ISO 100, OMD-EM1II and firmware 3.0?

Started 2 months ago | Questions thread
Cafe Racer Contributing Member • Posts: 525
Re: ISO 100 Compared to Overexposure

Architeuthis wrote:

Cafe Racer wrote:

Architeuthis wrote:

Cafe Racer wrote:


Thanks for that. Perhaps I should also open a new thread as what I'm trying to ascertain is not S/N ratio as base 200.

Hi Cafe Racer,

I am not sure whether I understand your question.

Hi Architeuthis,

You've put in a lot of work here so I'll try to explain what I was trying to find out.

I put my Panasonic G80 on a tripod, I select Raw, switch to manual exposure mode and take two photos. Both photos are of exactly the same scene (nothing in the scene changes).

Ist photo taken at ISO 400 - 1/500 sec - f4

2nd photo taken at ISO 200 - 1/250 sec - f4

Would you expect those two photos to look the same?

This is not a trick question by the way.

Hi Cafe Racer,

I forgot to mention that the series I posted was, of course, also in manual mode (thought this would be obvious).

Your question seems to me very easy to answer: At your ISO400 settings you have -1eV less exposure (exposure in its primeval sense of aperture/shutter speed) to the sensor compared to the ISO200 settings. Hence you collect half the light. What follows is that IQ will be worse at ISO400 compared to ISO200 (worse S/N etc...; provided only, of course, if the settings at ISO200 are not overexposing the sensor)...

Modern cameras have a lot of reserves, so the -1eV underexposure may not manifest much in the visible, final, outcome. It will show up, however, upon heavy post-processing (when increasing brightness of the shadows a lot). You need to take more extreme settings for comparison and will see immediately in what direction the problem goes with the your pure eyes, no histograms, metering etc. required (e.g.: ISO200; 1/250 sec / f4 compared to ISO ISO3200; 1/2000 sec; f8)....



I realised that what I was trying to find out is completely different to what your are and your answer confirms that.  I'm not asking about IQ, S/N or DR at this point. So now I'll be more specific.

Do you think the two photos will be exposed the same (exhibit the same brightness) or will one be darker/brighter than the other given the combination of ISO, shutter speed and aperture?

Yes I know, some people don't like to use the word exposure because of ISO. I understand that ISO has no influence on the light entering the camera, that's the aperture and shutter speed, but it does serve to brighten or darken a photo.

Once again this is not a trick question. It's just photography basics, like what we learned when we first started. I'm trying to get us on the same page.

Cafe Racer.

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