"Cheap" solution for splits (Sony)?

[ChrisH]

25 minutes ago, RomiK said:

Beautiful Brother! 👏 To me it's even more interesting with sloping water line.

Thank you! Controlling the water line is much easier with the big dome port. It gets more a "numbers game" with small dome ports where you have to shoot a lot of frames to get the shots you are looking for.

[Guest]

I see a few misconceptions here

a fisheye 15mm lens has less depth of field of a rectilinear 14mm lens 

the fact fisheye have field of view doesn’t mean they have more depth of field

I have a 230mm dome it requires apertures that range from f/20 to f/14 if you adopt precision manual focus to be safe stop down 1/3 more

with a matty smith 12” you gain around 2/3 of a stop this may be important if you want to use a longer lens with full frame 

with cropped sensor taking splits is simpler and i have used my 7” acrylic and 180mm dome

the bigger the dome the better if the water is not still

Edited May 28 by Interceptor121

[Adventurer]

On 5/28/2024 at 12:04 PM, Interceptor121 said:

the fact fisheye have field of view doesn’t mean they have more depth of field

Yes, this might be one of those strongly wrongly shared piece of advice which needs to be de-mythed and broken up.

 

Has anyone a good DOF calculator for fisheye lenses at hand? Preferably one that’s free and online.

[Guest]

16 minutes ago, Adventurer said:

Yes, this might be one of those strongly wrongly shared piece of advice which needs to be de-mythed and broken up.

 

Has anyone a good DOF calculator for fisheye lenses at hand? Preferably one that’s free and online.

You dont need one. The subject is typically in the center the lens remain the focal length it is despite the distortion

This is why people like alex mustard shoot a fisheye behind a 12" radius matty smith dome. He has the 230mm dome however even with that you are looking at very small aperture

People confuse the effect in water of the field of curvature that improves the edges of a fisheye behind a dome with depth of field

 

However in the topside part of the split this goes away anyway and the lens is simply a 15mm lens and if you try a topside shot with focus at 30cm vs 60cm you see that you have less requirement for small aperture as you focus further away

 

[Johno1530]

On 5/25/2024 at 12:13 PM, ChipBPhoto said:

Nice split!  Terrific shark detail with the split creating a unique angle.  I too own a WACP-C and have done a similar image with manatees.  It’s a fun perspective.
 

The issue is cost vs usable dome size for splits.  That does not really fall into the cheap category once everything needed is added up.  There will be those that will chime in with lots of math, but here are my findings from a practical perspective.

 

A wider dome is needed to more evenly disperse the water along the dome face.  While a small 140 dome can do splits, it must be in similarly flat conditions as the one in your image.  Obviously this is relatively rare.

 

A 230 dome is the common go-to due to its wide surface.  It is also compatible with almost any lens, Canon 8-15 fisheye or rectilinear.  The down side is the cost and size issue.  If you have an occasional interest in doing them,  this may not be the best solution, unless you are able to rent one.

 

A 180 dome can do some decent splits, but again this is a smaller surface than the 230 which is not as forgiving in real-world conditions, but larger than the 140.
 

The Nauticam 8.5” acrylic dome is both relatively cost effective and compatible with a wide range of lenses.  At 216mm, it is similar to the 230 size.  As it is light weight acrylic, it will be much more “floaty” than your WACP-C and will pull the front of your rig nose up much more easily.  The fact that it is made from acrylic keeps the cost down, but also is susceptible to scratches much easier than glass.  On the positive, the scratches can be buffed out if needed.  
 

Lastly, if you want perhaps the best for splits, but is only for splits, not diving, Marty Smith makes a massive 12” dome that is fantastic.  The large front disperses the water quite evenly and allows for a very user friendly experience.  The down side is it is only depth rated to perhaps 15’, meaning it is intended for only splits.  The acrylic build is also quite floaty.

 

Be sure to factor in that basically all these options are made for the N120 port system.  You will need to start with the N100 to N120 adapter which adds to the cost, as well as the appropriate extension depending on your choice.

 

As for lenses, the Canon 8-15 with adapter (Metabones or Sigma MC-11) is the standard for Sony users.  This would give the ultra wide perspective, with ultra close focus capabilities.  Rectilinear lenses can include the Sony 16-35 (the 16-35 f/4 PZ is very small and light), Tamron 17-28, etc.  Phil Rudin really likes the Sony 20-70 as an all around option.  

 

I hope this gives some insight into your options and at least a starting point to compare.  Good luck and let us know where you end up.  -Chip

 

 

This is exactly the answer I wanted from my most recent post 😁 and now I have it. Thank you for more information. 

[ChipBPhoto]

2 hours ago, Johno1530 said:

This is exactly the answer I wanted from my most recent post 😁 and now I have it. Thank you for more information. 

So happy it was useful!  

[Chris Ross]

On 5/28/2024 at 6:11 PM, Architeuthis said:

 

P.S.: Today I got an EMail from FUN-IN Underwater Photo Equipment Co., the company that distribute Athena from far east. They write that Athena does not exist anymore, so no chance for a 200mm glass port at present... ☹️

 

 

So if you are after a 200mm dome port you could look at this S&S dome:

 

https://www.backscatter.com/Sea-Sea-DX-200-AR-Underwater-Dome-Port

 

Can be used on Nauticam N120 by changing out the rear lug ring.  Confirm with the dealer before buying that you can still source the lug rings (and that S&S still have them as a bolt on piece).  Likewise you should be able to adapt Isotta ports.  Finding the lug ring for sale might be a an issue though Backscatter mark them discontinued.  I see now though they have a 20mm Nauticam to S&S extension ring:  https://fotografit.eu/products/36-nauticam---dslr-ext-rings/420-sea-amp-sea-to-nauticam-extension-ring-20/