Polarizer and neutral density filters?

[thequintessentialman]

Had a box full of different effect filters I used with my old FE2 but never got any when I transitioned to digital.  They were much too small so I gave them to a friend.  There have been a few things I've wanted to do over the years but I just did without.  Now I'm thinking of getting a polarizing filter and a neutral filter for my D800 lenses.  The little bit of research I've done said NOT to get a linear polarizer for a digital, but to get a circular due to issues with the electronics..  Recall one of the cool things with my FE2 polarizer was it rotated; taking pictures of fish in water I could control how much glare I wanted in or out by rotating it.  Will I be able to do that with the circular polarizer, the tutorial didn't mention anything like that. 

I'm considering a variable neutral density, what are the pros/cons of variable vs a set of fixed density? 

Any pitfalls or beginners' mistakes I need to be aware of? 

Had a bit of fun with those old filters though, got the starter kit at the BX, then some years later ran across a big box full at a yard sale.  They were square and had a cradle that screwed into the end of the lens (forgot the brand name) but those old lens were tiny compared to the ones on the D800. 

Thanks

[William Michael]

For photographic application, we can group Polarizing Filters into two categories: Linear Polarizing Filters; and Circular Polarizing Filters. Linear polarizing filters were used first and are still available, especially second hand, and are typically the least expensive. Importantly, if a Linear Polarizing Filter is used cameras with through-the-lens metering (TTL) and autofocusing (AF) systems: basically all 'modern cameras' then there can be problems to the functionality of the TTL and/or the AF systems.Circular polarizing filters do not produce these adverse effects.

Circular Polarizing Filters, usually are coded "CPL". Circular Polarizing Filters are typically thicker than most other filters - they can produce an Optical Vignette when used on wide lenses. CPL Filters have two bits. One bit rotates. If you are using a Lens Hood and a CPL, then you might come to grief trying to rotate the CPL, especially if you have chunky thumbs (like me). One work around is to carefully cut a window in the Lens Hood (at the underneath as it sits on the camera) so you can get one finger on the front bit of the CPL Filter, to rotate it.

Circular Polarizing Filters have a limited FoV (Field of View) of effect. That is to say, as a CPL is used on a wider lens one might see the effect of the CPL in a patch of the scene and not across the whole scene. Two typical examples of this:
i> when using a CPL on a Landscape Scene for the purpose of enriching the sky, when using a wide lens the sky might have a good patch of rich blue, but that rich blue will not extend across the whole area of the skyline
ii> when using a CPL on a Water Scene for the purpose of removing the reflections on the water, when using a wide lens the water might have a good patch of clarity with no reflections, but that clarity will not extend across the whole area of the water.

***

A colleague of mine, a Landscape Photographer, only uses Singh-Ray Variable ND. I am happy with my two ND Filters - Hoya Pro 5 stop and 10 Stop ND. My two filter are about half the cost his one filter. For my uses these two suit me perfectly: I've not been in a situation where I could not adjust the ISO and/or Aperture, to suit the use of 5 stops or 10 stops of attenuation to make The Shot that I wanted.

There are reports of "X" artifact across the image with some Variable ND filters; you should research this. My colleague says he has no such issue with the Singh-Ray - and I expect that's one reason why it is more expensive than most (all?) others. One comment he does make however is the accuracy of the indication dial on the filter representing the exact attenuation of the filter, this can be problematic for attaining the exact "correct" exposure.

The other difference is the comparative thickness of the filters - the Variable ND will typically be thicker than an ND, although I believe Singh-Ray make a slim model: the extra thickness may cause an optical vignette when used with WA and UWA Lenses. Typically, especially for landscapes, cityscapes and seascapes, ND filters are used often on WA and UWA lenses.  Similar to using a CPL, if you are using a Lens Hood then you might come to grief trying to rotate the Variable ND with the Lens Hood on - and you can't see the indicator dial with the lens hood on: these might be minor factors, or major factors - depending on your own situation and the individual shooting scenarios.

WW

[Ed_Ingold]

The use and effects of a linear polarizer and circular polarizer are identical. Both have plastic membranes sandwiched between two layers of glass. The difference is the addition of a quarter-wave "plate" (membrane) on the camera side of the polarizing membrane. The purpose is to un-polarize light passing through the filter so that phase-sensing AF detectors can operate normally.

High quality (ie, expensive) polarizing and ND filters tend to be more neutral than cheaper filters. I prefer B+W (Schneider) filters for this reason. My variable ND filters are thicker, and larger in diameter than their mount would dictate, to minimize vignetting. The lens hoods of my Sony lenses must be attached first, then the VND filter. Polarizers fit normally, and some Sony lens hoods have a small door to facilitate their adjustment.

Light reflected from transparent, non-metallic surfaces (ie, glass and water) is polarized. The most intense polarization occurs in a fairly narrow range of angles, centered on the Brewster Angle, approximately 53 degrees for an air-water interface.

[conrad_hoffman]

There are circular polarizers that are quite thin and I always look at this spec before buying any filter. Any polarizer is pretty much worthless with wide angle lenses and skies because polarization of the sky changes with angle. I've been pretty happy with Hoya HRT CIR-PL UV filters- thin, decent and not too expensive.

https://www.polarization.com/sky/sky.html

https://atoptics.co.uk/fz1013.htm

https://en.wikipedia.org/wiki/Rayleigh_sky_model#:~:text=Light from the sky is,-south plane%2C or meridian.

 

Edited May 14, 2023 by conrad_hoffman

[JDMvW]

The advice about linear vs. circular polarizers is well-founded, but the negative effects are not quite so damning as generally represented.

 

You might find this interesting

https://www.photo.net/forums/topic/460812-spiratone-and-spiratone-colorflow™-polarizing-filters/#comment-460550

 

 

Edited May 14, 2023 by JDMvW

[conrad_hoffman]

That Colorflow was interesting- had never heard of it, though I loved looking at the Spiratone ads back in the day.

[glen_h]

18 hours ago, William Michael said:

(snip)

Circular Polarizing Filters have a limited FoV (Field of View) of effect. That is to say, as a CPL is used on a wider lens one might see the effect of the CPL in a patch of the scene and not across the whole scene. Two typical examples of this:
i> when using a CPL on a Landscape Scene for the purpose of enriching the sky, when using a wide lens the sky might have a good patch of rich blue, but that rich blue will not extend across the whole area of the skyline
ii> when using a CPL on a Water Scene for the purpose of removing the reflections on the water, when using a wide lens the water might have a good patch of clarity with no reflections, but that clarity will not extend across the whole area of the water.

(snip)

Circular polarizers are a linear polarizer followed by a λ/4 wave plate. 

The linear polarized is mostly not angle dependent, but the λ/4 wave plate is.  It is also wavelength dependent.

As someone else notes, sky polarization changes with direction, and so the effect of polarizing filters.

Light meters and AF systems might be sensitive to polarization, but the biggest one for digital cameras is the optical anti-aliasing filter.

[William Michael]

Yes, well explained. Thank you.

WW

[paddler4]

Another thing to be wary of with ND filters is color casts. As one would expect, these tend to be worse with denser (darker) filters. In my limited experience, the severity of the color cast is not well correlated with price. Some expensive and well regarded filter manufacturers produce NDs with pronounced color casts. These color distortions are not always easy to get rid of in post.

I had a very ugly interchange with one expensive manufacturer to which I will give the unwarranted courtesy of leaving unnamed. I bought one of their expensive NDs and tested it. I found a distinct color cast. I emailed them the photos (photos of white paper under identical conditions) to show the problem. Initially, one of their staff replied, saying that my evaluation was not "technical" and that they consider only technical reviews. When I persisted, I got a nasty note from the head of the company saying that they can't be bothered by the complaints of a nobody like me. 

It's been years since I bought mine, but at the time, I found Marumi NDs at lower and mid densities to be very good. For a 10-stop, I found the Hoya pro as neutral as anything I could find. But again, that was years ago. My recollection is that I was able to find reviews that discussed this for particular filters.

Edited May 15, 2023 by paddler4

[Robin Smith]

Best to get a circular polarizer to be safe. They use to be an issue with the DSLR meters that worked using reflected light from the mirror which caused polarization so metering could be affected. I don't think this is the case with mirrorless cameras. Agree with the others the biggest issues with variable NDs is a color cast. Some people also complain about irregularity of polarization with them too. This is more noticeable the more opaque they become. I have circular polarizers, but I don't seem to use or need them with digital. They can to some extent be used in place of a ND if needs be by holding back a stop or two of light.

Edited May 15, 2023 by Robin Smith

[maris_rusis]

I've tried several variable neutral density filters based on the principle of contra-rotating polarisers and they all have limitations:
Polarisation efficiency is not the same for all wavelengths of light. As the filter is adjusted to maximum density colour casts appear.
Polarisation efficiency is compromised by oblique rays not being polarised the same as normal (straight through) rays. Fully crossed polarisers seen from a distance might look uniformly dark but up close, like when screwed onto a lens, the dreaded "dark cross effect" appears. The ND effect is not uniform over the field of view.
The slightest strain, mechanical or thermal for example, introduces a twist in the plane of polarisation somewhere in the filter (usually near the edge) and again non-uniform ND is the result.
All of these problems are most severe at or near maximum ND. For example I tested a Variable ND filter marketed as a ND1000 (about 10 stops) and it was useable up to about 5 stops. That's when I bought a solid 10 stop ND filter...works perfectly.

[david_henderson]

Since changing to digital c 15 years ago I've found much less use for filters than I did when using slide film.  Increasingly, as post processing software improves, I've found it better to carry out certain tasks in post than to use filters.  So the use of polarisers to darken blue skies or intensify colour  is for me unnecessary nowadays.  The use of grads to reduce the brightness range of an image has pretty much gone now too.  

I still carry polarisers for the limited occasions on which I want to alter reflections, and neutral density filters (10x and 6x)  for when I want to slow down water or people.  I probably go months at a time without using them but when I do need them they're indispensable, & I wouldn't think about making a trip without them  I 'm not tempted by variable ND filters - expensive, risks having to mess with images to get rid of a colour cast unnecessarily, and saves a very minor amount of weight.  

[Ed_Ingold]

ND filters are essential for outdoor video. High shutter speeds cause a stoboscopic effect on rapid moving subjects, which is best avoided by using a shutter angle of 180 degrees or so (eg, 1/125 second at 60 fps). Likewise you should avoid small aperture settings, to manage DOF and avoid softness due to diffraction. 

[hjoseph7]

Neutral Density filters are essential when you want to use slow shutter speeds, but your camera wont let you due to your iso/shutter speed/aperture combination, as well as the ambient light. If its too bright outside such as mid-day sun at the beach, your camera won't let you use wide apertures, or high ISO numbers or slow shutter speed for fear the picture will come out over exposed . Some cameras have ISOs lower than 100 which is the base ISO, so that you can use wider apertures with slow shutter speeds, but sometimes even that is not enough.

In comes the Neutral Density (ND) filter to the rescue ! The ND filter will cut down the amount of light by 1, 2, 3 even 10 f- stops so you can use slower shutter speed numbers with wide apertures. The (ND) filter is not to be confused with the Gradual (ND) filter that is used to tone down the available light on only part of an image such as the skyline. The Gradual (ND) filter usually tones down about 1/3 of the entire image. 

BTW - You can get by with a circular polarizer as both a polarizer filter and an ND filter. A circualar polarizer filter cuts down the ambient light by about 1.5-2 f-stops depending on the position of the outer rim of the filter. I never really got the hang of polarizers. It was always hit or miss with me. You have to be standing  at a 90 degree angle from the sun for it to work correctly, but sometimes your subject is not at a 90 degree angle, or the sun is directly above you, it can get really confusing... Then there is the problem of using them with wide angle lenses. Things can get really messy there.  Unfortunately, this is one of the only filters that you can't mimic using Digital Software. However, once you learn how to use to it, you might never want to take it off your camera. 

[paddler4]

Quote

Some cameras have ISOs lower than 100 which is the base ISO

ISO values lower than base ISO aren't true ISO values, and there are drawbacks to using them--reduced dynamic range and a risk of clipping. The best bet, if base ISO isn't slow enough, is an ND filter. 

One current camera, the OM Systems OM-1, emulates an ND filter with firmware, but I have no idea how that works or how good the results are.

[Robin Smith]

Results are very good. It takes a number of exposures and then combines them in camera to produce a final RAW, but it is best used for fast moving water, waterfalls and clouds etc and you need a tripod. It is not much use for shooting wide open in sunlight to get lots of bokeh. However, most current digital mirrorless cameras have 1/8000 top speed and with electronic shutter even higher 1/32000, so I find that I am rarely challenged for shooting wide open in bright sunlight. I also routinely shoot in low ISO modes if necessary, I have not noticed a diminution in quality, although I am sure it exists. This is why I have essentially given up with ND filters. However even with the Olympus system you may find that it is too bright to successfully use the in-camera ND function for fast-flowing water without stopping the lens down to tiny apertures (f22) which impacts sharpness for certain, especially in m43.

Edited May 23, 2023 by Robin Smith

[conrad_hoffman]

I'll use a ND filter for water and such. I do notice that a very dark filter can be hard to work with because of focus issues- either the camera has trouble or I can't see well enough to do it manually. I've sometimes resorted to focusing without the filter, then installing it. Polarizers can do things that are impossible in post, like killing reflections on water so you can see below the surface. Sometimes useful for copying artwork and such too, especially if you use polarized lights.

[AlanKlein]

You may need an internal ND or external if you're shooting video. The best setting for video is twice the frames per second.  So if you're shooting at let's say 30fps, you want to set the shutter at 1/60th which may be too slow for a bright scene and require a ND filter.