I have both lenses, and to be honest I do not really care for the 14mm 2.5. The other thing you want to consider is the fact that when you are under water you will want to use a lower f-stop to gather more light. So for me I would choose the 20mm 1.7. If you want to purchase the 14mm 2.5 I would be glad to sell you mine :-).

Best Regards

grab the 14mm and add the fisheye lumix adapter on it, is a pain in the ass to focus underwater, so you want to choose the closest to a panfocal lens

I don't THink I Will Put Any Shitty Fish Eyes On it Sorry. Otherwise i might as well use a gopro but im guessing the general consensus is go with the 20mm?

the shit goes right up and stays there, because there are 2 panasonic adapters that panasonic made specifically for the 14mm to go wider, look for the reviews they are pretty good, you are asking for an economic way to get a useful lens underwater, the best way is to get the wider possible lens, because wide lenses have a shorter focus rack(?i dont know if this is the right word in english), meaning that is easier to get something in focus, even using the same speed on 14mm than on the 20mm you will get a bigger depth of field on the 14mm wich is something that you want for underwater because it is hard to get what you want in focus.... having said that, it also depends of the housing that you are going to use, because both lenses are pancakes, so the camera is going to be really slim, and maybe you'll get some of the housing in frame if you go too wide....

I have the 14mm pancake with Pannys wide angle adapter ( not fisheye) and its quite good, no light loss with the adapter, only very slight difference in corner sharpness. The other option is to use the GoPro in 1080 30p medium mode which has only a tiny amount of fisheye. The GoPro3 BLK compares quite well against the gH2 with 14mm+ ADp if you also set the gopro on Cam RAW whitebalance and Protune mode and colour correct in post.

You've answered your own question, if it's image quality, no fisheye, more light, better bokeh, "itching for 20mm for regular use" then the 20mm has all that over the 14mm. As for what FOV you require for the type of diving you're doing, only you know that.

Good luck manually focusing with either lens, a half press AF is the better option or AE/FL lock button.

If it were me and I could justify the cost, I'd use the 7- 14 Panny. I think when you try use the 20mm underwater, you'll realise why.

@rambo "If it were me and I could justify the cost, I'd use the 7- 14 Panny. I think when you try use the 20mm underwater, you'll realise why." WHY? You got me scared!

What are your favorite subjects underwater? Wide Angles then you need either a 9-18, 7-14 or a 8mm FE, if it is macro then you need a macro lens. 20mm...It is a 52mm (Full Frame equivalent) lens if use behind a flat port, with maximum reproduction ratio of only 1:7.7, it is not a popular choice for use underwater.

@TATZU

See my post in this thread for DSRL underwater use:

http://www.personal-view.com/talks/discussion/comment/113965#Comment_113965

Regarding UW best lens I completely agree with @kkfok: 7-14 or 9-18 are the best choice. Based on your subjects and places another great lens is the 8mm fisheye. It's one of the best fisheye out there irrespective of the mount. If you shot in shallow water with a red filter without artificial lights the 8mm it's the best. Unfortunately has a FOV so large that it's very tricky (actually a PITA) to cover all the FOV with your lights. You easily end up having headlights frames. In the thread above you can see some of my video shot with 7-14 and 8mm so you can compare them. Nauticam 4.33" dome buit for the 8mm fisheye works also with the 20mm pancake. One year ago I made a small test in a pool just for fun:

But I think it's really useless underwater. Here same question arises and there is a guy who uses the lumix adapter on 14-42 and 14mm.

http://wetpixel.com/forums/index.php?showtopic=52068&hl=

Another compromise could be the Oly 12-50. Nauticam has a port which permits using the macro function but I don't know if 10Bar has the same option.

http://wetpixel.com/forums/index.php?showtopic=51160

Best regards

Davide

Personally, I´ve shot a couple of times with voigt 17.5 underwater. Just decide on subject distance and don´t touch the focus after that. (move further / closer to subject to get in focus). Obviously, it doesn´t work for all applications, but it´s a good way to work with manual glass.

On that kit just 14 or 20mm. You need a different dome for other lenses. Not.to be rude but for less you could get aused nauticam kit with better options. Try the wide angle converter on 14mm or find a dome.

Best

I think im going to go with the 14mm because the 20mm wouldn't be wide enough even though i would love to have the 20mm for above ground use. How would that wide angle converter work with this port.

Try to ask to Jack here:

http://www.opticaloceansales.com/housings/mirrorless/panasonic-housings/10bar-panasonic-gh-2-housing.html