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View Full Version : OM-D high ISO question.....


DJMC
15th July 2012, 06:50 PM
What ISO setting would I need to use to get the same shutter speed as the m45 1.8 lens at ISO 100 when using my m14-140 at 14mm f:4?

Just trying to establish how I can get the low light performance out of an m43 which I like so much about my XZ-1's 1.8 lens.

Thanks for any help.

;)

steverh
15th July 2012, 07:30 PM
Around ISO 400 unless my maths is completely :confused:

brianvickers
15th July 2012, 07:46 PM
I agree....
You start with f1 which is fully open then multiply by 1.4 for each stop.

So 1 x 1.4 = f1.4 (as per the Lumix 25mm f1.4)
1.4 x 1.4 = f2 (as per f1.8 lenses)
2.0 x 1.4 = f2.8
2.8 x 1.4 = f4

so the 1.8 you mention is closest to f2 and you have an f4 so that 2 stops
so ISO400 would be needed to get the same exposure with an f4 as an f1.8 at ISO100.

Alternatively the shutter speed could be reduced by one stop and the ISO increased by 1 stop...or the shutter speed reduced by 2 stops using ISO100.

hope that helps

DJMC
16th July 2012, 04:55 PM
Thanks for the info!

;)

SteelD
16th July 2012, 05:35 PM
Actually, f1.8 is almost half a stop from f2 so f1.8 compared to f4 is closer to 2.5 stops different so the nearest equivalent ISO would be 640 IMHO.