Oly 45mm F/1.8 for UW?

[MarkHerm]

I understand that this lens is probably far from being optimal for uw use but I have it anyways so why not give it a shot (until the 60mm macro is going to be available ). Anyways, does anyone know if the lens will fit into the Nauticam 4,3" dome that was made for the Panasonic fisheye? AFAIK the Olympus 12mm will fit into it and the size of the Olympus 45mm is about the same as the 12mm if I remember correctly.

 

[unclebob]

Not a problem fitting this lens into the Nauticam 4.33" dome and there's plenty of room for several diopters on the front of the 45mm. Underwater the 4.33" dome creates a virtual image that is about 0.14m (for objects very, very close to the front of the dome) to 0.20m for objects at infinity. The minimum focus distance for the 45mm is 0.5m. So you'll need a diopter to drop the minimum focus distance to closer to 0.10m. A +5 or +6 diopter might be a good starting point...

 

[tamas970]

Hi Phil,

What would be the effect of using an extension ring behind the 1.8/45? (There is a Kenko AF extension ringset available. )
This would bring it closer to the port glass and I guess turn the lens into macro.

 

[PHIL RUDIN]

With an extension tube you loose light, 1 to 2 stops depending on the length of the extension tube. So if you are using say F/8 without the tube you would now need light for F/11 or F/16 with the tube. You also reduce distance between you and your subject to increase subject size in the frame. For the cost of the 45 F/1.8 and the extension tubes you could have the 60mm macro which is a much better macro lens. I shoot the 45 F/1.8 out of the water and it is a great lens but not so much underwater.

Phil Rudin

 

[tamas970]

An other - cheaper option: Raynox 150 or similar 4-8 diopter close-up ring - as you earlier mentioned. This would keep AF, and lens speed.

Question here is, what is the combined effect of a WA100 and a dry close-up lens? (How strong close-up is needed once to compensate the dome effect and on top of that give some macro capability)

The Raynox 150 looks interesting, its +4.8 diopter and nice 3 element design. (+The 45mm+Raynox with a step-up ring is about the same size as the 9-18mm - the same semidome could be used in theory)