Lens f-Stops Between 4/3 and FX

Started Nov 4, 2012 | Questions thread
smilingcdn
New MemberPosts: 22
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Re: Lens f-Stops Between 4/3 and FX
In reply to exdeejjjaaaa, Nov 12, 2012

exdeejjjaaaa wrote:

smilingcdn wrote:
If I got my understanding right, FF at f4 will get 1/2 the light of the m4/3 at f/2.8

no, FF sensor with FF lens @ f4 will get twice more total light than m43 sensor with FF or M43 lens @ f2.8... because if has 4 times bigger light collecting area... you reduce relative illumination by 1 stop (2 times less) but with 4 times more area to collect 2 times lesser light per unit of area you still collect 2 times more total light.

Thanks for the correction.  the +'s and -'s are hard for me to keep straight and this explains it for me.  So, all things being equal (regardless of DOF impact and same shutter speed), if a 4/3 registers 1600 ISO at f2.8, then FF at f4 would give an ISO of 800?  If so, this would allow me to go to a faster shutter speed or go to FF f5.6 to get back to 1600 ISO?

In case you are wondering why so much focus on ISO 1600 is that a lot of my indoor shots with my GX1 float around ISO 800 to 1600, sometimes ISO 3200.  For example, tonight I took a couple of living room pics with my kids using my Panasonic 25mm at f1.4, shutter at 1/60 and ISO at 1600 (set at S priority to "freeze" the kids a bit).  Trying to do the math in my head, I wonder what would it have taken to get the shutter speed near 1/125 (or even down to 1/250) and/or f4 to f.56 with a FF.  Something tells me the FF would need to be at least ISO 3200 since shutter speed 1/2's the light and the f4 1/4's the available light (from f1.4).  Seems like the newer sensors can be cranked up to ISO 3200 for very nice pictures (4x6 or 8x10).

Will need to give it some thought as to what would have happened.  Beside trying to do the math after the fact, I was also wondering what could I have done to get the ISO down myself to improve the shot (such as better flash, turning on more lights, etc.)

Either way, the responses are definitely making me be more aware of my camera settings and what I need to do to get a less noisy picture and better quality picture.

Thanks!

Cheers,

George

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