Where does the push/pull happen in the process?

[Phil Gerke]

Hi all,

 

This is a new area for me and though I have learned much from lurking these threads, one thing I can't figure out is where exactly the push or pull occurs.

 

I understand that in a push situation you rate your film faster than it is, correct? If I was going to push an ISO 250 I would shoot at EI 500. Essentially underexposing a stop, then in the development it then gets pushed for that lost stop.(I realize that you could push any film regardless of how it was exposed.) So at what step does the push happen? Is it in the processing of the original film, or do you push the internegative, interpostive? Or does it happen for the final print? And is it a chemical process or is it an exposure technique? Meaning do you push it with how long you use certain chemicals or do you push how long the film gets flashed with light? Does that makes sense?

 

I assume the oposite is true for a pull process. In a pull process the DP is overexposing, desiring a denser negative right? This is more or less an aesthic or philosophy matter right?

 

Hopefully this all makes sense. I guess there are a couple questions in there I apologize if this has been covered way too much, I just have a few gaps in my understanding that I can't quite nail down. I appreciate the help.

 

Thanks a lot!

 

Phil Gerke

[Michael Nash]

Pushing or pulling is typically done on the camera original. Pushing can be done either by increasing the heat or by lengthening the time in the developer. Perhaps Dominic can explain the differences better than I can...

 

Since pushing or pulling changes the density on the neg after developing, the DP may choose to compensate for that change by under- or over-exposing (respectively) while shooting, to arrive at a "normal" density. But it just depends on the desired result. If you want the attributes of that altered density, then you wouldn't change your exposure.

[Paul Bruening]

Hello,

 

While sometimes, pushing and pulling are done for artistic effect, it is most commonly done in a push to allow the DP to shoot in low light conditions. One stop push is common. Some DPs will go as far as two stops and not worry. Three is about the limit as picture quality degrades significantly.

 

Pushing and pulling usually occur while processing the negative. While temperature can be adjusted, it is usually easier to run the processor faster of slower thereby leaving the film in the chemicals longer or shorter. This kind of thing can be done at any step of the optical print system as well. Also, chemicals can be altered, added or left out entirely to suit the needs of the customer. Much of that depends on how game that particular lab is with goofing with its machinery and the very fine balances that are quite hard enough to maintain. Cost comes into play, needless to say.

 

With DI becoming so prevalent, push processing and occaisional tricks like skip-bleach are most of what's done these days. DI can do most of the rest that was once done in the processors.

[Phil Gerke]

I want to be clear, when we talk about the negative we are talking about the film exposed in the camera correct? That being so, is'nt it potentially risky to be doing any atypical processing when working with the negative? Because if you screw it up, its screwed forever right? I understand the pushing and pulling are pretty standard business, but skip bleach and such things at this step is a pretty bold action it seems. Isn't this why internegative/positives are around? As kind of a step of undo if something gets botched. Granted $$$ probably adds up with all the prints being made, and is generation loss an issue as well?

 

Thanks again for helping me out with this. I appreciate the "conversation" hopefully its not too remedial.

[Michael Nash]

I want to be clear, when we talk about the negative we are talking about the film exposed in the camera correct?

 

Yes, that's why I said "camera original" (I didn't say "negative" because you can push/pull reversal film as well).

 

That being so, is'nt it potentially risky to be doing any atypical processing when working with the negative? Because if you screw it up, its screwed forever right?

 

Yup. Welcome to film! :D

 

Isn't this why internegative/positives are around?

 

Sometimes alternative processes are done to the intermediates as a matter of cost and practicality, but the look isn't necessarily the same. It depends on what you're doing. For example, you can't "push" an internegative from a normally-processed, underexposed negative and bring up the same shadow detail that pushing the camera original would give. And performing a bleach-bypass on an interpositive doesn't give you the same rich, dense blacks that silver retention on a print gives you, because a normally processed print has "normal" black density (alhough the other visual characteristics of silver retention are preserved).

[David Mullen ASC]

Also, the intermediate stock used for IP's and IN's are really slow-speed, fine-grained, low-contrast and are designed just for duplication -- they don't react as well to alternate processing tricks as camera negative does, because they don't need to be. The processing tends to be more standardized for dupe intermediates.

[Phil Gerke]

I want to be clear, when we talk about the negative we are talking about the film exposed in the camera correct?

 

Yes, that's why I said "camera original" (I didn't say "negative" because you can push/pull reversal film as well).

 

 

Ok, ok. I just wanted to confirm, Paul had refered to the "negative" and I had assumed that meant "camera original"

 

Scary stuff, processing is. Are studios generally cool with these kind of techniques? It seems to be more prevelent lately, but then again maybe I am just seeing more DI work. Basically all the power is in the camera original.

 

So the purpose of the interpositve or internegative is simply for making prints from? Are there always both or is it either/or depending on if you shot negative or reversal? Surely you don't make your prints from the camera original?

 

Thanks again, this is great.

 

Also, the intermediate stock used for IP's and IN's are really slow-speed, fine-grained, low-contrast and are designed just for duplication -- they don't react as well to alternate processing tricks as camera negative does, because they don't need to be. The processing tends to be more standardized for dupe intermediates.

 

Did not catch you post until after mine. So yes IP's and IN's are basically your dupe master.

 

Again, I am still unclear if in normal procedure both IP and IN are created. Is it like this; Camera original (negative) to IP to IN to prints? Now that I think about it, it has to go this way right? You can't create a negative print from another negative print can you? There has to be a positive in there right? Again, gen loss?

 

Thanks!!!

Edited April 5, 2007 by Phil Gerke

[David Mullen ASC]

Unless reversal is involved, it's always a neg-pos process, so camera neg --> IP --> IN (aka dupe negative) --> release print.

 

The camera original may be printed a few times -- for example, it's often printed three or four times for answer printing, and it is not unusual to make several "show prints" for screenings. At some point, though, after the answer printing determines the printer lights, a color-timed interpositive is made as a protection master before more prints are struck off of the original negative.

 

The intermediate stock is the same for IP's and IN's -- whether it is a negative or a positive merely depends on the previous generation. If you copy the image from a negative source, it becomes an interpositive.

 

The only difference is that the stock is available on acetate and Estar base. With an internegative that has an Estar (polyester plastic) base, you can strike about a 1000 prints off of it before it wears out.

 

Camera negative stock is usually acetate base, under the theory that if the camera jams, it's better that the film breaks rather than the camera. You can tow a pick-up truck with another truck using Estar-base film as the rope...

 

There was a stock called CRI (color reversal intermediate) back in the 1970's for making a dupe negative from a negative without needing an IP, the idea being that it would be cheaper and save a generation. But CRI stock was not very good, it was contrasty, and it later turned out to have the worst color stability of any stock.

 

Plus by skipping a generation, your emulsion end up on the "wrong" side in contact printing (which is usually emulsion to emulsion) unless you printed through the base (which causes softer focus) or made the CRI using an optical printer.

[Phil Gerke]

Alright, now I am getting somewhere :D Thanks a lot David, that made a whole lot of sense, though the last bit about emulsions introduces a few concepts I am not overly familiar with, though I get the point. I have very little insight on the actual developing stages and processes, B&W still developing is all I really have been exposed to.

 

I just made the connection between IN/IP and DI, duh! Now that process makes a lot more sense. As far as "signal flow" is concerned.

 

Here is one last (maybe) question, how do dailies fit in? Are these struck right from the camera original?

 

Again, thanks to everyone who has posted. Very enlightening for me.

[Charles MacDonald]

the last bit about emulsions introduces a few concepts I am not overly familiar with, though I get the point. ... B&W still developing is all I really have been exposed to.

 

Here is one last (maybe) question, how do dailies fit in? Are these struck right from the camera original?

 

The printing process is just like the ocntact proff sheets that you might make from a roll of still negatives. The enuslion of the negative is placed againt the emulsion of the print material. The print reads right from the emusion side, the negative reads right from the base side.

 

With the Inter-positive to make an internegative your image reads the same way as an original negative.

 

The film enulsion faces the lens in the camera, but the base would face the projector lens in a contact print from a negative. If you shoot some Kodachome and project it the enuslion will face the projection lens.

 

And yes if they still make a rush or work print it would have to be struck off the negative (there is no intermediate at this stage.) - the norm is rapidly to do a scan from the neg and display the work digitaly.

Edited April 5, 2007 by Charles MacDonald

[Mark Henderson]

For years I have pushed and pulled photography and cinematography. It simply means to process longer (push) or process for less time (pull). You may do it because you do not have enough light available -- the sun is setting, you are wide open and you are still one or two stops under. In this case you shoot wide open and then tell the lab to push it one or two stops, whatever is needed to bring the film back to normal exposure. Some times you push or pull because you need to shoot at an f-stop that gives you the correct depth of field while unfortunately giving you the wrong exposure. Simply push or pull process to bring it back into correct exposure.

 

You must always watch out for reciprocity, however. This causes a "color shift" in the film. The film has three layers that effect the blue, green and reds. Unfortunately the layers are effected differently when exposed or processed over a "lengthened" amount of time. One color layer may be effected more/less from simply being processed or exposed longer. Film that is pushed over 3 stops will usually go noticeably red because of this effect.

 

Mark

[David Mullen ASC]

Here is one last (maybe) question, how do dailies fit in? Are these struck right from the camera original?

 

Yes, although a transfer from neg to video is more common now for editing on a computer, rather than striking a workprint and editing that.

[Matt Workman]

I suppose this depends on the lab and other things but in general how do you inform the lab you want to push process by 1 stop.

 

- On the camera report for the whole roll?

- On the camera report for certain scenes? (dial readings)

 

One or two my rolls have some underexposed shots ( only 1 stop ) mainly the wide night shots but its only select shots. I suppose pushing the whole roll wouldn't be horrible. Can I request a push per scene if I'm not supervising.

 

I almost want to process completely normal and fix the one stop in Final Touch, but that would mean more grain right?

 

Thanks,

 

Matt

[David Mullen ASC]

Push or pull processing can only be done to whole camera rolls, hence why if you know that a shot will need to be pushed, you put it on a separate roll.

 

You label the film can, the camera report, and the lab work order as to the processing instructions.

[Mark Dunn]

Pushing is just the same as for B/W- extended first development, the step which produces a silver image.

In a continuous cine processor, you can run the machine slower, but this increases unnecessarily the time the film spends in all the other baths. So you can increase the time by putting extra racks in the first developer tank so the film has further to travel. Increasing the solution temperature of an entire machine isn't very convenient.

[Phil Gerke]

The printing process is just like the ocntact proff sheets that you might make from a roll of still negatives. The enuslion of the negative is placed againt the emulsion of the print material. The print reads right from the emusion side, the negative reads right from the base side.

 

Now I understand, that helped a lot.

 

The film enulsion faces the lens in the camera, but the base would face the projector lens in a contact print from a negative. If you shoot some Kodachome and project it the enuslion will face the projection lens.

 

This is because Kodachrome is a reversal stock right?

 

You must always watch out for reciprocity, however. This causes a "color shift" in the film. The film has three layers that effect the blue, green and reds. Unfortunately the layers are effected differently when exposed or processed over a "lengthened" amount of time. One color layer may be effected more/less from simply being processed or exposed longer. Film that is pushed over 3 stops will usually go noticeably red because of this effect.

Mark

 

That is interesting. Generally speaking a 1 or 2 stop push will still render color correctly? That seems to be what I am hearing.

 

Ok, so here is a new one; The three layers of color film are RGB, is it possible or has it been done to use Cyan Magenta and Yellow? Am I nuts? I know a graphic artist who does a lot of print work and I am pretty sure he told me CMYK yeilds better results. I know that is a little off topic but it popped into my head.

[K Borowski]

Now I understand, that helped a lot.

This is because Kodachrome is a reversal stock right?

That is interesting. Generally speaking a 1 or 2 stop push will still render color correctly? That seems to be what I am hearing.

 

Ok, so here is a new one; The three layers of color film are RGB, is it possible or has it been done to use Cyan Magenta and Yellow? Am I nuts? I know a graphic artist who does a lot of print work and I am pretty sure he told me CMYK yeilds better results. I know that is a little off topic but it popped into my head.

 

I've never played around with pushing or pulling reversal films. When you push or pull a reversal, you do get color shift, which must be accomodated for experimentally by using colored filters during shooting. One stop should have negligable color shift, but there will be a build up in contrast, and blacks will basically start looking more and more like "dark browns" the more you push Kodachrome.

 

I know Ektachrome and Fujichrome (E-6 & equivalent respectively) films are more pushable by design, as they have two developers, the first of which is a true B&W developer, sort of like dektol perhaps. ECN-2 or C-41 are only going through one developer, and it is a special color developer where the color couplers attached to the latent imaged silver halides are transformed into visible colors. For some reason these color developers, at least when altering temperature or duration that the film is in the developer during processing, don't seem to yield as large of a true speed gain as B&W or E-6 films do. Basically, part of the effect of push processing is actually just an illusion of speed gain, because you often don't get the full push's worth of shadow detail in the pushed film. If your shadow detail is a stop underexposed with color neg or B&W neg film, you'll end up with clear areas on the negatives, which were not affected by pushing any more that they became more contrastier because of lost tonality and gained base fog, which further heightens the visibility of grain.

 

Just as David Mullen has recommended here before (correct me if I'm wrong please), you only want to increase exposure 2/3 of a stop for every stop of push you give color negative film in development, so with say 400 speed film, you'd rate at 640 when you push a stop to 800, and you'd rate at 1000 when you push two stops to 1600. This helps preserve more printable shadow detail on the negative, at least enough to gain back some evidence of shadow in the print or telecine. I've done a few pushes of C-41 film, one inadvertantly longer than I had expected. There's no real pushing possible past two stops, you just increase the base fog further and further, because there's no more developable image detail present, understand?

 

The reason why color shifts in negatives that are pushed aren't a problem is that you just dial in a new filter pack. If you push too far, or jack the temperature up too high you will have problems with something known as "color crossover" where the film's response to a certain primarly color differs in areas of shadows and highlights, as the curve becomes distorted from extreme push or pull processing.

 

Frankly, unless you're shooting Kodachrome 200 in a still camera, I probably wouldn't adjust exposure to Kodachrome if I were you. The only adjustment I'd make personally would be to underexpose it by maybe 1/3 of a stop to obtain more saturated colors. However, in a crunch, you can actually get as many as five stops of extra exposure out of E-6 films, like the 400 speed. Currently though, I think that there's only a 100D and 64T stock offered in the Ektachrome line, plus Fuji's Vlevia 50. I wouldn't push more than two stops on those either. WIth a higher speed stock, were it to become available in cine lengths and perforations, you could probably push three usable stops out of it, three true stops, like a 400 film to 3200. Kodak actually still makes a film that is about 400 ASA that is specifically designed to be pushable to 1600, or 3200 with extreme grain and extreme contrast and some color shift. It's called P1600. Kodak also claims you can get two stops out of their new line of E films' E200, up to 800 ASA

 

I guess I can't emphasize how important it is to test. If you do make a mistake on a roll, and the shot is important enough that you want to save it, then DON'T SHOOT ANYTHING ELSE ON THAT ROLL until you figure out what the push or pull is that the lab will need to do and whether that amount of push or pull would be excessive for other shots you'd need to shoot. If you figure out you need to push the film two stops, then you can just save that mag for shooting nighttime shots or shots that you had already scripted would require a push. If you have some shots that say need a one stop push and you made this blunder at 2, I'd say that's close enough that you probably wouldn't see that much of an increase in grain (just buildup in base fog) since the base exposure, if thich enough, acts to reduce graininess. With reversal though, again everything needs to be dead on, within 1/2 of a stop either way for best results. More than 1 stop either way and your shadows loose detail or your highlights block up, so much that reversal printing, photoshopping, or any other techniques you attempt aren't going to do much in recovering that obscured image detail.

 

Hope this helps and doesn't confuse you more.

 

Regards,

 

~Karl

 

Hope this helps,

 

~Karl Borowski

[Dominic Case]

Ok, so here is a new one; The three layers of color film are RGB, is it possible or has it been done to use Cyan Magenta and Yellow? Am I nuts?

No, not nuts, but not quite accurate in your premise.

 

The three emulsion layers of any film (negative, positive, reversal, all the same) are sensitive respectively to red, green, and blue light. (Red, green and blue being the three primary colours, corresponding to the way we see light through the cones in the retina in the eye.)

 

On processing, these three layers form cyan, magenta and yellow dyes. That is one reason why the film that comes out of a camera is actually a negative - the image is the opposite of reality: whites are black, yellows are blue, etc. This is still true for all types of film: when you make a print, it is actually a negative of a negative - which as we all know, makes a positive.

 

The way in which the yellow, magenta and cyan dyes work is that each of those secondary or complementary colours acts as a filter to absorb one primary colour and transmit the other two. So when you view, or print, the image in the yellow dye layer, it lets all the red and green light through, it just varies the blue light.

 

By laying the three dye layers over each other on the film, you get a full range of colour reproduction.

 

If the manufacturers used red, green and blue dyes in the same way, it would be impossible to reproduce a full gamut of colours: yellows for example would be impossible. There were additive methods used in film many years ago - they had a mosaic screen a bit like the mask on a CRT TV screen laid over a black and white emulsion, and were very slow and very dark.

 

 

Just a couple of other points from this thread: the colour shift you get with push processing is because the development process is designed to take a certain time, to do with how long it takes the chemicals to permeate to the lower layers of emulison among other things. Diffrent layers are affected in different ways by extended or shortened development time. That is not reciprocity or reciprocity failure as one poster suggested. Reciprocity is the relationship between exposure time and exposure intensity: if you have very long or short exposure times then the results are affected: but we are talking about less than 1/2,000 sec or more than a second or so.

 

Oh - and yes, processing original negative off-standard is risky, certainly. But if you do appropriate tests beforehand, and use a reliable lab, you are on safe grounds. It's no more risky than altering the settings on a digital camera for a particular look.

[John Pytlak RIP]

Hi all,

 

This is a new area for me and though I have learned much from lurking these threads, one thing I can't figure out is where exactly the push or pull occurs.

 

I understand that in a push situation you rate your film faster than it is, correct? If I was going to push an ISO 250 I would shoot at EI 500. Essentially underexposing a stop, then in the development it then gets pushed for that lost stop.(I realize that you could push any film regardless of how it was exposed.) So at what step does the push happen? Is it in the processing of the original film, or do you push the internegative, interpostive? Or does it happen for the final print? And is it a chemical process or is it an exposure technique? Meaning do you push it with how long you use certain chemicals or do you push how long the film gets flashed with light? Does that makes sense?

 

I assume the oposite is true for a pull process. In a pull process the DP is overexposing, desiring a denser negative right? This is more or less an aesthic or philosophy matter right?

 

Hopefully this all makes sense. I guess there are a couple questions in there I apologize if this has been covered way too much, I just have a few gaps in my understanding that I can't quite nail down. I appreciate the help.

 

Thanks a lot!

 

Phil Gerke

In most cases, the camera original film is "pushed" or "pulled" in processing. Most labs simply change the speed of the processing machine to affect the time the film spends in the developer, which is where the actual development occurs. Care is needed to assure the other solution and wash times are not compromised by changes in machine speed.

[Phil Gerke]

Just as David Mullen has recommended here before (correct me if I'm wrong please), you only want to increase exposure 2/3 of a stop for every stop of push you give color negative film in development, so with say 400 speed film, you'd rate at 640 when you push a stop to 800, and you'd rate at 1000 when you push two stops to 1600. This helps preserve more printable shadow detail on the negative, at least enough to gain back some evidence of shadow in the print or telecine. I've done a few pushes of C-41 film, one inadvertantly longer than I had expected. There's no real pushing possible past two stops, you just increase the base fog further and further, because there's no more developable image detail present, understand?

 

I do understand. Except, I can't quite wrap my brain around this.

 

If your shadow detail is a stop underexposed with color neg or B&W neg film, you'll end up with clear areas on the negatives, which were not affected by pushing any more that they became more contrastier because of lost tonality and gained base fog, which further heightens the visibility of grain.

 

So I understand that if you underexpose your negative is going be more clear, shadow areas will go totally clear. Are you saying that a totally clear spot in the negative acts much differntly than if there was a little of color to it? If you underexpose your blacks too much pushing in the development won't yeild a whole lot because there is no "information" there to begin with?

 

Also can you explain gain based fog, or rather what causes it, pretty sure I have seen it me own photos.

 

 

On processing, these three layers form cyan, magenta and yellow dyes. That is one reason why the film that comes out of a camera is actually a negative - the image is the opposite of reality: whites are black, yellows are blue, etc. This is still true for all types of film: when you make a print, it is actually a negative of a negative - which as we all know, makes a positive.

 

The way in which the yellow, magenta and cyan dyes work is that each of those secondary or complementary colours acts as a filter to absorb one primary colour and transmit the other two. So when you view, or print, the image in the yellow dye layer, it lets all the red and green light through, it just varies the blue light.

 

By laying the three dye layers over each other on the film, you get a full range of colour reproduction.

 

If the manufacturers used red, green and blue dyes in the same way, it would be impossible to reproduce a full gamut of colours: yellows for example would be impossible. There were additive methods used in film many years ago - they had a mosaic screen a bit like the mask on a CRT TV screen laid over a black and white emulsion, and were very slow and very dark..

 

Ok, I just can't figure out some of this. If the layers are sensitve to RGB, why is a negative created. As I think about your post further you state that "on processing" the layers form CMY. So its not negative until the correct chemicals enter the equation? I'm just having trouble grasping this. Why would it be impossible to create yellow?

 

Thanks a lot for all the responses, I am not getting more confused I am learning a lot, but its one of those things where one question leads to many more.

[John Pytlak RIP]

I do understand. Except, I can't quite wrap my brain around this.

So I understand that if you underexpose your negative is going be more clear, shadow areas will go totally clear. Are you saying that a totally clear spot in the negative acts much differntly than if there was a little of color to it? If you underexpose your blacks too much pushing in the development won't yeild a whole lot because there is no "information" there to begin with?

 

Also can you explain gain based fog, or rather what causes it, pretty sure I have seen it me own photos.

Ok, I just can't figure out some of this. If the layers are sensitve to RGB, why is a negative created. As I think about your post further you state that "on processing" the layers form CMY. So its not negative until the correct chemicals enter the equation? I'm just having trouble grasping this. Why would it be impossible to create yellow?

 

Thanks a lot for all the responses, I am not getting more confused I am learning a lot, but its one of those things where one question leads to many more.

 

Kodak has some good tutorials:

 

http://www.kodak.com/US/en/motion/support/...erationsP.shtml

 

http://www.kodak.com/US/en/motion/support/....4.15&lc=en

 

http://www.kodak.com/US/plugins/acrobat/en.../h247/h2407.pdf

[Dominic Case]

Why would it be impossible to create yellow?

Go to the tutorials that John Pytlak points to. That should help a lot.

 

There are three primary colours: Red, Green and Blue. Each corresponds to a different band of wavelengths in the visible spectrum.

An absence of all three primaries results in Black.

Combinations of two Primaries result in the Secondary (or complementary) colours: so

Red + Blue makes Magenta

Green + Blue makes Cyan

Red + Green makes Yellow

All three primaries together add up to White.

 

On a monitor, you have red, green and blue dots very close to each other, so they add up to make whatever colour you want - according to the rules above. No dots, black. All the dts, white. etc.

 

But in film, you have three dye layers, on top of each other, so light has to pass through all three layers when you look at the image. So with no dye in any layer, you have white light. Now, if you have one layer, and it is yellow, then it is transmitting Red and Green light (and absorbing Blue). If you have one layer and it is magenta, then it is transmitting Red and Blue light, and absorbing Green. So if you have those two layers on top of each other, then one will absorb Blue light and one will absorb Green light. That leaves just Red light getting through, and that is what you see when you lay yellow and magenta filters or dye layers on top of each other.

 

You can work it out for other combinations of yellow, magenta and cyan filter or dye layers, each controlling one of the three primary colours.

 

Now, if, instead, you built a film stock wtih Red, Green and Blue dye-forming layers, corresponding to the sensitivities of each layer, then each of them, by defintion, abosrbs TWO of the three primary colours, only transmitting one. So it is impossible to have any combination that transmits the two primary colours you need to see yellow.

[Dominic Case]

Why would it be impossible to create yellow?

Go to the tutorials that John Pytlak points to. That should help a lot.

 

There are three primary colours: Red, Green and Blue. Each corresponds to a different band of wavelengths in the visible spectrum.

An absence of all three primaries results in Black.

Combinations of two Primaries result in the Secondary (or complementary) colours: so

Red + Blue makes Magenta

Green + Blue makes Cyan

Red + Green makes Yellow

All three primaries together add up to White.

 

On a monitor, you have red, green and blue dots very close to each other, so they add up to make whatever colour you want - according to the rules above. No dots, black. All the dts, white. etc.

 

But in film, you have three dye layers, on top of each other, so light has to pass through all three layers when you look at the image. So with no dye in any layer, you have white light. Now, if you have one layer, and it is yellow, then it is transmitting Red and Green light (and absorbing Blue). If you have one layer and it is magenta, then it is transmitting Red and Blue light, and absorbing Green. So if you have those two layers on top of each other, then one will absorb Blue light and one will absorb Green light. That leaves just Red light getting through, and that is what you see when you lay yellow and magenta filters or dye layers on top of each other.

 

You can work it out for other combinations of yellow, magenta and cyan filter or dye layers, each controlling one of the three primary colours.

 

Now, if, instead, you built a film stock wtih Red, Green and Blue dye-forming layers, corresponding to the sensitivities of each layer, then each of them, by defintion, abosrbs TWO of the three primary colours, only transmitting one. So it is impossible to have any combination that transmits the two primary colours you need to see yellow.

[Sam Wells]

I was routinely pushing 7245 and 7274 with Colorlab, they use the temperature method.

 

Colors, contrast a bit bolder but they all "tracked" for me IOW I didn't notice uneven responses in individual layers.

 

Perhaps LAD tests would reveal "errors" but it all looked good, so......

 

"If you underexpose your blacks too much pushing in the development won't yeild a whole lot because there is no "information" there to begin with?"

 

One thing I was going for was a bit of what I call a 'chemical black crush'

 

-Sam

[Christian Janss]

So, there is a lot of information here, thanks to everyone for contributing. I have one question that I hope will be fairly simple, if I have my vocab mixed up I apologise, please correct me.

 

This much is clear; pushing/pulling only happens in the bath, and for the entire roll. But as I see it there are different ways to get that pulled/pushed stop(s).

 

The common way is to expose the film one stop over or under the recommended ASA (i.e. set the meter to 1000 or 250 for 500T), then tell the lab to push or pull one stop. They will leave the film in the bath for either more or less time as appropriate.

 

But, what would happen if you exposed the film normally (rating 500T at 500ASA on the meter) but then asked the lab to push or pull one stop? Would the outcome be the same as adjusting the exposure on my end (i.e. in camera by changing the meter's ASA setting)?

 

Also, what about exposing the film one stop over or under (again, set the meter to 1000 or 250 for 500T) but have the lab just develop normally? I'd imagine that the film would look either over or underexposed and basically look like a mistake.

 

Or am I missing the point... Is the key to pushing/pulling, returning the film back to the recommended ASA via time in the bath? Would pulling/pushing when not originally over/under exposing make any sense in the real world, or am I just over-complicating things?

 

As a side note, since most labs won't push/pull more than one stop, this could be a way to get a two stop pull/push by rating the 500T as 1000 then telling the lab to "pull"(?) one stop (this is where my vocab may break down, I don't know if I'm using "pull" correctly).

 

I guess that's a lot more than one question, but thanks in advance.

 

Christian