Underwater Video Tips: Polar Pro Red Filter for GoPro

Time for part two of the filter discussion that involves a review of the PolarPro Red Filter for GoPro

You can see in the featured image how the retail package presents, it is pretty simple inside we find the filter itself, a tether and a little bag to store the filter that also serves the purpose of cleaning it.

This is the cheapest removable filter for Gopro at a price of $29.99 and it is also available in Magenta version, that for reason explained in the previous post I recommend to skip entirely.

This is the image on the back of the package with the product details

_DSC0173

The declared working depth is 10 to 70 feet or 3-21 meters. For what we have seen in the previous post this is somewhat optimistic and will be true only in ideal conditions of blue sky and 100 feet visibility in clear blue water, in different conditions the maximum depth will be less.

The filter is made of Optical acrylic and there are no defects on it, it is fairly light and snap comfortably on and off the GoPro dive housing.

It may be worth seeing what is the effect of this filter on the GoPro

PolarProGoPro

As we can see the polar pro red filter actually casts a light magenta tint on the gopro image.

This is the same image without the filter

DCIM100GOPRO

So as a Hero2 user would I spend $29.99 for Polar Pro or $83.00 for the SRP dome the only true removable filters? Or should we say what do I get for additional $53?

Let’s have a look at performance of the two filters in daylight those are measured with another camera that can set a custom white balance keeping fixed shutter speed and ISO and seeing how the aperture changes:

             Polar Pro                                             UR/PRO

Temperature                  3200K                                                  2900K

Tint                                  M7                                                         M5

Fstop loss                       1+1/3                                                     1+1/3

So the UR/PRO is warmer than the Polar Pro and has got little tint to it. It may be useful to compare using a camera with custom white balance how the histograms look if we fix the white point and then apply the filters.

This is an image captured with a Sony RX100 after white balance

_DSC0176

The colours look natural as they should be we now put the PolarPro filter on the RX100 lens keeping the same shutter and ISO the camera opens the aperture to compensate for the light loss

_DSC0177

Warmer image with a magenta tint

If now we push the URPRO on the RX100 lens we get this image

_DSC0178

The image is globally warmer and has no obvious tint.

Let’s now have a look at the histograms this is the original image

NofilterRX100

Nice histogram pretty balanced, let’s have a look at the histogram with the PolarPro

PolarproRX100HistogramWe see the blue and green reduced but a behavior with spikes for all colors, this is due to the tint of the filter

If we look at the UR/PRO the histogram is typical of a color shift to warm

URPRORX100HistogramNote the lack of spikes and more balanced profile

Both the UR/PRO and PolarPro settle at identical exposure ISO400, f/2.5 1/50 of a sec with a 1 and 1/3 f-stop loss from the camera without filter that has a f/4 aperture.

So what does this mean? The UR/PRO behaves like a camera CTO filter most likely a CTO 1+1/2 if not double shifting the color temperature down in a similar fashion for the whole spectrum as it does not have a tint.

The PolarPro does the same with a less warm bottom end and a clear magenta tint that acts as a green filter. The magenta also creates spikes in the green and blur that are characteristic of a selective filter.

So which one is better? Overall the UR/PRO can’t be faulted as it does not introduce any tint and is warmer will most likely work in blue water at greater depths, how much greater is impossible to say. The UR/PRO is also very well balanced the proof is in the Gopro photo in auto there is no hue of any type which means this filter can be put in the camera at fairly shallow depths and still perform well.

The PolarPro seems to be a combination of a CTO filter plus a minus quarter or half green, this filter will be less effective at depth but work well both as red filter in blue water and because of the tint also in greenish water. It will however generate unnatural tint in blue water.

The ergonomics of the PolarPro are great the light piece of plastic is essential a design copy of the GoPro flat port cap the button is accessible and you can see the display if you need to. For $29.99 you can’t ask for more especially as it does well in water that is greener too. I can imagine it will require some tint correction in post in really blue water but this I have only seen in the Bahamas or Turks and Caicos anywhere else the green tinge was there and this cheap filter will take care of it. Also the Auto WB of the GoPro seem to love green so this will really do well in most occasions and I look forward to test it in fresh water where so far I have not used any filter.

Now that we know how the filter is done and what it can do how do we justify this?

A number of explanations, we have to hope that there has been no manipulation of the clips, so let’s continue with this assumption:

  1. The water color in California is quite green as there is plenty of kelp and algae
  2. The PolarPro has a magenta tint, the URPRO is just warming the color temperature
  3. The SRP dome has a design issue as there is a layer of water between the lens and the filter that may absorb color and can’t be recovered
  4. The GoPro White balance itself is pretty green

The combination of those factors could explain the difference in performance in this test.

Now coming to the Hero3 what about SRP Blurfix 3 versus PolarPro considering the filter themselves are the same?

The SRP blurfix is now closer to the lens so not affected by water between lens and filter, it has a 55mm thread which means you can add a polarizer very useful for outdoor shots on the boat, total cost:

SRP Naked $32 + Red Filter $77 + Polarizer $31 = $140

Polar Pro Red Filter $29.99 + PolarPro Polarizer $29.99 = $60

A hefty $80 difference for a piece of equipment the Hero3 that costs $399 is this justified? If we take out the Polarizer and consider the SRP dome for Hero3 at $77 the difference is still $47.

I would say it depends, for the average user that has an Hero2 or Hero3 and uses it at normal depths and is not after the maximum quality the PolarPro is just fine affordable and keep the overall cost down, it can also be removed and the ergonomics are great.

If instead you want to use the filter at greater depths and especially in water that are really blue the URPRO cannot be beaten however the price differential is substantial.

Now some people will say hang on a minute filters have to be tested in water etc etc. Well that is not definitive either because filters perform differently in different conditions, different locations so there is not an absolute best ever this is why cameras have custom white balance. Filters are not rocket science there is a lot that can be foreseen just by looking at histograms and temperature and we can set our expectations quite easily.

If you are in the market for a removable GoPro filter at $29.99 the PolarPro Red filter is a killer as it works well in green water too.

If instead you are not after a removable filter just get yourself a sheet of Lee double CTO and a pair of scissors and cut it to go inside the housing, this will cost 50 cents and be perfectly fine.

If you are a perfectionist and want to push your gopro to the maximum working depth of a filter and want a removable option the SRP UR/PRO is for you.

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