S2 Pro - Recommedation for macro lens

Scorpio,

Thanks for a well framed and executed post. I have really learned a lot from this one.

Cheers

James

Flat port it is then. Thanks for all your help guys, i even understood most of it!

Interesting statement about Ikelite’s dome ports. I’ve used Ike’s domes for years with out having much choice. I build my own housings and have used compass domes that worked nicely with very small diameter lens. The last camera was the Nikon series Cool Pix with the WC-E24

wide converter. I used a compass dome of 5.25 diameter which worked great. When I made my housing for my Fuji S2 Pro I opted to use Ike’s dome port because I couldn’t find a 6"or 8" compass manufactured. One problem that I have with Ike’s domes are their hard to clean. I haven’t been able to clean them with out scratching them. Ike claims to have superior optical properties, what’s your incite to your statement.

Marc

My response should be more diplomatic, but the scorpio_fish opinion "that Ikelite dome ports are the worst optical quality dome in the market" indicates complete ignorance.

Our dome is the only one actually produced by a molder of lenses to specifications for underwater photography. The mold was twenty thousand dollars way back when. An optical company was amazed at the consistency of the molding just a year ago. Most other domes come from a compass heritage which is not overly demanding for optics.

The only absolute difference in 3" and 4" radius domes is location of the apparent image which is where the lens must focus.

I clarify my earlier statement, lest Ike hunt me down and brain me with a dome port

I go only go by results. When using a 24 lens behind the 6" dome port, I found the dome optics to be fine with this lens. The 24mm lens has an 84 degree angle of coverage. When using the 20mm lens with a coverage of 94 degrees, the Ike dome produced huge amounts of distortion toward the outside sections of the frame, far more than I've seen and experienced with other domes. I am not alone in this observation.

It is just a limitation of the "one size fits many" solution. Although I mentioned coated optical glass domes as ideal, I don't use any myself, because the benefits do not outweigh the costs, as in $$$ and scratching.

An Ike dome costs what, about $150? Compare that with as much as $600 for other dome offerings. Ikelite products are about value. If you are going to use nothing wider than 84 degrees, then you will see no quality issue with the Ike dome.

The image quality is determined by the particular lens and its placement. We have seen spectacular results from 20mm, 17mm, and even 15mm fisheye lenses behind our dome. I jump up and down when I hear ridiculous statements about our dome when it is the highest optical quality in the industry. How any particular lens performs depends on the design of the lens and its centering in the port system. The price is what I placed on it without cost justification. I have to laugh at the multi thousands of dollars some people ignorantly spend. Like try to catch a new Corvette or Viper by spending three times more money............

To get the best optics you have to place the virtual image created by the dome at the anterior nodal point of the lens. I will leave it to the pros to determine that. The quick and dirty way is to open up the lens all the way and line up your reflection in the dome with the center of the lens aperture. If you can move the housing around and your reflection stays in the center of the aperture then the lens is at the proper location for the dome port you are using. No matter how fine the quality of your dome and/or lens you will not get a high quality image if your lens is not lined up properly. This is where reports of a Dome giving lots a distortion come from. If your lens/ dome are correctly lined up you will get good results with most dome ports. Certainly Ike's ports will give good results if properly used.

I actually use a flat port for my 60 mm lens. The convenient out weighting the optical advantages of using a dome. :ph34r:

Bingo,

The diameter of the dome isn't really that important, provided your lens doesn't vignette.

What matters is the radius of curvature of the dome, which determines the location of the virtual image. The material in question (glass or acrylic) also plays a minor role. Acrylic is VERY optically clear and has a diff index of refraction than glass.

So, if your lens is placed so that the nodal points are on top of each other, and the lens doesn't vignette, then it DOESN'T MATTER what the diameter of the dome is.

Big monster domes are cool because they can have a larger radius of curvature - but they are not always necessary.

My 2 cents,

James

The greater the light bending, or refracting power of a lens the greater the chromatic and lenticular aberrations that will occur. This is because these effects are caused by minutely different times at which light hits the outer edges of a lens vs. the center or the lens. For this reason a lens that has less refracting power will have less aberration. Polycarbonate has an index of refraction (n) of around 1.7 where as optical glass has an n of around 1.5 . Also a larger diameter dome has a longer radius of curvature and hence less refracting power. This is why theoretically a large diameter glass dome will have less aberration than a smaller diameter dome or a plastic dome. This advantage can be quite theoretical as in many case the design and quality of construction is the most important variable. It is why though high quality large diameter optical glass domes are considered sharper, though typically at great expense. Many times any real advantage is lost when the user sets the lens closer than the optimal distance. This allows the lens to focus closer but at a cost in sharpness. :ph34r:

"I jump up and down when I hear ridiculous statements about our dome when it is the highest optical quality in the industry"

"Specially designed for the 20mm wide angle, this port provides extraordinary resolution and virtually no edge distortion or aberration."

-Seacam

"Unlike other, universal dome ports SUBAL dome ports are specifically designed for each lens for a no compromise performance "

Everyone has the best dome port in the industry.

"img src="http://www.imagestation.com/picture/sraid11/p72c989726779fa85c12d7766e55c60f7/fe12bf0f.jpg"

No edge distortion there, eh? Ikelite dome with Nikon N90s and crappy old 20mm 2.8AF-D Nikon lens.

"img src="http://www.lozuk.com/coz0498/angel1.jpg"

No edge distortion there, eh? Ikelite dome with Canon 20mm lens.

Let's try those images again.

My wideangle shots taken w/ the Sigma 14mm lens and S2 using the Ike domeport don't have that problem:

and:

That second one even has a coral down in the lower left corner that is pretty sharp. Just in case anyone asks, these are not crops from bigger photos - these are full-frame.

The 14mm Sigma lens on my DSLR comes out to about 21mm - so pretty wide.

So what is the problem w/ Scorpio's setup? Sounds like the camera/tray/housing combo might put the camera too close to the dome. Tough to say.

HTH

James

I see a touch of softness, but not much, definitely acceptable. Got the aperture info somewhere?

Maybe the cropping effect of D-SLR? Although I don't see why. I will have to think on this one for a while. I hope it is, as this will solve many problems.

As far as positioning of the camera/lens in the housing, there is little/no play in the Ikelite housing. This is a good thing, as my Aquatica has a quirky system of securing the camera and has some slop in it. One system is a pure Nikon, the other is pure Canon.

James, Marc and ScorpioFish,

On Ikelite dome ports and lenses...... I've owned housing with the huge dome ports, and shot them with fixed focal length lenses plus zoom wide angle lenses. For the last few years the Ikelite dome ports (standard #5503 and extended versions for the Nikon 18-35mm ED lens) have produced publishable results at tremendously lower cost. Edge focus has more to do with aperture and apparent depth of field. If you don't believe me check out Pro Dave Fleetham's photos which he has been using Canon cameras with the Canon Fisheye W/A lens for years behind Ikelite domes. And selling lots of photos!

For years I also heard fixed focal length lenses would always be sharper than the new zoom lenses above water Pros were migrating to. Constantly learning and trying something has convinced me to the point I use zooms exclusively now, above and below. The #5503.50 extended dome port with a +4 diopter on my Nikon D100 (= 27-52.5mm) has proven a great shark and dolphin lens. Just buy a good (like B&W) diopter and most folks will be extremely satisfied. And the standard #5503 dome port works great with no vignetting on Nikon's 16mm AF fisheye lens. Kind of a slightly curved edge (but sharp!) 23-24mm lens. This lens is also a better buy for wide angel underwater work than the Sigma 14mm, which does have some flare problems. A lot more compact, and when Kodak's 14N hits the streets we'll all have our full frame lens angles back.

David Haas

Scorpio:

Shallow water shooting at f8 for those shots posted. I'm not a very good wideangle shooter so the lighting sorta sux, but you get the point.

I have some other shots from the flowergardens using the same lens at f5.6:

Not the best photo, but that one shows VERY little softness in the lower corners, even at f5.6

I too would love a full frame sensor so that I can shoot the Nikkor 20mm lens. It will probably be a while for me though since I own the S2 setup now.

Cheers

James

Am i right in saying that because the CCD in a DSLR is smaller than the surface area of a film, the camera effectively uses a smaller central area of the lens and hence dome?

If this is the case then it would help to overcome any distortions or abberrations towards the outside edge of the lens/dome

Am i right in saying that because the CCD in a DSLR is smaller than the surface area of a film, the camera effectively uses a smaller central area of the lens and hence dome?

Yes.

If this is the case then it would help to overcome any distortions or abberrations towards the outside edge of the lens/dome

Yes, I think. Just tyring to think it through. The 14mm creates a virtual image with a >100 degree view. The CCD then crops the central portion, making it the same as a 21mm, but a true 21mm image would cover more of the dome. But I could be wrong.

Question for David Hess

The #5503.50 extended dome port with a +4 diopter on my Nikon D100 (= 27-52.5mm) has proven a great shark and dolphin lens.

Which zoom are you talking about? I assume 18-35mm. I intend to use my 17-35mm AF-S for my wide work. Sure, it's the equivalent of 25.5-52.5, but I find it easier to work wide angle in the 24mm range anyway.

David and I have talked about this. (He's at Dema).

The 18-35 f3.5 ED is the lens that will work w/ the stock Ikelite port.

The 17-35 AFD has a different diameter and length - don't know if it will work. I think not though (gut - it's a monster lens, right?).

HTH

James

James and other DSLR shooters,

I'm leaving for Lost Wages (Las Vegas) tomorrow and stumbled through posting a few sample images at:

http://homepage.mac.com/davidhaas/PhotoAlbum2.html

Be happy to share information when I return. Some are actually older images taken with a Coolpix 990, WC-E24 wide angle lens and Ikelite housing (with 1-2 Ike DS50 strobes) but the majority with the Nikon D100, 18-35mm ED lens and single Ikelite DS125.

Hope you enjoy them.

David Haas

Shooting flm, I would have to say the Nikon 17-35mm might be the sharpest lens I own. Many will dispute it, but I believe that it is sharper than many fixed focal length lenses such as the Nikon 20 and I really can't tell the diff from a Nikonos 15mm. As for the images above you are right in saying that a shallow depth of field could cause the edge blur. Also where your focus is. One hugh advantge of the Nikonos 15 mm is the caliphers that show you the depth of focus for each F stop.. With an auto focus SLR one thing to try is to focus on in front of your subject and lock focus. Your depth of focus should be 1/3 in front of your subject and 2/3 behind it.

As per previous posts proper distance of each lens from the dome will give you the sharpest image. This is probably more important than the quality of the dome in most cases. In the case of the 17-35 I mentioned above Subal came out with a 60 mm extention ring for their wide angle port. Mind you they allready had a 66 mm extention ring for years, but found that 6 mm made a significant improvement. :ph34r: