Issue with Magenta Tinting

[FelixA7]

Hi all,

I own an EOS t7i and, in the last 7 months or so, I've struggled with magenta tinting of my photographs. No amount of white balance adjusting helps to bring the coloration back to what it is in real life. I could make the colors have a green or gold hue, but those look even more unnatural than the magenta. 

I am separately an astrophotographer and several of my astrophotographs, when perfectly tracking at long exposures, have a field of tiny, magenta/red grain to them. I've tried various astrophotography specific approaches to eliminate the grain, which some of the professionals in the field refer to as "walking grain." None of those approaches have worked. I'm wondering whether that tinted grain is related to the magenta base that I get when using auto whitebalance. 

Thanks!

Felix

P.S. This is my first time posting on this forum and I apologize if this topic has been covered elsewhere. 

[ebiggs1]

John, I believe the OP has a camera setting and/or photo shoot set-up issue more than a camera fault. The reset and  outdoors test will confirm it.

[jrhoffman75]

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@ebiggs1 wrote:

John, I believe the OP has a camera setting and/or photo shoot set-up issue more than a camera fault. The reset and  outdoors test will confirm it.

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I agree. 

Based on his astrophotography images I consider the results to be expected. The T7i isn't a high ISO champ. 

I think the room environment for the easel shot is challenging the capability of the camera auto WB capability. Room seems to have a green bias when the adjusted image is available. Red/magenta is opposite green on the color wheel. 

Your advice for an outdoor shot is right on. 

[ebiggs1]

"...  there’s still the magenta tint or, less frequently a greenish tint."

OK here is what you need to do. First reset the camera back to Canon defaults. Menus, Tools, Clear all settings and Clear all custom settings. Important do both. Now set the camera to P mode. One shot, not Ai-servo and just one center focus point. ISO 200 and auto WB. Preferably Raw but foe this test jpg is OK.

Go outside on a nice day and take some random shots of varying subjects. Look them over in PS without adjustment. If they look great, there is nothing wrong with your camera and all the tinting is coming from you. My guess that will be the case but let's make sure. Do the test.

[jrhoffman75]

 Did you take a dark frame image as well as multiple sky images?

The stacking software may have the capability of zeroing out the sensor noise by subtacting the dark frame image info from the sky images.

[ebiggs1]

"I own an EOS t7i and ..."

... and what lens are you using? Perhaps it has excessive chromatic aberration. If it is the kit lens I suggest you get a better lens for astro work.

[FelixA7]

Hi all!!

I’m sorry for the 6 month delay in responding to all the great responses.  I’m so appreciative.  So, I reset the settings as per the recommendation of multiple people who posted above. My outdoor shots were clear of the magenta! Even at iso 800 and 1600.  I struggled with white balance indoors, however. I used all the various pre-set lighting condition options for WB.  All of them tilted one way or another — too green or too magenta.  And, when I tried to correct afterwards, there was always a lingering hue.

But, over time, all the old magenta issues returned.  As I used remote/wifi settings, set different focus distributions and switched back and forth to RAW …:

what’s more, I was never able to get rid of the red grain in the astrophotography.  Note that, for the deep sky photos, I’m hooking my t7i to an 80 mm or 230 mm aperture (not FL) telescope with high quality glass. The shots are guided electronically to control for periodic mount error. I use a field flattener. I am taking dozens of frames and then stacking them with a special astrophotography program.  I use Darks, Flats and Bias frames for calibration.  That red grain is a problem even in the individual frames, but it really flares up after stacking and after I use levels and curves to draw out the nebulosity around the stars. 

What John Hoffman did in Lightroom is amazing.  I will play with those corrections when I next process astrophotographs.  However, I do feel like some of the nebulosity and faint shapes are lost after the Lightroom adjustments.  And I worry that, when I have hours and hours of stacked exposures, there will be even more nebulously and subtle color to lose.

the telescopes, by the way, are f/4.5 and f/10 respectively.