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Archive 2012 · Canon Pixel Clarification
  
 
mptnest
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p.1 #1 · p.1 #1 · Canon Pixel Clarification


Yeah, I know, this could fall in the post processing forum, but this is relavant to Canon gear as well and...most of the guys from that forum are here along with many others with great insight.

Ok, I'm trying to get a grasp on "pixels". I know there are a lot of misconceptions on this topic, so the intended purpose of this thread is to get a better understanding of how "pixels" influence the picture quality.

First question, is one pixel on a camera equal to one pixel on a computer monitor? The resolution of a monitor is capable of being adjusted, this in turn changes the visual "size". Also, the native resolution in pixel pitch varies from monitor to monitor, so how is it all connected. Does one pixel from a camera equal one pixel on a monitor and we just see the image larger or smaller depending on the monitor resolution setting? Can I draw the conclusion a higher resolution monitor will "seem to be smoother" and a low resolution monitor appear to be "grainier" because of pixel spacing?

Second question. as far as "reach" we take a photo of a subject, but the subject only covers 50% of the sensor. To keep the math simple, lets say we have a 20mp camera. The subject would then cover 10mp. Then keeping things simple again, we have a second camera. This one has a 30mp sensor (same physical size sensor) We take the same photo at all the same distance, etc. So, I'm assuming the subject area (50%) would then cover 15mp.

Now back to the computer monitor if a pixel of camera equals one pixel of monitor (both images on the same monitor), Would the image from the 30mp camera be the equivalant of 5mp larger than the 20mp camera (1.5 or 150% larger)? Also, then this "gain" due to pixel density would be carried out to the output device, printer or whatever?

The exact math is not what I'm after, I'm just trying to get a grasp on the relationship between the peripherals.

Thirdly, Boiled down deeper, I'm trying to understand why some folks think the denser the sensor, the more "reach" and more "pixel per duck" they will attain, which will result in bigger and better image quality. Based on this theory, it seems to make sense, but in the real world where everything is not equal due to physical limitations, etc ie. pixel size 7D vs 5D the relationships seem to get skewed. I thought I'd go simple first before we go complex on comparing different sensor sizes, different pixel sizes, etc.


Al



Jan 11, 2012 at 10:43 PM
Ian.Dobinson
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p.1 #2 · p.1 #2 · Canon Pixel Clarification


mptnest wrote:
Yeah, I know, this could fall in the post processing forum, but this is relavant to Canon gear as well and...most of the guys from that forum are here along with many others with great insight.

Ok, I'm trying to get a grasp on "pixels". I know there are a lot of misconceptions on this topic, so the intended purpose of this thread is to get a better understanding of how "pixels" influence the picture quality.

First question, is one pixel on a camera equal to one pixel on a computer monitor? The resolution of a monitor is capable of being adjusted,
...Show more
If you look at the resolution of a sensor Eg. 7D has a sensor that's 5184x3456 then if you had a monitor that had a screen with that many pixels the yes 1 pixel would be 1 pixel. As you probably don't then no. But when you click that dreaded 100% button you are putting each pixel on a screen pixel. That's why when you click 100% on different resolution cameras you get a different amount of image shown (click 100% on a 4mp 1D and you basically just fill the screen of a modern monitor with the image.)

Second question. as far as "reach" we take a photo of a subject, but the subject only covers 50% of the sensor. To keep the math simple, lets say we have a 20mp camera. The subject would then cover 10mp. Then keeping things simple again, we have a second camera. This one has a 30mp sensor (same physical size sensor) We take the same photo at all the same distance, etc. So, I'm assuming the subject area (50%) would then cover 15mp.

Now back to the computer monitor if a pixel of camera equals one pixel of monitor (both images on the
...Show more
Q2 and 3 can be condensed into much the same answer.
If you have a 2 cameras with the same physical sensor size (let's just say the 8mp 20D and 18mp 7D) then if you display the image un cropped on screen or in print then you have no extra 'reach' as you don't need it (you do have extra resolution for more detail but that's a different thing) . Where the extra 'reach' comes in is in those extra pixels . So you can crop the 18mp file down to the same 8mp dimensions of the other file . Now you have the same amount of pixels but the cropped file has less of the whole image. Display or print both these files to the same size and the subject in the cropped file will appear larger. Hence the term 'reach' and 'pixels per duck'

Muddy the waters a bit further and mix the sensor sizes and pixel counts .
Eg keep the crop 20D but add in the 21mp 5D2 . Now shoot the same subject with these at the same distance and focal length and the 20D will appear at first to have more reach when displayed (at sesame size again) but crop the 21mp file down to 8mp and you find that they will end up basically the same . Because the 1.6 8mp sensor enlarged to full frame size would be about 21mp

Al




Jan 12, 2012 at 12:56 AM
mptnest
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p.1 #3 · p.1 #3 · Canon Pixel Clarification


But when you click that dreaded 100% button you are putting each pixel on a screen pixel.
Good information. Is that the same in all DPP, ACR and PS? And 1:1 in LR?

So you can crop the 18mp file down to the same 8mp dimensions of the other file . Now you have the same amount of pixels but the cropped file has less of the whole image. Display or print both these files to the same size and the subject in the cropped file will appear larger.
Ok that makes sense. Same sensor size. The image will fill the same area of both sensors, but the one has more pixels, so when cropped will appear larger. Makes sense.

If you have a 2 cameras with the same physical sensor size (let's just say the 8mp 20D and 18mp 7D) then if you display the image un cropped on screen or in print then you have no extra 'reach' as you don't need it (you do have extra resolution for more detail but that's a different thing)
There's a real key point. Same 'reach', but more resolution. So, the question that come to mind; is a pixel of the 7D equivalent to a pixel of the 20D in image quality?


Because the 1.6 8mp sensor enlarged to full frame size would be about 21mp
Sorry Ian, not quite following you here. Can you please explain? My thinking is the 8mp 1.6 would be more equivalent to 12.8mp full frame.



Jan 12, 2012 at 01:34 AM
Ian.Dobinson
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p.1 #4 · p.1 #4 · Canon Pixel Clarification


On the last point . You did the wrong sum. You x 1.6 and yes you get 12.8 but your dealing with total area . So it's a much bigger figure . I can't remember the actual Maths of it (it's late here)
But if you look up the sensor specs on a site like the 'the digital picture' you see that the 5d2 and the old 20D have the same pixel size (pixel pitch)

Other sensors of different size but same pixel pitch are the old 12mp 5D and the 8mp 1D2

As far as quality goes you have to take into account technology age. The 5D2 is much younger than the 20D so even if you could just blow the 20D sensor up to the same size you would not get anywhere near the same quality.



Jan 12, 2012 at 01:51 AM
mptnest
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p.1 #5 · p.1 #5 · Canon Pixel Clarification


Great stuff Ian. Greatly appreciated. It looks like I have a bit of learning to do on understanding the sensor specs. Here again, I thought the 5D and 5DII had the same size sensor, so the pixel pitch, in my mind, would be much lower on the 5DII (21mp) vs the 5D (12mp).


Jan 12, 2012 at 02:10 AM
RazorTM
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p.1 #6 · p.1 #6 · Canon Pixel Clarification


Because sensor area is in 2 dimensions, you take 8mp x 1.6^2 instead of 8mp x 1.6 to get the equivalent megapixels for a full frame camera.


Jan 12, 2012 at 02:26 AM
mptnest
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p.1 #7 · p.1 #7 · Canon Pixel Clarification


Because sensor area is in 2 dimensions, you take 8mp x 1.6^2 instead of 8mp x 1.6 to get the equivalent megapixels for a full frame camera.
There we go, that makes sense. Thank you Timothy

Al

Other sensors of different size but same pixel pitch are the old 12mp 5D and the 8mp 1D2
i misread this. Please disregard the previous post.
Here again, I thought the 5D and 5DII had the same size sensor, so the pixel pitch, in my mind, would be much lower on the 5DII (21mp) vs the 5D (12mp).
The comparison is the 5D and 1D2; not the 5DII



Jan 12, 2012 at 02:49 AM
Tenn.Jer
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p.1 #8 · p.1 #8 · Canon Pixel Clarification


Ian.Dobinson wrote:
Other sensors of different size but same pixel pitch are the old 12mp 5D and the 8mp 1D2


I think Ian meant "here are two other examples in which the sensors are different sizes, but the pixels themselves (i.e., "pixel pitch") are the same size."

You are correct in thinking the 5D and 5DII have the same size sensor (more or less), and the 5D "classic" has larger pixel sites...

To complicate the issue even further, larger pixel sites with their larger micro-lenses that actually do the gathering of light are associated with lower noise and therefore higher IQ...so, more "pixels per duck" may show more detail (resolution), but the clarity of that extra resolution may be sullied by the higher density, smaller pixel pitch...

Take a look at Brian Carnathan's The-Digital-Picture.com and his review of the 5DII; near the beginning of the review is a chart that shows the sensor size, the pixel size, viewfinder magnification,etc. of 30 or so models of Canon cameras, from the 10D to the 1DX...his reviews are chock-full of handy specifications like that - good for reference...

Let me say up front that the aforementioned is my unscientific understanding of (for me anyway) a very complicated and confusing technical aspect of the photographic art; I'm not prepared, nor do I desire, to argue the correctness of my stated impressions...indeed, if anyone wants to point out the fallacy of my simplified understanding, I will scratch my chin, tilt my head, and say "hunh...okay, that makes sense, too..."

I'm just trying to help, and increase my understanding at the same time.

Jerry

(edit: sometimes it takes me so long to compose a post that I end up repeating something that was posted while I'm checking my grammar and spelling! sorry about that...)



Jan 12, 2012 at 02:53 AM
mptnest
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p.1 #9 · p.1 #9 · Canon Pixel Clarification


So, let's dig a little deeper. the 5DII and the 7D are similar sensors. The 7D would be the equivalant of a 46mp 5DII. So why does it seem a 5DII image is more croppable than a 7D with IQ in mind?

(Not trying to start anything here. No debates please. Maybe this is an incorrect statement? Just going for clarification.)



Jan 12, 2012 at 02:58 AM
AJSJones
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p.1 #10 · p.1 #10 · Canon Pixel Clarification


mptnest wrote:
So, let's dig a little deeper. the 5DII and the 7D are similar sensors. The 7D would be the equivalant of a 46mp 5DII. So why does it seem a 5DII image is more croppable than a 7D with IQ in mind?

Because it has bigger pixels



Jan 12, 2012 at 03:04 AM
 

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Tenn.Jer
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p.1 #11 · p.1 #11 · Canon Pixel Clarification


Well, that's what I thought; the 7D's pixels are almost exactly 2/3 the size of those of the 5DII; and the 5DII's are about 4/5 the size of the the 5D (classic) pixels - could this be why users of both sometimes say the older camera's files are "richer", or "cleaner"...?


Jan 12, 2012 at 03:11 AM
mptnest
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p.1 #12 · p.1 #12 · Canon Pixel Clarification


Hey Jerry, Happy New Year. Nice being together on a thread again. Thanks for joining us.
Well, that's what I thought; the 7D's pixels are almost exactly 2/3 the size of those of the 5DII; and the 5DII's are about 4/5 the size of the the 5D (classic) pixels - could this be why users of both sometimes say the older camera's files are "richer", or "cleaner"...?
My thoughts exactly


Edited on Jan 12, 2012 at 03:37 AM · View previous versions



Jan 12, 2012 at 03:37 AM
RazorTM
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p.1 #13 · p.1 #13 · Canon Pixel Clarification


The 7D actually has a much stronger anti-aliasing filter, according to what I've read on the internet (the-digital-picture and other sites). So the 5DII appears much sharper straight out of camera.


Jan 12, 2012 at 03:37 AM
Imagemaster
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p.1 #14 · p.1 #14 · Canon Pixel Clarification


Some further reading to confuse you more:

http://www.luminous-landscape.com/essays/quality-vs-value.shtml

http://www.luminous-landscape.com/tutorials/understanding-series/res-demyst.shtml

http://www.luminous-landscape.com/essays/rant23b.shtml

http://www.luminous-landscape.com/essays/sensor-design.shtml



Jan 12, 2012 at 03:44 AM
Tenn.Jer
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p.1 #15 · p.1 #15 · Canon Pixel Clarification


Thanks for those reference articles, Tony; the second, especially, directly applies to this discussion, and probably even provides the resolution ( ) to our dilemma...


Jan 12, 2012 at 04:15 AM
AJSJones
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p.1 #16 · p.1 #16 · Canon Pixel Clarification


RazorTM wrote:
The 7D actually has a much stronger anti-aliasing filter, according to what I've read on the internet (the-digital-picture and other sites). So the 5DII appears much sharper straight out of camera.



From the digital picture

I'm guessing that the 7D's anti-alias filter is a little stronger relative to the individual pixels on this sensor compared to the T1i or 50D. And that the 50D and T1i's anti-alias filter are a little stronger relative to their individual pixels compared to the 5D II and some other prior DSLR models.

That's from the 7D review from the digital,picture after a disclaimer about not knowing how the sharpness settings in DPP affect the processing of the raw data from the different cameras. We don't know about the AA filter strengths. Some folks guess (and say they're guessing) and then others take it as gospel and amplify it into "much stronger AA filter"
YMMV



Jan 12, 2012 at 04:26 AM
digitalbug30d
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p.1 #17 · p.1 #17 · Canon Pixel Clarification


its all relative....


Jan 12, 2012 at 05:24 AM
RazorTM
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p.1 #18 · p.1 #18 · Canon Pixel Clarification


AJSJones wrote:
That's from the 7D review from the digital,picture after a disclaimer about not knowing how the sharpness settings in DPP affect the processing of the raw data from the different cameras. We don't know about the AA filter strengths. Some folks guess (and say they're guessing) and then others take it as gospel and amplify it into "much stronger AA filter"
YMMV


Sorry, I wasn't trying to put words into TDP's mouth, but it's less of a guess and more of the obvious when you compare the 7D and 5DII.



Jan 12, 2012 at 06:37 AM
mptnest
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p.1 #19 · p.1 #19 · Canon Pixel Clarification


Tony, there is some really good information on these links. Thank you.

I wanted to copy some highlight points, but the site strictly forbids it. So, good reading there. Some of the "muddy water" of confusion is turning a bit more clear.






Jan 12, 2012 at 11:50 PM





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