LUT & ENR

[Walter Ryans]

Hi. I'm new to this forum and to cinematography. I was just reading American Cinematographer about Shutter Island. They keep talking about LUT and ENR, but I do not know what they stand for. I figured someone here would know.

 

Thank You.

[Stuart Page]

ENR basically uses chemical bath treatments during the printing process to retain a controlled amount of silver in the negative, adding density and contrast to shadows and blacks generally. Also, pushing for an even harsher look for selected scenes, filmmakers added a bleach bypass treatment on top of the ENR look for those sequences. Both are processes Kaminski has used extensively in the past for Spielberg, such as in the famous opening sequence of Saving Private Ryan.

 

For LUT definition go here http://www.theasc.com/magazine/april05/conundrum2/page5.html

[David Mullen ASC]

ENR basically uses chemical bath treatments during the printing process to retain a controlled amount of silver in the negative, adding density and contrast to shadows and blacks generally. Also, pushing for an even harsher look for selected scenes, filmmakers added a bleach bypass treatment on top of the ENR look for those sequences. Both are processes Kaminski has used extensively in the past for Spielberg, such as in the famous opening sequence of Saving Private Ryan.

 

ENR is actually a print-only process because it involves adding extra b&w processing tanks to the ECP-2B print processing line. Unlike simply skipping the bleach step, which can be done in either the ECN-2 negative processing or ECP-2B print processing, ENR at Technicolor (and CCE & ACE at Deluxe, and perhaps OZ at Technicolor) all involve additional processing in a b&w bath to permanently develop a certain amount of silver so that a certain percentage can still be removed in the bleach, fix, and rinse steps.

 

But in this case, they are talking about a digital simulation (using a LUT) of an image that was printed with the ENR process, i.e. higher contrast, deeper blacks, and less color saturation.

 

The basic idea with a skip-bleach process is that in normal color processing, an equal amount of color dye is formed while exposed silver halides are being processed into silver, and then the bleach step converts silver back into silver halide so that it is all removed in the fix and rinse steps, leaving only the color dye clouds. If you skip the bleach step, you leave all the developed silver in the film as well as the color dye clouds. The ENR print process allows you to control the percentage of silver that remains after processing rather than just have all or none of it.

[Walter Ryans]

Thanks for the replies. So ENR is a process that allows you to control the amount of silver left in the negative and is done chemically. LUT is a digital approach. But what exactly is LUT? Is it a process, a digital system like a DaVinci? Sorry for the novice questions and thank you in advance.

 

 

ENR is actually a print-only process because it involves adding extra b&w processing tanks to the ECP-2B print processing line. Unlike simply skipping the bleach step, which can be done in either the ECN-2 negative processing or ECP-2B print processing, ENR at Technicolor (and CCE & ACE at Deluxe, and perhaps OZ at Technicolor) all involve additional processing in a b&w bath to permanently develop a certain amount of silver so that a certain percentage can still be removed in the bleach, fix, and rinse steps.

 

But in this case, they are talking about a digital simulation (using a LUT) of an image that was printed with the ENR process, i.e. higher contrast, deeper blacks, and less color saturation.

 

The basic idea with a skip-bleach process is that in normal color processing, an equal amount of color dye is formed while exposed silver halides are being processed into silver, and then the bleach step converts silver back into silver halide so that it is all removed in the fix and rinse steps, leaving only the color dye clouds. If you skip the bleach step, you leave all the developed silver in the film as well as the color dye clouds. The ENR print process allows you to control the percentage of silver that remains after processing rather than just have all or none of it.

[David Mullen ASC]

Thanks for the replies. So ENR is a process that allows you to control the amount of silver left in the negative and is done chemically. LUT is a digital approach. But what exactly is LUT? Is it a process, a digital system like a DaVinci? Sorry for the novice questions and thank you in advance.

 

Didn't I just say that the ENR process was for prints only?

 

A LUT is a Look-Up Table.

http://en.wikipedia.org/wiki/Look_up_table

http://en.wikipedia.org/wiki/3D_LUT

They are just a set of image parameters created to transform an image, often to create the correct gamma for the display device without affecting the original files. Think of it as a pre-set look that then can be applied to an image without actually editing the original file -- either for just viewing, or to be applied and recorded as a new image. They are used in software based color-correction systems.

 

So it's a bit different than normal color-correcting in the sense that applying the LUT does an automatic overall adjustment to the values in the image. Of course, to create the LUT you may have worked in a color-correction system.

[Adrian Sierkowski]

LUT just stands for Look Up Table. Think of it as a way of approximating on a monitor what a final version will look like. It's designed to "map" the values of one medium onto another, in essence.

For example, film can record a lot more information than most monitors can show, so we use a LUT to make the monitor look "closer" to how the film will look. Same goes for monitoring digital sources, such as a Genesis camera or the like... or for a basic understanding, just run through your computer monitors color calibrations... those are essentially LUTs.

[Sean Lambrecht]

LUT- Look Up Table. I'm just sure I'd mangle an adequate explanation to some degree. Try these:

 

http://www.lightillusion.com/usingluts.htm

 

http://en.wikipedia.org/wiki/3D_LUT

 

Peace,

S-

 

 

Edit: David and Adrian seem to be up earlier than me. What they said... :rolleyes:

[Dominic Case]

ENR is actually a print-only process because it involves adding extra b&w processing tanks to the ECP-2B print processing line. Unlike simply skipping the bleach step, which can be done in either the ECN-2 negative processing or ECP-2B print processing, ENR at Technicolor (and CCE & ACE at Deluxe, and perhaps OZ at Technicolor) all involve additional processing in a b&w bath to permanently develop a certain amount of silver so that a certain percentage can still be removed in the bleach, fix, and rinse steps.

In fact the sequence for ENR/CCE/ACE is slightly different. In a normal process the film goes through the developer, which produces a silver image and a colour dye image. Then after the stop it goes through a first fixer to remove the unexposed silver halide. Then through the bleach to convert the silver image back to silver halide (ionised silver), which can then be removed in the second fixer. All that's left is the colour dye image.

 

In the ENR etc process, after the bleach converts the silver image back to silver halide, the film is run through a black & white developer, which simply reverses the process of the bleach - but to a partial, controllable extent. As a result you end up with just as much of a silver image in additon to the colour dye image as you want.

 

It seems convoluted,but it is the way you get complete control of the extent of the effect. In comparison, the bleach bypass process simply skips the bleach (as the name suggests) leaving you with a full silver image. It's an all-or-nothing process. Some labs may offer "partial bleach bypass" but the bleaching operation is far less controllable than development, so the results aren't really reliable.

 

Finally, ENR, ACE, CCE cannot be done in the negative process because there is no first fixer. Hypothetically I guess a lab could convert their neg process to allow a first fixer as well as a redeveloper etc: but it's probably not a viable option.

[David Mullen ASC]

Thanks, I knew you could explain the development steps more accurately than me!

[Keith Walters]

Hi. I'm new to this forum and to cinematography. I was just reading American Cinematographer about Shutter Island. They keep talking about LUT and ENR, but I do not know what they stand for. I figured someone here would know.

 

Thank You.

For an explanation of Look Up Tables (and in particular, what Floating Point Look Up Table - FLUT - means ) keep an eye on the "pinned" discussions at the top of the RED folder. The significance of these terms are somewhat difficult to explain meaningfully unless you're an electronics engineer, if you try to avoid excessive Jargon and hand-waving :rolleyes:

 

Hopefully over the Easter break I'll have time to get back to that project, and start on a couple of others.