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Re: [OM] Re(2): pushing film

Subject: Re: [OM] Re(2): pushing film
From: Gene Mayeda <gmayeda@xxxxxxxxxxxxxxxxx>
Date: Fri, 09 Jan 1998 08:24:28 -0600
Peter:
Perhaps some of our astronomers could share their knowlege of hypered
film.I've seen the ads for it in the back of the astronomy magazines.I
think that the film is bathed in some sort of gas before camera exposure
and it results in much higher real film speed.Also freezing (In liquid
nitrogen?) film was a technique used before hypering that also resulted
in actual film speed increases(not pushing).

Peter Leyssens wrote:
> 
> Again, a summary :
> 1) Gene : So, if I take your point that Rodinal has sharp edges on the
> grains, the fact that you get a lot of grain by pushing can be explained
> because there's more contrast in the picture.  Because the grain next to
> this one will be a big difference in tone and therefore you notice the
> grain more, right ?

Pushing or overdevelopment makes all of silver halide crystals reduce to
metallic silver proportional to the increase in development time.More
development equals larger metallic silver "grains" in your negs.Under
development gives you smaller metallic silver "grains".The contrast
increase with over development has to do,I believe,with proportionally
more silver developing in the highlights than in the shadows of the negs
as developing time increases.It also blocks the highlights up.This is a
rule of thumb.There are some exceptions depending on exposure,type of
developer,and choice of film.I've noticed that low contrast grade paper
shows less graininess than say a #5 or #6 paper.(From the same
neg.)Often pushed film negs are thin and a high paper grade is needed to
make acceptable prints.This is when I first noticed the effect.

> 2) Gene : So Uncle Ansel is really saying : overexpose to get as much
> info on the negative, then develop in such a way that the darkest spots
> still show textured black.  And I'm saying : I don't want a lot of info
> on my negative, but I want to see it all anyway !  Right, I can
> understand that you won't get the results the film manufacturer wants
> you to get if you mistreat your film this way.

You can't develop shadow detail that has not rendered itself on the
exposed film.You can only develop what is in there to begin with.This
includes fog.Pushing lets you develop what is there,especially in the
midtones,to a density that would be there otherwise with normal exposure
and normal development.ISO speeds for film must meet a certain curve
shape that represents average pleasing looking photos.
 BTW has anyone else noticed that T-Max 100 does not have an ISO
speed?It has an E.I. speed(exposure index). I assume that its curve does
not conform to ISO specs...hmmm.That is why prints made from T-Max 100
do not print the same as negs made from Plus-X.Funny how Kodak doesn't
have a lot to say on the instructions about this.

> 3) Shawn : I should get myself a copy of The Negative.  I can feel it in
> my toes that this is a book I'm going to learn one hell of a lot from,
> but at this moment, those Roman figures are driving me nuts.  I've
> written down the ISBN number already ...  Now : am I going to wait for
> my birthday (end of march) to ask it as a present, or will the
> temptation be to large ?
> 4) Shawn : how do you do that, measure the negatives on a light table
> with the spot meter ?
> 5) Lars : 'grain like macadam', got to remember that expression.  If I
> understand Gene correctly, the grain doesn't get larger, only more
> noticable.  Or is it really possible to get a "Single-Grain Negative"
> (tm) ?
> 6) Lars : Thanks for mentioning the pre-exposure !  There are tricks
> like that that I have forgotten (because I only knew they existed and I
> never tried them).  A pre-expose button would be great and would
> certainly position the OM-5 as a professional camera !  More like
> Hasselblad than like Leica.
> 7) Marco : What is the procedure for pre-exposing (or rather -
> post-exposing) in the darkroom ?  You can't just turn on the light with
> the film laying there, the exposure would be too uneven and the time
> would be uncontrolled, wouldn't it ?
> 
> Thanks for all the hints and all the theory !
> 
> --
> Peter Leyssens
> Eonic Systems
> 
> Support mail : support@xxxxxxxxx

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