Optimal ISO

[dcuthbert]

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Just noticed this and thought "hmmm wonder if any of the Leica boffin's over at the LFM know of a M8 way of getting the same benefit"

 

dokumentary fotografr: Canon 5D Mark II ISO Settings and Noise

 

I'm sure I read it here that using exposure compensation to -1/3 was a good idea, but I could be wrong

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[Angelos Viskadourakis]

very interesting graph,i wish someone will doit for M8 after the addition of the interval iso

80-250-400-500-800-1000 with the new firmware.

[chris_livsey]

Just noticed this and thought "hmmm wonder if any of the Leica boffin's over at the LFM know of a M8 way of getting the same benefit"

 

dokumentary fotografr: Canon 5D Mark II ISO Settings and Noise

 

I'm sure I read it here that using exposure compensation to -1/3 was a good idea, but I could be wrong

 

As I understand it Canon use two amplifiers to achieve their iso settings. Thus in an M8 base iso 160 you would use a x2 amplifier to obtain 320. Canon use a second amplifier to obtain the intermediate thus 1.5 amp gives 240 iso the problem with this is that each amplifier adds its own noise thus certain iso settings have two sets of amplifier noise, as shown in the linked graph which has been shown by others for other Canon models,which can be avoided by choosing an iso setting which uses only one amplifier.

Leica does not offer intermediate settings so there is only one amplifier and no strategy thus exists to choose a low noise setting. I have not looked in detail but I understand that Nikon does not use this approach to obtain intermediate settings thus the noise increases smoothy with all iso settings, as does Leica.

 

The -1/3 is a red herring. Early software versions seemed to give best exposure with this slight reduction but at some software release and I'm sorry I don't recall the number, this appeared to be corrected and the consensus was it was no longer necessary. Certainly that was my experience. The -1/3 did not, and if used now still does not, affect the iso setting it is an exposure compensation. Thus on an "A" exposure setting the camera will use a 1/3 stop faster shutter speed than indicated by the meter to reduce the exposure the iso is not affected.

 

I hope this clarifies and if I am in error other more technically literate posters will I hope correct me.