Color correction: filter vs. software?

[CT-Rich]

When I started making videos I was using a GoPro camera with their limited quality editing software. I bought a red filter to use diving and was pretty happy with the results (except for the lack of image stabilization). After ruining/ losing two of them, I switched brand to the less expensive SJcam and bought some Corel editing software, but red filters I had are no longer useful and I started usin software to balance the color.

So my question is this: which is better, filter or software? Here is my logic and hopefully someone with a much more sophisticated and practical understanding will offer some guidance. A red filter works by cutting the amount of non-reds getting to the camera sensor and thus restores reds by not recording data about all the colors. I.e. You block a lot of light from the sensor. This makes sense from the days of film cameras because there were limits to what could be accomplished in the darkroom when editing film or making prints.

When recording video without a filter, you get a lot more light hitting the sensor but it skews heavily towards the blues and greens. The software balances it by bringing up the reds (for which there is less data) and bringing down the blues and greens.

I know somewhere out there someone who has done the massively anal amount of research to give a definitive answer. Any takers?

 

[rek_diver]

I recently got a GoPro Hero 4 and did a weeks worth of diving, shooting mostly movies. I did not use any filters, this trip was a "trial run" to see what sort of quality I can get using 2 video lights mounted on a tray.

The videos were very good, but still skewed towards the green except when I was very close to what I was filming. I have tried various video editing programs in the past, with an older camera set up, with mixed results but I figured with this new rig and lights I'd get much better results.

Attempts to shift the colors toward red were not very good, it only made a bit of difference and made a lot of the shots "too warm" and the background water turned a magenta color.

I did a lot of research, read a lot of reports by other divers, and I have since purchased a 3 filter set and look forward to much better results on my next trip.

 

[cmrangel]

The problem with trying to correct the red in software is that you can't restore what isn't there. When the RGB gets recorded, it is very possible that the red channel is clipped to black or very close to it. Trying to restore that will not work. This is because the camera is trying to expose to the luminance value which is driven more significantly by the green and blue channel. One trick if your red channel is almost completely black, is to use a channel mixing editing tool to mix in some of the blue (and maybe green) channels into the red. This will help get you something but will still not restore the image to what you saw.

Using a red filter blocks the blue and green making for significantly less light reaching the sensor. This causes a more noisy image since the camera is exposing for a lower light image but at least there is data in all of the Red, Green, and Blue channels.

 

[Kharon]

Both.

 

[Slamfire]

The problem with trying to correct the red in software is that you can't restore what isn't there. When the RGB gets recorded, it is very possible that the red channel is clipped to black or very close to it. Trying to restore that will not work. This is because the camera is trying to expose to the luminance value which is driven more significantly by the green and blue channel. One trick if your red channel is almost completely black, is to use a channel mixing editing tool to mix in some of the blue (and maybe green) channels into the red. This will help get you something but will still not restore the image to what you saw.

Using a red filter blocks the blue and green making for significantly less light reaching the sensor. This causes a more noisy image since the camera is exposing for a lower light image but at least there is data in all of the Red, Green, and Blue channels.

I posted a similar thread a few weeks ago. One of the conclusions I got is that with filters the subtractive color correction is applied before compression, whereas software is applying it after compression. I do not know how relevant this will be to the end results.

Another trick I use is to lower the saturation slightly when altering the RGB channels. It ends up reducing the dominance of blue or green water. See below.

 

[Andy Willett]

ambient filters

 

[Andy Willett]

ambient filters

my ambient filters article covers overview on using ambient light, then adding filters to the camera and then adding a ambient filter to the lights. Let me know what you think
Andy