14 replies to this topic

[Nautilus Cairns]

I would appreciate some advice on the pros and cons of these two ports when used with the Panasonic 8mm fish eye lens. I have a NA-EM5 housing and will be getting the Pany 8mm FE, but not sure as to which dome port to go with it, primarily for CFWA. What are the respective close focussing distances for these two ports?

[Interceptor121]

You should really get the wider 4.33" dome as the other port has vignetting at 4:3 aspect ratio according to the port chart

Based on the size of the glass the smaller dome should focus 4cm closer 17 vs 21 cm however the design of the two devices is different as the dome is flat on the housing and the port has an extension already built in so it is not possible to calculate what is going to happen on paper

[oosantoo]

It will not vignette

 

http://wetpixel.com/...c=46536&page=15

 

https://www.facebook...4086315/?type=1

 

3.5'' dome = closer focus + make smaller subjects look bigger + dome is smaller

4'' dome = more depth of field at same aperture

[Interceptor121]

Thanks for that. The vignetting comment is on nauticam port chart probably relevant to other cameras. Those 4 cm seem to make a difference looks like the 3.5" is more a macro wide angle port than a proper dome

[Nautilus Cairns]

Thanks Oosanto for that earlier reference. Makes the 3.5 rather compelling according to Alex Mustard.

 

Not sure what you mean Interceptor121 about it being more a macro wide angle port than a proper dome? The photo Alex took of the diver photographing the sponge looks pretty wide angle to me.

[Interceptor121]

I meant seems suitable for the type of shot of the small duck. The shape of it seems designed for lenses with longer focal length. Nauticam has designed the 4.33 as a true dome (has not got the metal Barrell on the side) shape. Either way both ports are tiny. I would not think that 0.83" makes a difference in over under shots. Seems like the 3.5" happens to work for some reason but nauticam didn't expect it to. For cfwa i would think the 3.5" is better.

[nudibranco]

I have both and for CFWA the 3.5" is fantastic.  The size is also a big plus compared to the 4.33".  I would use the 4.33 only for over/under shooting.

[oosantoo]

I would use neither for over/under. they are both too small

In fact I find very disappointing that nauticam has not made a large dome to be used with fisheye lenses

[-Sven-]

It will not vignette

I use the 3.5" dome with the NA-EM5 housing and I have vignetting with the 8mm Pana in 4:3 aspect ratio.

 

-Sven-

[nudibranco]

I use the 3.5" dome with the NA-EM5 housing and I have vignetting with the 8mm Pana in 4:3 aspect ratio.

 

-Sven-

we have the same but mine will not (even in RAW)... strange

[Interceptor121]

I think nauticam are not stupid hence they suggest the 4.33" dome as cameras vary a little unit by unit. The comment on the 3.5" protects from complaints

[coroander]

nudibranco, would it be possible to do some pool tests with the panasonic 8mm behind both the 3.5" and 4.3" domes sometimes? I'd really like to look at the corner sharpness at different apertures with these two domes.

Cheers!

[nudibranco]

dont have a pool but the sea  ...  unfortunately i just started the dive season and have little time for now...  but will do more testing eventually.

 

Anyway Alex M.  did a test in the pool which showed both in the pool 

http://wetpixel.com/...c=46536&page=16

You can see the depth of field in the back of the pool improved by using the 4.33" but the CF of the 3.5" is fantastic...Corner sharpness seems Ok in all of my shots also.

[Jock]

Hi nudibranco,

Are you sure that the "improved" DOF has to do with the dome?

When you take a photo with the 3.5 dome, the same f/stop and the same aspect ratio (= poor duck is the same size in the pic), DOF should be the same. Please correct me when I am wrong.

Corner sharpness - well, I am still spoilt from my old Nikonos RS lenses. Until I switched to digital, I did not even know that this was something to talk about... With my 3.5 dome and the 8mm I do get unsharp corners, especially noticeable when viewing the corners at 100% at my monitor. Does it matter? Not so sure, because in a CFWA pic your view is caught by the more or less dramatic subject, so why care too much about the corners? Just my 2 cents.

And the same here, on my photos taken in the field I did not notice any vignetting. So unless one is into taking pics of tiles in a pool, I think vignetting is neglectable when deciding which dome to buy.

Jock

Edited by Jock, 08 May 2014 - 09:06 PM.

[Interceptor121]

Depth of field only depends on magnification and aperture. If two things look the same and they are shot at same aperture depth of field is the same. If with your 3.5" dome you can get closer things will look bigger depth of field at constant aperture will be worst hence you need to shoot smaller aperture with a smaller dome if you get closer. Corner sharpness is affected the same way smaller dome = less sharp corners. You also have to consider that the two ports have a different construction one is a proper dome the other is a wide angle port with a curved lens at the end. Optically the wider lens that resembles a dome more will be superior in the corners but as jock points out to what extent are you bothered??

Edited by Interceptor121, 08 May 2014 - 09:34 PM.