Originally posted by LensBeginner I've pondered for quite a time if I shoulld buy a GH2... need something that can be hacked to remove the 30' recording limit (often need 1 to 2hrs unattended)
Problem is that even with an adapter my Pentax lenses would have too narrow a FoV... I could use the Sigma 10-20, but it hasn't got an aperture ring, and the aperture control on adapters is often quite primitive. Plus it would weight what? two times the weight of the camera? XD
Buy a cheaper and newer GX85, not GH2 . US model has no 30 min limit. European model does. Can confirm I can record 4K up to 1h44 on battery on my GX85, and that's with the screen off. You may need the AC adapter to go longer. Or second battery. Even then, I think there is a break at 96GB / 1h44 . Have not tested it fully yet. My needs are not beyond 1h44. I wonder if this limit was put in to match the run length of theatrical movies.
My GX85 with battery, SD card and strap weighs exactly 1 lb. My Sigma 10-20 also weigh 1 lb exactly, including lens hood and front cap (attached with lens keeper) and a 77mm UV filter.
The Fotodiox adapter weighs 4 oz.
It's true that volume wise, it looks a bit strange to have a tiny camera with such a big lens. But then again, you have people with APS-C DSLRs shooting with Sigma 50-500mm Bigma ... It's much less ridiculous than that.
Here are a few pics in no particular order of
GX85 with Fotodiox K mount adapter, Sigma 10-20 K-mount, no hood or front cap
GX85 with Fotodiox K mount adapter, Sigma 70-300 APO K-mount, at 300mm and focus ring extended, with hood, no front cap
GX85 with 12-32mm, retracted (can't shoot), no front cap
K-30 with Sigma 70-300 APO K-mount, at 300m and focus ring partially extended, with hood, no front cap
Big lenses like the 70-300 are just going to look huge regardless of the body they are attached to.
I have a K-1 II as well, not pictured because it's currently on its way to Precision camera for damage repair estimate. That 70-300 lens still looks huge on it. Gets a lot of attention in public places, I have to say. I never fail to get asked to shoot pics, lol.
What I can say after a few months of owning the GX85 with PK adapter is that the Fotodiox aperture ring adapter works fine. The aperture ring on the adapter works whether the lens has an aperture ring or not. It is more difficult to take out the lens if there are two aperture rings, for example with this Sigma 70-300 .
But the lens will be very secure for sure, even a lens that big. Due to having cut my nails very short yesterday, I needed a screwdriver to pull the tab on the MFT adapter while rotating the 70-300 lens. So I can highly recommend the adapter.
Focus a Pentax lens manually on the GX85 is ... interesting. And quite challenging. On the one hand, the EVF can get magnification and do focus peaking. On the other hand, there is notable lag. This is much worse with zoom than with wide angle lens. Worse, it's very hard to choose the focus point while doing that to magnify the part you want to be sharp. The only method that I have found that works is tapping my nose around on the touch screen. Maybe there is another method. If shooting handheld, it is very challenging to focus that way.
To me, this is one of the huge disadvantages of the GX85 having a touch screen. Some functions can only be performed with the touch screen. There is just no hard button option. And due to the small MFT body, the buttons are in short supply. This makes the ergonomics really dubious for stills vs a larger Pentax APS-C or FF body.
The stabilizer in the GX85 is much less effective than the K-1 II . I actually ran a test recently on the forums. But this was confirmed again today.
Also, even though you set the focal length in the GX85 for stabilizer purposes when using a non-native lens, that focal length does not get recorded into the EXIF. Very annoying. On a Pentax, I could set 8mm for my Samyang fisheye, or 800mm for my Samyang mirror, and that ended up in the EXIF.
This is all for stills. I just can't recommend using the GX85 for stills with non-native lenses due to the extreme difficulty of manual focusing, at least for me. Even with native lenses, I just will not take many still photos with this camera. It will be mainly used for video. It is still not pocketable even with the smallest 12-32 lens. So, my Galaxy Note 8 cell phone will remain the camera of daily opportunity for stills. And Pentax for all planned shoots.
Now, if your use case is video only, on tripod, everything changes significantly. There is no shake that the subpar Panasonic stabilizer can't fix - you turn it off on tripod.
You can focus the lens using the full LCD rather than the smaller EVF, and magnify your focus area relatively easily. Main challenge is not to move the camera while pressing the touch screen. Heavier tripod will thus be better even for such a tiny camera.
Biggest issue with the Sigma 10-20 IMO is that it just isn't that sharp, at least my copy. That remains the case whether I shoot on a natively K-1 II or K-30 or K200D, or on GX85 with adapter. My sharpness tests are with text readability. The Pentax bodies do better of course due to larger sensor. But readability is still poor. This is clearly not what an ultra-wide angle lens is meant for, of course. For concert, it will be more than enough. If you are recording, say, a lecture, and there is projected text, there may be readability issues, because of both the lens and MFT sensor, depending on lighting conditions. Keep in mind I'm just an amateur playing with cameras mostly at home. My GX85 has barely left the house, and even then, only half a mile on a walk, unlike my Pentax bodies.
I also experimented with the Sigma 10-20 on my K-1 II in FF mode using a Tamron 1.4X AF teleconverter. Was not happy with results. There is still significant vignetting. And higher IQ from FF mode isn't really noticeable. Only if you wanted to do crops, maybe. But then you wouldn't be using an ultra-wide angle. Perhaps for some security application recording a crowd and doing face recognition on a large number of people. At which point you would be using interval shooting in FF mode, or recording 4K video instead. Either way, it's hard to justify keeping my Sigma 10-20 at this point. Selling it won't pay for a Pentax 15-30 . Not even 1/3rd of an Irix 11mm or 15mm which is manual focus only and seems to have significant IQ issues too per PF's review.