Push, pull, contrast etc.

"Tomas Daniska" wrote in message
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I admit I became a bit puzzled about what
'push-processing' of film *in
reality* achieves (and, consequently, how to correctly
shoot for
push-process).

Until now I have been convinced by many people that
push-processing simply
increases sensitivity (and as a side effect, color
saturation etc.). I have
been instructed - even by the lab stuff - to shoot at -1EV
if i wanted them
to push-process the film. Results were usually really poor
in shadows...
Overall "exposure" of the print was usually OK (I assume
that because of lab
doing the corrections, and not as a direct result of
push-processing). I
suppose I just hit the lower threshold of the negative.

But - aimed to improve my skills a bit - i have read a
little stuff on the
zonal exposure system. Basically the rules as I understand
them were like
'Shadow density is controlled predominately by exposure.
Highlight density
is controlled predominately by developing time'. Putting
1+1 together my
assumption is that push-processing 1) increases contrast
and 2) moves the
gray point one stop closer to the highlights. Which only
by very very far
might be considered a "iso upgrade".

Can anyone elaborate or point me to something that explain
push processing
correctly please?

My assumption now is that if I intend to push process
(speaking of
lab-processed C41, no B/W@home) I:
- should expose "as usually" for shadows, *no*
constant -1EV correction
- will get higher-contrast negatives, also more saturated
colors
- will not get a higher-iso equivalent of the negative
- insert your own comments here


any hints appreciated!

--

deejay


You have it pretty well figured out. Increasing contrast
does somewhat increase effective speed because it increases
the shadow density a little. However, it mostly increases
overall contrast. The reason it works in B&W is that the low
density range of the film, called the toe, has a lower
contrast than the normal exposure part of the film curve.
So, one can increase the shadow contrast enough to get
decent (but not excellent) prints. Anything in the picture
getting more exposure will be pushed up on the higher
contrast part of the curve and will become difficult to
print. Pushing can get you images where you would otherwise
get none but its not a substitute for faster film, if its
available, and can not compensate for incorrect exposure.
Since color film is essentially B&W film with an added step
to produce the dyes, all the above applies to them.
The method used for measureing the speed of B&W pictorial
films leaves little room for underexposure error but a very
large margin for overexposure error. Many films have better
shadow detail when give about one stop more exposure than
the ISO speed indicates.
Color film is developed to much more standardized
conditions than B&W. While color will push the survival of
color fidelity varies from type to type. You really have to
test to find out.


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

post.usenet.com does not seem to spread my messages any longer so i'm trying
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repost via something else


Alan Browne" wrote in message
...

Okay? Well no. It turns out that the 1 to 1 pushing for underexposed
film is not quite right for all films.

EliteChrome 200 for example. Pushes very nice, but the EI (exposure
Index) should not be one to one with the processing... rate it at 320
and push 1 (eg: under expose by 2/3, but push 1).

...rate it at 640 and push 2.

A common practice with Portra 160 is to over
expose it by 2/3... EI at 100. But no 'pull' processing is required.
It just looks best this way (of course taking advantage of the
overexposure tolerance of the film).

Many shoot Velvia at 40 'stead of 50... they want the saturation lowered
a bit (slide film here) and the slide 'thinned out'. No 'pull' during
processing is applied.

[BTW: It is best, where equipment allows it, to use the ISO setting to
EI the film, leaving EXP COMP for those individual frames where the
meter needs compensation due to scene reflectivity...]


lots of thanks to you Alan, and also Richard Knoppow and others for your
brilliant answers - I think I now have an idea to "ping" my favorite lab
with test shoots and find out how to take shoots so I can get the most bang
from them.

If I could start one more flamewar here (c'mon Michael!), the question would
be:

How about time-based vs. temperature-based pushing?


The guy at the lab swears there is no difference in one- or two-stop pushing
when performed using either of the methods. I assume that for the most part
of the exposure range more-or-less he is right, but there might be more
significant differences at the toe and shoulder... or not?


Thanks again


--

deejay

In rec.photo.darkroom Tomas Daniska wrote:
: post.usenet.com does not seem to spread my messages any longer so i'm trying
: to
: repost via something else


: Alan Browne" wrote in message
: ...

: Okay? Well no. It turns out that the 1 to 1 pushing for underexposed
: film is not quite right for all films.
:
: EliteChrome 200 for example. Pushes very nice, but the EI (exposure
: Index) should not be one to one with the processing... rate it at 320
: and push 1 (eg: under expose by 2/3, but push 1).
:
: ...rate it at 640 and push 2.
:
: A common practice with Portra 160 is to over
: expose it by 2/3... EI at 100. But no 'pull' processing is required.
: It just looks best this way (of course taking advantage of the
: overexposure tolerance of the film).
:
: Many shoot Velvia at 40 'stead of 50... they want the saturation lowered
: a bit (slide film here) and the slide 'thinned out'. No 'pull' during
: processing is applied.
:
: [BTW: It is best, where equipment allows it, to use the ISO setting to
: EI the film, leaving EXP COMP for those individual frames where the
: meter needs compensation due to scene reflectivity...]


: lots of thanks to you Alan, and also Richard Knoppow and others for your
: brilliant answers - I think I now have an idea to "ping" my favorite lab
: with test shoots and find out how to take shoots so I can get the most bang
: from them.

: If I could start one more flamewar here (c'mon Michael!), the question would
: be:

: How about time-based vs. temperature-based pushing?

They both work. The problems with temperature based pushin (or pulling) is that
it's harder to control. It will also take you from the optimal temperature for
the developer.


--




Keep working millions on welfare depend on you
-------------------

Alan Browne wrote:


Many shoot Velvia at 40 'stead of 50... they want the saturation lowered
a bit (slide film here) and the slide 'thinned out'. No 'pull' during
processing is applied.


Fuji used to have a webpage showing why you might want to expose Velvia
at 32,40,50 or 64. All depending on what final image you wanted. Seems to
have gone missing from the main Fuji website. Found part of it on the
Canadian website

http://www.fujifilm.ca/Faq/FaqAnswer...104&ID =297#2

Nick

Frank Pittel wrote:


They both work. The problems with temperature based pushin (or pulling) is that
it's harder to control. It will also take you from the optimal temperature for
the developer.


It's also essential to control all solutions and wash to match the
temperature push, and to use plain water before and after any stop bath.
At high temperatures, emulsions loaded with an active developer (high
pH) suddenly switched to an acid stop-bath can microreticulate causing
excessive grain clumping (even with no visible reticulation pattern) -
all chemical changes need to be controlled to avoid this, just as you
control any risk of sudden temperature changes. Also, at high
temperatures a hardening fix is desirable, and this can extend required
wash times by 400 per cent.

So time-based pushing generally wins out - or a gentle combination of
moderate temperature lift plus extra time.

David

"David Kilpatrick" wrote in message
...


They both work. The problems with temperature based pushin (or pulling)
is that
it's harder to control. It will also take you from the optimal
temperature for
the developer.


It's also essential to control all solutions and wash to match the
temperature push, and to use plain water before and after any stop bath.
At high temperatures, emulsions loaded with an active developer (high
pH) suddenly switched to an acid stop-bath can microreticulate causing
excessive grain clumping (even with no visible reticulation pattern) -

do i understand it correctly that this might increase grain even more? or
does it cause different image errors?

all chemical changes need to be controlled to avoid this, just as you
control any risk of sudden temperature changes. Also, at high
temperatures a hardening fix is desirable, and this can extend required
wash times by 400 per cent.

So time-based pushing generally wins out - or a gentle combination of
moderate temperature lift plus extra time.

i've always tried asking the guy to use time-based push. he sweared he
could not modify the settings that way on the machine...

therefore all the push-processed negatives were available next-day as he had
to do that in the evening (takes time to have the temps stabilized)


thanks

--

deejay

Tomas Daniska wrote:

"David Kilpatrick" wrote in message
...


They both work. The problems with temperature based pushin (or pulling)

is that

it's harder to control. It will also take you from the optimal

temperature for

the developer.


It's also essential to control all solutions and wash to match the
temperature push, and to use plain water before and after any stop bath.
At high temperatures, emulsions loaded with an active developer (high
pH) suddenly switched to an acid stop-bath can microreticulate causing
excessive grain clumping (even with no visible reticulation pattern) -


do i understand it correctly that this might increase grain even more? or
does it cause different image errors?


As a rule, increased temperature has a greater tendency to produce high
granularity, compared to normal temperature with increased time (or with
a higher activity developer). This applies to most films except T-Max
and Ilford Delta, which are formulated to allow a higher temperature
process. I believe all the Agfa APX films are now high temperature
tolerant, and APX 400 was the last one to change.

all chemical changes need to be controlled to avoid this, just as you
control any risk of sudden temperature changes. Also, at high
temperatures a hardening fix is desirable, and this can extend required
wash times by 400 per cent.

So time-based pushing generally wins out - or a gentle combination of
moderate temperature lift plus extra time.


i've always tried asking the guy to use time-based push. he sweared he
could not modify the settings that way on the machine...

therefore all the push-processed negatives were available next-day as he had
to do that in the evening (takes time to have the temps stabilized)

In a machine process that is very true. But most machine processes are
using developers which simply don't give the finest grain anyway - they
tend to be loaded with tolerant developers having good replenishment
rates or anti-oxidation, long tank life, etc. And of course, all the
temperatures do match up well in such systems.

If you can find someone still willing to do hand development - expensive
- and to use specialised developer chosen to match the film, with
appropriate technique, you *may* get considerably finer and more regular
granularity for the same effective speed.

There are other things to consider - with long development times,
agitation every minute or every 30 seconds is normal, and the film
benefits from static periods, during which the balance of micro-contrast
to overall contrast, and the production of acutance effects, is
enhanced. High temperature short development times call for continuous
agitation, which always favours overall contrast rather than producing
what Geoffrey Crawley used to call an 'engraving-like' image. Sharpness
may be lower because acutance lines (adjacency effect caused by
by-products of development) are absent entirely.

It's a complex thing, but a higher dilution, higher pH developer with a
normal temperature and far longer development time can produce quite
exquisite negs at very high effective filmspeeds - while a highly
active, concentrated, high temperature shorter development may produce a
neg only suitable for a press photographer in a real hurry.

David
http://www.freelancephotographer.co.uk/

"Nick Zentena" wrote in message
...
Alan Browne wrote:


Fuji used to have a webpage showing why you might want to expose Velvia
at 32,40,50 or 64. All depending on what final image you wanted. Seems to
have gone missing from the main Fuji website. Found part of it on the
Canadian website


http://www.fujifilm.ca/Faq/FaqAnswer...104&ID =297#2

Nick

thanks for the link

--

deejay

david,

seems like i finally will go for manual c41 at home...


thanks for your help!

--

deejay

"David Kilpatrick" wrote in message
...


Tomas Daniska wrote:

"David Kilpatrick" wrote in message
...


They both work. The problems with temperature based pushin (or pulling)

is that

it's harder to control. It will also take you from the optimal

temperature for

the developer.


It's also essential to control all solutions and wash to match the
temperature push, and to use plain water before and after any stop bath.
At high temperatures, emulsions loaded with an active developer (high
pH) suddenly switched to an acid stop-bath can microreticulate causing
excessive grain clumping (even with no visible reticulation pattern) -


do i understand it correctly that this might increase grain even more?
or
does it cause different image errors?


As a rule, increased temperature has a greater tendency to produce high
granularity, compared to normal temperature with increased time (or with
a higher activity developer). This applies to most films except T-Max
and Ilford Delta, which are formulated to allow a higher temperature
process. I believe all the Agfa APX films are now high temperature
tolerant, and APX 400 was the last one to change.

all chemical changes need to be controlled to avoid this, just as you
control any risk of sudden temperature changes. Also, at high
temperatures a hardening fix is desirable, and this can extend required
wash times by 400 per cent.

So time-based pushing generally wins out - or a gentle combination of
moderate temperature lift plus extra time.


i've always tried asking the guy to use time-based push. he sweared he
could not modify the settings that way on the machine...

therefore all the push-processed negatives were available next-day as he
had
to do that in the evening (takes time to have the temps stabilized)

In a machine process that is very true. But most machine processes are
using developers which simply don't give the finest grain anyway - they
tend to be loaded with tolerant developers having good replenishment
rates or anti-oxidation, long tank life, etc. And of course, all the
temperatures do match up well in such systems.

If you can find someone still willing to do hand development - expensive
- and to use specialised developer chosen to match the film, with
appropriate technique, you *may* get considerably finer and more regular
granularity for the same effective speed.

There are other things to consider - with long development times,
agitation every minute or every 30 seconds is normal, and the film
benefits from static periods, during which the balance of micro-contrast
to overall contrast, and the production of acutance effects, is
enhanced. High temperature short development times call for continuous
agitation, which always favours overall contrast rather than producing
what Geoffrey Crawley used to call an 'engraving-like' image. Sharpness
may be lower because acutance lines (adjacency effect caused by
by-products of development) are absent entirely.

It's a complex thing, but a higher dilution, higher pH developer with a
normal temperature and far longer development time can produce quite
exquisite negs at very high effective filmspeeds - while a highly
active, concentrated, high temperature shorter development may produce a
neg only suitable for a press photographer in a real hurry.

David
http://www.freelancephotographer.co.uk/

Tomas Daniska wrote:

david,

seems like i finally will go for manual c41 at home...




Well, I had wrongly assumed you were talking b/w films, and the
principles don't fully apply to C41 because all C41 films are designed
to be processed up to 38C or thereabouts without risk of damage, and
they are also designed to take the transition from dev to blix without
even an intermediate bath.

The stuff I said about microcontrast, edge effects etc does not apply to
C41 unless special developers are used - Neofin Color was supposed to
give enhanced sharpness this way, but in my experience it just gave
awful negs. There are some effects, but the removal of silver from C41
films means some of the worst granularity damage is limited.

However, if your processor is boosting temperatures above the normal
machine process for C41 it's not a good thing. All the film tech data
sheets I've seen refer to process time for pushing rather than
temperature though I am sure some lab info sheets cover that. Large lab
machines don't vary temperature (it would take far too much time to heat
and cool between runs) and do vary time.

My experience with trying higher temperatures in hand-line processing
C41 was that base fog levels increased.

David