What Kodak says about "C41 Push Processing"

This should add some fire to the fuel?

Push Processing

 

The following comments provide additional sensitometric information

relative to the film performance as a result of the application of

push processing.

 

Push processing is achieved in the laboratory by reducing the

transport speed of the processing machine, thereby increasing the

development time. Push processing is often used to recover density

from under exposed camera originals. Ideally, the density loss from

under exposure is exactly compensated by the increased density

provided by push processing. The compensation is not perfect however,

and the final result is typically higher contrast images with a color

bias and reduced photographic speed. Increased granularity is also a

by-product of push processing. These effects are generally

independent of film code or emulsion differences.

 

Sensitometry:

 

Contrast:

Contrast build up from pushed processing is generally most dramatic

in the bottom (cyan and magenta) layers of negative film and least

dramatic in the top (yellow) layer. This is because development is a

diffusion limited process. Contrast mismatch problems are introduced

with pushed processing resulting in high red to blue and high green

to blue contrast. The relatively high red to blue and high green to

blue contrast of the negative produces yellow highlights and blue

shadows in the print when mid-scale neutrals are balanced. In many

cases the yellow highlights may have a red bias because the mismatch

tends to be higher in the cyan layer compared to the magenta layer.

It should also be noted that contrast mismatch varies with exposure;

stronger effects with over exposure, weaker effects with

underexposure. Under exposure, combined with pushed processing, tends

to lessen the effects of increased contrast from pushed processing

alone. Differences in exposure and scene content may have a

significant effect on the perception of color in the resultant print,

when pushed processing is used.

 

Speed:

ER speed increases with Push processing may be significantly less

than needed to offset speed loss from under exposure. With the given

conditions above, Push 1 processing produces ER speed increases of

less than a 1/3 of a stop and Push 2 produces ER speed increases of

around 1/2 of a stop. Push 2 taken in combination with two stops of

under exposure represents a stop and a half loss in real speed. The

end result is smoky shadows in prints.

 

Granularity:

Regarding granularity, the following general comment is true: push

processing increases the granularity for all films. Further, it is

apparent that under exposure also produces increases in the

granularity for all films. The combination of push processing and

under exposure may produce additive increases in granularity up to

the extent of 10-12 units, compared to normal exposure / normal

processing. It seems probable that some customers might complain

about grain (and color rendition) when comparing under exposed , push

processed originals to normal exposure and normal processing

conditions.

 

AMT:

AMT (sharpness) numbers decrease with under exposure with all films.

The combination of under exposure and push processing produce lower

AMT's compared to normal exposure, normal processing. The loss in

sharpness from under exposure may not be objectionable in pictures

however, because this loss may be compensated subjectively by the

apparent increase in sharpness associated with the higher contrast

from push processing.

 

Summary (Push Processing):

Push processing is not recommended as a means to increase

photographic speed with Kodak C41 materials. Push processing produces

contrast mismatches notably in the red and green sensitive layers (

red most) compared to the blue. This produces reddish- yellow

highlights, and cyan- blue shadows. Push processing also produces

significant increases in film granularity. Push processing combined

with under exposure produces a net loss in photographic speed, higher

contrast, smoky shadows, yellow highlights and grainy images, with

possible slight losses in sharpness.

 

Pull Processing

 

Summary (Pull Processing):

In a similar analysis, pull processing combined with over exposure of

Kodak C41 films, produces a noticeable improvement in granularity, a

reduction in overall contrast, a slight color bias (yellow shadows

and blue highlights) with no perceptible change in sharpness.

Fuji & Ilford have similar warnings on their web sites.But I

suppose the PHOTO.NET film processing "experts" will disagree?

 

Steve is referring to this thread, to bring anyone interested up to date.

 

 

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=007ED4

 

Why he is posting this common knowledge and claiming to add fuel to a fire is beyond me. These known results of 'gain for loss', with push/pull processing posted here, have nothing to do with him being wrong there.

I like making quotes to. From the "Common Dreams Newsletter":<I><P>The original term moron was coined by an American Psychologist in New Jersey during the early part of the century. Moron was added to the US version of the IQ test to screen out people who looked intelligent but weren't. A moron was considered to have an IQ between 50-75.

 

</i><P>

I'm not aware you can safely decrease the transport time of a dip -n- dunk processor if it's the conventional hydrolic type (Kodak is obviously referencing a mini-lab roller transport), although if you tweak the flux capacitor just right..... I'm also wondering if this Kodak tech tip you dug out of their archives also had a 'Shirley' wearing love beads, ala 1970's reference materials. The comment about 'smoky shadows' in prints would indicate some films around, circa, 1980s as well since all the modern C-41 and E-6 films don't have issues with fog at a 1 stop push. VPS didn't behave well when pushed, and neither did VPH as per my personal experience with them, and this appears the technology level being addressed here - 15year old films. I've seen Kodak publications claiming PRN had less contrast than Portra NC as well.<P>

 

When you increase processing time you increase granularity and contrast, and when you decrease processing time you decrease granularity and contrast. Are we learning something here, or is there a point to this other than the part time 18yr old at Motofoto knows more about C-41 management than than you ever will.<P>

 

In regards to "Expert", which you put in quotes to obviously bring attention to the fact there's an inferiority complex at play, I used to be so good at judging our C-41 lines I didn't even need to run control strips because I could visually tell by looking at HD minus LD on a reference neg exactly where the plots lied visually. I then used to make bets with our C-41 lab rat and see if I could come within 2-3 points of the actual plot when he ran the control strip. I won about 2/3 of the time.<P>

 

Your continued claims that E-6 and C-41 films can't be pushed is like saying Boeing Corp. doesn't build airplanes, but just helicopters, and is really detrimental to giving proper advice in this forum. Given the signal to noise ratio of the Internet though it's not unexpected. It's one thing to have a disagreement, but some of us who have pushed a lot of film in our life times and worked at professional labs are really wondering if you are honestly this ignorant.

<P>Somebody else play with this guy....I have other things to do.

I was given a Flexcolor processing kit by Kodak when it came out; in the 1970's. The Kodak C41 seminar then said to keep the temperatures the same; and decrease/increase the time; for a asa drop/increase. They also said that this a real slight decrease/increase in real asa; not like wild claims by B&W developing changes with radical changes being possible in asa.. My friends old lab either faked off the C41 processor; to add a time to the development. I have also heard of increasing the temperarure gambit; if many rolls are to be pushed at once. Today many labs just give their "push c41 customers" more attention; ie do exposure adjustments in printing; and fib and use the same C41 process. The C41 process was made to be a high temperature standard process; to shorten the development time. The older C-22 was alot closer to "normal" developing temperatures; required alot more time.

Using color negative for aerial photo, I have had to push process 70mm portra 160 NC to get enough speed for short enough exposure times. Works excellent = no noticable loss in resolution & color-balance (the possible shift obviously being handled during the color-conversion done during scanning). Agfa recommend push-processing for their C41 aerial color-neg films when the speed is needed.

I've been on duty tonight watching to see what's killing some late night back-up jobs on my AS/400's, so I've had time to do some research.

 

I really hate kicking a dog when it's already been hit by the train, but I found the tech pub Steve was referring to. Here's a screen shot from Kodak's web-site, and the references he's making are from 1982/84 and in regards to Kodak motion picture film. So, we're talking about 20yr old film technology, and MP film at that.

{Yawn} Sorry about that. Ok, what was I talking about again? Oh yeah...trying to stay awake here.

 

Here's a screen grab from Kodak again. This one is their application matrix from Supra 400/800. Note sports fans that Supra 400/800 are somewhat newer technology than 20yr old MP film.

As instigator of the intitial question on the other post "getting pushy" cross

referenced within the post which has been corss referenced below, perhaps I

can comment.......

 

Peak Imaging offer a push service on C41 developing. Consumer labs do not

because (I am told) they can not alter the development time on the automated

machines which they use to process.

 

I sent five films to peak imaging from my holiday, four were pushed C41 (3 x

Reala, 1 x Superia) and one was standard (unpushed) Reala.

 

The pictures came back varying in quality, The superia should have chucked

in the bin instead, although I suspect that a lot of that was to do with me and

not the method (tungsten / fluoro bulb colour cast, inability to hold steady on a

travellator, not focussed correctly etc.).

 

The pushed Reala stuff where exposure was OK had a slightly more

noticeable grain, particularly in complex detailed areas but if I told you it was

400 speed and not Reala 100 then you would not bat an eyelid.

 

If you are really bothered then I can scan and post.

 

Just to reiterate that within "Getting Pushy", some told me to throw it in the bin

as it was "toast".... if I had done that then I would have lost some unforgettable

holiday memories......

Thanks for following up <A HREF="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=006jkS">

on your "Getting Pushy" thread</A>, Nicholas.

Interesting that the Reala pushed well, as predicted.

That's good to know.

Thanks Scott for correcting Steve's post.

 

If all photographers shared Steve's aversion to experimentation, the world of

photography would be a very dull place.

Nicholas, I�m glad to hear that all was not lost, and that that thread with all it�s bantering was worth the various burns some of us received amongst the flame throwing. I came back a couple of weeks later asking so.

The constant red herring I see in push process threads is shadow speed. Just because you can't get a dramatic increase in shadow speed doesn't mean pushing is useless. Getting the midtones and highlights where you want them is often enough, and if a little shadow detail goes AWOL it's generally not missed.

 

Re: Kelly's assertion that labs fake pushes: Yup, I've seen it done, but if you hold the "pushed" neg up next to a normally-processed neg it's obvious--the mask is denser on the pushed film. If the mask densities match, somebody's got some explaining to do. And yes, I have made a scene in front of other customers before I left the lab for the last time.

 

My experience is that Costco/Walmart/Drugstores are hard to make push, but independently-owned 1-hour labs mostly will.

 

Notably, in my actual experience (not just theory) NHG II/NPZ pushed 1 and rated at 1200 looks less underexposed and grainy than either of the current 1600-speed films shot at 1200.

 

Also, as more and more printing is accomplished digitally, cross-casts are less of an issue--in an enlarger they're unfixable; in Photoshop they're trivial.

If you think you are getting something useful from 'pushing' go right ahead. Dream on.....

ignore the troll ladies and gents

Hi Nick, good to hear your pics turned out fine. You said there was roll of Reala developed normally. How did it compare to the pushed ones?

Considering Kodak publishes push times it's hard to call push processing expermenting. Kodak's lawyers likely read everything long before we do and anything that might even be close to risky gets cut.

Robert:

Dream on....

I should add that if you miss the correct exposure slightly (not sure by how

much though) and / or are out of focus then the prints look cack, particularly if

your image has loads of pale colour / white.

 

However, I forgot to check the negs to make sure they had'nt cheated at the

print stage... will do that tonight..... I may be eating humble pie tomorrow...

fortunately I have broad shoulders....

 

The stuff that was not pushed and processed normally by Peak Imaging (12

pounds a go for 36 at 7.5" x 5") looked like Claude Monet had added the

colour personally. Bear in mind however that all my previous experience is

with Kodak approved CONSUMER (i.e. 6.50 for 36 exp's at 7" by 5")

processing.... Despite the hiked expense I now use Peak Imaging as my

standard lab.

 

Perhaps Hans, you would care to guess "push" or "unpushed" to a selection

of 10 unaltered (I do not have photoshop but I have a flatbed scanner) prints

of my holiday...... this may put a stop to being labelled a troll.....

 

By the way, I always carry some NPH 400 now, and some Superia "Super G"

1600 in case I am really desparate. If I forget to take it out the fridge then I buy

Kodak high definition (ISO400) which is even available in UK petrol stations

now.

"The stuff that was not pushed and processed normally by Peak Imaging (12 pounds a go for 36 at 7.5" x 5") looked like Claude Monet had added the colour personally."

 

What does this mean? Incorrect colors ? I'm really intersted to get a good idea how your results turned out, as I was one who pushed for pushing in the original discussion.

Dream on, dream on, dream on

 

Dream yourself a dream come true

 

Dream on, dream on, dream on

 

Dream until your dream comes true

 

Dream on, dream on, dream on

 

Dream on, dream on, dream on

 

 

 

Sing with me, sing for the years

 

Sing for the laughter 'n sing for the tears

 

Sing with me, if it's just for today

 

Maybe tomorrow the good lord will take you away

Sometimes it gets really comical... Oh yeah.

I never suggested that you cant push color neg films,I only question why anyone would need to?As for chrome stocks,same question?This isnt 1970 ,film manufacturing has come a long way,and high speed emulsions are readily available.The only reasons to push any film,in my ever so humble opinion,would be to correct an exposure error involving a non re-shootable event.To create a special effect or to enable shooting in very low light,in lieu of faster film.The original question here was regarding using zone system type contrast/tonal expansion/contraction development by manipulating procesing times with chromogenic B&W films.I said that this was basically impossible for a variety of reasons,the main one being lack of labs that will alter development of C41 films.In my experience with pushed C41 the emulsion layers when layed out on a graph tend to criss cross,rather than create nice linear H&D curves.Again in my experience,this makes for crappy prints(your mileage may vary).

Right... I am going to start a new post.... all have a sneeky peek at "Getting

Really Pushy".

 

That way the two threads tie together, and this thread can remain on topic.....

Steve, come on man, how can you say all this within two threads?

 

�I never suggested that you cant push color neg films,I only question why anyone would need to?�

 

�Since the C41 process time & temp is written in stone, Id say no.�

 

�I dont see what differnce exposure makes with film that gets the same time/temp every time in development?�

 

�How on earth does one alter dev times with C41 materials? The labs I use,(Millers & North American)would laugh at the suggestion.�

 

No one has suggested that you get �better� results with pushing. However, some films do look better pulled when over exposed, Provia 400 @ 160 pull 1, and similar method for Velvia 50. Some here have been in situations, repetitively, where you have no choice to shoot at 1250 asa with ambient house lights.<div></div>

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