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Csacwp

Filter question

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I’m extremely anal about dust getting on (and into) my lenses, so I put B+W MRC nano filters on my lenses (UV or clear depending on the lens). The problem is I also like to do long exposures and use ND filters a lot. Can I stack the ND filters onto the protective filters, or should I learn to live with the protective filters off except in especially dusty or wet environments?

Edited by Csacwp

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As you probably realize extra glass on the front of a lens can give light rays more chance to bounce around.

 

I use clear filters on the front of my lenses because I live in a desert and blowing fine grain sand is a constant problem (almost invisible until enough accumulates and it is also slightly electronically sticky).

 

I usually detect no discernible difference when I've experimented on a shot with the filter off and then on, but I suppose bad filters might show variance. I use the word 'bad' instead of 'cheap' because in some tests (that Polish site comes to mind) the most expensive filter has not always come out as the 'best'.

 

BUT! stacking filters adds not just more glass, potentially degrading, I think, your pics but can add enough depth to the end of your lens to become visible as a vignette (depending on the lens' focal length.)

 

With filters I believe 'less is more/better'.

 

Worth noting : As I am not fanatic about checking that my filters are always tight, I have found, more than once during a cleaning session, that I have gotten lint/dirt BETWEEN the filter and the lens. I can only guess that the force of the wind gets crap in the threads that then works its way into this position.

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1st point: Dust does not get into the lens from the front, it gets in from where the lens expands on focusing and other mechanical places. A filter will not change the amount of dust you get in a lens.

 

2nd point: I just remove the clear filter and replace with a different filter is required. It's not that hard or time consuming. Especially with long exposures, the moment hardly passes quickly! I only stack filters when I need the effect of two filters.

Edited by michaelwj

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Firstly, there is virtually no discernible difference between a photograph taken using a good 'protective' filter or without (believe me I've tested this to my own satisfaction

).

 

Secondly, the only practical exception is when a filter can cause reflection - shooting against the light or with strong light sources within the image or close to its edges. Then unwanted 'reflection' or 'flare' patches can be exacerbated as light is reflected internally from the filter's rear surface or rear of its front surface (or a mix) into the lens itself. In such situations its advisable to remove the filter. (Again this is my own experience)

 

Thirdly, stacking filters is in my experience a bad idea because of the second point (even more reflections) AND because shooting through multiple layers of glass causes multiple refractions, especially evident as the glass is placed further away from the front of the lens, and this can lead to image degradation. This is more obvious with wide angle lenses where corners can soften discernibly (polarisers on wides can cause this problem too).

 

So I personally always use a protective filter, except in conditions where it can cause problems, and I never stack filters. Just my way of working though.

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I found that the concern about protective UV filters causing image degradation, ghosts and flare became anitquated and obsolete with the advent of multi-coating such as used on the B+W MRCs and Heliopans, which transmits virtually 100% of incoming light.  As such, I have always stacked whatever I need on top of them and never had any incidence of flare or ghosting. 

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Do NOT stack as it inevitably causes chromatic aberrations, ghosts and flares....

One high quality MRC B&W is my maximum.

Albert

Real tests with 50 of them, and then with 5....

 

https://www.lensrentals.com/blog/2011/06/good-times-with-bad-filters/

 

Good filters.... and common sense usage.... make a difference.

 

Jeff

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Certainly, modern filters are good enough that they won't degrade the image in terms of resolution or (normally) contrast.  However, they do have the potential to cause additional reflections.  Even the nano-coated ones can create halos around bright point sources of light in your image.  And if the sun is in just the wrong angle they can create flare or veiling glare.  The particular angle will vary from lens to lens, but they are not completely harmless.  Close, but not completely. None of this will matter in the majority of images, but there is certainly the potential for additional reflections.  No filter coating passes more than about 99.5% of the incident light (depending on the angle).  

 

So, what's the benefit to filters?  I suppose if I lived somewhere really dusty I might want them.  It would reduce the frequency of lens cleaning.  But modern multi coatings on any current Leica lens are actually quite tough, so as long as you aren't stupid about cleaning with a cloth your shouldn't or in an inappropriate environment I don't see much of an advantage to a filter.  I suppose they can help protect from impact, but that's really what the lens hood is for.  

 

Anyway, assuming you are going to use the B&W filter... The only real reason to remove it would be if you were running into vignetting issues with the taller stack.  Easy enough to test and see.  If you aren't, then the stack of filters is probably no worse than the single filter.  Maybe a little increased risk of unwanted reflections?  Pretty minor.  I'd stack rather than fiddling with swapping in the field.  As long as vignetting isn't an issue.  Test that beforehand with the lens wide open.  Check at both close focus and infinity--I can't remember which of the two is more likely to cause vignetting, but one will be more susceptible than the other.  I think close focus is worse.  Would have to do a simple ray trace to be certain.  Just check both.

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As an aside, if you want to avoid the nuisance of having to continually screw and unscrew filters to change them Manfrotto has released its Xume range of magnetic filter holders.  You simply screw a Xume onto your lens and adapters onto your filters and it's just a case of pulling one filter off and attaching another with magnetism.  I have them on lenses I use with both my M8 and M10 so adding or removing UV/IR filters is very quick and simple.  (For disclosure I have no connection to Manfrotto or the filter adapters whatsoever.)

 

Pete.

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