Best B+W Film for Halation and Irradiation/Scatter Control

[Nikonic]

Which are the best commercial films available for control of halation and "irradiation" (apparently not the proper term) or scattering of light from highlights through the emulsion?

I'm looking to reduce softness and scatter around some intense highlights as much as possible.

Reading through previous threads on anti-halation backings and dyes, it seems I'm asking the opposite question to what most people ask—which is "how do I remove the anti-halation layer on my film"?

I'm asking which commercially available emulsion is best at controlling halation and light scatter.

Thank you!

-Nikonic

 

[Gerald C Koch]

A slow speed film which has a thin emulsion would best protect against light scatter in the emulsion. Using one with a surface acting developer such as the Beutler formula would be a good combination. Such developers exhaust themselves rapidly and thus only develop the top layer of the emulsion. In addition the Beutler method requires the thinnest negatives that will provide good shadow detain. Reducing the exposure would also reduce light scatter.

Of course a remjet coating would provides the best anti-halation effect but they are only used for color cine films. AFAIK the antihalation coatings of first tier films is very good and probably of equal effectiveness. You should avoid any films intended for surveillance work or microfilming as these usually do not have an anti-halation coating.

 

[Nikonic]

Hmmmm, very good thoughts, thank you.

So a thinner emulsion coating is better for controlling irradiation because there is simply less room—less distance and less physical material—for light to scatter through. Any scatter will be able to migrate a shorter horizontal distance across the emulsion of a thin emulsion film than a thick one. This reminds me of point spread.

Whereas dyes incorporated into the emulsion layers and backings on the back of the film substrate are better for controlling halation.

Halation is primarily caused by light bouncing off the film base back into the emulsion.

Does halation only occur when light bounces off the back of the transparent film base?

Does light ever bounce from the interface of the emulsion on the front of the substrate back into the emulsion? That is, there are two surfaces to the film base, the front upon which the emulsion is adhered, and the back. Why is the back of the film base the source of primary bounce rather than the front?

This reminds me about the little bit I know about fiber optics.

 

[Nikonic]

Also does anyone know what is in "Remjet"? What it's actually made of and how it is applied?

EDIT: Possibly this: https://www.google.com/patents/US23...ved=0ahUKEwii-7bIv4LKAhVIcT4KHYJECZYQ6AEIIzAB

 

[AgX]

Of course a remjet coating would provides the best anti-halation effect but they are only used for color cine films. AFAIK the antihalation coatings of first tier films is very good and probably of equal effectiveness. You should avoid any films intended for surveillance work or microfilming as these usually do not have an anti-halation coating.

The best location for an anti-halation layer is not the back-side of the base (as is the case with the remjet layer), but between the emulsion and the base.
But some films have got them combined with a non-curling layer at the back.

I do not know of halation problems with microfilms used for pictorial work. But chances are there.

 

[RobC]

Just look at the quoted potential "resolution" figures for each film. The higher that is the the less halation there will be.

See following which mentions antihalation coating:

http://www.adox.de/Photo/adox-films-2/cms-20-ii-adotech-ii/

 

[Nikonic]

I do not know of halation problems with microfilms used for pictorial work. But chances are there.

Out of curiosity, are there any microfilms left in 4x5?

I remember tech Pan. ADOX CMS 20 as linked above, appears to be for pictorial work, though I wonder if it is a microfilm that's bent to continuous tone pictorial with the special developer they demand you use.

Thanks

 

[Gerald C Koch]

The best location for an anti-halation layer is not the back-side of the base (as is the case with the remjet layer), but between the emulsion and the base.
But some films have got them combined with a non-curling layer at the back.

Any anti-halation coating must be removed when the film is processed. A remjet coating being insoluble must be on the back of the film. Any coating between the emulsion and the base must be removed either by being decolorized or by some other method. I am afraid that I was sidetracked by the effectiveness of the various types of coatings and did not consider their placement. Which brings up another point. A film manufacturer will use a coating that matches the film. So in reality the coatings for general purpose films are probably equally effective for their intended purpose. Note the qualifier "general purpose" which removes special purpose films from being considered. However no coating is perfect and the film user must avoid those lighting situations that cause halation such as back lit subjects.

 

[AgX]

Out of curiosity, are there any microfilms left in 4x5?

Yes, a bit larger though. You will have to cut sheets to size.

Agfa makes it for EPM.