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What's a double interpositive?


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#1 Jim Hyslop

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Posted 06 December 2008 - 10:05 AM

Hi,

I've been reading the American Cinematographer Manual. The article "Comparison of Film Formats" (page 25 in the 9th edition) refers several times to "double IPs" but doesn't define what a double IP actually is. In each case, it's referring to cross dissolves, titles, or other optical effects.

I know what an IP (interpositive) is, but what's a double-IP?
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#2 Simon Wyss

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Posted 06 December 2008 - 11:44 AM

Double interpositives can be seen as true duplicates of a double-band original in the formats 35-CinemaScope or, more often, in 16mm. Whatever form the original (negative) is in, you have two bands, usually called A and B band, that permit those overlapping effects.
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#3 Jim Hyslop

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Posted 06 December 2008 - 07:58 PM

Double interpositives can be seen as true duplicates of a double-band original in the formats 35-CinemaScope or, more often, in 16mm. Whatever form the original (negative) is in, you have two bands, usually called A and B band, that permit those overlapping effects.

Thanks for the reply, Simon.

I'm not sure I quite follow you. Let me quote one of the places the term is mentioned. The section of the article is listing the disadvantages of shooting 1.85:1 on 35mm film:

"3. Photographic opticals (dissolves, repositions, etc.) tend to be grainier than anamorphic 2.40. However, when created digitally or within the Digital Intermediate process, opticals will appear seamless.
"Another technique is for editors to order 'double IP' opticals, compensating for the smaller negative area of 1.85. This improves the quality of photographic opticals, but at greater expense."

Could "double IP" in this context mean "double-size", i.e. using 65mm film for the interpositive?

Oh, I just thought of something. It seems to me there are two places in the workflow where the optical effects can be done: from the camera original negatives onto a single interpositive, or from two interpositives onto the internegative. Maybe the first one is the standard procedure, but the "double IP" opticals would use the second technique. Although I don't see how that would improve the quality of the opticals. Grasping at straws here!
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#4 David Mullen ASC

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Posted 06 December 2008 - 08:59 PM

It sounds like they are referring to the old trick of making two interpositives off of the same negative and combining them to make a new dupe negative, in order to reduce the grain build-up from duping. This practice died down as the last few generations of color intermediate stock got better by the mid-to-late 1990's, with hardly much increase in grain between the IP and IN steps.
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#5 Jim Hyslop

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Posted 06 December 2008 - 09:41 PM

It sounds like they are referring to the old trick of making two interpositives off of the same negative and combining them to make a new dupe negative, in order to reduce the grain build-up from duping. This practice died down as the last few generations of color intermediate stock got better by the mid-to-late 1990's, with hardly much increase in grain between the IP and IN steps.

Ah, I see. Thanks for the clarification. That makes sense now.

Except.... if the practice has died down, how come it's still mentioned in the latest American Cinematographer Manual? Guess that's more a question for the editors of the manual, though :-)
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#6 K Borowski

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Posted 06 December 2008 - 10:09 PM

This practice died down as the last few generations of color intermediate stock got better by the mid-to-late 1990's, with hardly much increase in grain between the IP and IN steps.


And apparantly the practice of improving intermediate stocks died down at Kodak too. Besides completing the transition to Estar and silver-free soundtracks, has there been *any* improvements in print stock since Vision circa 1996?
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#7 David Mullen ASC

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Posted 06 December 2008 - 11:13 PM

And apparantly the practice of improving intermediate stocks died down at Kodak too. Besides completing the transition to Estar and silver-free soundtracks, has there been *any* improvements in print stock since Vision circa 1996?


The current color intermediate stock, 5242, was introduced in 2001. Vision 2383 and Vision Premier 2393 print stocks came out in 1998. But they all have been tweaked over the years since then.
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#8 K Borowski

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Posted 09 December 2008 - 09:03 AM

The current color intermediate stock, 5242, was introduced in 2001. Vision 2383 and Vision Premier 2393 print stocks came out in 1998. But they all have been tweaked over the years since then.


Sorry, I think I was recalling the '98 number. Didn't see '42 mentioned in any of the Kodak film chronologies. Even still, 7 years is quite a long time when you consider that that is enough time for Kodak to go through two iterations of film improvements (or at least two iterations of improved marketing campaigns :rolleyes: )

It's good to know that they have been tweaking them though. What changes have you noticed in them since '98 David?

One of the things that will forever irk me about the Big K is that they will improve things without letting you know, and let you know about a product through renaming it even though there have been no changes made!

I remember one time they renamed a 100-speed C-41 film as a 200-speed film, even though they made no changes whatsoever!
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#9 David Mullen ASC

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Posted 09 December 2008 - 11:44 AM

Mainly they monkey around with contrast within the first two years of a stock's release, to fine-tune it and answer customer complaints. Sometimes they also make adjustments to match lab practices regarding development. Vision 2383 print stock is the most obvious example -- everyone complained it was too contrasty when it was released, so Kodak reduced the contrast. Now that everyone is used to more contrast in prints, and D.I.'s and stocks seemed to have gotten flatter-looking, now Vision 2383 looks a bit low in contrast.

But at the time Vision 2383 was originally released, most people were shooting on EXR neg stocks and were used to the combination of that contrast with the contrast of the previous print stock ('86 I think). Basically Kodak decided at the time to start lowering the contrast of the neg stocks and increasing the contrast of the print stocks to compensate.
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#10 Dominic Case

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Posted 09 December 2008 - 05:17 PM

Even still, 7 years is quite a long time when you consider that that is enough time for Kodak to go through two iterations of film improvements (or at least two iterations of improved marketing campaigns )

Although there are many other areas in which stocks can be tweaked (contrast, colour fidelity, fade resistance of the dyes, etc), it is the relationship between speed and grain that has always been the most testing part of a film emulsion's characteristics.

And this is most crucial in camera negative: which is also the area in which Kodak's traditional business is most threatened (by their filmstock competitor as wll as by digital capture).

So you can expect to see the most dramatic changes in camera negative stocks - progressively better speed/grain ratios, better shadow grain etc.

Those improvements do flow through to intermediate stocks: but grain and speed aren't really issues in print film. However, there are constant tweaks there- in no less important properties such as the durability of the emulsion (and the base) on multiple runs through projectors, various behaviours during processing, etc.
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#11 Brian Pritchard

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Posted 10 December 2008 - 05:49 AM

Although there are many other areas in which stocks can be tweaked (contrast, colour fidelity, fade resistance of the dyes, etc), it is the relationship between speed and grain that has always been the most testing part of a film emulsion's characteristics.

And this is most crucial in camera negative: which is also the area in which Kodak's traditional business is most threatened (by their filmstock competitor as wll as by digital capture).

So you can expect to see the most dramatic changes in camera negative stocks - progressively better speed/grain ratios, better shadow grain etc.

Those improvements do flow through to intermediate stocks: but grain and speed aren't really issues in print film. However, there are constant tweaks there- in no less important properties such as the durability of the emulsion (and the base) on multiple runs through projectors, various behaviours during processing, etc.

It is quite surprising how few intermediate stocks there has been over the years compared to camera stocks.
1956 - 1976 5253
1976 - 1992 5243
1992 - 2001 5244
2001 5242

Brian
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