Polarisers on Enlarger lenses?

[Light Capture]

The reasoning is twofold. Polarization and UV. UV is probably more important.

Light sources produce unpolarized light but if you use diffusion enlarger with filters, film and lens in part diffractions might polarize either areas of image or whole image if they happened in diffusion chamber area (Durst 2501 has a very large diffusion chamber). I can't say whether amount of scattering and reflections present in an enlarger is enough to make a difference.

As per CTEIN's book Post Exposure UV light is very visible and causing focus shifts that reach up to 15mm with some variable contrast papers. This is not applicable for older graded filters.
Focus shift reaches down to 2-4mm with strong UV filtering.

This is quote from Tiffen's Circular Polarizer specifications:
'This filter eliminates ultraviolet rays from outdoor shots as well as polarizing the light to remove reflections, and increase color saturation, without affecting the overall color balance'

These detrimental effects don't affect image very visibly but they do create some amount of veiling flare that would appear in prints with newer VC papers. Veiling is usually not pronounced but sometimes it's hard to judge if not. I have definitely noticed some difference in contrast with VC papers on my enlarger with probably the same diffusion chamber as on 2501.

Polarizing filter will offer both UV filter and control of Polarization. If light is not polarized it won't have any effect on that component but will still act as ND and UV.

I got UV filter sheet and other options but haven't had a chance yet to try this and do comparisons with VC papers. CTEIN's testing and graphs were done with Kodak Polymax and Agfa Multicontrast. Not sure how the VC papers available today would behave when it comes to UV.

CTEIN's book is at the moment available as a free download here: https://ctein.com/booksmpl.htm
It's well worth reading.

 

[DREW WILEY]

The lossy quality of an uncoated Tiffen polarizer filter itself over an enlarging lens will far exceed any alleged focus shift differential, which is nonexistent in most modern enlarging lenses anyway. I strongly disagree with the quoted Tiffen notion that polarizing filters have no effect on color balance. Ctein is a helpful guy and a friend, but a lot of his lens and paper tests in that old book apply to products of a former era. He should be applauded for making it available for free online.

 

[pentaxuser]

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.

Can I ask: If the polarising filter was used to attenuate the contrast a little with fixed grade papers but can be done by multi-grade filters with VC paper does that mean that polarising filters have no benefit with VC papers so are unnecessary with VC papers?

Were polarising filters used instead of SLIMT to reduce contrast because it was easier that way?

Can I also ask how you came across a thread that was 10 years dormant? Were you just browsing through our historical dormant threads on joining us that day or was this a subject that you had maintained an interest ín and on joining Photrio decided to see if we had ever discussed it? I often can't find threads that have been dormant for a few weeks

Thanks

pentaxuser

 

[Anakhan]

Can I ask: If the polarising filter was used to attenuate the contrast a little with fixed grade papers but can be done by multi-grade filters with VC paper does that mean that polarising filters have no benefit with VC papers so are unnecessary with VC papers?

Were polarising filters used instead of SLIMT to reduce contrast because it was easier that way?

Can I also ask how you came across a thread that was 10 years dormant? Were you just browsing through our historical dormant threads on joining us that day or was this a subject that you had maintained an interest ín and on joining Photrio decided to see if we had ever discussed it? I often can't find threads that have been dormant for a few weeks

Thanks

pentaxuser

That's right, I was remembering this old practice and decided to undertake a search to get some new data on this subject (unbelievably I had not done it before), and I found this long abandoned thread.
Discussing with my husband (he was the director of a film processing laboratory) the new contributions you have made these days, I can add the following:
- the first polarisation was given by a treatment on the lower lens of the condenser (no film was used).
- a locally produced 'condenser-polarizer' and under-lens filter kit was marketed at that time (1960s) for Meopta enlargers, for amateur use and mainly intended to counteract the 'Callier effect' with a fixed polarization.
- since the mid 1970s, when Agfa closed its photographic department here (it is still active in the field of medical imaging), I have not heard of anyone using this type of equipment commercially.

 

[DREW WILEY]

Somebody needs to dedicate a museum to arcane old enlargers. Durst actually had (has?) one related to their own commercial models.

 

[polka]

You say he was a mural printer? Did he use a mirror under the enlarger to throw the image onto mural? If that's the case, then polarizer would make a lot of sense to eliminate the double image from the mirror. You see, unless you use the first surface mirror under the enlarger, you'll get two reflections - one from surface of the glass and another from the silver surface. It's been a while since I've taken the optics course, but polarizer might eliminate one and not the other as such improving sharpness of the image. However, I'm really just speculating here

I think that Anikin has here the simplest, most obvious "hypothetic" answer that could be imagined, not knowing any other detail about the way the enlarger was used by this guy. I do also sometimes large enlargements, but instead of using a 45° mirror, I turn my whole enlarger horizontally. But if I used a mirror instead, I would (if I had imagined it) try this method with an ordinary mirror much easier to keep than a first surface mirror... and experiment how well it would work.

POLKa

 

[MattKing]

I wonder if one could employ this with plane polarized blue and green light sources to adjust contrast for variable contrast papers?

 

[ic-racer]

I wonder if one could employ this with plane polarized blue and green light sources to adjust contrast for variable contrast papers?

I can't think of any enlarger that does that but it would be a unique solution.

Also, makes me wonder if the OP was witnessing two polarizers in use; a non-diffracting 'aperture' in function, to progressively lengthen printing times without stopping down too much.