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Equivalence thread (including posts moved here from other threads)

Discussion in 'Back Room' started by dalto, Sep 6, 2016.

  1. EarthQuake

    EarthQuake Mu-43 Top Veteran

    934
    Sep 30, 2013
    Image-level noise? Yes, absolutely.
    Per-pixel noise? No, of course not.
     
  2. fredlong

    fredlong Just this guy...

    Apr 18, 2011
    Massachusetts USA
    Fred
    Image level noise is a new concept to me. Can you explain what you mean by that?

    Fred
     
  3. DanS

    DanS Mu-43 All-Pro

    Mar 8, 2016
    Central IL
    What he's talking about is taking a 16mp image and a 24mp image, and then printing them out at the same size. or say resizing them to 4mp. The 24mp image will look better because you compressed(pick a verb) the image more.

    It's extremely flawed logic in my opinion, because it breaks down when you aren't drastically resizing your image.

    Imo, the only thing that matters is "Per-pixel" noise.
     
  4. Speedliner

    Speedliner Mu-43 Hall of Famer

    Mar 2, 2015
    Southern NJ, USA
    Rob
    No not technically. But lets use an example. Let's say you have an image you like and you print it 8x10. Then you decide you don't quite like it as is and you go back to your original and crop it down a god bit. Now you print the cropped image out to 8x10 again. The cropped print will appear noisier because you magnified a smaller part of the original image to 8x10. Doing so magnifies the noise in the file along with the good parts.

    It's hard to explain with words. Maybe there's a video on YouTube of the subject.
     
  5. EarthQuake

    EarthQuake Mu-43 Top Veteran

    934
    Sep 30, 2013
    Certainly, by image level noise, I mean how much noise is visible when viewing an image in its entirety, like normal people view photos. As apposed to pixel-peeping per-pixel noise, which tells one very little about the overall quality of an image.

    Here is an example. I've taken two photos of the same subject, at the same distance, with the shutter speed, ISO, and fstop, but at different focal lengths. One at 12mm, the other at 24mm. Then, I scaled down the 24mm to match the framing of the 12mm shot. Both photos were processed from raw in the same way.

    croptest02.png
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    croptest01.png
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    When viewed at the same output size, the cropped image has visibly worse noise. The photosite size, of course, has not changed.

    Consequently, what this shows is that, for equally efficient sensors, photosite size is not the determining factor for noise. The bigger sensor records more total light, more photons, which results in less noise.

    This is a crude demonstration of the differences you would see with a 64MP 35mm sensor and 16MP 43 sensor, given perfectly equal performance between the sensors. In this case it's a 16MP 43 sensor vs a 4MP section of that same sensor, but the principal applies regardless of the specific sensor sizes or resolutions one would choose to compare.

    Now, sensors are rarely perfectly equal when it comes to efficiency, but the variances in efficiency/performance tend to be much less than those between the basic physical limitations of a given sensor size.
     
    Last edited: Sep 7, 2016
  6. DanS

    DanS Mu-43 All-Pro

    Mar 8, 2016
    Central IL
    Yes, because no one in the history of photography has ever had to aggressively crop an image, or enlarge it!:dash2:
     
    Last edited: Sep 8, 2016
  7. pellicle

    pellicle Mu-43 Hall of Famer Subscribing Member

    Feb 10, 2010
    Killarney, OzTrailEYa
    pellicle
    no, increasing pixel density increases noise ... because there will be statistically fewer photons to be counted by each photo-site (thus increasing noise by reducing signal)

    I mean that instead of simply slicing a 5D sensor and making a 43rds sensor of the same density of pixels (which would be about a 5.46MegaPix 43rds sensor using the same pixel density as the 5DMkii data above), that you reconfigure that sliced sensor to be 16Mpix (which is what people see when they photograph with their 43rds and pixel peep). Its that that leads to more noise.

    I was attempting to agree with you. I suspect if we had a 6Mpix 43rds camera (with essentially the same size photo-sites as the 5D has that it too would be exceptionally low noise (but of course not be as many pixels which matters for marketing and those who aggressively crop rather than use their lenses appropriately)
     
    Last edited: Sep 8, 2016
  8. pellicle

    pellicle Mu-43 Hall of Famer Subscribing Member

    Feb 10, 2010
    Killarney, OzTrailEYa
    pellicle
    at the risk of feeding this (as everyone seems to be describing eggs with different words) I'll say that even before agressively cropping an image that 43rds is already a x2 crop of a full frame. However at manufacture that "crop" is also stuffed with more pixels resulting in each photo site getting less light

    :) 
     
  9. pellicle

    pellicle Mu-43 Hall of Famer Subscribing Member

    Feb 10, 2010
    Killarney, OzTrailEYa
    pellicle
    I think this is about as good an example as one could get without actually having a FF sensor with similar electrical properties as the 43rds sensor with both having the same pixel density.

    I suspect with some good intelligent pixel binning (as perhaps done by Nokia on their pureview stuff) may even reduce the noise more on the "scaled down" image
     
  10. Nathanael

    Nathanael Mu-43 Veteran

    462
    Oct 12, 2015
    kill me :026:
     
    • Agree Agree x 3
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  11. pellicle

    pellicle Mu-43 Hall of Famer Subscribing Member

    Feb 10, 2010
    Killarney, OzTrailEYa
    pellicle
    no ... join us in suffering:Welcome:
     
  12. pdk42

    pdk42 One of the "Eh?" team Subscribing Member

    Jan 11, 2013
    Leamington Spa, UK
    I think you missed my point. There are two reasons why FF sensors are better than u43 sensors:

    - The photosites are bigger with correspondingly larger charge-well depth. This improves the per-pixel noise
    - Given no cropping, you enlarge the FF image less. This reduces the apparent noise in the final output

    I think we agree, it's just a question of how it's phrased. I personally hate this "total amount of light/more photons" line of reasoning since all my instincts tell me we shuold be looking at the light per unit area.
     
  13. pellicle

    pellicle Mu-43 Hall of Famer Subscribing Member

    Feb 10, 2010
    Killarney, OzTrailEYa
    pellicle
    I think it comes from people who grew up reading text books in the film era who's authors ignored or oversimplified the fact that photons still had to interact with halides.

    In digital there is a well that has a photon counter at the bottom. Same thing really.

    Looked at another way if you put out a bucket or a test tube in the rain both will catch the rain. If the rain is sparse then the bucket is more likely to be accurate than a thin test tube in registering how many inches of rain fell.

    You won't find a rain gauge in fractions of an inch opening for that reason.

    A good primer
    Does Pixel Size Matter Clarkvision.com
     
  14. fredlong

    fredlong Just this guy...

    Apr 18, 2011
    Massachusetts USA
    Fred
    Ok, so bigger noise equals more noise. I disagree. Signal to noise ratio is the same.

    And if you crop out three quarters of the noise, don't you actually have less overall noise ;) 
     
  15. hazwing

    hazwing Mu-43 Hall of Famer Subscribing Member

    Nov 25, 2012
    Australia
    Blah blah equivalence, noise, sensor size, etc. So over this cr@p
     
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  16. ijm5012

    ijm5012 Mu-43 Legend Subscribing Member

    Oct 2, 2013
    Pittsburgh, PA
    Ian
    Why not just frame your shot better in the first place, or use the appropriate lens? I don't go trying to shoot motorsports with my PL25...
     
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    • Funny Funny x 1
  17. DanS

    DanS Mu-43 All-Pro

    Mar 8, 2016
    Central IL
    Understanding how and why stuff works, is more important today, than at any point in history. It baffles my mind, that the average consumer basically wants to be blissfully unaware nowadays.
     
  18. Turbofrog

    Turbofrog Mu-43 Legend

    Mar 21, 2014
    The crop is an analogy for sensor size...
     
    • Like Like x 2
  19. DanS

    DanS Mu-43 All-Pro

    Mar 8, 2016
    Central IL
    huh? Pretty much all image editing software has a crop feature.
     
  20. Turbofrog

    Turbofrog Mu-43 Legend

    Mar 21, 2014
    Speedliner was saying that the image quality effects of printing the original image and then cropping the image and printing it at the same size is analogous to taking the image with a bigger sensor camera and a smaller sensor camera and then printing them both at the same size.

    It's a reasonable statement in my mind.

    Anyway, EarthQuake showed it perfectly in a visual way with his alarm clock photos. You can't really get clearer than that by way of explanation.
     
    • Like Like x 2
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