Canon Dreb kit lens + diopter = scratched domeport 5503

Hi Ike,

Well this is how I perceived the info.I suspect there are others out there who think and percieve the same way. I just made the happy discovery that there is at least one more dreb shooter on my little island who has recently bought the exact same setup as me. He also had understood that the diopter was required. Well, maybe we just aren't the smartest fish under the pier.

Hopefully the good thing that came out of this thread is that you will be spared from a stampeding hord of future newbie dreb shooter sending you their scratched ports...

I also understood the information to mean that a diopter was required based on the SLR port chart (*) in front of the Drebel kit lens and now the D70 kit lens. I nearly purchased a diopter for the D70 housing, but held off on it because some users here recommended that I wait. I was planning to do some pool testing to sort it all out. I was suprised at how easy it was to scratch the port. I haven't had this housing in my hand but my expectation was that it would be pretty obvious if the lens was contacting the port. I envisioned that I would zoom delicately at first until I was sure that it fit correctly. Also, the D70 kit lens has internal focusing so the front element doesn't rotate (Think drill) like the Canon kit lens, so it may be less of a problem. I'm sure all of this will be much more clear once I have the housing in my hands.

So, my question is: should I also disregard the diopter requirement for the D70 housing? The Ikelite port chart still lists a diopter (*) as required for the 18-70mm kit lens. The minimum focusing distance is 14" as listed on the Nikon site which is greater than the 1 ft that David Haas recommends. The Canon kit lens will focus down to 0.9 ft.

General rule: If a lens cannot focus to 1 foot or less it will need a diopter to "see" the apparent image a dome port creates.

I'd also like to commend Ike for doing the right thing on this issue. No one expects everything as complex and rapidly changing as DSLRs to work right 100%. But Ike has shown time and again that he cares about his products and the development of digital photography. I'm grateful to this forum and his, and other's, participation to getting all the bugs worked out.

Thanks,

Guys,

Unless Ike has determined anything different, YES, a +4 diopter will be required for the new Nikon 18-70mm DX AF-S lens to focus at all zoom lengths underwater.

You may also want to note that adding a diopter to a zoom lens for underwater focus will effectively disable it for surface shooting through the port. You might be able to do a pre-dive test shot 6" - 1' distance to check your strobes, etc. But you won't be able to shoot 2' or farther away due to the diopter magnification.

Your point about an AF-S lens (and some Canon USM internal focusing lenses) is a good one in determining if a lens will hit the inside of a port during intial set up. The Canon kit lens come VERY close to the inside of the specified #5503 dome port. But it never hits it and focuses throughout the full zoom range. If I left my thin Hoya UV filter on it would scratch the inside....So, always assume a manufacturer's specified port length for a lens is without any extra surface shooting filters.

Zoom lenses are a great tool underwater!

David Haas

Thanks David,

So if the Diopter is required, what do you do to acomplish over/under shots with this lens? Is there another (nikon) lens you would recommend for this type of shooting?

Thanks

With a diopter, you can't focus past 3 feet. By definition, a +1 diopter will bring your infinite focus to 1 meter. A +4 diopter will bring your infinite focus to .25 meters.

A good lens choice for under-overs is the 15mm fisheye.

Cheers

James

As James states, the Sigma 15mm fisheye is an easy choice to try over/under shots with. Costs about $375.00-$400.00 and focuses to 5.9". You can shoot this lens right through the port above water for neat shots and then below water, too.

That said, I shot some over/under photos with my Canon 18-55mm EF-S lens last night in a dimly lit pool. Have to look at them closer on the computer. You usually get a sharpness difference between the above and below parts if you shoot at anything less than f11 or so. But this type of shot depends on what you as the photographer deem the most important part of your image.

Hope this helps!

David Haas

Hi,

beside a suitable lens (15mm fisheye in this case) you need a real big dome to achieve sharpness from almost the waterline to infinity (on land). You have to get the waterline away from your lens.

8" and above is the way to go.

Julian

There is a nice new clarification on the ikelite port chart for the canon 18-55mm lens port recommendation. This is very good and clear. Here's what the new text says:

(?*) This zoom lens will focus close enough that adding a + diopter close-up to the lens is not required in most situations. Longer port may be required to stack filters or close-up lenses

Thanks Ike!

In what situations (re: *? designation) would the diopter be required?

I was wondering about that too. I uses the D300 Ikelite housing and the #5503 dome port. No problem focusing at the wide (ish) end and the close up. Also good for Sigma 15mm FE

I'm still not clear if using a diopter will result in sharper images or easier focus with the dome port. Just because the lens can focus close enough (just) to see the virtual image, is this the ideal situation if it's at the extremes of the focus range? I'm afraid my knowledge of optics and dome ports in general isn't up to sorting this out, and as it's 1:55am my brain is starting to hurt thinking about it. I'm sure someone here knows the definitive answers to all this.

You guys are making it increasingly difficult for me to give answers that may be vague or not based on facts. Zoom lenses historically did not focus as close in telephoto as in wide angle setting, so I left this loop hole in the recommendation. Appears this EFS 18-55 Canon lens actually does focus at twelve inches throughout the zoom range, and works fine in our dome port with no diopter period.