OMD-EM1- fastest Sync speed when using Inon Z240 strobes? Nauticam housing? lenses?

[Interceptor121]

Using a macro lens behind a dome gives much worse performance that a flat port.
If you embrace a system with changeable lens you want the best quality otherwise you would have been better off with a compact

 

[PHIL RUDIN]

True that a larger dome will get in the way more v. a smaller flat port but image quality wise you are dead wrong. It many not narrow the AOV to increase magnification but image quality is not effected all things else being equal.

 

[Interceptor121]

Image quality of a dome actually is better in general terms as flat ports have more chromatic aberration and assuming you can get closer there is less water in between practically though this is dictated by the animal comfort zone not your port
In practice at long focal length chromatic aberration is minimal and can easily be removed in post and the lens because of the flat port also has a 1.33x magnification compared to a dome that may be useful.
Considering you are shooting tiny critters most time the dome gets in the way and in practical terms only works up to portrait work so overall for me it has worse performance and unless I was shooting video and wanted to have the whole range of focal lenghts in one dive I would get myself a macro port

 

[jd950]

"Using a macro lens behind a dome gives much worse performance that a flat port."
"Image quality of a dome actually is better in general terms as flat ports have more chromatic aberration..."
"In practice at long focal length chromatic aberration is minimal and can easily be removed..."

You seem a bit unsure of your feelings on this

 

[Interceptor121]

Not really. Performance is not only image quality but also magnification and the ability to take the shot. There is a reason why dome and macro port exist since some 20+ years. Generally if focal length is greater than 35mm you shoot a flat port as the other advantages compensate the minimal issues in image quality.

 

[PHIL RUDIN]

Magnification is no different behind a dome port than it is behind a flat port given the same lens, for instance with the Olympus 60mm macro lens 1:1 is 1:1 regardless of the port only the distance to the subject will change a bit.

I agree the biggest obstacle to using a dome port v. a flat port is size the rest remains the same and you have given the impression that this is not the case.

I use the Olympus 12-40 F/2.8 zoom with a Zen 170mm dome port and I am able to get images at the 40mm end that are around 1:1.3 in 35mm terms without any Closeup lens. You are only limited by the placement of the dome. This is much greater magnification than you can get with the Olympus 12-50 zoom at the 50mm end without a closeup lens behind a dome.

 

[Interceptor121]

You achieve the same magnification at a distance of 1.33x with a flat port compared to a dome port. For re same reason the camera will focus closer with a dome port. The net effect is the same but you need to be closer with the dome as it cancels the air-water interface magnification.

 

[Wisnu]

I just got the 60mm flat port with my NA EM-1 ( I also have EM-5 with NA housing as well); I shot with 60mm with either the 4" semi dome and the flat port during my recent trip to Lembeh. I'm not smart enough to provide technical explaination but I (and the other people I asked for) can't differentiate the image quality taken with these ports.

 

[Interceptor121]

That's the expected behaviour after 35mm you can't tell the difference and the flat port and the dome. However you get the same magnification at 33%+ more distance

 

[PHIL RUDIN]

I know what 121 is saying seems to be logical but is is based on very old calculations using a fixed focal length lens under a dome port. The problem is that zoom lenses move in and out moving the point of focus so the ##% is not always correct. Lenses like the 60mm macro in the 4" glass dome sit very close to the port glass, the result is that this very short distance reduces to effect of the dome and makes it much more like a flat port. This is not coming from me but from the folks at Zen Underwater who design this stuff. Example, when you shoot the 12-40 zoom in the Zen DP 170 n85II dome port at 12mm the lens is wider than 12mm behind a flat for the reasons articulated by 121. But when zoomed our the 40mm the lens elements and the port element are much closer resulting in close to the same 33% magnification. Being able to gage the difference is different for each lens and how close it sits to the glass.