Why Are Blue Leds Purple in Digital Eos Rebel
medon78 • Contributing Member • Posts: 685
Intense blue turns purple
1
Could someone please point me at the corresponding threads?
My RP shows the same behavior my T2i / 550D did. It turns very intense blues into purple, and this with no clipped R/G/B channels.
My question: What is the purpose in Canon's color profile for this behavior? Flowers? Sky? Anything else?
Image:
### edited 2 minutes after initial post -- replaced ISO640 image with ISO100 image. Same purple anyway ###
In real life, the columns are just blue.
Here is what my other camera renders:
As you can see, there is a slight cyan cast towards the brightest parts near the top of the columns, but no severe purple.
Disclaimer:
Yes, 3rd party RAW converters like Lightroom render those columns blue. If you want to play and investigate, here are the RAWs:
https://www.dropbox.com/sh/0zoqkqof6tqlke4/AADlvOrIGROJuaGveIu6rBbqa?dl=0
What puzzles me is that the blue channel in the RP RAW is far from clipping in the columns, see:
Fujifilm FinePix X100 Canon PowerShot S110 Olympus E-M1 II Nikon Z6 II Olympus M.Zuiko Digital 45mm F1.8 +11 more
ANSWER:
This question has not been answered yet.
RDKirk • Forum Pro • Posts: 16,267
Re: Intense blue turns purple
1
Is that a phenomenon you see with other subjects? Have you tried using a controlled color patch target and observed the same results?
I hold the appearance of this phenomenon in a light source as suspect--it's too depending on the actual color temperature of the light source and the filter effects of the blue material. It's not particularly unusual for apparent color to shift with exposure under those circumstances.
-- hide signature --
RDKirk
'TANSTAAFL: The only unbreakable rule in photography.'
Canon EOS 5D Mark II Canon EOS 70D Canon EOS 5DS R Canon EOS 80D Canon EF 24mm f/2.8 +7 more
Re: Intense blue turns purple
3
RDKirk wrote:
Is that a phenomenon you see with other subjects? Have you tried using a controlled color patch target and observed the same results?
I hold the appearance of this phenomenon in a light source as suspect--it's too depending on the actual color temperature of the light source and the filter effects of the blue material. It's not particularly unusual for apparent color to shift with exposure under those circumstances.
Here a JPG of a spectrum taken with my EOS 5D MII - identical phenomenon (and EOS R does the same): The peak of the blue LED band (460 nm) shows a purple hue. This is a pure spectral blue, no other light source interfering,
NoTicket • Regular Member • Posts: 218
Re: Intense blue turns purple
medon78 wrote:
Could someone please point me at the corresponding threads?
My RP shows the same behavior my T2i / 550D did. It turns very intense blues into purple, and this with no clipped R/G/B channels.
My question: What is the purpose in Canon's color profile for this behavior? Flowers? Sky? Anything else?
Image:
### edited 2 minutes after initial post -- replaced ISO640 image with ISO100 image. Same purple anyway ###
In real life, the columns are just blue.
Here is what my other camera renders:
As you can see, there is a slight cyan cast towards the brightest parts near the top of the columns, but no severe purple.
Disclaimer:
Yes, 3rd party RAW converters like Lightroom render those columns blue. If you want to play and investigate, here are the RAWs:
https://www.dropbox.com/sh/0zoqkqof6tqlke4/AADlvOrIGROJuaGveIu6rBbqa?dl=0
What puzzles me is that the blue channel in the RP RAW is far from clipping in the columns, see:
Do all creative styles produce this effect? If it's present in jpeg and not in raw that suggests that a gain is being applied to the red channel during conversion. I can't say why but I'd be curious if DPP turns these purple in neutral or faithful.
OP medon78 • Contributing Member • Posts: 685
Re: Intense blue turns purple
RDKirk wrote:
Is that a phenomenon you see with other subjects? Have you tried using a controlled color patch target and observed the same results?
Personally I have not observed it too often, I think.
I hold the appearance of this phenomenon in a light source as suspect--it's too depending on the actual color temperature of the light source and the filter effects of the blue material. It's not particularly unusual for apparent color to shift with exposure under those circumstances.
Probably. The lighting in the subway station is probably blue LEDs on blue tiles.
BUT -- and this is my question - since none of the RGB channels are clipping, in fact even the blue channel being far from clipping... what is the motivation for Canon to implement their color profile this way?
Fujifilm FinePix X100 Canon PowerShot S110 Olympus E-M1 II Nikon Z6 II Olympus M.Zuiko Digital 45mm F1.8 +11 more
OP medon78 • Contributing Member • Posts: 685
Re: Intense blue turns purple
NoTicket wrote:
Do all creative styles produce this effect? If it's present in jpeg and not in raw that suggests that a gain is being applied to the red channel during conversion. I can't say why but I'd be curious if DPP turns these purple in neutral or faithful.
Checked already -- all picture styles have this effect.
Fujifilm FinePix X100 Canon PowerShot S110 Olympus E-M1 II Nikon Z6 II Olympus M.Zuiko Digital 45mm F1.8 +11 more
OP medon78 • Contributing Member • Posts: 685
Re: Intense blue turns purple
So here is the way how to emulate the effect using an AMOLED screen (mobile phone):
If you turn WB to the lower Kelvins, the blue screen turns purple:
Interestingly, in the subway station scene no extreme WB settings were needed. But I guess it is the same effect.
The RAW with the color checker and phone is in the same folder, link in the OP.
Fujifilm FinePix X100 Canon PowerShot S110 Olympus E-M1 II Nikon Z6 II Olympus M.Zuiko Digital 45mm F1.8 +11 more
Re: Intense blue turns purple
2
Phylloxera wrote:
Here a JPG of a spectrum taken with my EOS 5D MII - identical phenomenon (and EOS R does the same): The peak of the blue LED band (460 nm) shows a purple hue. This is a pure spectral blue, no other light source interfering,
How was that spectrum generated?
Very few LEDs or similar 'modern, low power' light sources provide a clean continuous spectrum. Also the response curves of camera sensors and the human eye are not identical.
-- hide signature --
Albert the lazy photographer
Having fun with my cameras in Scotland
Canon PowerShot G15 Fujifilm X-T1 Fujifilm X-T3 Sigma 70-300mm F4-5.6 APO DG Macro Fujifilm XF 18mm F2 R +6 more
Re: Intense blue turns purple
AlbertTheLazy wrote:
Phylloxera wrote:
Here a JPG of a spectrum taken with my EOS 5D MII - identical phenomenon (and EOS R does the same): The peak of the blue LED band (460 nm) shows a purple hue. This is a pure spectral blue, no other light source interfering,
How was that spectrum generated?
Very few LEDs or similar 'modern, low power' light sources provide a clean continuous spectrum. Also the response curves of camera sensors and the human eye are not identical.
That's likely a dispersion of white color source by a prism.
Re: Intense blue turns purple
Yes, I also noticed that when shooting blue things. That seems to be a deliberate shift in jpeg. The purpose is unknown. There are basically no deep blues in jpeg at all.
Re: Intense blue turns purple
forpetessake wrote:
AlbertTheLazy wrote:
Phylloxera wrote:
Here a JPG of a spectrum taken with my EOS 5D MII - identical phenomenon (and EOS R does the same): The peak of the blue LED band (460 nm) shows a purple hue. This is a pure spectral blue, no other light source interfering,
How was that spectrum generated?
Very few LEDs or similar 'modern, low power' light sources provide a clean continuous spectrum. Also the response curves of camera sensors and the human eye are not identical.
That's likely a dispersion of white color source by a prism.
Yes, but what 'white' source? It doesn't look like a continuous spectrum such as daylight or tungsten, although that might be a sensor issue.
-- hide signature --
Albert the lazy photographer
Having fun with my cameras in Scotland
Canon PowerShot G15 Fujifilm X-T1 Fujifilm X-T3 Sigma 70-300mm F4-5.6 APO DG Macro Fujifilm XF 18mm F2 R +6 more
Re: Intense blue turns purple
AlbertTheLazy wrote:
forpetessake wrote:
AlbertTheLazy wrote:
Phylloxera wrote:
Here a JPG of a spectrum taken with my EOS 5D MII - identical phenomenon (and EOS R does the same): The peak of the blue LED band (460 nm) shows a purple hue. This is a pure spectral blue, no other light source interfering,
How was that spectrum generated?
Very few LEDs or similar 'modern, low power' light sources provide a clean continuous spectrum. Also the response curves of camera sensors and the human eye are not identical.
That's likely a dispersion of white color source by a prism.
Yes, but what 'white' source? It doesn't look like a continuous spectrum such as daylight or tungsten, although that might be a sensor issue.
Photo was at my fingertips by chance. Light source is actually a halogen bub, light filtered by a fluorescence filter blocking parts of the spectrum which, however, are not relevant to this phenomenon.
Re: Intense blue turns purple
Heya,
I have the exact same problem and recently lost a gig to a Sony shooter because of it.
I primarily run into this issue where the blue is the light source; blue reflected light is something I still have some issues with, but a lot less frequently and more commonly on high ISO shots.
It's even worse when I use the Adobe Lightroom profiles for my R5. The camera profiles on the 1DX II seem to do alright, but the R5 images are useless.
Have you figured out any workarounds?
NoTicket • Regular Member • Posts: 218
Re: Intense blue turns purple
1
evilZardoz wrote:
Heya,
I have the exact same problem and recently lost a gig to a Sony shooter because of it.
I primarily run into this issue where the blue is the light source; blue reflected light is something I still have some issues with, but a lot less frequently and more commonly on high ISO shots.
It's even worse when I use the Adobe Lightroom profiles for my R5. The camera profiles on the 1DX II seem to do alright, but the R5 images are useless.
Have you figured out any workarounds?
This is not a problem in lightroom if using anything other than a camera matching profile, it is specific to the profiles Canon uses.
OP medon78 • Contributing Member • Posts: 685
Re: Intense blue turns purple
Didn't dive into it any further.
As already recommended, you might use an Adobe profile.
Side note: my recently bought Nikon Z6 does neither feature that color shift, it behaves like my Olympus (slight shift to cyan).
Fujifilm FinePix X100 Canon PowerShot S110 Olympus E-M1 II Nikon Z6 II Olympus M.Zuiko Digital 45mm F1.8 +11 more
Re: Intense blue turns purple
Fooled by perception.
What we see is not the actual world, but the world we expect to see.
Expect the coloumns to be blue and blue they are. Expect a red tint in the blue and you will see that. What we see and what colors we remember that we saw in real life is not real colors but colors invented by the brain. Our color memory is weak too.
Modern perception theory should be extremely interesting for anyone into photography. Color is wonderfully complex.
PicPocket • Veteran Member • Posts: 5,461
Re: Intense blue turns purple
1
Tristimulus wrote:
Fooled by perception.
What we see is not the actual world, but the world we expect to see.
Expect the coloumns to be blue and blue they are. Expect a red tint in the blue and you will see that. What we see and what colors we remember that we saw in real life is not real colors but colors invented by the brain. Our color memory is weak too.
Modern perception theory should be extremely interesting for anyone into photography. Color is wonderfully complex.
Did you read the whole thread? Specifically this followup post - https://www.dpreview.com/forums/post/63422607
There is also a question of different perception by different cameras. How do you explain that?
This is a color profile issue, and seems something Canon deliberately chose. I am curious about why too. No ones eyes are being fooled here, at least not about the issue being mentioned. Rendering perception, yes
Canon EOS R5 Canon EF 24-70mm F2.8L II USM Sigma 135mm F1.8 Art Canon RF 70-200mm F2.8L IS USM Canon RF 100-500mm F4.5-7.1L IS USM +13 more
Source: https://www.dpreview.com/forums/thread/4450750
0 Response to "Why Are Blue Leds Purple in Digital Eos Rebel"
Post a Comment