[biz-engineer]

The human eye is said to have about 6 million cones and 120 million rods. Cones discriminate colors, rods are sensitive to light intensity, from darkness to full sun levels.
When I look at the black & white version of a color image, I tend to feel as if the black & white image looks sharper than its color equivalent. I'm be interested to know if others also share the same experience.
Now if black & white images do look sharper than their color versions, would that come from removing color information let the brain with visual information coming only from the rods cells in our eyes, the 120 million rods instead of 6 million cones delivering more subtle gradation of light to the brain?

[pschlute]

Sharpness increases with contrast. A b+w image may appear more contrasty and therefore sharper ? My unscientific assessment

[CarlJF]

Contrast and lines are much better rendered in B&W than in colors. This is also the reason why you can have a B&W overlay for sharpness adjustments in Lightroom. Much easier to see what’s you’re doing...

[MJKoski]

Most color photos are taken with dud lenses with lots of aberrations and/or lack of microcontrast -> unsharp look. Only Zeiss lenses are usable at normal shooting apertures. This is my own finding of course based on my own collection of photos. Some modern lens designs like Pentax 50mm HD are sharp when looking at test chart results but that's it.

I think so, though "black and white" to me means "film", while what we're getting out of a DSLR is grayscale resulting from a conversion algorithm. They look different to me, and I suspect the reason is that the conversion in a DSLR takes aspects of the color of a pixel into consideration when making the conversion (saturation, etc), not just luminosity.

By the way, the numbers you quoted indicate an important fact: the "rods" are much, much smaller than the "cones", and we can fit gobs more luminosity receptors per square inch of retina than we can color receptors. And, for a person like myself, with red-green color blindness, the areas that would have been occupied by missing "cones" are taken up with beaucoup de "rods". That translates into better resolution (more pixels per unit of area), better dynamic range, and higher ISO, to make an analogy, than people with normal color vision. Moreover, color data generally does not inform my perception regarding contrast very much; I rely mostly on luminosity for contrast.

Since black and white film is only sensitive to luminosity, it provides me with the greatest contrast. The grayscale pictures that I see (never bothered with it myself) posted just look kind of muddy to me, like color pictures with the color washed out. Rather than more contrast, I think they have less.

[Kerrowdown]

Human eye perception of black & white photos

As my first love always has and will be B&W... I appreciate tonal graduations in a image, I just perceive these to be more visual in this medium.

I attach one of my recent images to try and illustrate what I mean.

[MJKoski]

Just use 850nm IR-filter to record ultra high contrast B&W with standard K-1. Exposure times are in multiminute-class but it works if lens works in IR. Results will be noisy though as all information is in red channel. Modded K-1 with pixel-shift is in class of its own here.

My plan is to have one K-1 modded to record pure monochrome.

The human eye is said to have about 6 million cones and 120 million rods. Cones discriminate colors, rods are sensitive to light intensity, from darkness to full sun levels.
When I look at the black & white version of a color image, I tend to feel as if the black & white image looks sharper than its color equivalent. I'm be interested to know if others also share the same experience.
Now if black & white images do look sharper than their color versions, would that come from removing color information let the brain with visual information coming only from the rods cells in our eyes, the 120 million rods instead of 6 million cones delivering more subtle gradation of light to the brain?

My Hobby Horse rides again. If you have a colour picture then apart from the greens and the reds and the blues you also have to deal with the complementary colours. I, for one, suffer (not really) from colourblindness. It means that I have difficulties in seeing colours that are in a picture especially on the borders between colours, that is, the complementary colours. Even people that are not suffering from colourblindness will have difficulties when looking at a variety of colours in a picture. In a black and white photograph there are no complementary colours on the borders of black, white and the grays. So between blacks and whites there is a clear border. That makes a that you experience the picture as "very sharp". Although I like B&W it is not natural, because life comes in colours and not in B&W's.

[Kerrowdown]

because life comes in colours and not in B&W's.

You wanna try living in Scotland with our weather...

[Not a Number]

The portion of the human eye responsible for high acuity vision is known as the fovea centralis has only cone receptors. I seem to recall that as the cone receptors are not responsive to low levels of light the fovea essentially becomes a blind spot at night. A trick astronomers and sailors use at night is not to look directly at dim objects since the fovea is located in the center of the retina.

Fovea - American Academy of Ophthalmology
Macula - American Academy of Ophthalmology

Visual acuity is less in the dark then in bright light or daylight. Consider also that color in images need more pixels than black and white. That's why black and white film and prints appears sharper or less grainy than color film and paper.

Read more about rods and cones. BTW: cones have a diameter of 0.4-0.5 microns vs ~2 microns for rods.
http://book.bionumbers.org/how-big-is-a-photoreceptor/

[StiffLegged]

You wanna try living in Scotland with our weather...

Aye, laddie, but there’s often a touch of blue there too. The colour of yer extremities, from personal experience, this efternoon. Ah’m foonert!! (roof repairs...)

[bertwert]

Only Zeiss lenses are usable at normal shooting apertures.

I think you may have a different opinion than thousands of others on the word "usable"....

[Kerrowdown]

Aye, laddie, but there’s often a touch of blue there too. The colour of yer extremities, from personal experience, this efternoon. Ah’m foonert!! (roof repairs...)

Aye, that wull be th' wey o' it.

[SSGGeezer]

The portion of the human eye responsible for high acuity vision is known as the fovea centralis has only cone receptors. I seem to recall that as the cone receptors are not responsive to low levels of light the fovea essentially becomes a blind spot at night. A trick astronomers and sailors use at night is not to look directly at dim objects since the fovea is located in the center of the retina.

Fovea - American Academy of Ophthalmology
Macula - American Academy of Ophthalmology

Visual acuity is less in the dark then in bright light or daylight. Consider also that color in images need more pixels than black and white. That's why black and white film and prints appears sharper or less grainy than color film and paper.

Read more about rods and cones. BTW: cones have a diameter of 0.4-0.5 microns vs ~2 microns for rods.
» How big is a photoreceptor?

This is correct as the rods populate the periphery of your eye. There is also a blind spot where your optic nerve comes int the back of your eyes.but the binocular vision allows your brain to ignore it.

When doing activities without night vision devices, the most dangerous time for activity is at duck before your eyes have dark adjusted completely; you try to use your central vision but it is not good and your brain has not switched to off center vision yet. (Requires training to be more effective, and smoking and drinking are negatives for good night/B/W vision in low light.)

[StiffLegged]

Most color photos are taken with dud lenses with lots of aberrations and/or lack of microcontrast -> unsharp look. Only Zeiss lenses are usable at normal shooting apertures. This is my own finding of course based on my own collection of photos. Some modern lens designs like Pentax 50mm HD are sharp when looking at test chart results but that's it.

Thanks for the laugh, been in need of one today. Cheers!