fausdick 0 Posted October 17, 2005 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 Share this post Link to post Share on other sites
anthp 0 Posted October 17, 2005 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). Share this post Link to post Share on other sites
Craig Ruaux 0 Posted October 17, 2005 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. Share this post Link to post Share on other sites
Chris Bangs 0 Posted October 18, 2005 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! Share this post Link to post Share on other sites
UWPhotoTech 0 Posted October 18, 2005 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. Share this post Link to post Share on other sites
Chris Bangs 0 Posted October 18, 2005 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 Share this post Link to post Share on other sites
UWPhotoTech 0 Posted October 18, 2005 Terry? Umm... your welcome! Share this post Link to post Share on other sites
Chris Bangs 0 Posted October 18, 2005 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 Share this post Link to post Share on other sites
petr 0 Posted October 24, 2005 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 Share this post Link to post Share on other sites
james 0 Posted October 24, 2005 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 Share this post Link to post Share on other sites
Viz'art 24 Posted October 24, 2005 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) Share this post Link to post Share on other sites
craig nelson 4 Posted October 24, 2005 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 Share this post Link to post Share on other sites
james 0 Posted October 24, 2005 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 Share this post Link to post Share on other sites
Arnon_Ayal 1 Posted October 24, 2005 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 Share this post Link to post Share on other sites
craig nelson 4 Posted October 24, 2005 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 Share this post Link to post Share on other sites
james 0 Posted October 24, 2005 I was just taking the piss Craig, I couldn't help it...:-) Cheers James Share this post Link to post Share on other sites
craig nelson 4 Posted October 24, 2005 I've been had.... here are a few more with the 18-70 craig Share this post Link to post Share on other sites
petr 0 Posted October 25, 2005 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. Share this post Link to post Share on other sites
UWPhotoTech 0 Posted October 25, 2005 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. Share this post Link to post Share on other sites
james 0 Posted October 25, 2005 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 Share this post Link to post Share on other sites
Viz'art 24 Posted October 25, 2005 Hello Petr, there should be no need for that strong a diopter, incidently the +3 would be the correct one for the optical characteristic of an 8" dome, jolly has a nice feature on that subject. http://wetpixel.com/i.php/full/dome-theory/ Share this post Link to post Share on other sites
