Improved T-Max 400

On Oct 29, 4:09 pm, (Thor Lancelot Simon) wrote:
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.

I photograph a standard subject (the houses across the street) in
clear sunlight in the morning. It is very easy to see differences in
shadow vs highlight contrast, graininess, color sensitivity to green,
etc. The clear sky shows grain quite readily. The shadows under the
awnings, and in the doorways, clearly show differences between films.

The house numbers show sharpness. It is useless to do trails of
materials except under conditions that mimic actual use.

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

No. I'm too busy doing things correctly.

--
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 29, 10:35 pm, "Richard Knoppow" wrote:

Richard:

It is easy to see the differences in shadow and highlight contrast in
Tri-X vs TMY, when developed for similar overall contrast, in
negatives taken in the same illumination at the same time of the same
subject matter . In Tri-X Pan, the shadows have more contrast and the
highlights have less. If you would take the trouble to do this sort of
test you will see it quite clearly.

I will try to respond at length later, but there is one
quick thing I would like to point out.

Richard Knoppow wrote:

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

s = 1 + 10log10 0.8/Hm

Is a convoluted way of very very nearly saying:

s = 10log10 1/Hm.

For proof of this look at the table from below
and notice that all you have to do to convert
DIN speed to the 0.1 density point is to divide
by minus 10.

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

DIN speed
or ISO Log
15 -1.5
18 -1.8
21 -2.1
24 -2.4
27 -2.7
30 -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.

I don't understand how you got that number.
When I use the OLD ASA formula for a speed
of 50, I get -2.3. Your number looks closer
to OLD ASA 100.


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

Thanks very much also,

Peter.
--

Nicholas O. Lindan wrote:

Sensitometry is usually performed at a color temperature
of 5,500K - a blue filter and a dim bulb (2,250K (?))
is the usual source. The bulb is calibrated to a
'standard' bulb.

It is 2360K (The same colour temperature as the old
acetylene sensotmetric lamps) screened by a liquid
Davis-Gibson filter to convert it to 5400K.
This was the standard adopted at the International
Congress of Photography in Dresden in 1931.

For less exacting purposes you can use a 2850K
sensotometric lamp screened with a Wratten 78AA
filter.

This is book-knowledge - I have no personal
experience with such things.

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.

1 lumen (lm) = 1/683 Watt at 555nm = 1 (non-existent) green candle (cd)
1 lumen / m^2 = 1 lux
1 lux-second = 1 cd-second/m^2

Or 1 lux-second is exposing the film to the light of a standard
candle at a distance of 1 meter for one second.

Sensitometry is usually performed at a color temperature
of 5,500K - a blue filter and a dim bulb (2,250K (?))
is the usual source. The bulb is calibrated to a
'standard' bulb.

Lumens/Lux are defined photoptically, using the spectral
sensitivity of the eye. Strictly speaking using lux for
film response is horse poop unless you use 555nm light.

The green light 'luminous efficiency' of 683 lm/watt
incident radiation is also used for the 5,500K source
as doing it properly opens a huge can of worms that
wouldn't really add anything useful.

There is no legitimate ISO speed for
film that has a spectral sensitivity that differs
significantly from that of the human eye.

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

ISO/ASA = 0.8 lux-sec / (lux-sec required for 0.1 OD on the film)

-2.1 - ISO B&W speed point (0.1 above base + fog)

Correct: 100 = 0.8 / lux-sec
lux-sec = 0.008
log (lux-sec) = log (0.008) = -2.097

-1.05 - where usual light meter tries to put the average

Here it gets messy ... but it's a good enough number -
~3.5 stops more exposure than that required for 0.1 OD.

Or, ~1/8 second at 1 meter from a candle - no lens
on the camera - gives an exposure creating a negative
that should print to 18% grey.

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index.htm
n o lindan at ix dot netcom dot com

"Nicholas O. Lindan" wrote

1 lumen (lm) = 1/683 Watt at 555nm = 1 (non-existent) green candle (cd)
1 lumen / m^2 = 1 lux
1 lux-second = 1 cd-second/m^2

Oh, I munged that up.

1 lm = 1 candle-steradian where a steradian is the solid
angle that illuminates 1 m^2 at 1 m (or 1 ft^2 at 1 ft).

1 lux-second = 1 cd-sr-sec/m^2
= the illumination of 1 candle at a distance of 1 meter
for one second.

As if anyone cares.

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index.htm
n o lindan at ix dot netcom dot com

"Peter Irwin" wrote in message
...
Nicholas O. Lindan wrote:

Sensitometry is usually performed at a color temperature
of 5,500K - a blue filter and a dim bulb (2,250K (?))
is the usual source. The bulb is calibrated to a
'standard' bulb.

It is 2360K (The same colour temperature as the old
acetylene sensotmetric lamps) screened by a liquid
Davis-Gibson filter to convert it to 5400K.
This was the standard adopted at the International
Congress of Photography in Dresden in 1931.

For less exacting purposes you can use a 2850K
sensotometric lamp screened with a Wratten 78AA
filter.

This is book-knowledge - I have no personal
experience with such things.

Peter.
--



The standard does not specify a color temperature for
the sensitometer. It refers to ISO standard 7589, which I do
not have but states that the color used for the sensitometer
exposure may be ISO sensitometeric daylight, studio
tungsten, or photflood and that the type of illuminant be
specified with the speed.
Per Nicholas Lindan's comment about the illuminant
please note that the standard we are refering to, ISO
6:1993:E is for black and white pictorial negative still
film. Films which have sensitization that is not similar to
the human eye, for instance IR film or X-ray film, are
covered by other standards. Even B&W negative motion picture
film is covered by a different standard.
For peter, the 0.8 factor is NOT the same as 1, it is 20%
different which is quite different. The density value I
stated is the value from the charts in the standard for the
log exposure at the speed point multiplied by the reciprocal
of 0.8, that is 1.25 and should be the log exposure at the
point on the toe approximating the Jones minimum gradient
point. The 0.8 factor is in the standard and it used to
calculate the speed.


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

"UC" wrote in message
ups.com...
On Oct 29, 10:35 pm, "Richard Knoppow"
wrote:

Richard:

It is easy to see the differences in shadow and highlight
contrast in
Tri-X vs TMY, when developed for similar overall contrast,
in
negatives taken in the same illumination at the same time
of the same
subject matter . In Tri-X Pan, the shadows have more
contrast and the
highlights have less. If you would take the trouble to do
this sort of
test you will see it quite clearly.


Well, I have used both films but haven't actually
exposed a roll of each to the same targets in the same
camera. I also have some favorite test subjects including a
row of houses across the street. I probably have a hundred
pictures of these from my front yard. I will have to get a
fresh roll of the two films and try this. My usual developer
is D-76 diluted 1:1. This is included in the charts for both
films and should work well with them. I don't know when I
will be able to get to this, I guess I will just have to
make the time. The problem is that unless one is shooting
sheet film one is required to sacrifice most of two rolls of
fairly expensive film in order to shoot the subject at
nearly the same time in the same camera. I guess I could
bracket and use up more film plus compare the tone rendition
for several exposures.


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

This reference was posted on APUG in a thread on densitometry.

It is a self-study guide (?!) in sensitometry:

http://www.kodak.com/US/plugins/acro...y_workbook.pdf

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index.htm
n o lindan at ix dot netcom dot com

"UC" wrote in message
ups.com...

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?

What part of that line/curve is actually useful for making photographs? You
never use the so-called shoulder - it is outside the useful exposure range.