• Welcome to Photrio!
    Registration is fast and free. Join today to unlock search, see fewer ads, and access all forum features.
    Click here to sign up

Polarisers on Enlarger lenses?

"This student is really kinda strange. I haven't said anything in months and he still comes around. I know! I'll throw a polariser under the enlarger and really make him confused...he'll wonder about this for years to come!"
 
More intriguing than that Flat Earth theory is that Hollow Earth theory, stating that we actually live in a world at the inner side of a sphere, not on the outer side.
 
AgX said:
More intriguing than that Flat Earth theory is that Hollow Earth theory, stating that we actually live in a world at the inner side of a sphere, not on the outer side.
Click to expand...

That's a delusion, not a theory.
 
It makes perfect sense if your skull is likewise hollow.
 
So what is your hypothesis of what a theory means?
 
Now that we're totally of topic, I can say that I've actually photographed the memorial statue of the man who came up some of the "hollow earth theory." it's located in Hamilton, Ohio. Dead Link Removed
 
ckpj99 said:
Now that we're totally of topic, I can say that I've actually photographed the memorial statue of the man who came up some of the "hollow earth theory." it's located in Hamilton, Ohio. Dead Link Removed
Click to expand...

On the base of that statue, is there an inscription describing what he was smoking/drinking/snorting/injecting??
 
Several years have passed without new contributions to this thread, and I can tell you that the use of polarized light combined with a polarizing filter for black and white enlargements was a common practice in the commercial laboratories that Agfa-Gevaert had in Buenos Aires. Fixed gradation papers were used (not variable contrast) and the contrast of very contrasted negatives was diminished by attenuating them a little with the polarizing filter. This is because the denser parts of the negative maintain the colloidal properties of the photographic emulsion and slightly depolarize the light that passes through them, while the lighter parts do not. By slightly blocking the passage of polarized light with the filter, differential control is gained over the light passing through the shadows and highlights.
 
Basic physics tells us that polarized light can become de-polarized when scattered by the emulsion, but not necessarily the other way around.

 

When was this? Was this for printing smaller negatives like 35mm, 4x4 cm , 6x6 etc or large format? A lot of this knowledge is gone. Welcome to Photrio!!!
 
ic-racer said:
Basic physics tells us that polarized light can become de-polarized when scattered by the emulsion, but not necessarily the other way around.

View attachment 348908
Click to expand...

The article you posted gives an example of how polarized light can be partially depolarized by scattering, but it says nothing about whether unpolarized light can become partially polarized by scattering. In fact, scattering often does polarize light: this is why reflections off some surfaces are polarized. The amount of polarization depends on the dielectric properties of the scattering medium. For example, https://sciencedemonstrations.fas.harvard.edu/presentations/polarization-scattering

I don't know, of course, whether scattering in the film emulsion was the real effect that the OP's master printer was trying to control with the polarizer. Printing (especially, I imagine, printing at very large sizes) is a craft that has a lot of empirically derived practices that should be physically justifiable after the fact, but aren't easy to deduce from theory in the absence of practice.
 

That is a fish tank not film. The reference I posted referred to effects of light scatter on photography film, though the fish tank experiment may also hold for film. Someone should put a polarizer on an enlarger and show the images to see what it does.
 
Last edited:
Let's see: Enlarger with polarized light source. Light passes through negative. The light that passes through the densest areas (highlights on the negative) is scattered more, hence, depolarized more. That "more-depolarized" light then passes through the lens and through another polarizing filter, which, depending on its orientation, can remove some of the depolarized light or (more importantly here) remove a portion of the polarized light, while not affecting the depolarized component. This latter would result in a reduction in overall contrast. Sounds like it might work.

The big question now: who's going to try it and report back

Doremus
 
A polarizing filter would have no significant effect unless the light coming from the enlarger itself was polarized first. Cross-polarization at copy stations is fairly routine practice when glossy reflective copy is involved. So how was that achieved in the enlarger head itself? We could each guess. But has anyone ever seen inside an enlarger head so equipped? A polarizing filter merely over the lens can't do it by itself.

First guess : a tungsten point light source with a polarizing sheet in the filter drawer above the lens stage.
 
Mmm.... I wonder if there is a quiet talented printer who never revealed what it was he was doing to Stephen and then placed a bet with a betting company that this would stimulate a short but vigorous debate on a small quiet talented photographic forum that would not reach a conclusion AND would be revived by a new member some 10 years later where a point v counterpoint debate would start again with no conclusion

This bet probably sounded so extraordinary that the company gave him astronomical odds. The quiet but talented printer is now about to become richer than Elon Musk, the betting company will file for bankruptcy, the Corleone family will pull out of its Las Vegas casino empire in fright and we shall never be any the wiser

Someone like Matt King who was a moderator then and with at that point a 10 year oversight on APUG behaviour could have prevented all of the above consequences had the betting company had the good sense to contact him

However it did not contact him and history shows that terrible consequences can follow tiny events such as the one Stephen Frizza describes all those years ago when a quiet talented printer did something strange with a polariser and no-one asked him why, or did they ask but never joined APUG to tell us the answer?

pentaxuser
 
mshchem said:
When was this? Was this for printing smaller negatives like 35mm, 4x4 cm , 6x6 etc or large format? A lot of this knowledge is gone. Welcome to Photrio!!!
Click to expand...

I guess anakhan is referring to the 50's and 60's when agfa manufactured photographic paper as did ferrania in Argentina. As for the type of film, in which this method was used, I don't think it was LF. It was almost non-existent in Buenos Aires.
As for the lost knowledge is a great truth, it is very difficult for me to get my father and his brothers to remember their methods, after 30 years that they left the profession.

Photo of a box of Agfa Argentina photographic paper of the time.
 

Attachments

  • agfa.jpg
    202.9 KB · Views: 87
Nopo said:
I guess anakhan is referring to the 50's and 60's when agfa manufactured photographic paper as did ferrania in Argentina. As for the type of film, in which this method was used, I don't think it was LF. It was almost non-existent in Buenos Aires.
Click to expand...
It just seem strange that as little as 10 years ago a talented printer seem by Stephen Frizza had decided to stick with graded paper and this method of a polarising filter. Maybe this was so unique a method that none of us with the exception anakhan knows anything about it? Hence the speculation as to how it achieved whatever it achieved

I presume that whatever this was, Stephen is not in a position to say what the prints were like nor what paper this quiet talented printer was using in terms of single grade or MG nor can he presumably compare any difference between the polarised print and what an ordinary print from that negative looked like

Maybe it was something that he used for all his negs rather than just those he thought needed the polariser Maybe after 10 years Stephen cannot shed more light on these or any of our questions

Maybe after 10 years he considers it a subject confined to history until it was resurrected

I have placed a bet with a betting company as to how long it will continue to generate interest.

pentaxuser
 
You must log in or register to reply here.
Menu
Log in
Register