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#1 L K Keerthi Basu

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Posted 10 September 2005 - 11:02 AM

This is a basic question but I dont know whether this is a valuable .Why the contrast Decrease when the ASA increases am I right? Why this happens? Why the sound negative films are developed to a higher Gamma value like 2.8 to 3.5?
In B/W motion picture films the negatives developing times are according to the ASA rating, but this not applicable in the Color films is it because of the DYEs?
Iam asking this because after shooting we can alter the contrast of the film during the developing if the cinematographer desires.
Why the Gamma values of both the negative and positive are fixed to a particular values? Is there any other reason other then Product Gamma?
Please forgive me for asking these silly questions.

Awating for the reply,

L.K.Keerthibasu
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#2 David Mullen ASC

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Posted 10 September 2005 - 03:44 PM

I don't think there's a gradual decrease in contrast as the speed increases -- the currect Vision-2 100T, 200T, and 500T are all very well-matched for contrast.

But generally there is a belief that the faster films have more exposure range recorded because they have both fast and slow-speed layers in each color. However, I don't know if there's a speed in which they start using two-speed layers, or if they all do these days except for maybe EXR 50D.

Obviously unless the stock manufacturer is designing a low-con negative, they generally try to match the gammas in a range of stocks of different speeds.
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#3 Dominic Case

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Posted 11 September 2005 - 07:42 PM

This is a  basic question but I dont know whether this is a valuable .Why the contrast Decrease when the ASA increases am I right?


Wrong. Contrast remains more or less the same over the whole range of negative stocks. Otherwise you couldn't cut them together and print them onto the same roll of print stock.

Why the sound negative films are developed to a higher Gamma value like 2.8 to 3.5?

Sound negative is essentially a black line on a clear (unexposed) background. Shades of grey are irrelevant: so gamma is very high to ensure the most rapid transition from clear to black (and therefore the sharpest edge to the line).

In B/W motion picture films the negatives developing times are according to the ASA rating, but this not applicable in the Color films is it because of the DYEs?

False premise. True, different emulsion types require different developing times, but this is related to the overall design of the emulsion, not just its speed.

For many years there was only one colour negative type: when others were introduced, they followed the same processing requirements for ease of use in the lab. Also, in most processing machines, dev time can only be varied by changing running speed: this affects bleach, fix, wash times as well. It was always going to be easier for manufacturers to standardise the process throughout. (And easier for labs to process all types together.

  Iam asking this because after shooting  we can alter the contrast of the film during the developing if the cinematographer desires. 
  Why the Gamma values of both the negative and positive are fixed to a particular values? Is there any other reason other then Product Gamma?

Variation of development time does affect contrast, and in b/w this is a useful tool. However, in colour processing, the different colour layers react differently to time variations. It takes time for the developer to get through to the bottom (cyan) layer, whereas it starts immediately on the top (yellow) layer. So the emulsion is designed to be much more resistant to processing change.

Please forgive me for asking these silly questions.

<{POST_SNAPBACK}>

OK. That's what this site is for, isn't it?
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#4 L K Keerthi Basu

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Posted 12 September 2005 - 10:57 AM

Thank you Mr. Dominic and Mr. David. I still have a question ,what is the way to bring the negative very contrast? I don't want to do this in lighting the scene. Is there any possiblities to do this in developing(color negative)? A contrast look like a picture photographed as that in a pan sound negative.

L.K.Keerthibasu

Edited by l.k.keerthibasu, 12 September 2005 - 11:05 AM.

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#5 David Mullen ASC

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Posted 12 September 2005 - 11:08 AM

There is a mild increase in contrast when you push process, but the stocks are resistent to changes in processing. There is also a mild increase when you print down a denser negative.

My suggestion would be to push one stop but not underexpose to compensate, and then print down the extra density.

There are ways of adding contrast in the print, from the minor boost from using Vision Premier, to silver retention processes.

If this is for telecine transfer only or D.I., then contrast can be added digitally.

The only way to achieve a serious increase in contrast in the color original would be to shoot color reversal, or even cross-process color reversal. Or skip-bleach process the negative.

Test, test, test.
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#6 L K Keerthi Basu

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Posted 12 September 2005 - 11:24 AM

There is a mild increase in contrast when you push process, but the stocks are resistent to changes in processing. There is also a mild increase when you print down a denser negative.

My suggestion would be to push one stop but not underexpose to compensate, and then print down the extra density.

There are ways of adding contrast in the print, from the minor boost from using Vision Premier, to silver retention processes.

If this is for telecine transfer only or D.I., then contrast can be added digitally.

The only way to achieve a serious increase in contrast in the color original would be to shoot color reversal, or even cross-process color reversal.  Or skip-bleach process the negative.

Test, test, test.

<{POST_SNAPBACK}>


Thank you Mr. David,

Iam actually trying to bring this effect in my project work which was shot in the total daylight. My expectation is to bring the negative to a gamma of 2.1 to 2.4 from 0.55 without the colors desaturated. The look should be a compressed tonal reproduction in the midtones. I have tested with the Bleach bypass but the colors are desaturated.


L.K.Keerthibasu
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#7 David Mullen ASC

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Posted 12 September 2005 - 11:42 AM

  Iam actually trying to bring this effect in my project work which was shot in the total daylight. My expectation is to bring the negative to a gamma of 2.1 to 2.4 from 0.55 without the colors desaturated.

<{POST_SNAPBACK}>


There is no way of doing this to a negative without severely screwing up the colors, I suspect, not without being able to take over a lab and experiment with your own processing chemicals, and even then, you are likely the screw up the linearity of the color response and create odd biases.

The simplest way to get that high a gamma with accurate colors is to shoot 5285 Ektachrome E6. But you'd have to dupe it to an I.N. Or cross-process it, but then the color accuracy is lost. Or make a print of the negative and use that print as a positive original and make an I.N. off of it.

You can't expect to be able to do anything you want to an image without resorting to complex post techniques; you can't simply alter the basic look designed into a color negative without some sacrifice in quality.

Besides, you said you SHOT the project already, so at this point, adding contrast has to be done to another generation or digitally.

Why are you asking this question now instead of before you shot it?
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#8 John Pytlak RIP

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Posted 12 September 2005 - 07:12 PM

Thank you Mr. David,

  Iam actually trying to bring this effect in my project work which was shot in the total daylight. My expectation is to bring the negative to a gamma of 2.1 to 2.4 from 0.55 without the colors desaturated. The look should be a compressed tonal reproduction in the midtones.  I have tested with the Bleach bypass but the colors are desaturated.
L.K.Keerthibasu

<{POST_SNAPBACK}>


A four-fold increase in color negative gamma is well beyond the realm of normal process adjustment. :blink:

The only thing I can think of would be to experiment with a much more active developing agent, perhaps switching from CD-3 to CD-2. The process would then be so abnormal that all bets are off of maintaining any semblance of matched curve shape.

Increasing contrast by that amount doesn't "compress" tonal range, it would yield a negative where only a small range of tonality could ever find its way to the screen in a print or transfer. :rolleyes:
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#9 Dominic Case

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Posted 12 September 2005 - 09:44 PM

If you've already shot your material, then you can't do much with the negative.

Anything you do that increases negative gamma to 2 or more will have a very odd effect on the image - and colour reproduction is likely to be very unpredictable too. But if you haven't shot yet, then shooting on positive print stock is one possibility - though that would give you a gamma about double what you want.

Another possibility is making a print fom your conventional negative, and using that as an IP, then printing a DN from that. The lab will have to know what you want, know what it's doing (for example, in making the DN they will have to add an orange filter to correct the balance, as the DN stock is expecting to see a masked IP), and they will have to want to play around in this way - and charge you appropriately, of course.

Everything that David and John have said holds true for the unpredicatbility or infidelity of colour reproduction if you use this - or any other - deviant photochemical method. These stocks and processes were designed for accurate and true repeatability, rather than for creative flexibility. If you want that . . . go digital!
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#10 L K Keerthi Basu

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Posted 13 September 2005 - 10:21 AM

Thank you Mr.David,Mr.John and Mr.Dominic,

Actually the director has decided this after shooting the project, thats why Iam asking this. I know this is a painful work. I will put tests on your suggestions.

Thank you once again.

L.K.Keerthibasu

Edited by l.k.keerthibasu, 13 September 2005 - 10:24 AM.

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