What are the advantages of small domes?

I'm not sure, but it is nice to have a big dome to hide behind!

It is a glass dome and did not scratch. More pertinently, the tiger was not biting the dome (look at the position of its teeth), but just mouthing it to try and figure out what it is...

It was a challenging shot to light as you can see

58 minutes ago, adamhanlon said:

So, There is no issue with shooting subjects on the dome with an 9" dome!

While I understand that small domes can fit into smaller spaces, you still need to get the lighting in too!

Intended as somewhat of a joke, but it was also shot with a 9"dome...

Mini domes offer more magnification so can make smaller subjects seem larger in the frame, which can of course be a creative advantage. However, unless all you are shooting is this type of image, I am unconvinced that the optical disadvantages outweigh the creative advantages!



 

Nice images, Adam. However, obviously it all depends upon one's situation and subject matter. Not everyone shoots large subjects in open water with artificial lighting. I'm normally shooting small subjects in shallow freshwater streams with natural lighting. And yes, many of my wide angle shots could not be gotten with a large dome. Here are a few examples with subjects less than an inch from a 4" dome (closer than a large dome could get) and/or with the housing pressed against the stream bottom (lower than a large dome could get):

3 hours ago, adamhanlon said:

So, There is no issue with shooting subjects on the dome with an 9" dome!

While I understand that small domes can fit into smaller spaces, you still need to get the lighting in too!

Intended as somewhat of a joke, but it was also shot with a 9"dome...

Mini domes offer more magnification so can make smaller subjects seem larger in the frame, which can of course be a creative advantage. However, unless all you are shooting is this type of image, I am unconvinced that the optical disadvantages outweigh the creative advantages!



 

I heard Mimmo Roscigno using the same terminology mini dome offer more magnification. That does not sound correct. Assuming the minidome is actually a full semicircle and it is correctly positioned a mini dome only offers a shorter working distance things at infinity and field of view would be unchanged.

If you are on a cropped format this shorter distance may not be material example smaller dome 4.5 cm radius normal 5.5. cm 1 cm matters little

Full frame large dome 12.5 cm radius smaller dome 5 cm radius difference is significant and does give that 'magnification' effect

However other than a full frame crowd there are zoom fisheye lenses on relatively small domes so nobody really cares about those distinctions that are mostly for a full frame user having issues of bulk/space/proximity

One of the main reasons for me to use small dome ports is because the water is too shallow to use a large one. I have used the Seacam fisheye macro port FMP and wide port WP for this with the Nikkor 10.5, 16, and 8-15mm and Canon 8-15mm fisheye lenses. The WP is not made for fisheyes but when the fisheye lens used with it is focused very close, it will not vignette. The WP is also the least expensive Seacam dome and given that the ports are often scratched by rocks being tossed at them by my photo subjects need to be considered expendable.

First attached shot shows a Sockeye Salmon pair preparing to spawn. The other pix show Sockeye Salmon gathered at the mouth of a creek located about 2 km away from where I am sitting. They are gathering here prior to final maturation to beach spawn in the lake around the mouth of the creek. I planned on staying here several hours to do the shoot..... The creek as you can see is very shallow - Pink Salmon spawn here. Even the FMP is too big to fully submerge at some some spawning locations in the creek. I have used this creek to do a number of tests over the years (because it is so close and fairly clear).

Another type of small dome port about the same diameter as the port mount so looks like cylinder with a dome on the end made by Seacam was simply called dome port DP. They came in various lengths for different lenses. Alex Mustard mentioned a similar Subal port here a number of years ago. I have used my DP with macro focusing wide angles (the now long-discontinued 20-28mm f/1.8 Sigmas and the more recent Tamron 28/1.8 lens) and the Nikkor 60mm macro lens. The 20 in Nikon mount was used quite a bit with the D2X (i.e. APS-C or DX). I also have this in Canon mount but have only used it with the superdome (and 1D series full frame cameras). There is a curved field so smaller apertures should be used. In my experience the 60 macro with a DP is much better than using a flat port other than for night photography. I shot quite a few pix with this dome and the 60 near Kauai in 2019.

Responding to this thread, @Alex_Mustard and @adamhanlon chat through small dome ports' pros and cons. These offer some unique creative possibilities, reduced cost, and portability advantages, and have limitations that should also be considered.

9 hours ago, adamhanlon said:

Responding to this thread, @Alex_Mustard and @adamhanlon chat through small dome ports' pros and cons. These offer some unique creative possibilities, reduced cost, and portability advantages, and have limitations that should also be considered.

 

Is anyone else having problems getting this to play? 

It's working for me...but I would be interested in hearing from others...

51 minutes ago, adamhanlon said:

It's working for me...but I would be interested in hearing from others...

Also working here.

It’s working here.

Hmmm, my problem then. I'll play around!

Working here too!!

1 hour ago, TimG said:

Hmmm, my problem then. I'll play around!

Got it now!

Good video - thanks Adam and Alex! 

It seems to me that fisheye lenses in large domes are a problem, because most big domes are not hemispherical but truncated hemispheres. The Nauticam 230mm is about 70% of a hemisphere. So if you place the front entrance pupil at the centre of curvature, the dome mounting plate will vignette the lens. (I realise that with fisheye lenses the "front entrance pupil" is slightly arbitrary.) I made an 8" hemisphere once but it was so buoyant I never used it. I also made a 14" hemispherical dome for only over/under shots so buoyancy didn't matter, but it needed a rotating lead weight to persuade it to float in the right place. I was measuring the Nauticam 8.5" dome and the Aquatica 8" this morning and if you place a fisheye where it should be, both vignette a lot. So the lens needs to be positioned far enough into the dome so it doesn't vignette. Fisheyes seem very forgiving about this. I also have a 6" hemispherical dome I made and I can place the front entrance pupil of the 10-17 in the right place. I am not convinced that optically this will be better than the Nauticam 8.5" in the wrong place. I liked this 6" dome for travel with the D800 because the centre of curvature was perfect for both the Sigma 15 fisheye and the Nikkor 18mm. Has anyone compared results with a small hemispherical dome in the right place with a larger dome in the wrong place?

2 hours ago, PeteAtkinson said:

It seems to me that fisheye lenses in large domes are a problem, because most big domes are not hemispherical but truncated hemispheres. The Nauticam 230mm is about 70% of a hemisphere. So if you place the front entrance pupil at the centre of curvature, the dome mounting plate will vignette the lens. (I realise that with fisheye lenses the "front entrance pupil" is slightly arbitrary.) I made an 8" hemisphere once but it was so buoyant I never used it. I also made a 14" hemispherical dome for only over/under shots so buoyancy didn't matter, but it needed a rotating lead weight to persuade it to float in the right place. I was measuring the Nauticam 8.5" dome and the Aquatica 8" this morning and if you place a fisheye where it should be, both vignette a lot. So the lens needs to be positioned far enough into the dome so it doesn't vignette. Fisheyes seem very forgiving about this. I also have a 6" hemispherical dome I made and I can place the front entrance pupil of the 10-17 in the right place. I am not convinced that optically this will be better than the Nauticam 8.5" in the wrong place. I liked this 6" dome for travel with the D800 because the centre of curvature was perfect for both the Sigma 15 fisheye and the Nikkor 18mm. Has anyone compared results with a small hemispherical dome in the right place with a larger dome in the wrong place?

Great dome that you show on the photo (how much cm?)...

I have compared, but only on the small MFT sensor (Oly EM1II and EM5II):

Both Canon 8-15mm and Tokina 10-17mm perform at least equal with respect to corner sharpness, if not slightly better, when placed incorrectly behind the Zen DP170 (=11cm radius) compared to placement behind Nauticam 140 hemisphere (=7cm) the correct way. It seems that the bigger radius (and hence bigger virtual image that is further away) makes a greater effect compared to the wrong placement...

Wolfgang

Thanks Wolfgang for that info! That dome was about 18cm radius. I no longer own it.

10 hours ago, PeteAtkinson said:

. Has anyone compared results with a small hemispherical dome in the right place with a larger dome in the wrong place?

 

I have shot the 10.5 mm Nikkor fisheye lens "properly" mounted behind the hemispherical Seacam Fisheye Macro Port and Seacam Fisheye Port as well as "improperly" mounted segment-dome Seacam Superdome SD. The SD is far better even with just 12 megapixels (D2X).

Before moving on, I want to add more data to the graph from the previous section, which is very valuable for improving our understanding of using dome ports. As far as I know, this is the first time anyone has probably collected and certainly presented test data of this kind for different domes.

The 100mm (4”) dome port performs slightly worse than the 200mm (8”), while the 230 mm (9”) performs considerably better. However, do note the data for a 230 mm dome that was not placed correctly, using a port extension just 3.8cm or 1.5” too short — something I see lots of people doing. Like this, the expensive 230 mm dome now drops as much image quality at the 100 mm. The graph shows that big, expensive domes deliver on image quality, however, they must be correctly positioned to do so. (Also note that all domes give good sharpness in the center of the picture, the advantage of bigger domes comes towards the edge of the frame.)

Alex, it would be interesting to see a similar analysis and graph done for a fisheye lens.