I think I've found your solution: your ND filters are not 8 and 4 stops, but 3 and 2 stops respectively: to get the stop number, take the Nth root of the ND number, where the answer should be 2. So 8^(1/3) = 2 and 4^(1/2) = 2. Combined you only have 5 stops of ND, not 12. A correct exposure should then be 1/25 sec × 2^5 = 1.28 sec instead of 164 sec!
The numbers on ND filters are designed such that you can easily calculate the correct exposure time. Don't think of a number of stops, just multiply everything: 1/25 sec × 8 × 4 = 1.28 sec.
The MM+/- number is just a realtime exposure meter compared to a 'desired' value of 0. Point your camera somewhere dark or bright and you'll see this number go down and up. Nothing is compensated for, it's just a reading.
I’ve just gotten my first Sony body coming over from Nikon. I purchased the 50mm 1.8 as first general purpose lens and to test the camera. I’m now looking to get a wider angle but keeping budget lower currently. I shoot mostly landscapes and nature while hiking and throw in some travel images.
Has anyone used the newish Samyang 24mm 2.8 lens for landscapes? I am looking at purchasing that or the Zeiss 24-70 f4. Coming from zooms on Nikon I found I mostly just shoot towards the wide end of a 28-75 and compose my images based on that. I will likely add the 70-200 f4 later on for landscapes as well.
Thoughts on Samyang 24mm 2.8 new vs Sony 24-70 f4 used? Any votes for the Sony 28mm f2 and add the wide angle converter to 21mm? Thanks
thanks for your reply. yes ISO was fixed. it seems when I switch from A to M modes the only thing that changes on the back display is the Exp.Comp changes from just a +/- number to "MM+/- number.
then in M mode if I change the shutter speed, the MM+/- compensates for it. very frustrating. I just can't find a way to shut this off. Maybe this is just a flaw in the a5100??
If you are in manual mode and have ISO set on 100, by definition can there be no auto exposure compensation by your camera: all three exposure variables are fixed by your manual settings.
Your math is correct: if you meter 1/25sec at f/11 ISO 100, if you add 12 stops of ND the same exposure requires 164 seconds (or 2 mins 44 sec).
Are you sure you stacked the two ND filters properly?
Was your ISO fixed at 100 when you did the metering in A mode? Unlikely to be your problem as this would have caused under- instead of overexposure. Just trying to isolate your problem.