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10-28-2015, 03:37 PM   #16
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QuoteOriginally posted by wombat2go Quote
All this "truth" might sound more depressing
Great information. Only a little bit depressing. Probably means red will always pose a challenge.

Any suggestions on how to improve red in our photos.

10-28-2015, 04:07 PM   #17
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QuoteOriginally posted by RGlasel Quote
I don't think resolution is the differentiator, it's how true the colours are. The top pictures (with the 645Z, right?) are clearly better to my eyes on both of my monitors. I do think Pentax does an excellent job of recreating colours, to the point that I never make adjustments to individual RGB channels, even with my lowly K-30, and my son is constantly adjusting the colour on photos from his 60D. I've had in depth discussions about colour perception with a couple of paint reps over the years and you and I are naturally handicapped by our sex. I would be interested to know how obvious the difference is to women who aren't menstruating and drinking coffee (job requirements for pigment testers). When you consider who does the final appraisal of wedding photographs, I don't think this is a trivial matter for professional photographers.
Well that leaves me out.... TMI: still pre-menopausal and I drink enormous amounts of coffee... But I do love the way my K3 renders red, I have to say that I notice the difference in paint jobs on Jeeps that are supposed to be the same color of red as the one I have and I can tell when the base color or something is different because the paint throws off a faint magenta instead of an orange. I thought I was imagining it until my friend's husband who is a car painter showed me paint swatches of car paint and explained what I was seeing. lol for being so gender handicapped he is fantastic with colors. I find the info interesting, The tests and comparisons that are put up makes me more aware of what my photos look like, and now when I go anywhere monitors are displayed I wonder why they are not calibrated when I walk by.
10-28-2015, 04:22 PM   #18
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QuoteOriginally posted by sherrvonne Quote
Well that leaves me out
Only if you won't give up coffee on the job. It was an R-M rep who told me their colour testers were required to check their menstrual cycles and assigned different duties when their hormones affected their colour perception. I blame the prevailing sharpness fixation within photographic fora on a serious gender imbalance, because I truly believe colour and composition are far more important to how we react to a photograph than resolution is. Basically, too many grumpy old colour-blind men who haven't had an emotional reaction to an image for far too long.
10-28-2015, 04:33 PM   #19
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QuoteOriginally posted by RGlasel Quote
Only if you won't give up coffee on the job. It was an R-M rep who told me their colour testers were required to check their menstrual cycles and assigned different duties when their hormones affected their colour perception. I blame the prevailing sharpness fixation within photographic fora on a serious gender imbalance, because I truly believe colour and composition are far more important to how we react to a photograph than resolution is. Basically, too many grumpy old colour-blind men who haven't had an emotional reaction to an image for far too long.
Learn something interesting every day, I had never heard that before, it would sure be hard to give up coffee for the length of a work day.... thinks me as I sip coffee out of the nifty 'Lens coffee mug' my cousin sent me.

10-29-2015, 12:46 AM   #20
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QuoteOriginally posted by wombat2go Quote
The spectral quantum efficiency of the typical sensor well tends to peak at about 700nm and fall away toward blue and red. Red has the lowest QE because the longer wavelength lower energy photons go deeper into the depletion region and may not end up being stored as electrons. Also red photons may end up in adjacent wells. This is explained by Holst and Lomheim in "cmos/ccd Sensors and Camera Systems" To check this effect with the Pentax K-01 , I took photos of a gray card and a red T shirt, and directly converted (before the Bayer de matrix and de-gamma) the raw file to a hex file. This jpg is a copy of the spreadsheet I made to show and quantify the raw pixel values. https://app.box.com/s/7z4i3w4iey5h7r2eqmblgs28nduimcf5 Note that on the gray card LAB 50,0,0 , exposed normally so the camera histogram indicated about 50% brightness, the red wells are only 5.7% of full capacity. In decibels, the red wells are typically at minus 24 dB ( or minus 4 EV stops) of well capacity, and less than half of the values in the green wells. To prove these levels, I took an overexposed photo of the bright blue sky, to show that all wells do reach full capacity (approaching FFFF on the 12 bit K-01) It is apparent that the histogram displayed on the camera lcd is for the resultant jpg, after application of the Bayer de matrix coefficients, and the gamma etc. The camera histogram does not give direct information about the utilization of the well dynamic range. This low red level has a worse (by about 20dB compared to full well) signal to noise ratio, and worse (by 16 times), quantization noise by the adc because the adc on red channel is effectively only with a resolution of 8 bits (1 part in 256) All this "truth" might sound more depressing than it is. I don't know if the pundits consider this in the performance tests. However the Bayer sensor works rather well, I think. I suppose it is due to our forgiving eyes.
Understood. It makes sense to me. But then , there might be a reason why red pixels are not designed larger to cope with their relatively inferior s/n performance. Perhaps the human vision still require better green channel information and is less demanding for the red. However, that is an issue when converting from RGB to filtered black and white.
10-29-2015, 02:40 AM   #21
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QuoteOriginally posted by RGlasel Quote
colour perception with a couple of paint reps over the years and you and I are naturally handicapped by our sex.
It is possible to improve your colour perception, a common test involves sorting a set of 20 mid-grey tiles that deviate by +/-5 mired shift from 18% neutral grey. Several years ago I did such a test with a group of colleagues and the director of a studio where I work. My colour perception is about 93% accurate, the only male in the room that had higher accuracy was the director himself. The two women in the group had on par or higher accuracy than both of us. Though the bizarre thing is that my left eye perceives colours as being cooler, which is different from my (dominant) right eye which perceives colours as being warmer.

QuoteOriginally posted by RGlasel Quote
I would be interested to know how obvious the difference is to women who aren't menstruating and drinking coffee (job requirements for pigment testers)
I have never heard of this, but if I had to hazard a guess, it has to do with being completely unable to argue with a woman at that time of month over which colour to paint the lounge room..

A few years ago XKCD blog did a survey on this, the part at the bottom of the published survey is hilarious:

Lastly, here are some assorted things people came up with while labeling colors:


Last edited by Digitalis; 10-29-2015 at 03:03 AM.
10-29-2015, 05:58 AM   #22
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QuoteOriginally posted by wombat2go Quote
The spectral quantum efficiency of the typical sensor well tends to peak at about 700nm and fall away toward blue and red.
Red has the lowest QE because the longer wavelength lower energy photons go deeper into the depletion region and may not end up being stored as electrons.
Also red photons may end up in adjacent wells.
This is explained by Holst and Lomheim in "cmos/ccd Sensors and Camera Systems"

To check this effect with the Pentax K-01 , I took photos of a gray card and a red T shirt, and directly converted (before the Bayer de matrix and de-gamma) the raw file to a hex file.

This jpg is a copy of the spreadsheet I made to show and quantify the raw pixel values.
https://app.box.com/s/7z4i3w4iey5h7r2eqmblgs28nduimcf5

Note that on the gray card LAB 50,0,0 , exposed normally so the camera histogram indicated about 50% brightness, the red wells are only 5.7% of full capacity.
In decibels, the red wells are typically at minus 24 dB ( or minus 4 EV stops) of well capacity, and less than half of the values in the green wells.
To prove these levels, I took an overexposed photo of the bright blue sky, to show that all wells do reach full capacity (approaching FFFF on the 12 bit K-01)

It is apparent that the histogram displayed on the camera lcd is for the resultant jpg, after application of the Bayer de matrix coefficients, and the gamma etc.
The camera histogram does not give direct information about the utilization of the well dynamic range.

This low red level has a worse (by about 20dB compared to full well) signal to noise ratio,
and worse (by 16 times), quantization noise by the adc because the adc on red channel is effectively only with a resolution of 8 bits (1 part in 256)

All this "truth" might sound more depressing than it is. I don't know if the pundits consider this in the performance tests.
However the Bayer sensor works rather well, I think. I suppose it is due to our forgiving eyes.
Very cool. I'm not sure why it would be at all depressing though. As long as you get decent reds in your photos, contemplating what your camera has to go through to get them is nice, but not in any way negative, unless, you really are serious about getting better red. Most of the time there is some blue/ black detail in the reds that makes them appear sharper than they are. It's rare you have something that's just all red.
10-29-2015, 10:25 AM   #23
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QuoteOriginally posted by Digitalis Quote
It is possible to improve your colour perception, a common test involves sorting a set of 20 mid-grey tiles that deviate by +/-5 mired shift from 18% neutral grey. Several years ago I did such a test with a group of colleagues and the director of a studio where I work. My colour perception is about 93% accurate, the only male in the room that had higher accuracy was the director himself. The two women in the group had on par or higher accuracy than both of us. Though the bizarre thing is that my left eye perceives colours as being cooler, which is different from my (dominant) right eye which perceives colours as being warmer.



I have never heard of this, but if I had to hazard a guess, it has to do with being completely unable to argue with a woman at that time of month over which colour to paint the lounge room..

A few years ago XKCD blog did a survey on this, the part at the bottom of the published survey is hilarious:

Lastly, here are some assorted things people came up with while labeling colors:
LOL @ shark INVESTED water

10-29-2015, 10:37 AM   #24
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Here is a check of low light/long exposure looking at red and gray fidelity in the camera jpgs of 3 cameras.

The cameras were set to awb, iso 200 and the exposure time was about 5 second.
The Pentax cameras used the old SMC Pentax-M 1:3.5 28mm set at f/11.

1) the latest Verizon HTC phone HTC6535LVW
https://app.box.com/s/sz4nyxir8uhgarvpqh26muech4juh9e5
2) The Pentax ist ds
https://app.box.com/s/zugml5n4b86nfnr7sqiw29fhj82l7sju
3) The Pentax K-01
https://app.box.com/s/ha1hvcxjfiu5eh4upohenc2g66n8qa07

The K-01 is the winner however it did not give the jpg realistic colors in awb, so this photo is with K-01's Manual White Balance on the gray card.
The 11 year old ist-ds is clearly a lot better than the phone, so I still won't be throwing out that camera yet!
10-29-2015, 12:24 PM   #25
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QuoteOriginally posted by Digitalis Quote
it has to do with being completely unable to argue with a woman at that time of month over which colour to paint the lounge room..
I've been married to the same woman for 26 years, 3 months and 7 days, and I don't think there is any time of the month when one can argue with a woman over which colour to paint any room (even if she never sets foot in it).
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