High pixel count Vs large lens

[ali8]

Hello,
=
Suppose I would like to take a photo for the city from a high tower (+25th story). Ideally, I would like to be able to see (Afterwards) very small details in my photo (e.g. people, etc).

Suppose that with a 400mm camera (and 10 megapixels) I can "zoom in" and get an 8x larger objects in my photo.

Alternatively, I can go for a camera with 20 megapixels, then I would be able to "zoom in" and get 2x zoom (relative to the first method). Is this correct?

 

[KmH]

No. The lens is still 400 mm.

It's the optics in the lens that provides the magnification, not the number of image sensor pixels.

 

[TATTRAT]

The first thing that came to mind was this:



Lots of MP to equal that resolution.

Not sure if that is the scale or scope you are shooting for.

 

[TCampbell]

You may be thinking of doing something like this: The Canon EOS 7D & EF 400 f/2.8L IS II Break a Record « Canon Rumors

BTW - that image is a 320 gigapixel panoramic (a LOT of stitching).

The image is here: http://btlondon2012.co.uk/pano.html

If you were to try to create a detailed image with a single shot you run into a problem called Dawes' limit - Wikipedia, the free encyclopedia

Dawes' limit (related to diffraction limits -- and based on a theory assuming perfect optics so it's not a question of whether you have good enough optics or not) restricts the amount of fine detail you can get out of image based on the diameter of the lens being used. If a lens has a physically larger diameter then it's capable of resolving finer amounts of detail (assuming the optics are junk.)

When you try to enlarge or zoom-in on an image you increase the size of everything... which includes the size of the blurry / fuzzy edges that all objects in your images technically have. You can't zoom in to make people bigger without also amplifying the amount of blur.

 

[Juga]

You may be thinking of doing something like this: The Canon EOS 7D & EF 400 f/2.8L IS II Break a Record « Canon Rumors

BTW - that image is a 320 gigapixel panoramic (a LOT of stitching).

The image is here: BT Tower 360 Panorama of London

If you were to try to create a detailed image with a single shot you run into a problem called Dawes' limit - Wikipedia, the free encyclopedia

Dawes' limit (related to diffraction limits -- and based on a theory assuming perfect optics so it's not a question of whether you have good enough optics or not) restricts the amount of fine detail you can get out of image based on the diameter of the lens being used. If a lens has a physically larger diameter then it's capable of resolving finer amounts of detail (assuming the optics are junk.)

When you try to enlarge or zoom-in on an image you increase the size of everything... which includes the size of the blurry / fuzzy edges that all objects in your images technically have. You can't zoom in to make people bigger without also amplifying the amount of blur.

That was quite the experience. Mind officially...BLOWN :goodvibe:

 

[ali8]

Maybe I did not clarify my thoughts enough.

Is this statement (and the example afterwards) correct?

"Useful resolving power (roughly) depends on 1) Lens used, and 2) Number of Pixels."

So if the 400mm (w/ 10mp sensor) gives, say, resolving power of 1m for an object 1km away, then a 400mm w/ 20mp sensor should give 0.5m resolving power for the same object.

 

[enzodm]

Maybe I did not clarify my thoughts enough.

Is this statement (and the example afterwards) correct?

"Useful resolving power (roughly) depends on 1) Lens used, and 2) Number of Pixels."

So if the 400mm (w/ 10mp sensor) gives, say, resolving power of 1m for an object 1km away, then a 400mm w/ 20mp sensor should give 0.5m resolving power for the same object.

It depends on who is the bottleneck. In your example, you suppose that the sensor is the bottleneck.
However, if you consider linear resolving power, 20MP is not half of 10MP. 10MP is, e.g., 3888x2592; 20MP is 5456x3632; ratio is roughly 0.71.

 

[Tony S]

If you are taking the picture with the same lens then the 20MP camera would have more resolution to it. You could pick out one brick in a building and the 20MP camera would have more pixels making up that brick as compared to the 10MP camera, so it "should" be clearer and have sharper details all other things being equal.

 

[TCampbell]

Maybe I did not clarify my thoughts enough.

Is this statement (and the example afterwards) correct?

"Useful resolving power (roughly) depends on 1) Lens used, and 2) Number of Pixels."

So if the 400mm (w/ 10mp sensor) gives, say, resolving power of 1m for an object 1km away, then a 400mm w/ 20mp sensor should give 0.5m resolving power for the same object.

A lens can "limit" your resolving power and a low resolution sensor can "limit" your resolving power if they are not sufficient. But my point (and links) above were to explain that there are limits within the laws of physics. Improving quality of the lens and improving the resolution on the sensor only improves image quality "to a point".

A 10 megapixel APS-C camera is not diffraction limited at f/11, but it _is_ diffraction limited at f/16 (which means it's hit the barrier at which more pixels will NOT improve resolving power.)
A 20 megapixel APS-C camera _is_ diffraction limited at f/11 (but is not diffraction limited at f/8).

If you use a full-frame sensor camera, the "pixels" become larger so you reduce the bottleneck on diffraction limits. But only a bit.

A 20 megapixel full-frame camera is not diffraction limited at f/11, but _is_ diffraction limited at f/16.
A 36 megapixel full-frame camera (e.g. Nikon D800) is diffraction limited at f/11, but is not diffraction limited at f/8.

To take a thought experiment.... suppose your camera had just 6 pixels arranged in a 2 pixel by 3 pixel matrix. You'd have really awful "resolving" power. Clearly adding more pixels WILL help. When I have hundreds of pixels I'll get a better image. Thousands of pixels would be better still. And millions of pixels would be even better. So you see this trend that "more pixels is better" and think you can keep getting better by continuing to increase the number of pixels. But once once the size of the pixels gets so tiny that the size of the "Airy disk" can no longer fit within just one pixel then increasing the sensor resolution will no longer be helpful... you've hit a barrier.

We may think of light as traveling in a straight line, but at a quantum level light has a "wave" nature and this modifies how it behaves. When you get down to pixels sizes that are just a few microns across you hit barriers in which light can no longer be focused finely enough. NOW if you want to increase resolution you have to make the sensor physically larger. And then that hits a point and you have to make the glass lenses physically larger. And then even that eventually hits a point (actually it become ludicrously expensive to make glass large enough with high enough quality to be useful. (which is why large telescopes uses mirrors instead of lenses to focus light.)

You can read about diffraction limits here: Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

 

[ali8]

Maybe I did not clarify my thoughts enough.

Is this statement (and the example afterwards) correct?

"Useful resolving power (roughly) depends on 1) Lens used, and 2) Number of Pixels."

So if the 400mm (w/ 10mp sensor) gives, say, resolving power of 1m for an object 1km away, then a 400mm w/ 20mp sensor should give 0.5m resolving power for the same object.

A lens can "limit" your resolving power and a low resolution sensor can "limit" your resolving power if they are not sufficient. But my point (and links) above were to explain that there are limits within the laws of physics. Improving quality of the lens and improving the resolution on the sensor only improves image quality "to a point".

A 10 megapixel APS-C camera is not diffraction limited at f/11, but it _is_ diffraction limited at f/16 (which means it's hit the barrier at which more pixels will NOT improve resolving power.)
A 20 megapixel APS-C camera _is_ diffraction limited at f/11 (but is not diffraction limited at f/8).

If you use a full-frame sensor camera, the "pixels" become larger so you reduce the bottleneck on diffraction limits. But only a bit.

A 20 megapixel full-frame camera is not diffraction limited at f/11, but _is_ diffraction limited at f/16.
A 36 megapixel full-frame camera (e.g. Nikon D800) is diffraction limited at f/11, but is not diffraction limited at f/8.

To take a thought experiment.... suppose your camera had just 6 pixels arranged in a 2 pixel by 3 pixel matrix. You'd have really awful "resolving" power. Clearly adding more pixels WILL help. When I have hundreds of pixels I'll get a better image. Thousands of pixels would be better still. And millions of pixels would be even better. So you see this trend that "more pixels is better" and think you can keep getting better by continuing to increase the number of pixels. But once once the size of the pixels gets so tiny that the size of the "Airy disk" can no longer fit within just one pixel then increasing the sensor resolution will no longer be helpful... you've hit a barrier.

We may think of light as traveling in a straight line, but at a quantum level light has a "wave" nature and this modifies how it behaves. When you get down to pixels sizes that are just a few microns across you hit barriers in which light can no longer be focused finely enough. NOW if you want to increase resolution you have to make the sensor physically larger. And then that hits a point and you have to make the glass lenses physically larger. And then even that eventually hits a point (actually it become ludicrously expensive to make glass large enough with high enough quality to be useful. (which is why large telescopes uses mirrors instead of lenses to focus light.)

You can read about diffraction limits here: Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

This is really appreciated! Vary detailed reply and up to the point. Thanks!

I can now see what I was missing. I think I need to read even more!

Thanks again everyone.

 

[djacobox372]

Don't confuse "megapixels" with resolution.