A77 Translucent Mirror Design

Started Jul 22, 2012 | Discussions thread
Senior MemberPosts: 1,515
Re: A77 Translucent Mirror Design
In reply to theswede, Jul 23, 2012

theswede wrote:

DifractionLTD wrote:

Sure, but you are still going to loose 30% of the light during normal shooting...

About 1/3 to 1/5 stop, yes. Measurable, but not a big deal. A bit longer exposure and it's compensated for.

Comparing A77 against Nex-7 the images from Nex-7 are much sharper. Cannot conclude that this is because of the mirror, but...

Since the NEX7 images are not sharper than the A77 images, no such thing can be concluded, no. And anyway, light loss will not affect sharpness, especially not if it's compensated for in exposure.


30% loss is 1/2 stop loss. Still not a huge amount

Compare 70% to 100% converting to EV values, Log2(.7) = -.51 EV, Log2(1.0) = 0, i.e. 30% loss in light is -.51 stops. Given we do not know if the transmission is exactly 70% or is roughly 70% then saying -1/2 stop is close enough. Log2() is Log base 2. In Excel Log(X, 2) is Log2(X)

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