What is the definition of "resolution"?

I'm wondering what folks here mean by "low" or "high" resolution and how "resolution" should be quantified for digital cameras.

One of my least favorites is the popular 'line pairs per picture height' which technically gives me more "resolution" if I change to portrait mode, LOL.

Another is resolution = MP

However, I'm looking for others' views, please ...

Yes, wide open is probably best. I started this thread at Alan's suggestion when I asked him a similar question elsewhere. I am glad you said that they are related to resolution, not defining it.

Thanks for the link. Yes, MTF is helpful for some when deriving a definition for "resolution" - one such being the spatial frequency at which the MTF is 50%, often used for lens tests at various f/numbers, e,g, LensTip

Here's a Sigma SD9 curve from a QuickMTF slant-edge test, lens unknown:

Although it can measure detail beyond Nyquist up to 0.572 cy/px, that detail is false. So back to MTF, we see that MTF50 occurs at 0.282 cy/px which is OK but only on the per pixel basis. At the sensor, the resolution is 31 cy/mm, as in 31 lp/mm, not particular good compared to other cameras,

Now let's look at my Lumix DC-G9:

On a pixel basis, the 21 MP G9 compares miserably to the 3.4MP SD9: 0.157 cy/px versus 0.282 cy/px ...

... but, on a spatial basis (cy/mm), the G9 is the clear winner 47 lp/mm vs 31 cy/mm and additionally won't show as many artifacts as the SD9, if any.

From which I conclude that the better measure of resolution in this case is cy/mm aka lp/mm

Anecdote: I once sold a Panasonic Lumix m4/3 camera versus the SD9 based on cy/px, duh ...

The trouble with these discussions is that in digital media the output resolution is fixed by the device, the dot pattern of the printer or the pixel pitch of the screen. Which means that although the actual resolution of the camera may change, fundamentally if you view on screen from the same spot (your chair), then you view every image at the same resolution. The spacial frequency, or lp/mm, to the human eye remains at a fixed value and so the "visual understanding' of resolution is restricted to "zoom".

As we tend to relate understanding to experience then this becomes a problem. For instance if you view a 12mp phone shot and a 48mp FF image on the same screen then we fundamentally view both at the same resolution. No matter what the zoom setting is the viewing resolution stays the same. This is further complicated by our habit of "leaning into" the screen to see that difference in resolution more clearly!

What you never see with digital output media is the effect of increasing the lp/mm. Yes, I know that the output media has improved vis-a-vis retina screens and their spacial frequence, but you still never see the effect of change in output resolution as it is always constant. What we tend to do is look at the differences we see between our phone and FF shots and relate those to IQ and resolution. It becomes a difficult conversation when we assume what we see is absolute and that what we see on the screen is representative of higher resolutions as we can easily miss the fact that it's actually the same resolution.

lets step things up a bit. resolution to me is only justified with a "system", not just pixel numbers, and it defiantly cant be mapped on charts or maths.
resolution is my specialty but at 4-10x and i like to challenge others with there systems as to who can resolve the most detail with their system, i use a common subject and thats a house fly wing detail as they are everywhere in the world. its a combination of camera tech, sensor size ,pixel size, objective quality, tube lens design, lighting, camera setup. stacking style and software, motion, hormonic vibration control, and most of all consistency of frame separation and spacing. 😉
edit : view the images at 200% 😊

Hi,

High Resolution vs Low Resolution is a moving target. It was once 2.75 MP v 1.3 MP. The Nikon D1 v the Nikon E2.

Or Kodaks with 6 MP v 2 MP. Or Canons with 11 MP v 4 MP. And so on. Today is is 45 MP v 24 MP. Unless we talk about medium format digital, then it is 100 MP v 50 MP.

And it will all change again.

Stan

Looks like your definition of resolution is MP, Stan.

And yet there are two charts of real resolution posted above, so why did you say that? Please explain.

dprevived.com/t/what-is-the-definition-of-resolution/7281/post/102503/

Correct. When I zoom in 2X, 3X, 4X, etc. using Nearest Neighbor, one sensor pixel becomes 2x2, 3x3, 4x4, etc. on my screen. Not unlike walking closer in a location thereby affecting the human visual cpd of objects like picket fences in the scene.

So what is a correct definition of camera resolution independently of viewing media?

Used to be grains per square mm. Now its pixels. Same thing, only different. ;)

Stan

where are the images validatiing the charts are correct.

They were on my hard drive before being analyzed by QuickMTF. How can they "validate" that the charts are correct?

You said that resolution can not be mapped on charts.

I showed you that it can and asked if you can explain that: you have not.

Yes, grains per square millimeter on the same area of film (assuming 135 format).

Hmmm ...

Enter digital:

Ah, you never said just camera... 😬

Assuming "field of view" is constant, as we normally do, then in simplest form for a camera system it must be total pixels modified by lens sharpness.

A LF camera has a far higher resolution than a 35mm, with the same film. So again assuming constant field of view then it is total film area modified by film grain and lens performance. N.B. It is not absolute lens performance, only absolute system performance measured by, for instance, a test chart filling the frame at a certain distance where lp/mm can be measured (same field of view). LF lenses don't need to outperform lenses on a 35mm to produce higher res images.

THis is not the same as apparent sharpness.

Hi,

Yep. 135 film in my case. Such as comparing Tri-X to Tech-Pan under a microscope. Or, just printing an 8x10" prints from each type of film if one didn't want to go all techy. ;)

Stan