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Thread: ND Filter Causes "Fringing" Effects? HELP!

  1. #1

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    ND Filter Causes "Fringing" Effects? HELP!

    Been having problems with peripheral fringing (double-image) effects while using my 6 stop (64x) B+W MRC neutral density filter. Problem crops up with axial movements, and seems to increase as degree of movement increases. Possibly worse with rear base tilts vs front or rear axials...but not sure. Also, with base tilts, fringing effect noticeable mostly in foreground. Happened previously with "cheap" Hoya nd filter - so moved to B+W...and, lo and behold - the problem persists! Web search reveals nothing. Am desperate! Anyone?

  2. #2

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    Re: ND Filter Causes "Fringing" Effects? HELP!

    Usually double highlights with filters happen due to the inside filter plane reflecting between another flat plane in the lens, where one plane might be tilted slightly, and reflects (esp lights at night) into multi images (instead of in register)... There might be a misalignment in the filter ring/threads that allow some tilt... Or if the lens has a flat element, it might be loose and tilting a little... (Give the lens a shake to hear if there might be a little element play somewhere...) Do a night test on some distant light with a filter on to see if it happens with other filters or lenses...

    Good Luck!!!

    Steve K

  3. #3

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    Re: ND Filter Causes "Fringing" Effects? HELP!

    I've never had this issue with any of my nd's either round glass or square resin. Can you post some examples?

  4. #4
    Do or do not. There is no try.
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    Re: ND Filter Causes "Fringing" Effects? HELP!

    If it happens with two different filters on the same lens then why do you say it's the filter? Do you get this effect using the same filter(s) on different lenses? How close together are the fringes? Is there any chance it's a pinhole light leak in a lensboard? This might not have much impact in normal use but with a 6-stops filter it could be significant.

    It seems to me unlikely that it's light reflecting off the front of the lens and back off the filter. Uncoated glass reflects about 4%, and a multicoated filter less than 1%, so that would produce a reflection with at most about 0.04% of the intensity of the original source, about 11-1/3 stops down relative to the primary image-forming light after it's gone through the filter, and another stop down for a coated lens. I'd be surprised if this was it.

  5. #5

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    Re: ND Filter Causes "Fringing" Effects? HELP!

    Quote Originally Posted by Steve Goldstein View Post
    If it happens with two different filters on the same lens then why do you say it's the filter? Do you get this effect using the same filter(s) on different lenses? How close together are the fringes? Is there any chance it's a pinhole light leak in a lensboard? This might not have much impact in normal use but with a 6-stops filter it could be significant.

    It seems to me unlikely that it's light reflecting off the front of the lens and back off the filter. Uncoated glass reflects about 4%, and a multicoated filter less than 1%, so that would produce a reflection with at most about 0.04% of the intensity of the original source, about 11-1/3 stops down relative to the primary image-forming light after it's gone through the filter, and another stop down for a coated lens. I'd be surprised if this was it.
    Yes Steve, strange but true as I found out as I do a lot of night/tele work, and one lens would produce multi bright highlights when shooting distant very bright lights, and I scratched my head trying to figure what was up... I finally found that a flat element had been a little loose and with the CC filter on, it would set this up... A curved surface element would not set-up this reflection, but a flat element would reflect MUCH more back.. (I also noticed this effect when aligning telescopes using star images, so it does exist...) John's problem might be different, but I barely remember using heavy ND's years ago, but sometimes strange things crept into the images, but I'm thinking it was reflections then...

    Steve K

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    Re: ND Filter Causes "Fringing" Effects? HELP!

    Quote Originally Posted by John Layton View Post
    [...] Happened previously with "cheap" Hoya nd filter - so moved to B+W...and, lo and behold - the problem persists! Web search reveals nothing. Am desperate! Anyone?
    To cover all possibilities - there are counterfeit B+W filters, enough that B+W now has a special holograph and QR code combination to determine genuine products. I hope you did not get a counterfeit.
    .

  7. #7

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    Re: ND Filter Causes "Fringing" Effects? HELP!

    Which lens? Filter mounted to front or rear cell?

  8. #8
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    Re: ND Filter Causes "Fringing" Effects? HELP!

    6-stop ND filter means you are probably making fairly long exposures, right?

    My bet is that your filter is just fine, but the film is falling slightly after getting dislodged from sitting sideways slightly for a long period of time (it can get slightly stuck under the film holder's side rails, especially when shooting in landscape orientation). I've had this happen several times recently because I keep forgetting to rap the film holder in the direction it will sit in the camera on the palm of my hand to dislodge the film if it is stuck.

    This is a common problem when shooting really long exposures.

    I was looking for an example but I appear to have already deleted the latest one, from just last week.
    Bryan | Blog | YouTube | Instagram
    All comments and thoughtful critique welcome

  9. #9

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    Re: ND Filter Causes "Fringing" Effects? HELP!

    First noticed this with an 82mm Hoya 6 stop Multicoated ND...particularly when mounted on a 120mm f/8 Super Angulon with 5x7 format, and particularly when shooting vertically with fairly strong rear base tilts. Also with a 58mm B+W 6-stop Multicoated mounted on a 135mm Sironar-N with 4x5...again mostly when shooting vertically with rear base tilts. In each case, foregrounds affected most - upper 2/3rds of the image hardly at all.

    Filters tight in their mounts. Mounted to front of lenses. Lenses performing up to par otherwise (years of long exposures in many conditions, without filters, and, so far, good results with 3 stop filters). 135mm lens has fairly strong front-element and rear element curvature.

    Thing is (and this is what has me wondering)...each of these 6 stop filters was advertised (on B+H website) as simply "ND" - and yet each arrived also marked "digital." Question - is this just playing up to hype? Or...perhaps something is being messed with (to make them more digitally compatible?) - like the REFRACTIVE INDEX OF THE GLASS? (Bob Solomon...any comments?)

  10. #10

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    Re: ND Filter Causes "Fringing" Effects? HELP!

    I dunno, but maybe try shooting a test with the lens centered and image path on-axis and see if there is a difference... (Maybe the filter is too thick for WA use???) Strong ND's seem to set up reflections (as I remember???), so maybe with a lens that refracts more (and a dark filter that reflects back) smaller errors in the light path might form secondary images.. Or try shooting the filter with a normal or longer FL lens and see if it happens there... (Most WA's have flatish inner elements facing the iris/shutter blades...) These filters might work better as a gel, rather than glass...

    I'm getting ready to shoot with strong ND's again, so let me see if the old problem (that I can't seem to remember right now) rears it's ugly head again, and I can report back in a few weeks about it...

    Good luck/Don't give up...

    Steve K

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