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Frequently asked questions about DSLR lens ports

Most questions about product assembly and operation are covered in the product instruction manual. Please read your manual thoroughly before attempting to operate your Ikelite equipment.

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Choosing a port

Light behaves differently when it passes from water into air. Due to refraction, flat ports produce an magnify the apparent image and reduce the angle of coverage of a lens. This makes the flat port ideal when using standard, macro or zoom lenses to shoot small subjects.

A dome front corrects for this refraction, maintaining the lens' full angle of coverage. A dome port is recommended for lenses 28mm and wider (35mm film equivalent). Wide angle lenses may be used behind a flat port, but you will sacrifice angle of coverage and will typically experience vignetting. Vignetting is also referred to as a "port hole effect" or dark shading in the corners of the image.

A lens must focus to at least 12 in (30cm) to be used underwater behind a dome port. If your lens does not focus to at least 12 inches, a +4 close-up lens must be added to the front of your lens.

Some wide angle lenses which focus closely enough may still benefit from the addition of a +2 close-up lens to improve corner sharpness.

A close-up lens, or diopter, is an accessory piece which threads onto the front of your DSLR lens. It alters (shortens) the minimum focus distance of your lens, which may be necessary for your lens to focus underwater behind a dome port.

+4 close-up lenses are available online or through your local camera store. They come in a variety of thread sizes, so you will need to know the filter thread size of your lens. The front of the lens will often reference its filter thread size, often in the format Ø 52mm, Ø 67mm, etc.

Assembly + use

Typically, no. Since our DSLR lens ports are piston sealed, tighter port locks will not result in a better seal. Port locks should be snug but still able to slide freely. Over-tightening may result in stripping the screw hole and damaging the housing.

Usually port locks will "click" when closed, but we recommend visually inspecting them prior to each dive. The Port Lock Release Button should be flush against the port lock body.

Lubricant is intended to prevent the o-ring from rolling or becoming extruded - it does not have any waterproofing properties. Put a small amount of lubricant on your fingers and pull the o-ring gently through your fingers to lightly lubricate it. The o-ring should be a little shiny with no noticeable deposits of lubricant.

Use at your own risk - we strongly recommend that you do not. Rain-X and other similar products are likely to cause crazing or cracking of the port and/or housing. In some cases, we've seen Rain-X cause enough damage to result in leaking.


We find that many light exterior scratches will fill in with water and remain invisible unless shooting into direct light.

If scratches are becoming obtrusive, it may be possible to polish them out. NOVUS produces some of the best plastic polishes we've found. We offer it in sets of three grades in either single use packets or 2 oz bottles for the removal of light scratches from acrylic dome and flat ports. Results will vary depending on depth of scratches and method of applying the polish.

Where scratches are too deep to be polished, return the port to Ikelite for a reasonably priced repair or replacement.

Modular Lens Extensions can get a little stiff when they're under-lubricated or left attached for an extended period of time. For this reason, we recommend storing them detached in between trips. Try using a strap wrench, a friend, or simply a lot of force. If you can't get it un-stuck - send it to us!

Measuring for a Port