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Negative base matching


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#1 L K Keerthi Basu

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Posted 18 July 2005 - 10:37 AM

I basically have a doubt in the negative base. Why all the negative bases are not matching to each other from a same manufacturer? I think that they use same dyes for all the emulsion or they are different in each and every stock. The base density in each stock is differing why this happens?Did they happen due to the different ASAs grain size.
Why it is not possible to manufacture the films with same base density? Is there
any scientific reasons behind this?

L.K.Keerthibasu
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#2 John Pytlak RIP

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Posted 21 July 2005 - 05:33 AM

I basically have a doubt in the negative base. Why all the negative bases are not matching to each other from a same manufacturer?  I think that they use same dyes for all the emulsion or they are different  in each and every stock.  The base density in each stock is differing why this happens?Did they happen due to the different ASAs grain size.
  Why it is not possible to manufacture the films with same base density?  Is there
any scientific reasons behind this?

L.K.Keerthibasu

<{POST_SNAPBACK}>


The differences you are seeing are not due to the "base" (the clear plastic film support on which the emulsions are coated). The red/orange color of color negative film comes from the colored couplers used to form the dyes and provide color-correcting masking. Different film types require slightly different amounts and types of these colored couplers, and improvements have been made as Kodak films have gone from old technologies to the EXR, VISION, and latest VISION2 technologies.

Here are typical patents for the complex technology used in modern color negative films:

http://www.freepaten...om/5932403.html

http://www.freepaten...om/5591569.html

Although the technology used IN the film is complex, it helps make using the film simpler. Remember, George Eastman's goal in photography was "You push the button, we do the rest." :)
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#3 L K Keerthi Basu

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Posted 21 July 2005 - 10:00 AM

Thank you, John. I know about the Internal masking in the negative which produce these amber color in the base. I got it but what i like know is Why any two negatives let us take that 5212 and 5218 for ex.,dont have the same base color density? Why this is like that ? whether this is due to the usage of different color couplers for different stocks or due to the ASA of the film and grain size. I dont know why this slight density change in the amber color of the base.
I also found this will change because of the wrong processing controls in the lab.

L.K.Keerthibasu
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#4 David Mullen ASC

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Posted 21 July 2005 - 11:52 AM

But the question is, why does the color mask have to match in every stock after processing? What advantage would it give you if it did? 5212 and 5218 are SO similar considering the speed difference that clearly IF the color mask does not match perfectly, it doesn't matter from any practical standpoint. You're not generally going to mix the two stocks in the same scene.
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#5 John Pytlak RIP

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Posted 21 July 2005 - 01:59 PM

David is correct. Slight differences in D-min have no effect on the final image -- they are compensated during the color timing/grading process.

Why would you expect different films to have exactly the same formulation and D-min?

If your process is causing fogging, or if the stock is old or has been stored improperly causing the D-min to increase significantly, then you do have a problem that could affect image quality.
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#6 Dominic Case

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Posted 21 July 2005 - 08:26 PM

I know about the Internal masking in the negative which produce these amber color in the base.

But read John's reply again. The amber colour is NOT in the base. It is in the emulsion layers as a result of the colour couplers that form the y, m, c dyes in the exposed areas of the film.

The colour that you see is due to these couplers and also due to any heat or age fog which causes the d-min of each emulsion layer to rise. As manufacturers improve their products, they find that different amounts of colour coupler and different properties of the emulsion lead to the best image results on the screen. If they attempted to keep to one d-min and masking colour for all emulsions,, you would have inferior image performance.
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