GX7 vs E-M1 IQ difference?

Started Dec 17, 2013 | Discussions thread
GeorgianBay1939 Senior Member • Posts: 3,949
Re: I will stop after this

joeletx wrote:

Let me see if I can put it in a simple term. A stop is changes you make with regard to Aperture (F/Stop), ISO, and Shutter speed to retain an exposure value (EV).

Lets say, you are at EV; F-Stop; ISO; Shutter Speed:

Original values: 0.0; F/11; ISO-800; 1/1000 Sec

+1/2 Stop +0.5; F/8.0; ISO-800; 1/1000 Sec

+1/2 Stop, or +0.5; F/11; ISO-1600; 1/1000 Sec

+1/2 Stop, or +0.5; F/8.0; ISO-800; 1/500 Sec

+1 Stop +1.0; F/8.0; ISO-1600; 1/1000 Sec

+1 Stop, or +1.0; F/5.6; ISO-800; 1/1000 Sec

+1 Stop, or +1.0; F/8.0; ISO-800; 1/500 Sec

and other combinations.

If you set the mode to M (Manual) and set Aperture (A), Shutter Speed (S), and ISO to get 0.0 meter reading. You then change settings to increase or decrease the EV reading by clicking up or down the aperture, Shutter Speed, or ISO.

If the total click count is one, you have made 1/2 stop change; and you can observe the EV meter that said -1/2 or +1/2.

If the total count is two, you have made two 1/2 stops, or one full stop; you meter value should say +1.0 or -1.0; or 0.0 because you have changed up one click but change down one click. The total change is still one stop.

OK, I will stop now

This is useful for exposure metering which relates Exposure (average scene luminance, f/ and shutter interval) to output mid-tone brightness  via the "exposure equation " [which I would prefer to call the "metering" equation].

The graphs above the link illustrate your examples. But note that EV is independent of ISO.


Exposure, as you know, is UNAFFECTED by ISOspeed. It is only a function of EV (f/, shutter interval) and scene luminance.   Output brightness IS affected by ISOspeed (and other image processing variables).

The charts that illustrate your point are here:


Now, I'll stop!  


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