View Full Version : Weird Interference Patterns Using Lee Polyester Filters

Andre Noble
28-May-2004, 08:08
I am having problems with the Lee polyester filters. I am getting weird rainbow/banding/interference type patterns across my images when using them with wide angle lenses.

I was able to isolate this problem to the polyester type filters themselves. For example, I get banding in both the 4x5 Polaroid and 4x5 traditional negatives when using the Lee 23A Red and Lee 21 Orange, but not in an identical scene taken with corresponding B&W glass filters shot at the same moment. Furthermore, the polyester filters where used singly - not in conjunction with a polarizer or any other filter.

The problem appears limited to use with wide angle lenses. (Unfortunately, much of my own photography involves these parameters). At time of use, there was no direct sunlight striking either the filter or the filter holder which my have caused unwanted reflections. Furthermore, the problem seems to relate to the angle in relation to the sun at which the image is taken. The camera was pointed appx. 180° away from the sun in the 35mm slides using a 20mm lens, and approximately 90° away from the sun in the large format images using a 90mm Nikkor f/8 lens and front rise. Finally, rotating only the filter caused the “interference pattern” to rotate around inside the viewfinder in kind.

I also visualized the same problem with other Lee Polyester filters such as the Colour Temperature set.

After a couple phone calls to Lee Filters in England, they deny having ever experienced such problems before despite possible evidence such as this thread on Photonet:


Anyone else have a similar experience with these (or their Calumet equivalents)? Note: I am specifically referring to the thin Lee Polyester filters. I do not mean the thicker Lee resin filters, nor am I referring to the thin Kodak gel filters, which are both manufactured using a different technology than the polyester type filters.

Thanks in advance for any input you can share.

Philippe Gauthier
28-May-2004, 09:26
I never used these filters and therefore, never encountered the same problem, but when you described the interference patterns you got, it just sounded as Newton rings to me. OK, Newton rings normally occur when two flat surfaces are in close contact, but how far is your filter from your lens anyway? Given that polyester is quite flexible, is it possible that some wind could cause contact?

Just a thought...

Michael S. Briggs
28-May-2004, 09:36
My memory is that the directions that come with the Lee/Calumet thin polyester filters instruct one not to use them behind a polarizing filter. This is because some plastics partially polarize transmitted light, especially when stressed. If you view these plastics when stressed (e.g., stretched) with polarized light you can see interesting colored patterns because the polarization varies with the wavelength of the light. This is sometimes used to study stress patterns in engineering models. Of course, you are not using a polarizing filter. However, the directions that you describe relative to the sun are directions in which the natural polarization of skylight is near its maximum (e.g., see http://www.polarization.com/compass/compass2.html). Perhaps this partial natual polarization of skylight is sufficient to interact with the small degree of polarization created by polyester to show up in your photos. If so, the mystery is why you have this problem and so few other people do. I have used these thin polyester filters and never had a problem. Does your method of holding the filters stretch them or otherwise introduce stresses?

Ernest Purdum
28-May-2004, 10:14
I also thought of polarization as I read the question. Cellophane has a crystal-like structure which derives, I think, from being rolled under pressure during the process by which it is made. Maybe something in the manufacture of the polyester filters is causing a similar result.

Andre Noble
28-May-2004, 10:28
Thanks Philippe and Michael.

Phillipe, you are correct in that the images does look exactly like a Newton ring type phenomenon, despite there being no physical contact of the filter with any other surface whatsoever.

Michael, I suspect the reason I am getting the problem and few (but some) others have, relates to the angle of light as it passes through the filter. The problem is apparent when shooting my super wide 20mm lens in the 35mm format, or when using my 90mm Nikkor on the 4x5 for architecture when the image circle is shifted in order to take in the scene of a tall building, for example.

Unfortunately, architectural shots requiring shift , or expansive wide angle landscapes is not a special circumstance with the type of photography I do.

P.S., I have also ruled out mechanical deformation as the problem because it occured on numerous new Lee polyesters- while mounted in Lee filter holders displaying no physical deformations.

Furthermore, the interfernce pattern was very similar in the 5 Lee polyester filters I tried such as 05CC Green, 85B Color Temperature, and Magenta CC filters.

Specifically, on the 20mm Nikkor shots, it appeared as two multicolored/multiconcentric circles about 15 or 20 mm apart from each other in the upper 1/3 of the frame. These circles rotated around the frame as I rotated the filter.

In the 90mm Nikkor shots, it appeared somewhat differently: The interference pattern appeared as an inverted rainbow, swooping down the upper quater portion of architectural shots. The pattern was very similar as well using 3 different Lee Polyester filters for black and white film.

Struan Gray
28-May-2004, 12:38
Polyester film is usually birefringent, so using polyester filters with polarised skylight could well produce these effects. It is similar to how you can sometimes see the stress patterns in a car's windscreen even when not wearing polarised sunglasses.

Working at large angles makes it more likely that you will include a bit of the sky with a high degree of linear polarisation, and enhances the effects of multiple reflections back and forth inside the film.

You can confirm that this is your problem by putting a linear polariser in front of the polyester filter and pointing it at a diffuse lightsource like a light box or a white wall. You should see the same patterns. If you have a circular polariser, hold it reversed or the patterns will be almost certainly be different to the ones you see with skylight.

If the filter's response to polarised light is the problem, your only hope is to switch to resin or gel filters.

Steve Lewis
28-May-2004, 13:54
so using polyester filters with polarised skylight could well produce these effects

I had exactly the same problem a few years ago, and, after consulting with Lee, they confirmed that using polyester filters with a polariser is likely to produce these effects. HTH

Steve Lewis


Philippe Gauthier
28-May-2004, 14:34
Your theories about the PL filter being the problem are very interesting (good thing to know) but please André's question carefully: he says he gets the problem even when he uses the filters alone, not in conjunction with a PL or anything else.

My feeling, if there's no contact even in windy conditions, is that the problem is somehow refraction related. Must be a problem with the high angles between the wide glass and the filter, and the different refraction indexes of both. But it's just a guess and someone better versed in optics will probably know better.

John O'Connell
28-May-2004, 14:52
I use these same filters, and I remember there being specific instructions with them not to use them with a polarizer or some kind of ugly pattern would appear. I have, however, taken an awful lot of exposures with the yellow polyester filter on the Nikon 20mm which included large expanses of blue sky, and have never noticed this. I assume I've merely been lucky.

Are you using a holder that puts them under a lot of tension? Are these recently purchased filters, or fairly old? (Mine are about three years old).

Best of luck, and I'm sorry to hear that I may have three problem sheets of film waiting to be developed...

Andre Noble
28-May-2004, 15:35
Thank you Phillipe for helping to clarify! And also thank you to everyone else for taking your best stab at it too.

1) I am NOT using a Polarizing filter of ANY kind.

2)There is no filter contact with lens surface. There is no mechanical stresses. (Filter taught and smooth as a drum). Problem observed whether filter in Lee holder or held by hand in front of lens.

3) Interference patterns were of a very, very similar type and location across filter types on a given lens. (This helps to rule out (2) as cause). They rotate around as I rotate the filter around.

4) They are not due to simple internal reflection of skylight of filter surface and lens element because the bulleye's rotate in perfect unison as you rotate the filter while keeping lens steady.

Technically, I find it very interesting because of the uniformity of the patterns - on the Nikon 20mm, they look like 2 multicolored bull's eyes across 5 different Lee polyester filter types, for example.

In my haste, I sent all sample slides and negs to Lee Filters in U.K. (They have not gotten back to me with a satisfactory response yet.) So I don't have scans to post. Anyway, I know it's 'no more' polyester filters for me. Too bad because they're a lot less expensive than the Kodak gels.

Roger Scott
28-May-2004, 18:16

Was there anything around which may have polarised the light on you? Anything flat and shiny in the scene you're photographing will be directing polarised light at you. I'm thinking along the lines of a window, lake or something. Strangely though most of the filter manufacturers suggest you can use a polariser with polyester filters providing it's placed in front of the filter so I'm not sure this is your problem unless the light is getting between the filter and the lens. Have you tried it with a different brand of lens? It's not likely but I'm just wondering if it's something Nikon use in their coating which when used in conjunction with polyester filters is causing the problem. You're getting some sort of refraction happening where white light is being split into its component wavelengths or part of the light is being reflected and the other transmitted dependent upon angle. Polarised light such as reflected light off a shiny surface or light passing through a polariser makes it more pronounced as you lose the self cancelling properties of randomness. It sounds like the filter is the problem when used at certain angles but I'm not sure why others haven't come across the problem. Does the problem increase as the light angle increases? Out of curiosity try increasing the shift/rise/tilt so you're moving towards the edge of the lens coverage and thus increasing the angle. I suspect there'll be some angle below which there won't be a problem if my theoretical rambling has made any sense.


Chad Jarvis
29-May-2004, 08:31
Is one "bullseye" larger or brighter than the other?

Suppose you point the lens toward a spot in a clear sky that's 180 degrees from the sun, do you still get the patterns? How about 90 degrees to the sun?

Andre Noble
29-May-2004, 09:19
Chad, they were identical in size. I got these two bullseye with the Nikon 20-35 lens @20mm. They were most visible when lens pointed 180 degrees from the sun but also visble in the same area of the view finder at less obtuse angles such as 120, 135 for example, if I recall correctly. They would rotate around the finder when I rotated the filter.

The other pattern, with LF Nikkor 90 f8, was a single 'inverted rainbow'seen when lens at appx. 90 degrees to the sun.

In both cases, there was no direct sunlight hitting lens, no physical contact with lens and filter, no polarizer filter in use at same time, no second filter either, no bend in the polyester filters, etc.

Because these 90 and 180 angles in which interference patterns seen are not necessarly exhaustive, I would not read too much into them. They are just what I obsereved. I did not do super exhaustive test of various angles, because time is precious, and the polyester filters obviously were ruining my images when used for wide angle shots.

Whatever is causing it is an optics/physics interaction of the polyester filter with lens coating and/or skylight, I believe. Just what that mechanism is, I don't know.

29-May-2004, 09:57
>>Finally, rotating only the filter caused the “interference pattern” to rotate around inside the viewfinder in kind

The smoking gun clue is right there

Obviously something is causing the gels to deform. Since this is happening on more than one gel the problem is most likely in the holder Since it happens on wide lenses you are seeing a larger surface area of the gel, so you are most likely to see distrotion. Since it is in roughly the same place on the gels the cause is the same.

The biggest cause of this on plastic or polyester is not keeping it perfectly flat, you can see the same thing happen on polyester overhead projector sheets. Since the anomolies are circular I am even more convinced that they are not being held flat. Something is causing the gels to defrom. I would guess the holder. Take the gel out and sight along it. do you absolute best to keep it flat. Look for a reflection. If it is flat then the reflection will look correct. If it is not then the reflectio will be distorted; wavy. I would lay it on a sheet of glass or something and then site along it. Then put it into the holder and site along it. I bet you will see that the gels are being deformed by the pressure of the holder.

Hope this helps.

Andre Noble
29-May-2004, 11:32
Hi Mark,

I thought of the flatness of the filter too when the problem occured. So at the time of testing, I removed the filters from holder, rotated filters 90 degrees, while keeping holder in steady position, but the patterns rotated 90 degrees as well. Also, there were identical patterns across filter types on a particular lens. Whether mounted inside the Lee holder or outside holder, the flatness was really quite good due to the good design of the Lee holders. The evidence pointed to the physical property of the filters, not the holder.

I am a busy elementary school teacher and just recently discovered the fault when I finally had a chance to get some shooting in with the newly purchased filters.

I returned filters to Lee U.K. (I bought them from Robert White even though I live in California) and requested an exchange of $200 worth my 6 unused or minimally used polyester technical sets ( each containing 4 to 6 polyster filters) for 5 of their single resin filters on an equal-value exchange. They didn't initially seem accomodating even to this idea. I haven't gotten a straight answer from them, after 2 phone calls, all the while they are still in possesion of my filters.

I supported Lee filters by also purchasing about $1500US worth of their resin filters and accesories from Robert White. So I expect that they'll either come up with a satisfactory technical explanation of user error or failing that, give me a refund, credit, or exchange.

As I mentioned at the top of post, at least 2 other photographers have noted a similar problem with their Lee Polyester filters:

see http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005bh7 )

29-May-2004, 15:35
Another elementary teacher. Good to hear it.

I can't see how if could be user error unless you and the other guy both touched the gels with something on your fingers but let's face it no one is that brain dead. Good luck getting your money back. God knows teachers don't make enough to just flush it down the toilet.

Just out of curiosity, why did you buy from Robert White?

Roger Scott
29-May-2004, 17:27

I didn't wish to get too technical before as I was thinking through the problem so for those not so inclined please ignore this message. Refraction happens when the refactive index of a medium through which light is passing changes. Put simply it gets bent. How much depends upon the wavelength of the light, the incident angle as well as the refractive properties of the medium. The classical theory case is a pyramid sitting on a desk with a beam of light being projected through it parallel to the desk. The beam hits the first face of the pyramid, gets scattered slightly at first and then scattered further upon leaving the pyramid giving us a rainbow. Light entering or leaving a medium at the normal to its surface won't be refracted. Similarly light passing through something at small incident angles which has truely parallel sides will have refaction occur at both sides but which cancel each other out without visible effect. There is also the case to consider where part of the light is transmitted through the medium and part is reflected such as with coloured filters or when the angle of incidence is extreme. A physical analogy to the latter is stone skimming on water.

Initially when you mentioned rotating the filter and seeing the pattern move I thought you meant the pattern rotated around a fixed point but from later reading I understand that it moves on the ground glass as the filter is rotated - eg from upper left to upper right. If this is true then the problem is with a deformation in the filter either from external forces, slightly non-parallel sides, or its a problem within the structure of the filter itself. As I previously mentioned high incident angles such as when using wide-angle lenses or extreme tilts/shifts/etc, or having polarised light passing through the filter will exaggerate any problems. Also just to complicate things certain lenses will show the problem more than others due to either chromatic aberation, attempts to reduce it or filter coatings etc. Ultimately this means that either all polyester filters suffer from the problem to some extent and you've just hit upon unlucky circumstances or you've received a bad batch of filters. Either way I wish you luck resolving the problem with the retailer.


Andre Noble
29-May-2004, 18:21
Hello Roger and Mark,

Michael Briggs has solved the mystery. He posted a lucid explaination on the other LF site yesterday at:


Essentially the problem involves a phenomenon known as "birefringence" as he explains. Stress patterns (appearing like oil droplets on wet ashphalt) are induced in the filter itself during manufacturing process. They become visible under conditions of induced polarized light (or naturally occuring polarized light such as skylight that's at certains angles from the sun - as was my case - I did not use a PL filter in conjunction with Lee filters when this problem occured!).

PS, Mark, yes I have to remind myself I am JUST a teacher and therefore have to more carefully watch my expeditures. I got Lee filters at Robert White cause I saved a little bit more on some ND Resin Grad Filter sets purchased at same time. Overall, their prices for all Lee filters are close to B&H's though.

Graeme Hird
30-May-2004, 20:22

I believe Ernest Purdam and Struan Gray gave you the same answer in the third and fifth responses here, but that doesn't matter - you're satisfied and that's all that counts.

For the record, did you try viewing the scene through the "front" of the filter? Some polarising materials (eg circular polarisers and perhaps your filters) may show a reduction of the effect when viewed through the front of the filter.


Andre Noble
30-May-2004, 22:11
Yes, I see now Ernest and Struan are also correct. I don't know how I missed that, thanks.

Here's a picture of birefringence as it affected an actual exposure. In this case, I was using a Lee polyester 05CC Green to correct for a slight magenta cast in a Fuji stock of slide film:


It appears similar to 'ripples in a pond'. You can see it in the left 1/5 of the photo, particularly in the blue sky.

Thanks to all who took the time to reply. (And yes, I know the film still looks too magenta and red, but that's a whole other story :>)

William Curwen
1-Jun-2004, 11:40
Hello everyone, I have practiced large-format photography for many years, and one thing that has been drummed into me time and again, is to baffle off the front of the taking lens due to flare. Flare is particularly noticeable when using filters - any filters, either thick or thin, in front of the lens. So I make my own lenshoods which look like waste paper bins, they are that big! There is a lot to be said for matte black card and copious amounts of velcro. I am not averse to mounting filters behind the lens, which eliminates the problem completely. A lot of current work is dependent on Lee filters and they don't make and sell compendium lens-shades for nothing - and - they are very nice people to deal with. Methinks your problem is being compounded by flare.

BTW, I have lurked on this forum for awhile and am seriously impressed with the collective pool of knowledge here. If anyone wants to check me out, then do please visit my website at www.william.ws and feel free to make comment. I am involved with large-format for the duration, and more than happy to share with likeminded souls:)

Andre Noble
5-Jun-2004, 21:54
Happy Ending:

Lee filters just contacted me directly via email in regard to the return package of filters I sent to them. They were cool and willing to swap out the polyesters with an equal value exchange for a few of their resin filters, which are highly regarded.

They were very candid of the birefringence issue a few photographers have noted, and hoped to be able to nail the cause down with new tests currently under way. I wish them the best. I imagine it must be very diificult to manufactures these polyester type filters without internal stress patterns.

I am happy with the solution they offered me personally.