not make much difference in overall exposure
range. You are probably right that the exposure I found for
these ISO-400 films are about what you will find for ASA-200
films due to the 2X safty factor the ASA applied to Kodak
speeds in its 1943 standard.
The current ISO method includes a multiplier of
1.4x. This is not a safety factor but rather to adjust the
speed gotten from the exposure for a density of log 0.1
above gross fog and support density to the point where the
toe gradient is about 1/3rd the overall straight line
gradient. When the ASA adopted the new DIN method to replace
the Jones/Kodak method in 1958 it found by extensive survey
that for nearly all pictorial films the ratio between the
log 0.1 density point and the Jones speed point was about
this ratio, so the DIN speed is divided by 1.4 to obtain the
equivalent Jones/Kodak speed. The reason for changing the
method was that the Jones method proved very hard to use in
practice.
Jones and his associates at Kodak Labs conducted
extensive experimentation to find the practical mimimum
exposure needed by a film to deliver good tone rendition. He
found that the minimum shadow exposure had to be on the toe
no lower than where the toe gradient (or contrast) was 1/3
of the straight line gradient. Increased exposure had little
effect on tone rendition but perceived quality fell off very
quickly if the exposure was reduced from this point.
Jones chose to find the _minimum_ exposure because
films of the time had optimum grain and sharpness when at
minimum density. Modern films still have this property but
its much less now than in the period of the 1920's through
1940's when Jones did his work.
Kodak's approach to tone rendition was to standardize
the development of the negative so that a constant contrast
was obtained and to adjust print contrast, if necessary, by
choice of paper grade. This is about the opposite of the
Zone System which attempts to adjust negatives so that they
all print on the same grade of paper.


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

"Richard Knoppow" wrote in message
...

"Peter Irwin" wrote in message
...
Richard Knoppow wrote:

Assuming
the minimum usable gradient is somwehere around log -2.5

I had been under the impression that the Jones
point for a 200 old ASA film was at log -2.9.

I'm not really reliable at math, so I'd be glad
if someone would show me if I've gone wrong.

If the old ASA speed definition is:

old ASA speed = 1/(4xE)

then E = 1/(4x old ASA)

E = 1/(4 x 200)
E = 1/800
Log (E) = -2.903


I think you are refering to log exposure. I am going
to have to research this because I don't remember if the
ASA/Jones method used the same units (lux seconds) as are
currently used. In any case, the Jones method was based on
an exposure giving a minimum toe gradient of 1.3rd of the
overall straight line gradient. ^^^^^

Mis typed, should be 1/3rd.



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

Richard Knoppow wrote:


I think you are refering to log exposure. I am going to
have to research this because I don't remember if the
ASA/Jones method used the same units (lux seconds) as are
currently used.

Thanks. I think a metre-candle-second is the same as
a lux second.

I've been trying to get a handle on what the X axis
on the H&D curves means in practical terms.

Here is what I've come up with:

For ISO 100, units are log lux seconds:

-2.3 - Jones point (Old ASA 50)
-2.1 - ISO B&W speed point (0.1 above base + fog)
-1.05 - where usual light meter tries to put the average
-0.3 - where 100% reflectance goes if meter aimed at grey card
0 - enough to fully blow highlights on typical slide film

A difference of 0.1 is 1/3 stop.
A difference of 0.3 is one stop.
Thus for 400 speed film subtract 0.6 from these figures.

I think this (if accurate) is a fairly useful list to
keep in mind when looking at H&D curves.

I know there are theoretical problems with trying to
co-relate camera exposure with the figures on
the H&D curves, but it seems to me that we are essentially
doing just that whenever we set our light meters
based on the ISO value. I don't think I've seen
such a list anywhere so I've collected one together myself.

It would be great if someone would point out errors,
or add anything which seems useful.

Peter.
--

"Peter Irwin" wrote in message
...
Richard Knoppow wrote:


I think you are refering to log exposure. I am going
to
have to research this because I don't remember if the
ASA/Jones method used the same units (lux seconds) as are
currently used.

Thanks. I think a metre-candle-second is the same as
a lux second.

I've been trying to get a handle on what the X axis
on the H&D curves means in practical terms.

Here is what I've come up with:

For ISO 100, units are log lux seconds:

-2.3 - Jones point (Old ASA 50)
-2.1 - ISO B&W speed point (0.1 above base + fog)
-1.05 - where usual light meter tries to put the average
-0.3 - where 100% reflectance goes if meter aimed at grey
card
0 - enough to fully blow highlights on typical slide
film

A difference of 0.1 is 1/3 stop.
A difference of 0.3 is one stop.
Thus for 400 speed film subtract 0.6 from these figures.

I think this (if accurate) is a fairly useful list to
keep in mind when looking at H&D curves.

I know there are theoretical problems with trying to
co-relate camera exposure with the figures on
the H&D curves, but it seems to me that we are essentially
doing just that whenever we set our light meters
based on the ISO value. I don't think I've seen
such a list anywhere so I've collected one together
myself.

It would be great if someone would point out errors,
or add anything which seems useful.

Peter.
--


The ISO speed point is not actually log 0.1 density
above fog plus base density but rather the value gotten by
multiplying this by the factor 1.4. This is supposed to put
the point at about the same place as the Jones point.
Measured by the Jones method there really is not a fixed
density point since the speed is based on the relative
gradient of the toe vs: straight line of the film curve.
However, the research done by the ASA when they changed over
to the DIN method (fixed density point) showed that for the
great majority of films the two bore a fixed relationship.
The current ISO standard is uses the same method as the
1958 ASA standard with some ammendments in detail. For
instance, the old standard specified two developers, a
general purpose one and a fine grain one, neither of which
was much like any standard commercial developer. The current
standard does not specify a developer but requires that the
published speed identify the developer used for the test.
Thus a film can have more than one speed if the manufacturer
tested it with more than one developer.
The current standard specifies that development be
carried out so that a log exposure interval of log 1.30
results in a density interval of log 0.8 measured from the
point were the density is log 0.1 above fog plus base
density. This is a gamma of about 0.62, not too far from
typical practice.
The point at log 0.1 density is called log10 Hm and
arithmetric speed is S=0.8/Hm (note that the arithmetric
value rather than the log value is used). For log speeds the
formula is S (in degrees)=1+10log10 0.80/Hm
I was in error when a stated that the correction factor is
1.5, its 1.25, the reciprocal of 0.8. Thus the ISO speed is
about 80% of the value that would be calculated directly
from the 0.1 density point. If one applies the correction
factor to the density it would be 0.125
The standard has a chart of ranges of log10 Hm to speed
where several samples are measured. I think this is what you
want. Some rounded off values a
ISO speed Log exposure at 0.1 density point
25 -1.5
50 -1.8
100 -2.1
200 -2.4
400 -2.7
800 -3.0

Note that the exposure equivalent to the Jones point would
be about 1.25 times these values, i.e., about -2.63 for ISO
100 film.

Thanks for asking about this, its been educational to
figure out the answer.


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