56 replies to this topic

[Jolly]

Yes James, you are right.

But most people are very pernickety when it comes to conventional (topside) lens and camera image quality and buying selection. Lot's of magazines and forums are around which just deal with lens and camera equipment comparison in respect of image quality.

This has not been the case to the same degree when it comes to adapt these wonderful and expensive lenses for underwater use. Specialized literature dealing with these terms is hard to find and many manufactures provide very little or no information.

I totally agree with you that for most people it is not an important or interesting thing. But some still want to choose thoroughly their lens / dome combination as they do when buying good lenses and cameras for a lot of money.

My personal opinion is that a hemisphere provides the best versatility when it comes to using it with several different wide angles. It simply offers the same radius independent from the different angle of views , up to 180 degrees. This is of course also possible with a non hemisphere dome but just for one maximum angle of view. the non hemisphere dome can be seen as a part of the hemisphere. That’s why it is no problem to house lenses with less angle of view in a dome designed for bigger FOV.

I understand that the Sea & Sea and Aquatica domes are a hemisphere.

Regards,

Julian

[james]

No, the Sea and Sea and Aquatica domes are not hemispheres. The Aquatica spans about 120 degree and the Sea and Sea spans even less, much less in fact, perhaps 110 degrees.

Cheers
James

[Donovan]

10.5 mm nikor in 5503.15 Ikelite port.

[Jolly]

James,

that is very surprising to me. I have received this statement from Shuya Koda (Sea & Sea Japan):

211mm is the diameter of dome itself not including the port edges.
The dome is hemispherical. Therefore, radius is exactly half the diameter.

Also the german Aquatica distributor confirmed to me that the 8" Dome is hemispherical.

I really would not like to see that my Seacam fisheye dome type is the only hemisphere shaped dome around.

I am (was) almost finished with the "uw focus distance" tables for Eric. This would be very bad as I have used the above mentioned values.

Just to make sure I did not understood incorrectly due to my bad english:
a hemisphere is one half of a ball?

regards,

Julian

[Donovan]

10.5 nikor in 5503.15 ikelite port. Gulf side of the keys.

[Jolly]

Hey Donovan,

do you have an 100% crop of the edges / corners?

thank you,

Julian

[Donovan]

Julian,
The Yellowtail shot is cropped on the right side. The ray is cropped at the bottom. If I remmember correctly.
I will check the orig. to make sure.
Don Kincaid

[Jolly]

Thaks a lot Don.

[Donovan]

OOPS...correction... the yellowtail shot is full frame. the ray is cropped at the top about 5%. I have a number of versions of these shots so I guess I was mixing them up. Must be the PMS...Pre Mature Senility/
Splash,
Don

[paninaro]

Yes, a hemisphere is half a ball.

[Jolly]

And can you post the corner for example without resolution reduction? just a small part of the image from the corner but 1:1 resolution?

PMS - now I know what to call it in english when I have it again

Julian

[Jolly]

Thanks very much Chris.

I am really confused with James's dome information. At least it's not the language this time.

Julian

[Donovan]

julian,
full frame no crop

[Donovan]

full frame no crop

[james]

Hi Guys,

Those domes are not half of a sphere. I'm looking at the Sea and Sea dome right now. If you take a sphere, put your knife on the middle, then move it over a bit to the left or right and then CHOP, what falls off is what the Sea and Sea dome looks like.

I could be wrong though - I didn't measure it w/ a protractor or anything. If anyone wants to come by at Seaspace and check it out, I'll bring the Sea and Sea and Aquatica domes w/ me.

Cheers
James

[Jolly]

Hi Don,

thanks. I think I did not say it clearly. I meant a 100% crop. So not the entire image (maybe a small version of the image as you have posted). When opened in photoshop for example: just take a small part of the image in the corner and don't change image size or resolution. This would be very nice to judge sharpness, etc.

Thank you,

Julian

[Jolly]

example what I mean with 100% crop:



Julian