Maco IR film base compared to Kodak HIE and Antihalation layers

["Rolland Elliott" <rolland_elliott@xxxxxxxxxxx>]

I've been developing Maco 820 IR and Kodak HIE as slides over the past 
couple of weeks.  Just wanted to post a few quick observations for anyone's 
benefit.

1) When you strip off the emulsion from the Maco IR 820 you have a crystal 
clear base , just like they claim. When you strip off the emulsion from 
Kodak HIE, you have a crystal clear base TOO!  Therefore, Maco doesn't 
really have any real advantage here. In addition Maco IR is about 6 stops 
slower (Yes you read that correctly, about 6 stops slower!) than HIE when 
both are developed using Kodak's Tmax reversal kit. This difference in 
sensitivity is based on using an 87 filter with Kodak HIE and an 89b filter 
with Maco 820 IR. Typical daylight exposure for HIE is 1/100 @ f/16, for 
Maco 820 IR it's 1 second at f/16. Big difference!

2) Under normal light HIE has a bright green color and Maco 820 IR has a 
dark blue color due to it's antihalation layer.  I then looked at Maco 820 
and Kodak HIE unexposed film through my IR camcorder (with 88A filter over 
the lens). Surprisingly both of them look the same, a very light gray tone. 
Both of these bases allow IR light to pass freely through them.  It is my 
conclusion that Maco IR film's anti-halation coating is only effective for 
deep red wavelengths of light, not near IR light.

Furthermore, I think the reason Kodak doesn't have an antihalation coating, 
is that it wouldn't be effective in blocking IR light! Afterall these 
antihalation coatings are just dyes, and many people have noted that the 
dyes used in darkly colored clothes don't block IR light at all; instead of 
showing up dark in IR photographs many clothes are light colored/toned. Is 
there a dark colored dye out there that blocks IR light? Probably. Is there 
one that can economically be used in an antihalation layer? Maybe not?

Peace Rolland Elliott
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