This article should be read by everybody

Started Dec 12, 2013 | Discussions thread
K E Hoffman
K E Hoffman Veteran Member • Posts: 5,103
Summary of Article missed basic facts.. that even article has.

This is all interesting.. but the fact is .. its all very theoretical.. at one level.. and yet the very DXO distribution graphs will bear out what I am about to write here.. and goes against the simplified idea that that there is not a pixel density to noise relationship.

Look at Generations of Cameras..

A700 vs A900 A900 has larger pixels same as about 10 MP APC and it has a better noise profile.. at the pixel level.. as it also has more resolution you have the choice of cropping or scaling the image and gaining both the better pixel noise profile AND the image scaling noise reduction.. If you crop you only get one..

A77 va A700 va A99

Again.. A77 with newer sensor has less noise than A700 with double the pixels.. but it has more noise at the pixel level than A99..

Am I saying the physicist who wrote the article is wrong. No.. if you read closely he talks about how improvements affect things etc. He actually talks about what I just said.. and the trend lines in the noise results for the cameras show it.

Does more pixels mean more noise ALWAYS - No because there are a bunch of other Variables. like Sensor design. Camera Design., Sensor Generation. Where are the A/D converters located. [Sony likes to put them on the sensor. Canon has tended to put the off sensor.]

Sony can't volate the patents Canon has on doing noise read and cancel at each pixel so they work to reduce the noise in the circuit paths.. [This of course is a broad generalization]

If I make a sensor using the same design with the same electronics up to the A/D converter and one pixel is 50% larger the larger one will have less per pixel random noise..

The 70D is an interesting beast.. as Canon has put 40 Megapixels on the sensor.. each working separately to read focus and then as a team to read image. But this means there are in places double the supporting read circuits.. and the noise profile on the Canon 70D as soon as you get into the high ISO where the gain is being turned up before the A/D conversion it starts to get more noise faster than previous Canons tended to. (See this month's POP Photo Test of 70D)

If I tell you there is a 16MP APC sensor and an 24MP APC sensor can you tell me which one has more noise. NO YOU CAN"T because I didn't tell you who made them and which design they were based on.. That is what he is saying in the summary.. Pixel size ONLY does not correlate 100% to noise level..

But the trend lines on the charts and the and separation of FF to APC which also is a separation of larger sensor Pixel to smaller Sensor Pixel confirms the basic FACT. When you shrink the light bucket the % of noise leaking into the system will affect the image more PER PIXEL..

IF you scale them to the same size ALWAYS yes as TBCASS wants us to remember that act will done right will neutralize noise to a degree.. IE if I scale a 24 MP to 16 MP image size.. The noise will be very similar even in the same generation sensor.. But What if I just crop the center of the Image and scale both to 50% .. the 24 MP will have more color variation and or grain due to noise.

For those that want to pretend a smaller pixel is not going to mean more noise.. I did some diagrams. I know its "not about the pixel it is about the whole sensor" as the Noise Optimists say.

Problem is if I double the number of pixels using the same technology. While I didn't double the amount of random in sensor noise (yellow) I did double SOME of the read circuits and path ways..

So the noise coming from the supporting circuits between the sensor sites and the A/D is increased as whole across the sensor. Some parts don't double we multiplex the A/D converters etc etc.

I also reduced the maximum signal the sensor site can produce at each pixel

But there is more complexity in a sensor of the same size with 24MP than the was in 12 MP given the same design.. so there will be more total system noise in the final out put..

This is granting the idea that when the slice op the sensor in smaller pieces that the light gathering ability of the who sensor doesn't drop some because light loss between the pixels.. which micro lenses and back lit sensors help with.

So if Sony took what they did for the A77 and didn't do 24 MP but did 16 or 18.. there would be less per pixel noise and less circuit noise.. and you could crop close and not see it as much. Now if you always scale your un-cropped frames to 8x10.. you would see it less it would only show up as we see as the ISO goes up as the Gain is increased as the noise is amplified with the smaller signal.. ..

If you don't always print at one size but sometimes like to do larger prints.. or you sometimes don't have the 200mm with you so crop the center.. you would see the difference.. and that is where some of the A77 vs A57 debates happen. (See ;last chart below..)

[NOTE Dot Colors on Diagram do not represent NOISE COLORS in actual photos.. they are there to show different signal and noise sources in a camera]

Look at the potential % of noise in the system from a larger possible reading off the sense vs below

Percentage of noise that is possible in support or each pixel goes up. And there are more "red dot" noise sources on a more complex sensor.

DPR seems to have lost the A57 RAW so we do get to deal with possible variations of the JPG engine but in general the cameras are from the same generation and share lots of the same code and work from Sony. 16MP same generation same maker better noise profile that 24 MP.. which by the way beats the once LOW noise wonder of the Canon 7D a previous generation of 16 MP sensor.

Sensor size + Pixel Size + Technology Generation is a predictor or noise levels not only at the pixel level but collectively across the sensor. and as the gain is turned up at higher ISO the differences are magnified and will show up even in a scaled image.

That said the whole 1:1 noise comparisons are over done because we are cramming more pixels into same sized prints and web pages... and Sony's color accuracy end DR matter a lot.. but if you like to shoot ISO 3200+ I would want an a57 sensor over an A77 or even 7D sensor.

Would I trade the whole camera for the differences.. probably not. But some who like ISO3200 shooting would like a 16MP "A77-16" camera.. better.

This is all My Opinion and contains tons of simplification.. Sensors ore very complex and Canon and Sony work really hard to lower the noise then use that to increase MP.. more than most of us need but they do help even on lesser lenses. so More MP is not a useless feature but like "magic" is has its cost.

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K.E.H. >> Shooting between raindrops in WA<<

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