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. 

[jrhoffman75]

Welcome to the forum.

Can you post a link to a Dropbox or One Drive folder where you can post a RAW file f the images that you are describing?

[FelixA7]

Hi! 

Thanks for asking for the images. Here's a link to the folder: https://www.dropbox.com/sh/qclaw34fjkh1g38/AACih13aYJrhJ6Tql1dgBZkaa?dl=0. If you look hard at the astrophotograph, you can see the fine red grain. 

If you look at the photos of the elephant paintings and one of the figure drawings (be warned, the figure is unclothed but it's a drawing) you will notice the magenta tint. The second figure drawing shows the image after I changed the white balance. You can see that, even though the magenta is gone, there is still a tint -- a kind of drabness to the image. That is present regardless of exposure. 

Note -- I included an iphone photo of the elephant drawing that shows what the elephant painting looks like in real life. 

Felix

[jrhoffman75]

I can't tell anything meaningful about the sky photo since Canon DPP considers it an unrecognized file type. Can you post in DropBox the out of camera file?

The other images are off-color because of a white balance problem.

I am assuming that the door moulding should be white and the models hair black.

By doing that the images look correct.

What lighting type are you shooting in?

[ebiggs1]

The images are so small its difficult to do any real adjustments. But Photoshop has no problem placing ther color balance and WB wherever you want it.

My guesses!

The star shot is just too pixelated to work on.

[FelixA7]

Thank you for your great comments. I can adjust the color balance in photoshop, but I was hoping to figure out what is off with the color balance in the camera itself.

I am shooting photos of my drawings in an interior space with two studio lights, set to warm light, directed at the drawing from 45 degree angles. The lighting doesn’t matter — I can go in and set the white balance accordingly and there’s still the magenta tint or, less frequently a greenish tint. The tint drowns out the colors.

I’ll get a better JPEG of the astrophotograph. Out of the camera, the image is okay. It’s when dozens of images are stacked and processed that the red grain becomes pronounced.

[FelixA7]

Here's a smaller photo of a galaxy.  You can see the red grain when you zoom in. 

[jrhoffman75]

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@FelixA7 wrote:

Here's a smaller photo of a galaxy.  You can see the red grain when you zoom in. 

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There is a good chance that is color noise from a high ISO. What were the shooting conditions?

Here is your first image, first as posted imported into Lightroom and second, with color noise and luminance noise correction applied.

Your base image is very good; nice point stars. No lens aberrations.

[ebiggs1]

On your sky shot a simple WB adjustment in levels produces this. I have no idea if it is correct. The center of your star cluster is drastically overexposed so defining WB is more difficult.

I see lots of color in the out lying starts so I imagine it is close. More time in PS and a better exposure would yield nice results.

[jrhoffman75]

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@FelixA7 wrote:

Here's a smaller photo of a galaxy.  You can see the red grain when you zoom in. 

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Here is the image as imported into Lightroom with color noise and luminance noise adjustment applied. Masking and sharpening to accentuate the stars.

Nice point stars. No clipping anywhere in the image.

Since it was a jpeg I couldn't adjust color temperature, but generally astro shots look good at around 4000K or so.