I think I'm going to jump m4/3's ship because of UltraWideAngle

It has been some time that I've been considering a second body+UWA lens combo.
I want it to be light, compact and not so expensive. So, right now I think the best options are:
Olympus E-PM2 + Panasonic 7-14 and Sony a5100 + Sony 10-18

The case for the first option is that I have 2 other bodies and 4 more lenses of the system and it'd be about 100$ cheaper and the case for the second option is that the combo is lighter(569g vs 508g),smaller and all the advantages of a bigger sensor (lower noise, more DR, more resolution,...). For the impartial observer, it is a no brainer.

e-m5 and e-pm2 are identical in IQ.

What are your thoughts? Is it rational to invest in two systems?

What kind of photos will you be taking with your UWA?

It's been my experience that by the time most people get around to making posts like the original post, they've already made that emotional break anyway.  Many people at this point are just looking for validation.

I agree with whoever posted that going to Sony for the Lenses isn't something that happens every day, but needs change.  We can only presume that you are a rational adult with full knowledge of your needs and the options available to you.

Davud wrote:

What are your thoughts? Is it rational to invest in two systems?

It depends. If you intend to carry only the body and ultra wide zoom and never change the lens, then I don't think there's anything wrong with the plan. But if you plan to use the camera as an ILC, then you'll need to carry two sets of bodies, batteries etc and that will probably end up bulkier than just adding the 7-14.

I certainly think there are cases where it makes sense to invest in a camera body just for a single lens. For example, I often use the GM1 and 45/1.8 as a sort of fixed lens camera, and there is nothing else in that size that can match what that combo does.

simonallam wrote:

How about this, weighing in at 366g? That Sony looks pretty big and heavy now.

I was talking about the same focal length. Plus, your suggestion doesn't have any sort of stabilization.

john isaacs wrote:

You have Nikon and Olympus, and want to buy a Sony crop sensor? Sounds like a plan to me.

When you decide to go long, I recommend a Canon.

My Nikon is on the shelf eating dust. It is more like a memorabilia. If canon made a decent mirroless, maybe.

Soulhand wrote:

What kind of photos will you be taking with your UWA?

Architecture, landscape,... . What UWA is for anyway.

Davud wrote:

Soulhand wrote:

What kind of photos will you be taking with your UWA?

Architecture, landscape,... . What UWA is for anyway.

Did you consider an Olymous body + hires mode,? (which would also add stabilisation)

Well, you may have a slightly better sensor, but the Sony 10-18 is not exactly a stellar performer. The Panasonic 7-14 is the better lens. So you can compare sharpness of the sensor in the studio with standard prime lenses stopped down, but that won't tell you much about the superiority of any of those combo's.

Since you have Nikon dSLR, introducing a third (Sony) variant sounds like one too many.  The 7-14mm is a great lens, I have it, and can be bought new for much less than the RRP on eBay.  The GM series is great if you want something really small but again a third variant.  I have the GM1 but in combo with other Pannys. It is a jewel of a camera.

If you want some real fun, add the Samyang 7.5mm.  I think the lack of IS is less of an issue with UWA and has never been an issue for me - see Aurora link below for 7.5mm and 7-14mm images.

If you are shooting architecture you may want to consider one of the optical shift lenses.  The last time that I looked, Nikon and Canon both had them.

Davud wrote:

Architecture, landscape,... . What UWA is for anyway.

A VF is a must have for me in those conditions.  You'll need to move up to the Sony 6xxx series for that and the size/weight advantage disappears.

My thoughts are: Skip the PM2.

If you are on a budget, take the EM10 V1 instead.

Why? The IBIS of PM2 is nearly useless and the EVF ist not stabilized (both bad fore tele usage).

And no EVF.

And the shutter together with the inferior IBIS causes some blur.

With the EM10, you will gain a tilting LCD, an EVF, (half) electronic shutter and you can handhold your UWA shots down to 1/2s which is very useful for blue hour shots...