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H&D curves of different films



 
 
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  #1  
Old September 26th 03, 11:45 PM
Richard Knoppow
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Default H&D curves of different films


"Jytzel" wrote in message
om...
"Richard Knoppow" wrote in

message
nk.net...
"Martin Jangowski" wrote in

message
...
In rec.photo.darkroom Jytzel

wrote:
I'd appreciate if somebody can comment on the

characteristics curves
of the following films:


APX 100
APX 400
FP4 125
Pan F plus 50
HP5 400
Acros
Delta 400

What characteristic curves? Every developer and every

development
time will give different curves...

Martin


The developer will have some effect on the curve but

its
mainly determined by the distribution of sensitivity of

the
silver halide particals in the emulsion. This is turn is
controlled by the exact method by which the emulsion is
made.
Two extremes are the recently discontinued Plus-X Pan
sheet film compared to T-Max 100. Plus-X Pan sheet film

(the
roll film is different)has a curve which is constantly

swept
upward. In other words the contrast increases

continuously
with density. T-Max 100, OTHO, has a fairly straight
characteristic. The two will be different regardless of

the
developer used although some will give a slightly

straighter
curve with both than others.
The difference results in a difference in the tonal
rendition. When the same shadow and highlight points are
chosen the upswept type film will reproduce mid-gray

tones
darker than the straight line film. Kodak intended this

to
be used for studio photography where it was desired to
exagerate highlights. Tri-X sheet film is similar to

Plus-X
but not quite so steeply rising.
You will find a number of characteristic curves for
popular films in several developers at:
http://www.fotoimport.no/pg02/PG02-1-1.htm#tab

Most of these look reasonably correct.
The site is in Norwegian but one can navigate it

pretty
well.
--


Thanks Richard,
I know about tri-x, PX and TMX, but what about Verichrome

pan? To my
eye it seems that it has an upsept curve to a certain

degree (I tried
it with D-76, HC110, DK-50, and Rodinal) It was my

favourite film. So
bad it was discontinued. I'm looking for a replacement (PX

is not an
option). HP4+ seems to have an S-shaped curve. APX 100

seems to have a
unique curve - long toe round shoulder (?)- I'm not sure.

Can anybody
help me interpret them?


V-Pan was also a favorite of mine. I finished off the two
bricks I had and haven't seen any more. Probably the closest
is Plus-X Pan roll film. This has a similar (but not
identical) sort of curve and is also a very fine grain
relativly high resolution film. I think it gets short shrift
because people think its the same as the now discontinued
Plus-X sheet film. Its a very different emulsion. APX-100 is
very good film but grainier than Plus-X. FP-4 is also
similar but has somewhat different tonal rendition. Kodak's
published curves are pretty reliable. Agfa and Ilford tend
to publish idealized curves which makes them harder to
compare.
About the only way to really tell how a film responds
tonaly is to try some.
As pointed out elswhere in this thread developers have
some, but not a lot, of effect on curve shape, with the
exception of compensating developers, which create a
shoulder. i.e., they reduce the contrast of the highlights.
This is sometimes desirable but can also result in rather
distorted tonal rendition.
--
Richard Knoppow
Los Angeles, CA, USA


  #2  
Old September 30th 03, 12:15 PM
Jytzel
external usenet poster
 
Posts: n/a
Default H&D curves of different films

"Richard Knoppow" wrote in message news:fk3db.4510
V-Pan was also a favorite of mine. I finished off the two
bricks I had and haven't seen any more. Probably the closest
is Plus-X Pan roll film. This has a similar (but not
identical) sort of curve and is also a very fine grain
relativly high resolution film. I think it gets short shrift
because people think its the same as the now discontinued
Plus-X sheet film. Its a very different emulsion. APX-100 is
very good film but grainier than Plus-X. FP-4 is also
similar but has somewhat different tonal rendition. Kodak's
published curves are pretty reliable. Agfa and Ilford tend
to publish idealized curves which makes them harder to
compare.
About the only way to really tell how a film responds
tonaly is to try some.


Richard,

What do you mean by "different"?
 




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