Another Olympus E-M1 and SONY a7 walkabout test, high ISO

Started Jan 29, 2014 | Discussions thread
Daniel Wee
OP Daniel Wee Contributing Member • Posts: 537
Re: Thanks for the truth!

So, let me see if I can summarize some of what I understand from this debate:-

IF the following conditions are true:-

a) your mFT glass is 1-stop faster than your FF glass
b) you want to preserve the same DoF
c) you want to preserve the same shutter speed

THEN you will be able to shoot at 1-stop ISO advantage over the FF camera. For instance - mFT ISO 1600 0.8 sec @F1.4 vs. FF ISO 3200 0.8 sec @F2.8

On the other hand, IF the following conditions are true:-

a) you want to preserve the same DoF
b1) you don't care to preserve the same shutter speed
OR b2) your mFT glass is not 1-stop faster than the FF glass
OR b3) you are prepared to down-sample the FF image to the mFT size

THEN the above stated advantage no longer holds.

In terms of shooting for same DoF AND same shutter speed (something I personally don't worry too much about), you'd have something like the following two images:-

a7 ISO 3200, 0.8 sec @F8

E-M1 ISO 1600, 0.8 sec @F4

While by no means comprehensive or scientific, based on these two images, I would conclude, based on visual inspection, that:-

a) the a7 noise at ISO3200 is marginally less than the E-M1 noise at ISO1600
b) this advantage is even more pronounced when we downsample the a7 image to the same size as the E-M1

I usually shoot in aperture priority because I want to get the lowest DoF possible. Not always, but this is a personal preference. Furthermore, I like the CZ 55mm F1.8 but don't have any glass that can do F0.9 for mFT in my arsenal. Certainly none that will AF. Since I don't print, downsampling seems to be the norm when used with many web applications.

Therefore, for people who shoot like me, for whom:-

a) shallow DoF is a priority
b) maintaining the exact same shutter speed is not a priority
c) downsampling is always an option

The advantages of E-M1 over the a7 stated in this debate would lose some of their relevance. Furthermore, even if the conditions were met where the E-M1 could shoot at a stop better than the a7, there doesn't seem to be that much of an advantage noise-wise, judging from the samples above. Lastly, the a7 can go as low as ISO 50 so where shutter speed is not a constraining factor, there are more advantages that can potentially be realized, just as IBIS affords other potential advantages for the E-M1 in other situations.

So while I really love my E-M1 and its lenses, I think that in all fairness, for users who share my preferences and style, the noise advantage of the FF a7 is quite evident. I can also see that where the E-M1 has some real advantages is when you want the fastest shutter speed possible for a given DoF (and noise level). That said, for general usage, most of these issues don't come to mind - we just do whatever we need to go get the shot. So, hopefully, this is a fair summary of the debate as it relates to general usage - each tool for it's job.

 Daniel Wee's gear list:Daniel Wee's gear list
Olympus C-2000 Zoom Nikon D70 Panasonic Lumix DMC-GF1 Sony a7S Sony a7R II +10 more
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