Panasonic 9mm (wide angle rectilinear lens)

Does anyone think this would be a good lens to use underwater?  It is physically nearly the same size as the Pana 8mm F3.5 fisheye lens.

What makes a lens  good for underwater use?

46 minutes ago, Dann-Oh said:

What makes a lens  good for underwater use?

One that focusses properly inside a dome port (for wide-angle)! 

It's very hard, other than the ones we all know are tried and trusted in a specific dome with specific EXRs, to predict. To use one outside the Magic Circle (!) is a gamble.

1 hour ago, Dann-Oh said:

Does anyone think this would be a good lens to use underwater?  It is physically nearly the same size as the Pana 8mm F3.5 fisheye lens.

 

What makes a lens  good for underwater use?

 

 

9mm is relatively narrow to be able to work with a variety of ports. The lens has a focussing distance of 9 cm from the sensor plane so will focus almost in any port

It may well be a good lens on land but until someone tests it underwater it's a guess as to whether it will work well UW.  Being a prime it is probably going to be quite a good performer on land, but being a rectilinear lens behind a dome port, optical quality advantages tend to disappear when used behind a dome and you might just as well use a a more flexible zoom lens.

7 hours ago, ChrisRoss said:

It may well be a good lens on land but until someone tests it underwater it's a guess as to whether it will work well UW.  Being a prime it is probably going to be quite a good performer on land, but being a rectilinear lens behind a dome port, optical quality advantages tend to disappear when used behind a dome and you might just as well use a a more flexible zoom lens.

9mm is not that wide. I guess the question is I have the 8mm fisheye none of the wide angle zoom can I reuse the port?

The answer is should be possible with an extension quality needs to be checked but 100 degrees is not very wide

4 hours ago, Interceptor121 said:

9mm is not that wide. I guess the question is I have the 8mm fisheye none of the wide angle zoom can I reuse the port?

The answer is should be possible with an extension quality needs to be checked but 100 degrees is not very wide

Depends on the port, it will probably work behind a 4" dome port but the corners are probably going to be a bit ordinary.

12 hours ago, ChrisRoss said:

It may well be a good lens on land but until someone tests it underwater it's a guess as to whether it will work well UW.  Being a prime it is probably going to be quite a good performer on land, but being a rectilinear lens behind a dome port, optical quality advantages tend to disappear when used behind a dome and you might just as well use a a more flexible zoom lens.

I was thinking I could use the 9mm on my Olympus EPL10 in the AOI housing with the standard port, the 14-42 EZ is 61x48.2mm (dia x length) where the 9mm would be 60.8x52mm.  I'm pretty sure there is the extra 4mm in the housing to allow the 9mm to fit.  This would be a major plus for wide angle over the 8mm fisheye as I wouldn't have to bring along another port if I were to use the fisheye.

Writing from a position of complete ignorance about this lens, does it need a diopter inside a dome? That would be a few mm extra.

8 hours ago, Dann-Oh said:

I was thinking I could use the 9mm on my Olympus EPL10 in the AOI housing with the standard port, the 14-42 EZ is 61x48.2mm (dia x length) where the 9mm would be 60.8x52mm.  I'm pretty sure there is the extra 4mm in the housing to allow the 9mm to fit.  This would be a major plus for wide angle over the 8mm fisheye as I wouldn't have to bring along another port if I were to use the fisheye.

The standard port is a flat port?  is so no, the corners would be pretty bad.

17 hours ago, ChrisRoss said:

The standard port is a flat port?  is so no, the corners would be pretty bad.

Yes the standard port is flat. Im guessing I dont fully understand when there is the need to change from a flat to a dome port.

If it's wider than 24mm (35mm equiv) you need a dome port. In the range from 24-70 it depends on whether you want to use wet optics. If no, you also most likely want a dome port. 

Generally I think this lens might be interesting to use in a smaller dome that can also use the one of the fisheye lenses, if you need a rectilinear option. I'm afraid that would also mean that corners won't be amazing. Basically only an option for use in existing ports for special uses. Not something one would buy just for UW photography.

On 5/20/2022 at 2:14 AM, hyp said:

If it's wider than 24mm (35mm equiv) you need a dome port. In the range from 24-70 it depends on whether you want to use wet optics. If no, you also most likely want a dome port. 

Generally I think this lens might be interesting to use in a smaller dome that can also use the one of the fisheye lenses, if you need a rectilinear option. I'm afraid that would also mean that corners won't be amazing. Basically only an option for use in existing ports for special uses. Not something one would buy just for UW photography.

even 24mm in a flat port is not fantastic and 24mm is not that wide in UW terms.  Even 60mm lenses (full frame equivalent) have a little corner softening as noted in recent post by Alex Mustard on using a semi-dome port with such lenses.  There is no hard limit on this it gradually gets worse as the field of view increases.  This link discusses flat and dome port theory:  Understanding Flat Port and Dome Port Theory | Oceanity

The 18mm lens has a diagonal field of view of 100 deg, so that is a little greater than the maximum theoretical field of view of around 90 deg through a flat port, so the far corners of the lens vignette.