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Monday, 28 June 2021

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As I understand it, polarising filter is actually the only one (maybe apart from an infrared filter?) that cannot be replicated by digital means. Polariser does basically three things: 1-it removes reflections from leaves, roof tiles etc. 2-it removes reflections from glass or water so you can see through it and 3-it removes reflections from water droplets in the air making blue sky darker and clouds to stand out better. The last thing you could do on a computer, increasing the contrast and saturation. The first thing you sort of could sometimes do, but it can be a lot of work if you have thousands of leaves in a tree. The second one is impossible as you cannot see what is behind or under.

Hey, Mike, polarizers work as well with digital as they did with film. Get a high quality "circular" polarizer and it'll cut reflections, darken skies, saturate colors, etc. Don't use it with very wide angle lenses, and remember that the highest effect in skies is 90 degrees from the sun.

If you are using a digital camera, you will need a circular polarizer. I believe the reason has something to do with polarized light and the sensor array geometry.

I also don't use polarized sunglasses when photographing. I find the polarizing in the sunglasses makes the EVF go black in the portrait orientation.

I find polarizers work just as well on digital as they do on film. My only problem is remembering to take them out of the bag. The big problem with polarizers occurs in both film and digital when used with a wide angle lens in landscapes. The effect changes dramatically depending on the angle to the sun which shows up more and more as your lens gets wider,geometry.
I can envision those blue settings working quite well on a portrait of a man, not so much on a young girl

I use polarizing filters when photographing automobiles. The filter cuts reflections and can darken a clear sky into a nice rich blue - just like with film.

As for color theory in black and white photography, I think I prefer your earlier post that included a link to Tim Soret's explanation - https://twitter.com/timsoret/status/1251763478177644544

I keep a circular polarizer more or less permanently attached to my lenses, for the same reason that you like your polarized glasses. There's a filter factor at play; I use its effect in adjusting the filter, by observing how shutter speed and ISO vary as I turn the ring. (I usually shoot in aperture priority). There are "rules" and rules of thumb, but I've found this to be the easiest for me.

As I understand it, with modern cameras you need to use a circular polarizing filter so as not to interfere with the metering system. Probably more than the meter these days. So you need to check your filters or just experiment with them. Circular ones are usually labeled while older linear are usually not. They are the one filter that you can’t fake in post processing. You’ll get better answers than this for sure.
Thanks for the link. Very good article.

Re: polarizing filters on digital cameras, yes, they work fine. A circular polarizer is, indeed, like a ND filter and can cut a stop or so of light off the lens, depending on the filter’s position. But it does screen reflected glare and, consequently, give the impression of more saturated color. I rarely feel the need to use one, with the exception of photographing shallow tide pools where I’m trying to see animals below the water surface.

Re; “ Tonality is tougher than color; it has a wider range, and a broader range of expressive effects are potentially admissible and acceptable.”, I could not disagree with that statement more strenuously if I grunted aloud, Mike.

A 'grey' polarizer is in effect an ND filter but it also cuts glare and in the process it can result in more saturated colors especially in the sky. https://ascmag.com/blog/shot-craft/understanding-polarizing-filters
It is the only filter I use on my digital cameras and then only occasionally. I have a set of square ND filters of varying strength but they tend toward a brownish cast that I dislike. I also have a variable ND filter which is really two polarizers mounted together, one stationary and one able to be rotated. This works because a polarizer blocks scattered light rays that are vibrating in all different directions and allows only those vibrating on a plane to pass. As you turn the rotating part of the movable polarizer glass on a variable ND, the plane becomes narrower and narrower until the planes of the two polarizers cross, at which point virtually no light passes. It too can can some color distortion in extreme settings but it isn't as bad as the set of ND filters I bought.

... and wouldn't you know it, just minutes after posting my comment on CPL's, an ad for URTH polarizing filters appears on the Washington Post page.

I sometimes use a polarizer with digital. Digital still can't get rid of the shimmer of bright light on leaves or water, for example.

No. But I do have a story that goes some way toward explaining why!

I bought a polarizer probably about a decade ago and tried it out. It didn't seem to have any of the effects that it was supposed to have. Figured it was probably me, and moved on with my life.

A few years later I tried it out again, and found that it worked fine if you flipped it around! It had been assembled backwards!

It seemed well past any reasonable date to complain and anyways I rather like possessing this oddity. Some day I might even buy a reversing ring so I can use it. If I ever actually need a polarizing filter which I have not in the last 30+ years.

I am still using the same polarizers that I bought in the 70's and 80's. If I have to buy a new one I don't bother with the circular variety. Seems to work for me. I have no focus issues nor tonality weirdness. I am sure the technical tooties will disagree, but hey real world experience is always my go to.

Polarizing filters are excellent for reducing reflections from glass and water. Sky darkening is very dramatic, but overdone with wide angle lenses. Best to restrict the filter to 50mm and longer lenses.
I used a polarizer a lot with film, but seldom with digital. Rotating front elements, petal hoods and the way that digital sensors measure the exposure - someone please chime in with the technical details - made the use of the polarizer on digital a bit too awkward for me.
This filter is a try it and see what you think kind of filter.
In ON1 Photo RAW, I find that the Haze slider can give a similar effect.
Now excuse me, I have to get back to Sroyon's article. This is like opening up War & Peace. Good stuff.

I am constantly looking for best methods to convert to B/W. I find most presets/lightroom etc to be very blunt instruments.

Mostly when I ask I get a reply to fiddle with sliders on colours when converting.

I am sure some of you here have standard conversion settings/methods which you then finesse.

I am interested in hearing about your methods.

Regarding the polariser on digital, I would not be without one. They kill highlights which would otherwise be blown out. Also no one has every convinced me that digital manipulation after the shoot is close to using a polariser when shooting, plus it saves on post shoot work.

I use polarizing filters (sheets over lights) and on lens for photographing art work with glare (e.g., acrylic paintings). It allows controllable increase of saturation.

Notably skylight and wet leaves exhibit quite some polarized light, but in color I don't particularly look to affect the tonal range (if anything I may want to reduce saturation) and I do worry about deadening the image, by losing sparkle of directly reflected sunlight. (For the same reason it shows the bottom of shallow water, which is likely not so attractive.)

But if I came to it with a B&W background I likely would approach it differently. BTW for the times you want it you can use MF and manual exposure reading (if a problem/needed), so it avoids the potentially large extra expense of circular PL (likely can get used linear ones for moderate cost).

So, yes, I have used Pola filters on digital cameras. They were a "go-to" for me with film especially to intensify skies, but when I first used them again in digital daze I immediately was put off by the intensity of the effect. Was it me---more mature, more interested in natural/subtle looks, or was it digital? Don't know. I do know that today the drama can be easily gotten in post processing.

I am now using them only for reflections in casework/vitrines for my museum work. BTW, a new kid on the block, Breakthrough Photography, specializes in ND and Pola's. Great stuff, very color neutral, lifetime warranty, U.S.made (if that means anything to you these days...). Available at the usual suspects and their website.

Hi Mike,

Back in the days when I used primarily film SLR's and DSLR's, I made frequent use of a circular polarizing filter. They're not very expensive, and they offer several useful effects. When I made the switch to digital in ~1999, I didn't find any notable difference in the way the filters affected digital capture vs. film.

As with your sunglasses, in addition to darkening and saturating blue skies and enhancing saturation of most colors, the polarizer was very useful for reducing the light-scattering effect of haze. Living in an area where summer skies are often quite hazy, this was particularly handy.

You could rotate the filter to dial in the degree of effect desired - in my experience, the polarizing effect was generally strongest when the direction of the sunlight was more or less perpendicular to the direction your lens was pointed.

When I made the switch to digital in ~1999, I didn't notice any significant difference in the way the filters affected digital capture vs. film.


I hope this helps :-)

Cheers!
Dan

Rarely use them. Was given a basic Hoya one by a neighbour, and gave it a wee test on a 25mm lens, which is probably a bit too wide (on a 35mm sensor), in that it shows darker and lighter areas to the sky. I did find that it had a slight magenta cast, and did some correction adjustments for that.

The larger diameter and thinner Hoya Pro1 type that I already had, doesn't have any colour cast issues... to my eye.
Without filter (25mm; f/8; 1320"), and with filter (25mm f/8; 1/50").

I thought color filters are no longer needed, use color channels in post. The polarizer is important because it cannot be created in post, afaik.

I am probably asking a stupid question, but here it goes: What prevent you from photographing through the glasses to see the effect?

For darkening blue skies, I rarely use a polarizer anymore. That's under strong Rocky Mountain daylight - our arid Western skies tend to scatter less light in the first place, so they're naturally polarized, to a degree. Here in Colorado, it's a rookie mistake to crank your polarizer up to 11 and paint the sky deep indigo blue.

If it's a hazy summer sky, a polarizer will help draw out distant detail, such as mountains on the horizon. Those two purposes can also be accomplished in Lightroom with selective color and dehazing adjustments, though.

The polarizer's unique party tricks show up when you're looking at reflective surfaces, like water. The filter gives you control over what proportion of reflected and direct light you're capturing. It's also an effective ND filter, when you seek long, flowing exposures. Guess I'd go so far as to say that every time you're photographing water, you should carry a polarizer and experiment with it. How would it affect this photo? You have to judge that on the scene, on the screen.

When I moved from film to digital, I ended up saving a few odds and ends. I still have two Contax Polar filters. They’re linear polarizers, not the current “circular” design. BTW, for the younger crowd, “Linear” vs. “Circular” has nothing to do with the shape of the filter. They’re still discs of glass that thread into the front of the lens and rotate to achieve their effect. It has to do with how the polarizing material of the filter might or might not interfere with light meter sensors or AF sensors that are set behind semi-silvered slits in SLR and DSLR mirrors.

Anyway, I use these near-antiques along with more modern Polarizing Screens that I’ve picked up since. I use them selectively, as they are also defacto ND filters. I’ve seen no real performance difference between the oldies and the new stuff. Great for that Postcard Blue sky and also for seeing through non-specular glare (not reflections). The blue sky effect occurs at 90º to the sun’s position, so be aware that at certain times of day, and the direction you may be aiming relative to Old Sol, you may end up with the deepest blue appearing as a band sort of sloping though the sky, or you may gain little to no effect. Don’t forget to rotate filter while observing the effect.

To emulate filters with black and white film, I don’t desaturate. In Lightroom, I use the color sliders to simulate the effect the common filters for B&W gave, which was to lighten their own and similar colors, while darkening complimentary or near complimentary colors. Color theory does pay off in this regard. Hint: don’t just adjust one.

I’m not typically a Tony Northrop fan, but I do think that this video addresses many of the benefits often raised by users of polarizing filters, and whether modern digital PP techniques can substitute for each.
https://m.youtube.com/watch?v=-rBdqlBbNDE

Read this in a book decades ago and it served me well...

To determine the effectiveness of a polarizer for sky darkening, make a 90 degree angle with your thumb and index finger. Point your thumb at the sun. Now arc your index finger on the axis of your thumb. Along the arc, everywhere your index finger points will have the most darkening of the sky.

This is why it is best to avoid extreme wide angles. There will be too much variation in the lightness and darkness based on the lens capturing more than what is covered by the arc of highest effectiveness.

Ilkka: "3-it removes reflections from water droplets in the air making blue sky darker and clouds to stand out better."

That is incorrect. The sky is blue not because of water droplets but by the scattering light from oxygen and nitrogen particles. It gets darker because polarized filters remove parts of the light reflected. Clouds are made of water droplets and they do get darker through polarized filters, but those droplets are bigger than visible wavelengths so they scatter and reflect all colours, ie. white/gray.

About linear polarizers, they have no bad effect on digital image sensors but will affect TTL light metering and AF functions on SLR cameras so they went out of fashion a long time ago, even before digital cameras. Not sure if anyone ever used a polarized filter on Leica though.

Hi Mike,
I have two types of polarizers that I use with great effect on my digital camera. I have a circular polarizer for general photography and it works very well. I have a linear polarizer that I use in my home studio when I'm copying artwork. I use a cross polarization technique where I place polarizing film in front of my studio lights and a filter on my lens. It lets me dial in the amount of polarization I need to kill specular highlights on paintings. Since I'm metering manually in the studio I don't have to worry about interfering with the meter in the camera.

On my beach vacations I almost always shoot with a polarizer. But, because of the white clouds and sand in most of the scenes, it's imperative that I use a neutral grey polarizer. Some polarizers have funky green or brown tints that ruin different parts of a scene (e.g., clouds and sand) simultaneously. It's very difficult to get something decent in post-processing when that happens.

I wont buy a polarizer unless there's a good return policy. I examine polarizers on a light box and on a sheet of white paper and compare them to my reference polarizer, a B+W e, a very neutral filter that has always done the job just right for me.

On my last trip I fell in love with my new fuji 16mm/2.8 wide angle. I shot a ton of big sky stuff and had no problems with polarizer fall-off. What a fantastic lens :)

A lesson I learned the hard way using a circular polarizing filter on my digital camera. I was using it on one lens pretty much all day and when I wanted to manually stitch together 4-5 vertical images that I thought would make a great panoramic, it did not work out well. The reason is obvious, just like all exposures must be identical, the sky renditions are not because the camera position changes and of course this impacts the sky capture with different polarizing effect levels. I am sure most of your readers realize this, I did not, but now I know.

I use a polarizer when it will make a difference. Don't like to leave it on there because it cuts out quite a bit of light (2 stops?). You may not know how much glare you see off of regular objects because it's something you've seen all your life, so you are use to it. I mostly like it for vegetation, lots of glare on those leaves, and water, streams that is, where you can cut reflections and see those colorful rocks and pebbles in the creek bed. 2 tips - get a good polarizer so you aren't dealing with loss of detail, or a color cast, and 2, don't wear polarized sunglasses when taking photos, you will see one thing, your camera something else.

I don't believe that mirrorless digital cameras need "circular" polarizers, which are a confusing and non descriptive name for a polarizer with a quarter wave retarder plate since all the beam splitters for metering and autofocusing is gone. The wave retarder is a birefringent polyester film (fancy scotch tape) that is most effective at a particular wave length.

Better explanation here

Polarizers and birefringent antialiasing filters might have some sort of interaction, I don't know.

Speaking of quarter-wave retarders, why can't they put them on LCD panels? Having the display on a camera, laptop, or phone go away at some angles is annoying but having the dashboard of my car disappear if I'm wearing the wrong pair of glasses is VERY annoying.

Contradicting some of what I'm reading here, I use an old B+W linear polarizer on a Fujifilm X-T4 (X-trans sensor), and it works just fine. I do recall that in the film days, many SLRs needed a circular polarizer because some element in the metering system couldn't deal with linearly polarized light.

I leave polarizers glued to my medium and tele lenses, but use them judiciously on wide-angle lenses (weird sky shifts). Adjusting the polarizer allows me to control saturation and glare of surfaces that reflect light - grass, leaves and flower petals, fruits and vegetables, glass in buildings, plastic and metal objects, water, even glossy skin. The effect is sometimes hard to predict, but mirrorless cameras make it easy to preview and fine-tune the effect. I would encourage you to give one a try, Mike. Some experimentation will show you the many scenarios in which they will be useful. As someone here has already said, this is one of the areas in which digital post can't do what optical capture does.

I was with you on "Tonality is tough than color" until I did my first curated colour exhibition and was required by the curated to tonally match all my exhibition prints for consistency and lighting. I'm on the other side of that fence now - I agree B&W can be difficult aesthetically but digital makes presenting the chosen aesthetic pretty straightforward compared to colour!

Never tried polarising filters with digital. Having read the above comments, I'm going to.

If you’re out with one of your digital cameras, try shooting with one of the lens of your sunglasses in front as a variation and see what happens… as long as they’re not prescription…

I have a wide assortment of premium polarizers from my days using Minolta Rokkor lenses. Having moved in a three year span to modern Fuji XF lenses I was shocked by how good the modern coatings are and seldom use the filters. I pack too heavily and leave them behind, but I have good intentions. Should I leave the light meter behind instead?

"...the tonal differences with B&W are so marked and so different in their effects that we really need to make some fundamental decisions about tastes and goals."

To be contrary, picking this phrase out there's the germ of a decent argument to the effect that making a good black and white photo-essay is therefore actually easier than creating good colour one. Once the photographer has a some experience B&W allows the imposition of a clarifying set of rules far more easily than colour does.

Wow, there is a lot of misinformation being spurted out. One item is you need a circular polarizer for digital. NO! Where does this garbage come from? You need the circular version for cameras with mirrors and autofocus (mostly DSLRs). This applies to film autofocus, as well. The standard linear polarizer is fine for mirrorless digital, rangfinder and TLR film, manual focus SLR, and most other applications.

Polarizers have their uses for reducing reflections and also as a neutral density filter, but over use of them just results in photos that look ridiculous. If you want to darken a blue sky you don't need them (adjust blue channel luminance and saturation) it will probably do it more evenly with a wide angle than using a polarizer. As usual, this comes down to a question of taste, but when I see photos taken of Caribbean beaches with intense polarization I frequently think: who are they kidding? And why would you want to remove specular reflections from wet leaves, for example (not that you can do it anyway with a polarizer)? I regard polarizers rather as I regard neutral density filters for flowing water as a cliche of "good photography", although I can at least see that the latter adds something in showing something that is a real feature of the scene (movement).

When outdoors in the old days, shooting with film, I always used a polarizer. When I switched to digital in 2005, I continued the practice. BUT, in my observation, the result in darkening the sky is not as uniform on a sensor as it was on film. As an example, the upper left corner may be darkened and then the sky lightens as you move your eye to the upper right corner. Or the sky may be darkened in the middle of the frame, but lighter at the corners. I know that the polarizing effect is dependent on the position of the sun and the direction of the light. But I think there, somehow, is more variation and inconsistency with a digital sensor than with film. Has anyone else reached this conclusion?

I only use a polarizing filter if I need to rid of reflections or if my digital back screen is hard to see under the sun. I have experienced weird banding in the sky with a circular polarizer and learned years ago a ND filter does a better job for sky and area saturation..

I use polarizers for fine art reproduction. One on the lens and one for each of the two lights positioned 45 degrees from the artwork. If it's important to see the brushwork, I'll rotate the polarizer on the lens to allow light to bring out the texture. As for wide angle landscapes, I eschew polarizers because they only polarize a portion of the sky. I can achieve a pseudo polarized effect by selectively adjusting cyan and blue in post production.

I don't use them enough, but I use them some, and regularly carry one or two for my major lenses. Reflections from many materials (including most natural surfaces) are polarized (not from metal surfaces; and from glass it varies depending on angle), so a polarizing filter can be used to reduce or even remove them, which can increase saturation (if polarized glare is desaturating pieces of your scene) or remove reflections from water and glass (depending on angle). And they darken blue skies at some angles (with an ultra-wide lens you can end up with a very clear gradient in sky brightness because of this, which is mostly not what I want).

The other filter I use with digital is neutral density; base ISOs are getting so high that I sometimes need an ND to get a long enough exposure to get silky smooth blurred water, for example, without stopping down "too far" (into significant loss of sharpness due to diffraction, or into more depth of field than I want for the image). I've got a stronger-than-normal ND for that, maybe 6 stops, or 9?

I've been wondering for years about whether circular polarizers were necessary for mirrorless cameras. They became important when AF came in, and I thought it was the phase-detect sensors that cared, but in DSLRs those were mostly reached via a mirror, so it could be the mirror instead. I need to dig out an old linear polarizer and actually, like, test it on a mirrorless, I suppose (I can find so much conflicting information on the Internet that it's either a lot more complicated than I think, or else a lot of people are repeating things they've heard but haven't tested and don't fully understand; I don't fully understand the optics myself, and haven't tested it, so I'm still in the "I don't know" state).

Well Mike, you've been handed an idea for a future blog post: correcting the sadly all-too-common misconception that circular polarizers are needed for all digital cameras, when it's only cameras, film or digital, that use mirrors with a secondary meter behind them to reflect light into an autofocus and/or metering sensors that need them. Is this misinformation from websites or YouTube videos, or clueless or nefarious salespeople trying for an "upsell" who are spreading things that aren't true?

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