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ISO Settings in thirds


Paco Rosso

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My SL2 only shows the sensitivity in the full stops (100, 200, 400 etc) and I want to use thirds (100, 125, 160, 200, 250, 320, 400, etc). It can be used in video but I cannot find the place in the menu where to configure this kind of setting ¿Or maybe it cannot be done?
 

Edited by Paco Rosso
misstyping
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Sorry, but I don't understand this need. Are you shooting in JPG and not wanting to do any post processing? Even then, I still don't see the need. 

Why I struggle with this -and something that many don't understand- is that with digital cameras, ISO is not a real setting; it is merely a description in the metadata of the amplification applied to the light signal that the sensor receives.

Shutter speed and aperture are "real" settings that actually affect exposure, ISO is not.

Said another way; you can shoot at ISO 100 and push the exposure 1 stop in post, or shoot at ISO 200... if you compare images, there will be no practical difference (depending on camera, you may be able to push 2 stops or more and create an identical final image). So, I just cannot see why a fraction of a stop is critical. 

Maybe you can give a summary of your special use? 

Thanks,

Brad

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1 hour ago, kobra said:

Maybe you can give a summary of your special use? 

I am running a test about the performing of OCF flashes in outdoors mixed light. I need to mix the exposure of the light of the flash with the exposure of the ambient light. This mix is made with the shutter closing the diafragm to maintein the ambient exposure constant. But when you go over the sync speed then the flash begin to work in HSS mode, and this lost power (for 1/3 over the sync the flash lost 2/3 of power, for 2/3 over the sync speed the flash lost 1 full stop and for 1 stop over the sync my flash lost 1,5 stops of power). So when I reach the sync speed the way to mix both exposures is by the reduction of the sensitivity. For an shutter speed of 1/320 I need reduce the sensitivity to ISO 80/20 and for 1/400 go to ISO 64/19. When I run the test for ISO 400/27 I will need to reduce the sensitivity to ISO 320/26 and ISO 250/25.
(And that of sensitivity is a tag in metadata is an urban legend).
 

Edited by Paco Rosso
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The sensitivity is not changed by the ISO setting either. It only controls the amplification of the output of the sensor after digitalization in the process chain in firmware. 

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4 minutes ago, jaapv said:

The sensitivity is not changed by the ISO setting either. It only controls the amplification of the output of the sensor after digitalization in the process chain in firmware. 

And because the way the sensitivity is defined, it change. In photography the sensitivity is related to the amount of exposure to achieve a prefixed output value, and the value is the analog output of electrical current, so the amplifier changes the sensitivity, not only the charesteristics of the photosite.

 

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It is a common misconception that ISO is an exposure parameter. It is not Only the shutter speed and aperture control the amount of light hitting the sensor. The ISO setting only controls the final camera output. With an  ISO invariant system -which most if not all digital cameras are at least for a part of the ISO curve, the ISO value can be set just as easily in post-processing. The only effect in-camera is that the EVF goes dark. 

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19 minutes ago, Paco Rosso said:

And because the way the sensitivity is defined, it change. In photography the sensitivity is related to the amount of exposure to achieve a prefixed output value, and the value is the analog output of electrical current, so the amplifier changes the sensitivity, not only the charesteristics of the photosite.

 

No. The sensitivity of the sensor is always the same. The official ISO definition of a digital cameras is an equivalence to film densitometry . For this reason digital cameras can vary up to two EV values between brands, depending on the interpretation of the designer. It would have been much better if there had been a separate digital ISO sensitivity norm for digital cameras insttof referring to the film norm. Now after decades we are stuck with it. 

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6 hours ago, Paco Rosso said:

I am running a test about the performing of OCF flashes in outdoors mixed light. I need to mix the exposure of the light of the flash with the exposure of the ambient light. This mix is made with the shutter closing the diafragm to maintein the ambient exposure constant. But when you go over the sync speed then the flash begin to work in HSS mode, and this lost power (for 1/3 over the sync the flash lost 2/3 of power, for 2/3 over the sync speed the flash lost 1 full stop and for 1 stop over the sync my flash lost 1,5 stops of power). So when I reach the sync speed the way to mix both exposures is by the reduction of the sensitivity. For an shutter speed of 1/320 I need reduce the sensitivity to ISO 80/20 and for 1/400 go to ISO 64/19. When I run the test for ISO 400/27 I will need to reduce the sensitivity to ISO 320/26 and ISO 250/25.
(And that of sensitivity is a tag in metadata is an urban legend).
 

Thanks for explaining you use case; not one I'm familiar with, so sorry I don't have a workaround. 

But, can you explain what you wrote as highlighted above? Note I didn't say that ISO is about sensitivity, because it's not. But, all image capture settings are stored in metadata including ISO, so your comment is confusing. Thanks! 

BTW, I just noticed you may be new here, so Welcome! 

Brad

 

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