Bipod

Three things are being confused here: pixel count, perceived sharpness, and resolution

1. Pixel count is part of the physical and electronic design of a sensor.

Pixel count tells us very little about the sensor design:
* CMOS or CCD?
* Global shutter, rolling shutter, or no shutter?
* Photocell geometry?
* Microlens (on each photocell) specifications?
* Gaps?
* Surface flat or curved?

It takes three photocells with different color filters (RGB) to create one color pixel.
These three color planes are merged during demosaicing. At the same time, the
(usually hexagonal) geometry of the sensor is converted to a 2-dimensional
rectilinear array.

More pixels does not automatically translate to more resolution.
And given two sensors with the same number of pixels, one can have
much more resolution than the other.

Photocell geometry, performance of microlenses on each photocell,
whether or not there are gaps (with no photocells) in the sensor --- all
affect resolution in complex ways.

2. Resolution is a property of an optical system: the ability to distinguish
between ("resolve") fine details. An optical sysem can be designed to
have a given resolving power, and computer simulations can be run, but
only an emprical test can determine whether or not the goal has been met.

Becuse of manufacturing tolerances, identical lenss or sensors coming off
an assembly line can vary in resolution. The manufacturer must test each
unit and decide what range of resolution (and other measures of optical
performance) is acceptable.

Resolution is only as good as the weakest link: lens, aperture, sensor,
monitor or printer. The sensor resolution can no better -- and usually is a lot
worse--then the resolution of the image projected by the lens on the sensor.

On the display end, all thumbnails look sharp. So you really don't know
much about the resolution of an image until you blow it up -- either on
a large, high-res monitor, or in a large high-res print. Mere size is not enough:
the image reproduction must itself be high-resolution.

There are complex interactions between hexagonal photocell geometry,
rectilinear pixel array, and rectilinear display or printer dpi. At each step
a conversion algorithm is required.

3. Perceived sharpness -- or more properly "perceived acutance" is an aspect
of human visual perception. Increasing "edges" -- lines of local contrast --
increases perceived acutance.

An image can appear "sharp" because it has high resolution and good local
contrast, or it can appear "sharp" because lines have been drawn in it by
software -- or a sharp pencil. The difference is that a human being knows
what the photo is a photo of, and the computer doesn't. In a game of
"connect the dots", a human wins every time.

Side effects of "sharpen" algortihms include:
* reduced gradation
* artifacts: lines were there were no lines in the scene
* it's detectable: people will say "you ran dsharpen on this"

In general, optical systems cannot be miniaturized without severly affecting
image quality. There is a reason why astronomical observatories are as
large as they are. Diffraction is a function of the physical size of an aperture.
For a given angle-of-view and aperture, say f/11, the smaller the aperture, the
smaller the diameter of f/11, so the more the diffraction. The is a consequence
of the wave nature of light.

Unfortunately, technology cannot nullify science. Star Trek may have a
"warp drive", but camera's don't: they are bound by physical laws. For a lot
of people, this is a hard pill to swallow. Cameras are not sci fi nor are they
video games.

"If I'm willing to pay more, how come I can't get a warp drive? The ad said
I would go faster than light!"

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

Just my guess- Assuming sooc with the same lens and no cropping and an 8X10 print, I don't think that a human eye can decern the difference between an 8mp sensor or a 50mp sensor.

univac1103

Thank you all for your responses to my posting!!! Your wide-ranging comments and illustrations provided the kind of information and guidance which I had been looking for.

mwsilvers Loc: Central New Jersey

That's the case in your circumstance, but for current computers 1920 x 1080 seem to be the minimum configuration which is more than double the resolution of your monitor. And, many of us use large 4K monitors with a resolution more than 8 times as great as yours. So as you indicated, it depends.

catchlight.. Loc: Wisconsin USA- Halden Norway

Without a long reply, contrast is most likely the perceived sharpness answer.

Actual sharpness is more about steadiness and edge sharpness from nailing the shot. Photoshop can add any amount needed and the shake filter even more.

I can say that my old Canon 5D MKiii looked appreciably softer than the MK4 side by side at 100%. Sensors play a big roll for sure due to contrast, shadow detail and black saturation.

cameraf4 Loc: Delaware

About a year ago I did a quick-and-dirty dog and pony show here to answer just your question. See results here: https://www.uglyhedgehog.com/t-501318-1.html

SonyBug

Well said, Steve Perry. I saw a similar discussion of that on Ken Rockwell.com and he showed pictures of the difference. It is quite amazing, and yet I sold a d810 and went to a a7III. So, for me, I really don't need all that resolution as I don't usually hover over a picture with a magnifying glass pixel peeping.

Tjohn Loc: Inverness, FL formerly Arivaca, AZ

You can't exceed the sharpness of the lens.

R.G. Loc: Scotland

The question most people should be asking is "How much resolution do I need?" If you're not a pro and aren't likely to need poster-sized prints, or if your framing skills are OK and you usually don't need to do a lot of cropping, you really don't need a high resolution camera. And those smaller pixels come at a cost. With all other things being equal, bigger photo sites give better low light performance, which also means that brightening dark areas in PP is less likely to result in noise.

To put things in perspective, it takes just over two megapixels to fill a 1080p screen, so viewing on a typical monitor/TV screen doesn't need a high pixel count. Even if you do need large prints, upsizing software will get you there, perhaps not with the same amount of small detail, but with enough smoothness to avoid pixelation.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

perceived sharpness? You mean, do the users of 40MP+ camera's only Perceive a difference?
I shoot wildlife and I use the D500 and D850, both mounted on a Nikon 200-500 f5.6 lens. And yes, I see a difference between the SHARPNESS (not perceived sharpness) of the two camera's. Images on the D850 are different than those produced by the D500. Both are sharp and usable. But, on cropping, even making the subject on the D850 the same size as those produced by the D500, the D850 delivers sharper images. But, like I said, both camera's deliver great images.
Their is a difference, and it is not perceived, it is real.

joer Loc: Colorado/Illinois

I've owned and used for some time the D800E, D810, D850 and now the A7R3 as well as a plethora of lower pixel cameras. There is a difference but its not noticeable until you begin to crop away a large portion of the image.

If you see a difference in the uncropped images its not likely to be because of the pixel count.

The Villages Loc: The Villages, Florida

rplain1 Loc: Dayton, Oh.

I have a 50mp camera (Canon 5DSR). I didn't buy it for more sharpness and I doubt that I could detect any difference from my 5DmkII. I bought it because I take almost 100% wildlife photos and they are not always very close. That involves sometimes some heavy cropping. I also print mostly 13x19.
So yes, I do see a difference. I can print sharp pictures from this camera that I couldn't have from my previous camera. But no, for photos with less cropping, I see no difference.

Dikdik Loc: Winnipeg, Canada

The more DPIs, the greater is the potential for sharpness at enlarged photo size. If out of focus, it doesn't matter how many DPIs you have.

Dik

Bison Bud

As others have mentioned already, I think sharpness is more a factor of the lens than the sensor. However, there are real differences or perhaps perceptions to consider when it comes to high verses lower sensor pixel counts. The higher pixel count sensors should make better very large prints, but just how large does one need to go. One would have to go mighty large to really see a big difference, but if that's a priority than the high pixel count sensor has an obvious advantage. It also has an advantage when cropping the image just because there are more pixels to work with and this is probably the biggest advantage to a high pixel count sensor. However, it's also been frequently discussed here that larger pixels generally have better low light performance. Therefore, the lower pixel count sensors should have an advantage when shooting in low light conditions and especially in being able to use a fast enough shutter speed to get a sharp photo in the first place. All in all, it's about balancing your needs with the performance of either, but it might be difficult to really go wrong in either direction. Good luck and good shooting to all.