Site Sponsors
Results 1 to 13 of 13

Thread: Why are Native ISOs so much better in all dSLRs?

  1. #1
    Member
    Join Date
    Jan 2010
    Posts
    178
    Post Thanks / Like
    Images
    3

    Why are Native ISOs so much better in all dSLRs?

    http://www.zacuto.com/shootout

    The GH-1 is fine at low ISOs, the Nikon D3s ----

    What about the native ISO statements: 160, 320, 640, 1250, 5000, 10,000
    25,650 51,200 and up? Why are these ISOs so superior?

    I have heard this from others that the oscilloscope demonstrates that these ISOs are better than the others that are electronically produced from the native ISOs.

  2. #2
    Senior Member pellicle's Avatar
    Join Date
    May 2009
    Location
    Southport, Australia
    Posts
    1,429
    Post Thanks / Like

    Re: Why are Native ISOs so much better in all dSLRs?

    the analog parts of the circuits are tuned for them.

    You may find this interesting reading

    http://www.pages.drexel.edu/~par24/r...awScaling.html

  3. #3
    Member
    Join Date
    Jan 2010
    Posts
    178
    Post Thanks / Like
    Images
    3

    Re: Why are Native ISOs so much better in all dSLRs?

    Thank you for the link. I still don't understand why all dSLRs would have the same effect, but I guess the design specifications are the same so the imaging sensors all reflect their specs?

    I wonder if this means that the 160 multiples are better for still photography so that if I need ISO 6400 according to the camera metering system, I should manually set 5000 instead? Something to try in the dark some day!

  4. #4
    Senior Member
    Join Date
    Apr 2008
    Posts
    384
    Post Thanks / Like

    Re: Why are Native ISOs so much better in all dSLRs?

    wow, fascinating stuff. Thanks!
    My Photography Blog here

  5. #5
    Senior Member ggibson's Avatar
    Join Date
    Oct 2009
    Location
    SF Bay Area
    Posts
    743
    Post Thanks / Like

    Re: Why are Native ISOs so much better in all dSLRs?

    Quote Originally Posted by clark666 View Post
    I wonder if this means that the 160 multiples are better for still photography so that if I need ISO 6400 according to the camera metering system, I should manually set 5000 instead? Something to try in the dark some day!
    What did you see that makes you think that 160 multiples are better for still photography? The way I read is is that ISO 160 is actually just ISO 200 with some calculation applied. For all intents and purposes, there's no difference between shooting at ISO 160 vs shooting at ISO 200 and then post-processing. Am I interpreting that correctly?

    The aperture scaling from that link is interesting. It suggests that when using a manual lens with a wider aperture than f2.8, the camera will not apply a scaling percentage to compensate. It is slight though (~3% per stop), so it may be hard to notice.

    But all of this research was done with Canon cameras, so I'm not sure how much can be applied to m4/3 cameras. I think it's clear that there are native ISOs and pushed ISOs for all digital camera sensors. But even manufacturers using the same sensor have different methodologies for implementing ISO (like the E-P1 vs GF1).

  6. #6
    Senior Member pellicle's Avatar
    Join Date
    May 2009
    Location
    Southport, Australia
    Posts
    1,429
    Post Thanks / Like

    Re: Why are Native ISOs so much better in all dSLRs?

    Hi

    Quote Originally Posted by ggibson View Post
    What did you see that makes you think that 160 multiples are better for still photography?
    probably this...


  7. #7
    Senior Member ggibson's Avatar
    Join Date
    Oct 2009
    Location
    SF Bay Area
    Posts
    743
    Post Thanks / Like

    Re: Why are Native ISOs so much better in all dSLRs?

    I figured, but as much, but didn't know if the "still photography" part had any significance. Anyways, the author prefaced that with the following:

    Because of this "stretching" and "compressing" ISOs like 160 appear very good in the following noise graph and 125 and the like appear bad. This is however deceptive - it is a purely mathematical manipulation of the data and therefore when shooting raw is useless - the same effect can be achieved by shooting at whole ISOs and pushing or pulling the image during raw conversion. When shooting JPEG on the other hand the intermediate settings can be useful.
    It is interesting how in some instances (like the one above) ISO 200 is above ISO 100. The author states that this is not because ISO 100 is noisier, but rather that ISO 200 has a higher dynamic range in the example (see the full explanation here 30D).

  8. #8
    Senior Member pellicle's Avatar
    Join Date
    May 2009
    Location
    Southport, Australia
    Posts
    1,429
    Post Thanks / Like

    Re: Why are Native ISOs so much better in all dSLRs?

    It is interesting how in some instances (like the one above) ISO 200 is above ISO 100. The author states that this is not because ISO 100 is noisier, but rather that ISO 200 has a higher dynamic range in the example
    the stuff in the raw files represents what the Analog to Digatal Converter (ADC) made of it after signal processing, if it added a base biase to the signal and then clipped it (or infinity to one compressed it) then that will reflect in the signal to noise ration (which was plotted in that graph) and if the dynamic range is lower (for the same sensor) then you can bet that means more signal processing on the bottom end..

    If you're interersted try reading my exporaiton here. I noticed how much later (higher numbers) the G1 was beginning recording the signal when bracketing exposure; that would result in a reduced dynamic range.

    notice what level number data starts at here


    and then here


    note also the added clustering around the 3988 value? I was never able to get it to 4094 when dealing with this sensor.

  9. #9
    Subscriber Member Jonathon Delacour's Avatar
    Join Date
    Dec 2007
    Location
    Sydney, Australia
    Posts
    454
    Post Thanks / Like
    Images
    7

    Re: Why are Native ISOs so much better in all dSLRs?

    Is the "optimum" 160, 320, 640, 1250, 2500, etc ISO sequence shown above applicable to all sensors? IANADSE (I am not a digital sensor engineer) but I would have thought that different sensors would have different native ISOs (eg 80 or 100 or 125 rather than 160). Or that the same sensor in different camera models (either from the same manufacturer or different manufacturers) would have a different native ISO, depending on the camera. And, therefore, that the optimum ISO sequence would vary from one camera/sensor to another.

    Or am I simply revealing my ignorance? (It wouldn't be the first time.)

  10. #10
    Senior Member pellicle's Avatar
    Join Date
    May 2009
    Location
    Southport, Australia
    Posts
    1,429
    Post Thanks / Like

    Re: Why are Native ISOs so much better in all dSLRs?

    Quote Originally Posted by Jonathon Delacour View Post
    Is the "optimum" 160, 320, 640, 1250, 2500, etc ISO sequence shown above applicable to all sensors?
    I'm sure it will be a case by case basis ... take a moment to read the lists he compiled from others sending in files to him.

    http://www.pages.drexel.edu/~par24/r...ram/index.html

  11. #11
    Subscriber Member Jonathon Delacour's Avatar
    Join Date
    Dec 2007
    Location
    Sydney, Australia
    Posts
    454
    Post Thanks / Like
    Images
    7

    Re: Why are Native ISOs so much better in all dSLRs?

    Quote Originally Posted by pellicle View Post
    I'm sure it will be a case by case basis ... take a moment to read the lists he compiled from others sending in files to him.

    http://www.pages.drexel.edu/~par24/rawhistogram/index.html
    OK, so using the files he provides, it should be possible to ascertain the optimum ISO sequence for any camera model. Thanks for the link!

  12. #12
    compositor20
    Guest

    Re: Why are Native ISOs so much better in all dSLRs?

    with my e-p1 the iso 2500 is much better than iso 320 and iso 5000 much better than iso 6400... try it and you will agree

    i have my auto-iso to iso 1250 since if i need one more EV i can dial iso 2500 (the image quality limit that you should use to get good a4 prints)

    comparing iso1250 to iso 1000 you get more grain luminance at 1250

    comparing iso 1250 to iso1600 you get just a little more grain but noticeable less tonal range in the shadows so much less dynamic range then 1600

    i have made this test with real life samples and they show this

  13. #13
    Senior Member
    Join Date
    Jan 2010
    Posts
    315
    Post Thanks / Like

    Re: Why are Native ISOs so much better in all dSLRs?

    I have read this several times and still not fully understood it.

    Next week I have an available light shoot for which I'll use my Canon 5d. Am I being recommended to choose 1250 rather than 1600? The original 5d stops at 1600 (it has a H setting but I gather that is equally artificial).

    Tony

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •