Difference in Ikelite 6" dome ports?

[RonFrank]

yea. I am having to buy the 400+ 8" dome port for my new 10.5 fish eye and unfortunately, I already have three other dome ports so the fact that the new pricey
8" works for them all doesn't really help soften the blow of the price. I wish I could see images from the 6" next to the 8" with the 10.5 to see the edges and the amount of distortion. Everyone is telling me there is no comparison for doing split images with the 8 VS the 6, so guess I will bite the bullet after 15th. I love split images so...

I hear exposure under/over is tricky. Ron, I need you to figure all this out, so I can ask you!

Catherine,

You may want to hold off on the 8" dome port, and see the results of the smallest 6" you have first. I'm guess you will get vingetting, but the question is how much, and do you care. If you change the image from a fisheye to a standard perspective, you crop in any event.

As for over/under, I know in *theory* how to accomplish it. There is really only one way, and than adding a strobe as a variable if desired

You never want to overexposure a digital image, so you will need to take a reading topside, and use that. Say it reads with 1/250 ISO 100 @ f8. So you can use that for the exposure. If the UW exposure is underexposed you can either mask it in PS, and brighten the UW section, or attempt to up the overall exposure RAW, and play with the shadow/highlights to see if that helps.

The only other thing one can do (other than using graduated nuteral density filters, which may not even be possible) is to add some flash to the UW exposure. This will only impact the stuff within the flash range, but it likely would not hurt to try. You would have to position the strobe UW, which would make this whole thing tricky.

The good news is that if the topside exposure is at value X, then the water is lighted by the same lighting, and should only have slightly less exposure. These would likely work best where you have subject matter to shoot in the first few feet of water, so a shallow reef for example.

L8R,

 

[RonFrank]

It's not only the O/U shots Catherine. The *' does a much better job on wide angle, eliminating the softness around the edges that I have with my 6". Ron, check the Ike website because the 8" can be modified with different collars to fit different lenses. Another problem is the focus distance of the lenses. They might end up just being able to focus on the dome itself if they are not close enough to the end.

Thanks Dennis,

I was happy to learn that the 8inch dome has extention rings for various length lenses, that is until I found the price of those extention rings... $150! You can buy a 6" dome for that price... sheesh!

My 12-24mm focuses at less than 12", so I don't need a diopter. I also have an 18-35mm f3.5-45 and was hoping to use that in the same dome as the 12-24mm... I'll bag the idea of using the 17-35mm UW for now, it's a big lens, or much bigger than even my 60mm fully extended.

Looks like I'll need at least two ports, and will likely start out with the 6" dome for the 12-24mm and hope it works OK with my 18-35mm, and then get a flat port for my 60mm macro. The initial expense of doing all this is going to kill me! But once I have the initial expense out of the way, in time I can modify the system as necessary.

 

[Diver Dennis]

I use a flat port for my 100mm, Ron. It works very well for me. I didn't know the extension rings were that much! Pretty expensive. The initial investment is a shocker... What type of camera will you be shooting?

 

[dbh]

I hear exposure under/over is tricky.

Set your exposure above the water....immerse your dome....pop it up and shoot fast before the water spots.

This is my first attemt (it would have helped had I had more interesting subject u/w).

Dave

 

[Diver Dennis]

Nice Dave. I haven't tried it yet but I'll use your advice.

 

[RonFrank]

I use a flat port for my 100mm, Ron. It works very well for me. I didn't know the extension rings were that much! Pretty expensive. The initial investment is a shocker... What type of camera will you be shooting?

Well if I'm not careful, I'll end up with an expensive camera housing, and I won't be able to afford the actual camera (which is going to be LESS expensive than the housing and ports... grr...).

D200. They are starting to become available now, so I'll likely have one within the next month. I got to sell some other equipment first

 

[Diver Dennis]

Wow. I've heard a lot of good things about that camera. I'm just shooting the Rebel XT and my housing and strobes were more than twice the cost of the body. In fact one strobe set up was more than the camera... Not a cheap hobby but I'm hooked now.

 

[Cacia]

I need to print all these advice columns and put them in my camera bag....Thats what I will do! So, Ron when you say "take a reading" you mean put my camera on program and see what it calls for? I think the split images are very exciting and add a "divers" perspective to the image that shouts participation vs observer.... this image shot by a friend is a little cliché but has nice composition possibilities...

I don't understand why the 6" is three hundred dollars less....

I don't have that one either Ron. I have the one for the 60mm, the one for the 105 mm, and the one for the 12-24 mm. Thats is about 500 dollars in dome ports without any extension rings!

 

[RonFrank]

ISo, Ron when you say "take a reading" you mean put my camera on program and see what it calls for?

I don't understand why the 6" is three hundred dollars less....

I don't understand Ike's pricing either. The $400~ dome port comes with one extention, the others are an ADDITIONAL $150 each... ouch!

You don't have to put the camera in program mode to get an exposure reading. In manual mode, just adjust the exposure however you choose to do that (aperture, shutter, ISO) until the meter reading is a zero. It shold look something like this:
............|.............
-2...-1...0...+1...+2

Another way to accomplish this would be to use shutter or aperture priority, take a reading off a blue sky, or just the reading topside as matrix metering works pretty well, lock the exposure (AE LOCK option) and then recompose and shoot. Heck just shooting with whatever exposure the camera gives with the O/U composition is not a bad start. Review the histogram, adjust the exposure, and reshoot if necessary (always good advice with tricky exposures).

Look at the second shot done by dbh, and you can see an example of where the clouds are totally burned. This is the result of too much dynamic range for the camera. This may not be something that can be avoided, but one can try. This is what makes these types of shots tricky. His best bet would have been to turn around so he was not facing the sun I'm *GUESSING* but without being there it's hard to say.

The reality is that if the water is too dark, and the topside is too bright, something is going to not get exposed properly, and if the dynamic range is too great, then the camera is not able to capture all the details.

I like the shot you posted BTW. Who cares if it's chiche' it works. My only thought is that the diver here should be wearing a MUCH smaller swimsuit! :gr1:

 

[Cacia]

lol..... well, I have an idea, I will swim around and you can set my camera! see how easy that was?

Your posts are so packed with the info I need... I am just not understanding the pricing either, which is why I am holding off. I will read/study the exposure book first before I buy anything else. I can do a lot with what I have. It is just really bugging me that I have the 10.5 (Christmas present) and not the port and DENNIS is going to have the port in Bali. It is really eating me up. And he has CS 2 also. life is not fair. Tax time, so I better just be thankful I am going to Bali at all.

Okay, I understand the light scale. (I wondered what that was.... I was afraid to ask, did I mention I am really new at this??) thanks a million Ron.

and Dennis, whatever you do, please do not post images of your new 8" port, okay? I already know what it looks like, yes it is very sexy looking. I just don't need to have you rubbing it in my face. really, the 6" just doesn't have the impact....