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10-28-2019, 03:08 AM   #31
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QuoteOriginally posted by Dartmoor Dave Quote
We went over this at interminable length in the last equivalence thread. The physical size of the sensor is NOT optically enlarged to the physical size of the monitor. Once the charge collected by each photodiode has been read and stored as a digital value, that data has no physical size. It's just pixel values. Then, if we want to view that data on a monitor as an image, the data is resampled to the monitor resolution (almost always downsampled and almost never upsampled).

The physical size of the monitor is irrelevant, as you can confirm by the simple experiment of looking at the graphics settings in your computer's operating system and observing that there is no way to enter physical size. Only pixel resolution.

And to repeat: there is no magnification taking place in your original examples, but only upsampling, which is exactly the opposite of what usually happens when we look at digital images. After the stage where the image projected onto the sensor by the lens has been converted to digital values, there is absolutely no resemblance between digital photography and film photography in any way at all.
But the sensor is quite a bit smaller than most printed media. Megapixels is not as important as sensor size. Because if you squeeze 24 megapixels into a cell phone size sensor it isn't going to perform the same as a D750. It will perform worse -- a lot worse.

Anyway, rather than getting hung up on monitor size, think about printed size. I know no one prints photos any more, but it is probably useful in this discussion.

10-28-2019, 03:17 AM   #32
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QuoteOriginally posted by Rondec Quote
But the sensor is quite a bit smaller than most printed media. Megapixels is not as important as sensor size. Because if you squeeze 24 megapixels into a cell phone size sensor it isn't going to perform the same as a D750. It will perform worse -- a lot worse.

Anyway, rather than getting hung up on monitor size, think about printed size. I know no one prints photos any more, but it is probably useful in this discussion.
It's true that there are various reasons why a physically bigger sensor can have advantages over a physically smaller sensor. The important thing to remember in the context of this thread is that the reasons given in the original post are invalid, based on assumptions that some form of magnification is happening when actually it isn't happening.

As for prints: yes, sometimes we use upsampling in order to print bigger than we'd get at the usually accepted standard of 300dpi. But again, we have to remember that there's an important distinction between upsampling digital data and optically enlarging a film negative.
10-28-2019, 03:27 AM   #33
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QuoteOriginally posted by Dartmoor Dave Quote
It's true that there are various reasons why a physically bigger sensor can have advantages over a physically smaller sensor. The important thing to remember in the context of this thread is that the reasons given in the original post are invalid, based on assumptions that some form of magnification is happening when actually it isn't happening.

As for prints: yes, sometimes we use upsampling in order to print bigger than we'd get at the usually accepted standard of 300dpi. But again, we have to remember that there's an important distinction between upsampling digital data and optically enlarging a film negative.
What do you think happens when you shoot a similar image with a 24 megapixel K3 and with a 24 megapixel D750? The pat answer is that 24 megapixels is 24 megapixels, but the reality is that the D750 image is going to be able to be post processed harder than the K3 image because it comes from a larger sensor. This will not likely be an issue at all iso 100, unless you are shooting a really high dynamic range scene, but it is certainly going to show up at iso 1600 and 3200. At least that is my experience. Obviously yours is different, which is OK.
10-28-2019, 03:33 AM   #34
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I agree with you As I said, there are various reasons why a bigger sensor can have advantages. Just not the reasons given in the original post in this thread.


Edit:
I'd like to add a general comment about why I personally object to equivalence so strongly. It's because it's overly reductive. There are all kinds of complicated factors that affect the quality that we'll get from a digital camera, and the physical sensor size can indeed be one of those factors, but never in isolation. Equivalentists try to reduce all the complications down to a simplistic explanation, and in order to do that they distort reality to the point where their explanation loses most of its connection to the actual facts.

Sometimes it's better to just accept that something is actually really, really complicated. Then we can also accept that we don't have to worry about most of those complications when we're taking actual photos.

Over and out.


Last edited by Dartmoor Dave; 10-28-2019 at 03:47 AM.
10-28-2019, 12:08 PM   #35
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QuoteOriginally posted by stevebrot Quote
I agree

Upsampling = extrapolated data (mathematical best guess for what was never captured)

Downsampling = judicious pixel removal (mathematical best guess for retaining the gist of what was captured)

For fun and games one can do a 2X upsample followed by a 0.5X downsample and compare the end result with the original image of the same pixel dimensions.
Steve
just for fun. 5x up and down. At what viewing distances can you tell if you can tell. in no particular order original crop , up back down, up and back down 5 times, and 9 x copied.

I think it does show that magnification and up sampling are different beasts.
Would also be interesting to see with different programs.
Attached Images
 

Last edited by swanlefitte; 10-28-2019 at 04:20 PM. Reason: add info
10-28-2019, 12:08 PM   #36
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for reference
10-28-2019, 12:11 PM   #37
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Bottom left is the original. Everything else, toss up, but I would say
1x top left
5x bottom right
9x top right
10-28-2019, 12:44 PM   #38
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Up and down sampling creates patterns. They become stronger everytime.
The left is sampled. And it is perceived at different viewing distances.
Edit I should note I used png not jpg to copy.

10-28-2019, 01:24 PM   #39
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I probably shouldn't have checked on the phone
Now that I'm on the computer, left is clearly sampled.
10-28-2019, 01:37 PM   #40
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Here is an interesting thing. Change the monitor resolution. move back or forward until a picture on the left and right look the same across the top and then the same across the bottom. for me that viewing distance is the same but at 1920x1280 that it 7x and 9x distance (each square is 4" viewing is about 28" and 37". at 1020x760 that is 6" squares so 4x and 6x.
10-28-2019, 04:00 PM   #41
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QuoteOriginally posted by Serkevan Quote
I probably shouldn't have checked on the phone
Now that I'm on the computer, left is clearly sampled.
on my phone each square is 1" and to not see difference I need to be 9" away. With contacts everything is blurry that close and much farther away without contacts its blurry. It is at the limits of old eyes.
10-28-2019, 05:47 PM   #42
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so when I look at the entire photo at optimum viewing distance when my monitor shows the whole picture at 12" horizontal is at 18" that spot is about 1" viewed at 18x. twice the point where any difference is discerned.
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