Forgive my ignorance here, but my understanding is that the GH2 can effectively double its focal length using a special lossless crop setting (for instance, a 35-100mm lens becomes a 70-200mm lens). Does the GH3 have this capability as well?

Yes... taken from DMC-GH3 | PRODUCTS | LUMIX | Digital Camera | Panasonic Global (http://panasonic.net/avc/lumix/systemcamera/gms/gh3/video_shooting.html)

The Extra Tele Conversion function virtually extends the zoom range when recording image not in the full-size. So you can take telephoto shots even with lenses that don't normally allow zooming. You can take 2x zoom shots in still image recording*1 and 2.4x / 3.6x / 4.8x zoom shots in video recording.

That's great, thanks!

There are major loss with picture quality when you do that with the GH2 in video, probably the same with GH3.

I thought there was no loss??? Are there any image comparisons out there?

That is what the fan boys of Pany said, so I bought one just for that reason and sold it after a few weeks, it might be ok if you are using it at ISO 400 or less but anything above that when you are using the crop mode, it gets very grainy, and btw I did also installed the hack so it is not like I was using stock bitrate. Now this is with the GH2 not GH3, but I caution you to do research because the hype on the GH2 was pretty way out there, they don't tell you any bad stuff about it, the thing that bug me the most was the color of the lcd change once you hit record, so it was very hard to adjust the white balance manually, I found that to be true with everyone of them after I saw mine and did more research, they will also tell you that you can put any lens on it which is true, but if you have par focal lens from another brand and you put it on the camera with an adapter you will loose par focal. Now all this could be different with GH3. Good luck.

I think the better way to describe it is a significant increase in image grain when using higher ISO settings. This is from the imaging chip, not an artifact from the recording process. In a photo still it would look like film grain. If you do a lot of shooting in low light situations, a good zoom lens is a better option than the ETC function. Some people love ETC for event coverage but in my work I rarely use it.

Is there a favoured ISO setting for outdoor video with a GH2/3?

Ron

I wonder if GH3 allows to change ETC on the fly while recording?

That is what the fan boys of Pany said, so I bought one just for that reason and sold it after a few weeks, it might be ok if you are using it at ISO 400 or less but anything above that when you are using the crop mode, it gets very grainy, and btw I did also installed the hack so it is not like I was using stock bitrate. Now this is with the GH2 not GH3, but I caution you to do research because the hype on the GH2 was pretty way out there, they don't tell you any bad stuff about it, the thing that bug me the most was the color of the lcd change once you hit record, so it was very hard to adjust the white balance manually, I found that to be true with everyone of them after I saw mine and did more research, they will also tell you that you can put any lens on it which is true, but if you have par focal lens from another brand and you put it on the camera with an adapter you will loose par focal. Now all this could be different with GH3. Good luck.

ETC does work well if you understand it has limitations. Part of what makes DSLR's good in low light even with high ISO is that the images get scaled or binned or reduced in size. Whatever you want to call it the fact is that we are never seeing a 1 to 1 ratio of CMOS pixels to recorded pixels. This helps smooth out the noise.

In ETC mode you actually are using a 1 to 1 pixel ratio so you do not gain any of those size reduction advantages. This doesn't mean ETC is bad. In fact it is no different then a normal single chip video camera. ETC basically acts like a single 1/2" CMOS 1920x1080 chip. On those type of cameras going to 9db or 12db of grain looks pretty bad. Heck some don't even like the look of 6db on some of those camcorders.

So yes ETC can visually have more noise then normal modes but not because it is inferior or a useless feature. It has more noise because it acts as a normal CMOS chip would in a regular video camera. Normal shooting modes on the GH2 just help mask some of that noise so you can push the ISO much higher and it still looks clean. In good lighting ETC is awesome. In moderate lighting ETC is decent. In low light forget about ETC. Of course in that kind of light good luck finding a tele lens fast enough anyway. If it really does get that dark your options get very limited if you still need to reach far. Just the way it is.

So you can buy a camera without ETC mode but then you have no option at all. At least with the GH2 and GH3 the option is there if you need the extra reach. If you do the kind of shooting where you want to shoot like a video camera then really you should buy a video camera. A DSLR can look awesome but it is not a 100% replacement for event work unless you want to work around the limitations.

I use ETC all the time. Originally I thought the picture looked worthless because when you engage ETC the picture gets soft and fuzzy in the LCD until you press record. Then it gets nice and crisp. I avoided ETC for a long time because I didn't bother to hit record after seeing the preview.

ETC is just like a digital camcorder zoom. thats it.

Actually it's not. There's no loss of quality.

ETC is just like a digital camcorder zoom. thats it.

That is 100% not correct when shooting video. If you are shooting stills then perhaps but most of us are talking about shooting video.

The chip has a lot more pixels then HD video. In HD mode that huge number gets reduced to 1920x1080. In ETC mode the center 1920x1080 chunk of pixels on the chip are used to make the 1920x1080 recording. No digital scaling beyond what HD video needs. It in essence acts as a smaller HD video chip. Roughly a 1/2" chip.

Digital zoom scales the already native resolution. Because DSLR cameras have a lot more pixels then native HD ETC works very well.

The other major bonus to ETC is no moire or aliasing because no funky scaling or binning is taking place and you are taking the pure 1920x1080 pixels from the center.

Is it softer? Yes of course it is but that is how bayer chips work. Any native 1920x1080 bayer chip is going to be softer then a 1920x1080 3 chip or a bayer chip at double or large the resolution. Just the nature of physics of how single chips work.

So ETC is softer but it is also artifact free. It is not nosier but noise shows up easier. It really is a very fascinating feature of the camera. Because of how clean it is I considered buying the 7mm lens to only shoot with ETC mode. You get some amazing results when you do this.

A good review of the GH3, plus links to various video clips taken in different conditions can be found here:

Panasonic Lumix DMC-GH3 Review (http://www.ephotozine.com/article/panasonic-lumix-dmc-gh3-review-20489)

The camera was due for release November 15th, but I've recently heard that Panasonic will be holding back until mid-December 2012, which means that it may be difficult to get hold of an actual camera body (at least in Europe) before Christmas. So January 2013 looks like a more feasible date for buying the new GH3 (unless you pre-order).

Tony, thanks for posting. A short review without much on video, but it does have some good examples of studio stills and ISO noise etc. For stills it does seem to be a big improvement. I wished they had allowed tethering, but depending on how the iOS/Android control works out, could negate the need for this in studio use.

There is a user review linked in the comments, which is more targeted at video use. Here's the link..
Workstation ? Amsterdam | +31(0)20 67 56 252 | Film-en (HD) videoprodukties (http://www.workstation.nl/gh3eng.html)

I use the GH2 crop mode and like it very much.

Here is a video taken with it and a manual Nikkor ED 400mm f/5.6.

http://youtu.be/uss34quKxx8

Release date for the GH3 is now 13th December.

Update: I now see that UK has received its first shipment of Panasonic GH3 and are now in stock at Wex

Panasonic LUMIX DMC-GH3 Black Digital Camera Body (DMC-GH3EB-K) - Wex Photographic (http://www.wexphotographic.com/buy-panasonic-lumix-dmc-gh3-black-digital-camera-body/p1532809?cm_mmc=googlebase-extension-_-cameras-_-compact-system-cameras-_-panasonic-lumix-dmc-gh3-black-digital-camera-body_1532809&utm_source=googlebase-extension&pcrid=14570406489&gclid=cins6v3d7bmcfufjtaodefgaqw)