4.6k Ursa Mini magenta issues?

[Akos]

There is quite a long thread on the official forums about the 4.6k having a magenta cast and/or magenta-toned vignetting. Any owners here notice this?

https://forum.blackmagicdesign.com/v...hp?f=2&t=46112

[vicrattlehead]

There is quite a long thread on the official forums about the 4.6k having a magenta cast and/or magenta-toned vignetting. Any owners here notice this?

https://forum.blackmagicdesign.com/v...hp?f=2&t=46112

No problems whatsoever with my copy of the camera. All is well. : )

[KKeller]

It sounds like their tests are really unscientific but since there is no tinting adjustment in camera some green or magenta pollution would be a little expected.

[RyLo]

No problems whatsoever with my copy of the camera. All is well. : )

Have you done the test of shooting a completely evenly lit white surface? Your camera could still have the issue and it just isn't as severe as the others.

I'm a little surprised this issue wasn't fixed when we saw it in some of the beta footage.

[vicrattlehead]

Have you done the test of shooting a completely evenly lit white surface? Your camera could still have the issue and it just isn't as severe as the others.

I'm a little surprised this issue wasn't fixed when we saw it in some of the beta footage.

To verify, I just shot it on an evenly lit wall at 2500k with and without a lens, and in both cases no visible magenta vignetting or color cast whatsoever, live or on playback. Tried iso 800 and 1600, results were the same.

Also went through a bunch of clips I have in both ProRes and 4:1 RAW, interiors and exteriors, various lighting conditions, and no issues in any of my clips.

Using pro Nikon lenses (ais, afd's and g's) with Redrock Micro adapters.

[RyLo]

To verify, I just shot it on an evenly lit wall at 2500k with and without a lens, and in both cases no visible magenta vignetting or color cast whatsoever, live or on playback. Tried iso 800 and 1600, results were the same.

Also went through a bunch of clips I have in both ProRes and 4:1 RAW, interiors and exteriors, various lighting conditions, and no issues in any of my clips.

Using pro Nikon lenses (ais, afd's and g's) with Redrock Micro adapters.

That's great news, thank you. Hopefully there are more cameras like yours than the ones having issues.

[JLdp]

this user did some tests, there is definitely magenta but the alexa and dragon are green. i wish he used a color chart but i guess he had a short period of time.

http://bmcuser.com/showthread.php?16...gon-comparison

[mstrouty]

Not trying to dig up an old topic, but I was doing some IR cut filter tests with a couple of my NDs, and was surprised to see that the 4.6k needs a IR cut even without any ND filtration. First shot is with a Hoya IR cut and second is no filtration at all. Brought both DNGs into camera raw and set the WB and tint the same. I have been taking out a little magenta on all my grades with the 4.6k and wonder if just shooting with the IR on all the time would solve it for me.

I know it's probably old news to you BM guys, but I'm coming from Sony land where I don't think I used any IRNDs until over 4 stops and even then it was minor. Shooting adjustment for me, for sure.

Oh, and I did the no lens against a blank wall test and didn't see any weird magenta sensor issues, so it definitely doesn't appear to be affecting all cameras.

With Hoya IR Cut
withIR.jpg

No Filtration
woIR.jpg

[Note Suwanchote]

Not trying to dig up an old topic, but I was doing some IR cut filter tests with a couple of my NDs, and was surprised to see that the 4.6k needs a IR cut even without any ND filtration. First shot is with a Hoya IR cut and second is no filtration at all. Brought both DNGs into camera raw and set the WB and tint the same. I have been taking out a little magenta on all my grades with the 4.6k and wonder if just shooting with the IR on all the time would solve it for me.

I know it's probably old news to you BM guys, but I'm coming from Sony land where I don't think I used any IRNDs until over 4 stops and even then it was minor. Shooting adjustment for me, for sure.

Oh, and I did the no lens against a blank wall test and didn't see any weird magenta sensor issues, so it definitely doesn't appear to be affecting all cameras.

With Hoya IR Cut
[ATTACH=CONFIG]18329[/ATTACH]

No Filtration
[ATTACH=CONFIG]18330[/ATTACH]

interesting! Thanks for this. I'll check against my set of Hoyas also.

[Adam Roberts]

Not trying to dig up an old topic, but I was doing some IR cut filter tests with a couple of my NDs, and was surprised to see that the 4.6k needs a IR cut even without any ND filtration. First shot is with a Hoya IR cut and second is no filtration at all. Brought both DNGs into camera raw and set the WB and tint the same. I have been taking out a little magenta on all my grades with the 4.6k and wonder if just shooting with the IR on all the time would solve it for me.

I know it's probably old news to you BM guys, but I'm coming from Sony land where I don't think I used any IRNDs until over 4 stops and even then it was minor. Shooting adjustment for me, for sure.

This is pretty much the same with the BMCC. Some surfaces reflect more IR than others and so will have a bigger impact on IR pollution. The BM camera have very weak IR filtration in the sensor glass.

[Adam Roberts]

There is quite a long thread on the official forums about the 4.6k having a magenta cast and/or magenta-toned vignetting. Any owners here notice this?

https://forum.blackmagicdesign.com/v...hp?f=2&t=46112

No issues on mine. The corners do drop off in exposure but there is no shift in colour.

[Frank Glencairn]

No magenta anywhere on my camera

[AndrewDeme]

One interesting read that I came across might explain why some struggle more than others in relation to Magenta and is worth noting that Magenta is a color mix.

"The spectrum of magenta, a color that can't be made with monochromatic light, could look like this"

magentaspectrum.jpg


"Both blue and red have a high amplitude, and the mix of blue and red frequencies looks like magenta or purple to the brain."





http://www.marktaw.com/design/ColorTheorya.html

http://lodev.org/cgtutor/color.html

[Steven Abrams]

So this is the edges of Benton's image put next to each other:



And this is the top and bottom of John Brawley's Leica put next to each other:



Benton you are doing just fine! Don't worry about it. John said he never had an issue getting great images from his Leica, and many cameras like Red, Canon, etc have this same thing with non-uniformity.

On the topic of overall magenta casts, seems like Sony has the issue enough that someone made a LUT specifically to address magenta casts, maybe someone do the same for the 4.6K?

http://www.hingsberg.com/index.php/2...magentakiller/

[AaronChicago]

So this is the edges of Benton's image put next to each other:



And this is the top and bottom of John Brawley's Leica put next to each other:



Benton you are doing just fine! Don't worry about it. John said he never had an issue getting great images from his Leica, and many cameras like Red, Canon, etc have this same thing with non-uniformity.

On the topic of overall magenta casts, seems like Sony has the issue enough that someone made a LUT specifically to address magenta casts, maybe someone do the same for the 4.6K?

http://www.hingsberg.com/index.php/2...magentakiller/

Exactly. I use an "orange" killer LUT on GH4 footage. Look's like that LUT above does the same thing except dial down magenta.