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Blue turns Purple w/ Green dropped

Posted: Wed, 2nd Mar 2011, 3:05pm

Post 1 of 15

Skywing269

Force: 0 | Joined: 2nd Mar 2011 | Posts: 1

Member

Hi All,

I am trying out Photokey 4 Pro for use with a new client of ours and I am having an issue with maintaining original colors. All the green is dropped without issue, however with a number of subjects wearing light blue shirts I am finding that the blue is shifting to more of a purple tint after processing. Could anyone be of assistance as to what needs to be adjusted to prevent this color shift?

Thanks.
Posted: Wed, 2nd Mar 2011, 4:26pm

Post 2 of 15

Axeman

Force: 17995 | Joined: 20th Jan 2002 | Posts: 6124

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SuperUser

Adjust the spill Suppression. If the photos are good and there isn't any green color spill on the subject, you can turn the Spill Suppression off entirely, and your colors won't be affected at all. If there is some green spill present, though, PhotoKey will have to alter the colors somewhat to remove the green still present, so try the different Types of suppression available, and adjust the Strength until you find the best compromise, where the colors are still as close as possible.
Posted: Fri, 11th Mar 2011, 6:50pm

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njush

Force: 1720 | Joined: 29th Jan 2010 | Posts: 46

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This is often more than if "the photos are good and there isn't any spill".
The thing is that many shades of "blue" (particularly light-blues and colors the teal range) actually contain a significant green channel value that will can tamped down by any color spill suppression calculation. When this happens, blue and red channels are left untouched, so they are relatively elevated ... leaving a "purple" look.

If you have photoshop, use the info tool over the "blue" clothing in your original photo as well as a PK Export to read the Red/Green/Blue channel values and I think you'll see this clearly in the channel values.

You'll pretty much always need the color spill suppression, though, due to partially transparent edge pixels that contain both foreground and background color (particularly for whispy hair).

In more advanced compositing, this would be handled by pulling an extra core matte key to protect against color adjustment, but PK isn't quite to that level of complexity yet (and rightfully so, as complexity doesn't typically translate to "easy to use").

A quick fix inside PK is to draw a mask over the clothing using the "retain alpha" setting. This will protect the clothing from the spill suppression calculation.
Posted: Wed, 8th Jun 2011, 4:42pm

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MamaCas

Force: 750 | Joined: 1st Oct 2010 | Posts: 16

PhotoKey 4 User

Gold Member

I have been having this problem but not too seriously. I take pictures of lots of children and the girls wear pretty barrettes. Sometimes the barrettes are clear, which means that they will pretty much become the color of whatever background i use. Other times, the colors are just not reproduced accurately, like yellow balls on the bareetes become orange after green screening. I tried my best to get them back to bright yellow, but when I did, there was a lot of light green spillage around the hair. I have taken to copy/pasting the barrettes from the original photo back onto the finished product in Photoshop, resizing them as necessarry (sp?). It's a little extra work, but it gets me accurate results. if anyone can tell me of a quicker solution I'd be very happy and grateful. smile
Posted: Tue, 17th Jan 2012, 1:15am

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sliip

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So it sounds like the the best way is to create a mask for these instances? If you are shooting a large group with this problem are there other workarounds besides the mask? and spill suppression?
Posted: Tue, 17th Jan 2012, 5:13pm

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Axeman

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SuperUser

Spill Suppression does what it can to remove the green and retain the original colors. Masks allow you to force specific areas to retain the original colors, no matter how the image is processed.

Those are pretty much the two options.
Posted: Wed, 18th Jan 2012, 2:13pm

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Joe@Barksdale

Force: 20 | Joined: 22nd Feb 2011 | Posts: 14

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Rating: +1

This has been a huge issue for us and we find that if a subject is wearing any sort of teal, it gets shifted to purple because of spill suppression. Also watch out for lemon yellow. That gets shifted to a gold as well.

Its easier and faster to simply turn spill suppression off and brush the remaining color out in Photoshop.

If spill suppression could be "brushed onto selected areas" rather than simply applied to the whole image it would be a phenomenal tool. As it stands it's a great tool, but a double edged sword as it can harm other seemingly unrelated colors and you need a keen eye to spot it because there is not a good way to compare before and after images.

One potential cure for this would be to have the mask tool be a brush-able option rather than a point click one.
Posted: Wed, 18th Jan 2012, 2:26pm

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Simon K Jones

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FXhome Team Member

Thanks for the feedback! Improved spill suppression is an area we are researching.
Posted: Fri, 9th Mar 2012, 7:50pm

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chrisjimphoto

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Gold Member

wow..a "brushable" mask and spill suppression would be freaking amazing. any chance of this in the new upgrade?
Posted: Fri, 9th Mar 2012, 8:12pm

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eapmike

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that would be great to have. is there any time line for the new version?
also, i hate to ask here but, what other programs are there for doing chroma keying? i have looked a lot thru google but photokey seems to be the best out there. but with the way the spill suppression works it makes a lot more work for my team. i do school photography and i have to mask out 30 to 40% of the kids because there are wearing blue, yellow, teal, and green. I know that i can't do much with a kid with green stripped shirt but a paintable spill suppression would be stellar and save us so much time.
Posted: Tue, 27th Mar 2012, 3:04pm

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Joe@Barksdale

Force: 20 | Joined: 22nd Feb 2011 | Posts: 14

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Is there any news on how V5 will handle this color shifting? Posting to FB and emailing from within the app are great, but I'm very anxious to hear (or see) some news about the performance of the main task of the program.
Posted: Tue, 27th Mar 2012, 3:21pm

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Simon K Jones

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FXhome Team Member

Hey Joe. The new spill suppression filter is very powerful and provides much more control than the old systems.

The best thing about it is the new despill view, which shows you exactly what parts of the image are being affected by the spill suppression (similar to the matte view for seeing transparency). You can then adjust the area that is affected. In the case of some blue/yellow clothing being affected, this means you can check to see if the clothing is being accidentally suppressed and easily make adjustments.

We'll be saying more about this and showing some examples next week once we've finished our office move.
Posted: Tue, 27th Mar 2012, 3:40pm

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Joe@Barksdale

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Thanks for the teaser, Tarn. That sounds promising!
Good luck with the move - we all look forward to V5.
Posted: Tue, 27th Mar 2012, 4:24pm

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Simon K Jones

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FXhome Team Member

Rating: +1

OK, I couldn't leave it there, so here's a really quick preview of some of the new spill tech, though I literally just threw this together so forgive any rough edges to the composite:

TOP LEFT = no spill (note the green on the dress. This is simply the original photograph with the green screen removed)
TOP RIGHT = normal spill suppression (green removed, dress is now a neutral grey)
BOTTOM LEFT = spill replacement. This is one of the optional new features. The green spill has essentially been replaced with a pink spill, matching the pink background. This is different to the light wrap filter, though, in that it only affects areas the the original green spill affected. In other words, it's a 1:1 replacement of the bounced light, from the green of the green screen to the pink of the new background. Note how the skin tones are completely unaffected. The intensity of this effect can be adjusted - I've got it quite high here to make it obvious what's happening.
BOTTOM RIGHT = the despill view. Much like the matte view, this shows the areas that are being spill suppressed. So in this example you can see how the pink spill replacement is primarily affecting the rear of the skirt and the hair.



It's a VERY powerful tool when used appropriately. You won't want to use it all the time, of course, but having it as an option is pretty useful.
Posted: Thu, 29th Mar 2012, 2:38pm

Post 15 of 15

Joe@Barksdale

Force: 20 | Joined: 22nd Feb 2011 | Posts: 14

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Very interesting - Thanks for further teasing!

I'm curious to see how it works without a background as we export knocked out PNG's and use Kodak DP2 to apply assorted backgrounds in our hi-volume workflow.