Is There a Plugin That Provides the Effect of a Polarizer in Post Processing?
/
This is the polarizer that I use. It is from B+W and is fully multicoated using nano technology. It uses Kaesmann polarizing foils and only costs 1 - 1.5 stops of light
Hello neighbours. This question shows up relatively regularly and sadly the answer is a short on.
There is no post processing filter that provides the effect of a polarizing filter used at time of shoot.
The reason for this is quite simple. When you make a photograph, you are dealing with the light as it is and to filter for polarized light, you need to intercept that light before it gets to the sensor. On digital cameras, we do that with what is called a circular polarizer.
What Does a Polarizing Filter Do?
This filter only has one job, which is to filter for polarized light. The effects that we see appear to be multitudinous but really the filter only does this one thing.
Light that has been reflected or refracted in some way creates glare, lack of saturation as well as a loss of some detail. This can be by the light travelling through water droplets in the air, light being reflected off water, light being reflected off painted metal. The polarizing filter passes the light that you want, in accordance with mathematical formulas that describe how the filter passes light. A simple example is that a polarizing filter pointed at the light source or precisely opposite the source has little effect, whereas the maximum effect happens at 90 degrees to the direction of the source. Do note that a polarizing filter has no impact on specular reflections off unpainted metal and chrome. To deal with those reflections, you have to physically change the camera position at time of shoot.
It should be noted at this point, that the light source needs to be a point source. Highly diffused light has no specific direction, and so the effects of the polarizing filter are minimized.
This is why a polarizing filter used on an ultra wide lens for a landscape will often show a significant difference in the blue of the sky on a clear day, because the angle of the filter to the source is different in an ultra wide as you look across the angle of view.
Because of this critical angle to source relationship, polarizing filters have two rings. One mounts the polarizer to the lens, and the other allows rotation of the polarizing element to allow the creative to select the amount of polarizing filtration.
Avoiding the After the Fact Problem
Once the image has been recorded, there is no way after the fact to apply a polarizing filter because the source is no longer in place. While there are plugins that claim to do polarization, they don’t do it. What they will do is try to simulate the effects of a polarizing filter by increasing saturation, increasing dehazing, increasing contrast and performing rudimentary sharpening, which as you already know is just increasing contrast between adjacent pixels of differing luminosity.
You may find these plug in effects perfectly acceptable, but they won’t work to remove reflections from painted metal, such as automotive bodies, or from water, as one might wish to do for oceans, lakes, rivers, pools etc. To try to manage reflections, the only method that actually works is the use of a polarizing filter at time of image recording.
There are some photographers who deal with this by leaving the polarizer mounted when photographing outdoors, even if that person does not rotate the filter for every shot. While the probability of being at perfectly 90 degrees to the source is low without some effort, so too is the probability of being right on or at 180 degrees to the source, and so by merely having the filter mounted some level of polarized light gets passed to the sensor.
While this may sound lazy to some, odds are in the favour of the person who does this in getting richer colour and reduced reflections, and the photographer who chooses to spend the 2-3 seconds to rotate that outer ring will pay off even more.
This is simpler than taking the filter on and off which is a great way to introduce dust, dirt and fingermarks.
In the past, before we had the incredible sensors that we have today, photographers would worry about the necessity to raise the ISO up to two stops to counter the loss of light that happens in a circular polarizing filter. This is not really as bad as it sounds. If you were outdoors, shooting without the filter at 100 ISO, you would be shooting at 400 ISO with the filter. This level of sensitivity on any sensor built in the last ten years does not increase noise so long as you do your job of getting the exposure correct. If you use the principles of exposing to the right, you further negate the risk of noise, although you accept that you will need to do editing on your image.
You Forgot Your Polarizer
Now let’s say that you got home and realized that you did not use your polarizing filter when photographing. Can you fake it out in post? You could use plugins to do this, but within the limits of fakery, you can do some things.
In your editor of choice, move to whatever allows management of Saturation and Luminance by colour band. This is often called HSL. For the colours that you want to richen, increase their saturation and reduce their luminosity. You’ll probably get kind of close to where you want to be. Next move to the Curves module and increase the contrast by making a gentle S curve, pulling the line down gently in the dark to shadow area and pushing the line up gently in the highlight to white area. Many pieces of software offer a one button preset to do this.
This method will not deal with surface reflections very well if at all, but more often than not it gets you partway there. Your software may have a Dehaze function which you could use very sparingly as it behaves with no subtlety at all, or if you use DXO software, their Clearview function is very good at this within the limits that the reflections still exist.
In Summary
A stepping ring made of brass. Brass is best, aluminum is a cheap and unpleasant choice
Therefore the best route to get the effect of a polarizing filter is to actually use one. As is true of all optics, better glass and better components make for better filters. The lowest cost no brand or house brand polarizer will produce questionable results whereas a filter from a respected filter house will do a better job. You do get what you pay for, so don’t put a cheap polarizer on the front of your expensive lens. I recommend buying the largest diameter polarizer that your largest front element lens can use, and then buy inexpensive stepping rings to use that same polarizer on lenses with a small front diameter and filter mount.
Do you have an idea for an article, tutorial, video or podcast? Do you have an imaging question unrelated to this article? Send me an email directly at ross@thephotovideoguy.ca or post in the comments. When you email your questions on any imaging topic, I will try to respond within a day.
If you shop with B&H Photo Video, please consider doing so through the link on thephotovideoguy.ca as this helps support my efforts and has no negative impact whatsoever on your shopping experience.
If you find the podcast, videos or articles of value, consider clicking the Donation tab in the sidebar of the website and buy me a coffee. Your donation goes to help me keep things going.
Click this link to submit your questions
I'm Ross Chevalier, thanks for reading, watching and listening and until next time, peace.
