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09-03-2016, 10:03 PM   #1
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Pixel Explanation

Can anyone enlighten me on the difference between pixel count I. E. 40 mega pixel sensor and the pixel density of a sensor. It would appear from my reading that you can get a higher pixel density from a lower pixel sensor which in theory should give you a better picture.

09-03-2016, 10:08 PM   #2
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Pixel density = number of pixels (megapixels) / sensor area. Pixel count is important, but you don't want the density to be too high, as then high-ISO performance suffers. At the same time, a resolution that's too low would prevent fine details from showing up clearly.

https://www.pentaxforums.com/forums/55-photography-articles/228535-how-why-se...s-compact.html

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09-03-2016, 11:02 PM   #3
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QuoteOriginally posted by Mapleleaf-Mick Quote
Can anyone enlighten me on the difference between pixel count I. E. 40 mega pixel sensor and the pixel density of a sensor. It would appear from my reading that you can get a higher pixel density from a lower pixel sensor which in theory should give you a better picture.
You have 40 people. Each person is a pixel.

Now put those people in a room that is 100 foot by 100 foot. How dense is it?

Then put them in a room that is 20x20 how smooshed up together is everyone?

There's your answer.
09-03-2016, 11:12 PM   #4
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QuoteOriginally posted by Mapleleaf-Mick Quote
It would appear from my reading that you can get a higher pixel density from a lower pixel sensor which in theory should give you a better picture.
Define better and for what purpose? If you have a physically larger sensor with the same or less pixels vs a smaller sized sensor with an equal or greater number of pixels a few things in that case are true...

On the bigger sensor with less pixels means each pixel so to speak is bigger. In that case you have better ISO performance.

I noticed that difference going from a K-5 to a K-3. 16mp vs 24mp on the same size real estate.

However if you go to super low pixel counts you lose resolution which also isn't good.

There has to be the perfect balance there for the intended purpose.

09-04-2016, 05:01 AM   #5
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QuoteOriginally posted by alamo5000 Quote
You have 40 people. Each person is a pixel.

Now put those people in a room that is 100 foot by 100 foot. How dense is it?

Then put them in a room that is 20x20 how smooshed up together is everyone?

There's your answer.
Denseness with people has nothing to do with pixels.

RONC
09-04-2016, 07:28 AM   #6
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QuoteOriginally posted by rechmbrs Quote
Denseness with people has nothing to do with pixels.

RONC
a·nal·o·gy
əˈnaləjē/Submit
noun
a comparison between two things, typically on the basis of their structure and for the purpose of explanation or clarification.
"an analogy between the workings of nature and those of human societies"
a correspondence or partial similarity.
"the syndrome is called deep dysgraphia because of its analogy to deep dyslexia"
a thing that is comparable to something else in significant respects.
"works of art were seen as an analogy for works of nature"
09-04-2016, 11:06 AM - 1 Like   #7
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QuoteOriginally posted by rechmbrs Quote
Denseness with people has nothing to do with pixels.

RONC
I thought it was a very good analogy. People do pretty well when given enough space. Scrunch them together and they get hot and tend to not function very well. Things can also get pretty stinky pretty fast.


Steve

09-04-2016, 02:23 PM - 2 Likes   #8
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QuoteOriginally posted by Mapleleaf-Mick Quote
Can anyone enlighten me on the difference between pixel count I. E. 40 mega pixel sensor and the pixel density of a sensor. It would appear from my reading that you can get a higher pixel density from a lower pixel sensor which in theory should give you a better picture.
Not all semi conductor photo sites aka Pixels ( Picture Elements) are created equal. An often used analogy is water buckets.

Large buckets capture more rain ( photons) than small ones in the same amount of time. As buckets get smaller, the ratio of orderly, well behaved photons vs ill behaved juvenile delinquent photons (noise) increases and their useful sensitivity becomes increasingly less. And this happens before the digital electronics which amplify the captured light energy, another source of noise. Although the electronics are getting very, very good and nearly noise free.

If the bucket is filled to 100% of capacity, it's an ideal exposure value. Sensor designers call this full well capacity or how many photons fill it up, an optimum signal to noise ratio.

If the bucket is barely filled, the image is underexposed. S/N ratio is much less.

So fill the room with buckets. If the room is APS-C sized, the only way to get 24 million buckets in the room is to use smaller buckets, placed closer together ( pixel size & pitch) vs 16 million buckets. You can look up pixel size & pitch for most digital sensors.

It is the primary reason cell phones are so limited is sensitivity. While sensor technology gets better and better, there are limits due to the wavelength(s) of light. A single photon can spill into multiple photo sites.

In practical terms, my 16 MP K5IIs bodies serve me very well for the low light, high shutter speed challenges of dance performances. My 24 MP K3Ii gives me very welcome higher resolution in studio and portrait sessions. If I end up with a K-1, I'll use APS-C modes for most performance images as file size and volume of images is a significant consideration. I would use FF mode when it made sense like something intended for large promotional images. Haven't shot a K-1 but I have rented the 645z and because of the larger pixels & pitch, the dynamic range is just wonderful.

I'm in the process of finishing a print order for a client who ironically is an Adobe rep. (did his headshot). He sent me some iPhone 6 JPEGs he made on vacation which I edited and enlarged to 12x18. They're going on metal ( aluminum) and I ran full size glossy proofs. He had lots of light and the images look great. So it all depends on the application.

Last edited by Brooke Meyer; 09-04-2016 at 05:48 PM. Reason: Fix spelling
09-04-2016, 03:46 PM   #9
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QuoteOriginally posted by stevebrot Quote
I thought it was a very good analogy. People do pretty well when given enough space. Scrunch them together and they get hot and tend to not function very well. Things can also get pretty stinky pretty fast.


Steve
Plus that fact that the other half says I can be pretty dense, so people and pixels is a perfectly acceptable analogy .
09-04-2016, 07:49 PM   #10
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Thanks Adam for that terrific thread. Very very informative.
09-04-2016, 11:16 PM   #11
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QuoteOriginally posted by Adam Quote
Pixel density = number of pixels (megapixels) / sensor area. Pixel count is important, but you don't want the density to be too high, as then high-ISO performance suffers. At the same time, a resolution that's too low would prevent fine details from showing up clearly.

https://www.pentaxforums.com/forums/55-photography-articles/228535-how-why-se...s-compact.html
The K-3 at 24mp and the K-1 at 36mp. Correct me if I am wrong, but it appears to me that the K-3 and the K-1 have the same size pixels. If a larger pixel size equals better high ISO performance, then these two cameras should be the same or similar for noise? However, I can shoot at 6400 ISO on my K-3, and get less noise on my K-1 at 20,000 ISO. Where am I in error?
09-04-2016, 11:18 PM   #12
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QuoteOriginally posted by divert Quote
The K-3 at 24mp and the K-1 at 36mp. Correct me if I am wrong, but it appears to me that the K-3 and the K-1 have the same size pixels. If a larger pixel size equals better high ISO performance, then these two cameras should be the same or similar for noise? However, I can shoot at 6400 ISO on my K-3, and get less noise on my K-1 at 20,000 ISO. Where am I in error?
The K-1 has larger pixels. See the table in the article I linked

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09-05-2016, 01:55 AM   #13
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QuoteOriginally posted by divert Quote
The K-3 at 24mp and the K-1 at 36mp. Correct me if I am wrong, but it appears to me that the K-3 and the K-1 have the same size pixels. If a larger pixel size equals better high ISO performance, then these two cameras should be the same or similar for noise? However, I can shoot at 6400 ISO on my K-3, and get less noise on my K-1 at 20,000 ISO. Where am I in error?
The K-1 has same size pixels as the K5, it just has more of them than the K3 has. Bigger pixels, on an individual level tend to have more dynamic range and less noise. So if you look at pixel level, the K5 has less noise than the K3. But when you go to print/view a photo, most of that goes away because the K3 has more pixels. Now, the K-1 has a lot more pixels than either of those other cameras, so it has more pixels and it has a higher quality pixel -- basically at the K5 level and so the end result is that you can shoot higher iso with better results (assuming you are printing/viewing at the same size).
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