Mystery item: Optician's red filter

[syncrasy]

Another mystery item from my dad's darkroom...

This is a vintage 6" handled red glass filter. The red disc is about 2.5" wide. The metal handle is marked "Belgard, Inc. Opticians, Chicago."

1. What would an optician have used it for?
2. What might it have been used for in a darkroom? Selective dodging?

Thanks!

 

[AgX]

Selective dodging... interesting. I mean, in contrast to shading by use of an non-transparent shade here you still see what is shaded.
To what extent this is actually benefitial I am not sure yet.

 

[syncrasy]

I just realized dodging is by definition "selective" so perhaps that was poor word choice. Perhaps I should have said "reduced strength" or "soft" dodging. Then again, would a red filter actually reduce the intensity of the light of a b&w enlarger?

 

[Az Prospector]

I just realized dodging is by definition "selective" so perhaps that was poor word choice. Perhaps I should have said "reduced strength" or "soft" dodging. Then again, would a red filter actually reduce the intensity of the light of a b&w enlarger?

It isn't, so much, reducing the light intensity as it is the lack of sensitivity of the paper to red light.

 

[syncrasy]

I just found this in another forum...

I also use it [red filter] for burning and dodging so I can place the wand to the right place before going for it. This was a lot more important with the Condenser enlarger I used to use which gave very short printing times, now with the diffuser type I use it wouldn't be absolutely necessary I assume. Still, it has become a habit and wouldn't want to stop doing it.

https://www.photrio.com/forum/threa...to-get-best-picture-area.138695/#post-1811723
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Maybe that's what my dad used it for -- as a "preview" tool, in conjunction with his regular dodging wands.

 

[pentaxuser]

[QUOTE="syncrasy, post: 2310479, member: 88310"
Maybe that's what my dad used it for -- as a "preview" tool, in conjunction with his regular dodging wands.[/QUOTE]
Sounds good to me. I think that's the answer I get my dodging tool in exactly the right place by shielding the whole illuminated projected picture with my safety red filter and then flip it out of the way

pentaxuser

 

[AnselMortensen]

Maybe it was originally used to test for color-blindness ?

 

[syncrasy]

Maybe it was originally used to test for color-blindness ?

That's what I was thinking, too. A little more Googling reveals that this is probably an "eye occluder." There are versions of the tool that feature both a plain red lens and a Fresnel-like red lens called a "Maddox Rod" lens (https://www.fresnel-prism.com/produ...ofessional-occluders/maddox-rod-and-red-lens/). It seems the Maddox Rod lens was used to test for lateral and vertical phoria of the eyes (muscle balance) and the plain red lens was used to test for double vision (perhaps in addition to testing for color blindness.)