Nikon D70S, w/18-70mm, & +4 Diopter

Hello Everyone!

Well I finally did it. I sold all my film "stuff" and went digital. I recently purchased a Nikon D70S with the 18-70mm lens and also a 60 mm lens for macro use. I housed all of that into a Sea & Sea housing, twin stobes and a flat port for the 60mm. After reading some other articles I bought a compact dome port for the 18-70mm lens and added a +4 diopter lens to the camera.

So here I am 3 weeks from heading back to Belize and I try all the pieces together and everything seems to be fine. EXCEPT, when I screw on the B & W +4 Diopter (Model NL-4, from B&H Photo) the camera here on land won't focus and it won't take a picture in AUTO mode?

What am I doing wrong?

Any advice or suggestions would be greatly appreciated.

Thank you!

Fausdick

Don't worry fausdick. It should work fine UW. Maybe try it in the hotel bath/sink to ease your mind.

Remember that UW, the camera is focussing on a virtual image which is much closer to the camera than you'd normally be focussing on land (if that makes any sense at all).

With a +4 dioptre in front of your lens, "infinity" focus is less than a metre from the front of the lens. You can't focus on anything further away than that. When you are in AF-S mode, the camera will not fire if it is not detecting focus of some sort.

When you have the lens behind a dome port, "infinity focus" is within the one meter or so limit, because you are focusing on a virtual image that is within that distance.

Stick it in the pool and it should work.

I think a +4 may be a bit to much! you may consider using a lower power diopter. You need to know what the port virtual focus distance is then get the lowest diopter will bring your lens MINIMUM focus to that point or closer.

also get a high quality "multi element" diopter! The extra expense is a fraction of your system cost and well worth the improved image quality!

I think a +4 may be a bit to much! you may consider using a lower power diopter. You need to know what the port virtual focus distance is then get the lowest diopter will bring your lens MINIMUM focus to that point or closer.

 

also get a high quality "multi element" diopter! The extra expense is a fraction of your system cost and well worth the improved image quality!

<{POST_SNAPBACK}>

The +4 Diopter is correct for this lens/port configuration. A "multi-element" diopter lens is for use with Macro Lenses in a Flat Port not with Wide Angle lenses in a Dome Port. I would however recommend you purchase the best diopter lens you can afford. I'd recommend the B+W brand.

The +4 Diopter is correct for this lens/port configuration. A "multi-element" diopter lens is for use with Macro Lenses in a Flat Port not with Wide Angle lenses in a Dome Port. I would however recommend you purchase the best diopter lens you can afford. I'd recommend the B+W brand.

<{POST_SNAPBACK}>

Thanks Terry for the heads up on diopter use.

I do not use zooms except for the 12-24. Now that I think about it, I would guess that the thickness of the multi element dipoter is why they are not recomended for WA use since they may vignette at the widest angle of view

oops too early in the AM here in Japan. I have to stop trying to post on two boards and answer email all at the same time. task loading for me you know

So, how do you focuse on an object that is further then the 1m. I have similar problem with this lens and +4D. I can focus on the close objects ( up to 1m let say). But if I want to shoot a picture of a fast moving fish I can't focus if the fish is further...... Any advice?

I wonder how you can use this lens for the fish portraits?

Cheers,

Petr

With the proper diopter and dome port, you should not lose your infinity focus underwater. The "virtual" infinity will be brought in close to the dome, but it sounds like it's beyond the range of your lens+dome+diopter. It sounds like the +4 diopter is too strong - perhaps you should use a +2 when you intend to do fish portraits.

Cheers

James

I agree with james and/or terry AKA Dave about the diopter issue. B&W and try a +2 for starter, I had a formula somewhere for calculating the proper diopter for a specific dome radius. I'll try to fish it out off the bookcase <_< . the reason every thing is kosher undewater is the fact that your dome become an integral part of the optical formula, bending light around the axis of a sphere (your dome) this create a virtual image at +/- 4 times the radius of your dome from the optical axis, thus you have a 6" dome that image will be projected at very close to 9" in front of the dome, remember that the axis is inside the dome, so one radius is lost inside the dome the other three are outside, also important is the diameter of your dome, the bigger the dome the further away the projected image, the easier it is to focus on that image.

Your dome need to have a liquid body in front in order to see the reaction to refraction, that stuff only happen when you have two medium of different density interacting, IE: air and water, water becoming an optical factor at this point (remember your mask when is it immersed and the difference in size between reality and perception)

Hello All

Ok I've used the 18-70 with a +4 with great results.. I just wanted to try it to see if it worked and it did, i was quite pleased actually.

Dont shoot me down in flames lads for using a KIT lens will you.

take a look, these are a couple of shots from my very first outing with the D70 back in august.

D70 with 18-70 iwith +4 in DX-70 with Dual Sb105's Compact Dome port with 40 extension ring.

regards

craig

No doubt - the 18-70 is an extremely good kit lens.

OK, so I've been looking at your center photo for about 10 mins now and I still can't find the pygmey seahorse - I give up!

Cheers

James

So, how do you focuse on an object that is further then the 1m. I have similar problem with  this lens and +4D. I can focus on the close objects ( up to 1m let say). But if I want to shoot a picture of a fast moving fish I can't focus if the fish is further...... Any advice?

I wonder how you can use this lens for the fish portraits?

 

Cheers,

 

Petr

<{POST_SNAPBACK}>

As Viz'art explained very well the combination of lens+diopter+dome act very different u/w and on air.

I use the 19-70 with +4 B&W behind Ike's 6'' dome port with no problems to fucus at far distancees

James

I wish there was one there !!!, No so lucky in the RedSea, Its just one of those Shapes and textures kind of shots....

just playing around..

I hope to get some critters when i goto Sipadan Kapalai and Mabul next year.. B)

thanks

craig

I was just taking the piss Craig, I couldn't help it...:-)

Cheers

James

I've been had....

here are a few more with the 18-70

craig

Well, that could be the reason I couldn't focus. I use the 8inch Aquatica dome port. I have used the +4D behind. I will try the +2D and will see. Does anybody use that lens with the 8inch dome port with the +2D? Thanks guys for the advice.

Well, that could be the reason I couldn't focus. I use the 8inch Aquatica dome port. I have used the +4D behind. I will try the +2D and will see. Does anybody use that lens with the 8inch dome port with the +2D? Thanks guys for the advice.

<{POST_SNAPBACK}>

The +4 Diopter is used with a 6" Dome Port with the 18-70 lens. With the Aquatica 8" Dome port no diopter is required, but a +2 diopter can be used if you desire. My recommendation would be to try this setup without a diopter lens installed.

My guess is that Fausdick was following the blanket +4 recommendation made here and other places on the net. A +4 is only needed with a very few lenses and small ports like the 6" Ikelite or the Sea and Sea compact dome.

Cheers

James