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| p.1 #2 · 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?
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 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.
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