Using a magenta filter for daylight?

Mack

Mu-43 All-Pro
Joined
Jan 14, 2018
Messages
1,869
From the LibRaw guys: https://www.libraw.org/articles/magenta-filters-on-digicam.html
and https://www.libraw.org/articles/white-balance-in-digital-cameras.html

The magenta got my interest and I had to try and see if I could null the three colors in the RAW histogram based on a gray card. I used a Godox TT350-O flash since it's dark out. Camera was the Olympus E-M1 Mark II and Olympus 12-100mm f/4 Pro lens. Base ISO 200 and lens at f/5.6 to minimize vigentting I got at f/4 which widened the spike.

I ended up with a lot of Magenta filters and a couple of Cyan from my old Unicolor Color Printing Filter Pack which gave me what I think they were getting at in the first article's link.

Note the three-color spike in upper right histogram from FastRawViewer below:

FastRawViewer.jpg
Subscribe to see EXIF info for this image (if available)



And one from RawDigger for good measure:
RawDigger-Gray-Card.jpg
Subscribe to see EXIF info for this image (if available)


The RGB are in alignment with the Magenta 0.95 and Cyan 0.25. I discovered that a Lee #002 Rose Pink filter does the same job on my E-1 Mark II.

On my Nikon Z7 II the lighter Lee #110 Middle Rose worked best (About a 0.30 Magenta plus a 0.075 Yellow.). However, not as good as the E-M1 Mark II though as the red channel still lags a little to the left in the histogram in the Z7 II - but not by much. Requires less over-exposure though.

Generally on the camera's LCD, the histogram of the gray card has all spikes aligned if WB is nulled. The RAW histogram of the same shot always looks different in where the spikes land.

Pitfall was it took maybe another stop and a half of light for the filters, but the gain is reduction of blue and red channel noise by filtering back the green channel. Green still receives same amount of light given the exposure increase, and allows more of the blue and red channel light to even out the noise in the three channels.

At least that's what I get out of it. :confused: Might be useful for the astrophotography guys and their noise.
 
Last edited:

Mack

Mu-43 All-Pro
Joined
Jan 14, 2018
Messages
1,869
Took the E-M1X out into the backyard and threw peanuts at the CA Scrub Jay.

I put a Lee 100mm filter carrier on the Olympus 300mm lens. I put cut out 100mm square Lee #002 Rose Pink filter into the holder and shot away. I based the exposure off the red blinkies (ETTR) off a sunlit white Styrofoam ball which later would be used with the WB eyedropper tool in ON1 Photo RAW 2021.

On the RAW/ORF images in ON1, I used the eyedropper on the white ball which nulled the filter's magenta color to white. Right clicked on the RAW image and clicked on "Save Settings." Then clicked on all other RAW/ORF images (CTRL+mouse click), and the on an image a right click and clicked on "Paste Settings" which corrected all the OEF/RAW images as show below.

Interesting as to how easy it was against trying to do all the edit work normally done. How much noise reduction is avoided by using the Lee #002 Rose Pink filter I'm unsure of, but I'll take the LibRaw guy's word for it. Red JPG is the origional as shot through the filter, and the RAW/ORF is the WB adjusted image.

Lee-002-Filter-Test.jpg
Subscribe to see EXIF info for this image (if available)



One from above:
_A160455-filtered.jpg
Subscribe to see EXIF info for this image (if available)
 
Last edited:

Latest threads

Links on this page may be to our affiliates. Sales through affiliate links may benefit this site.
Mu-43 is a fan site and not associated with Olympus, Panasonic, or other manufacturers mentioned on this site.
Forum post reactions by Twemoji: https://github.com/twitter/twemoji
Forum GIFs powered by GIPHY: https://giphy.com/
Copyright © Amin Forums, LLC
Top Bottom