Fantasea/Epoque/Ikelite 46mm wide angle lens differences?

[robzr]

So Fantasea makes some wide angle lenses (FWAL-01 and FWAL-02), 52mm and they include 46mm step-down adapters. You can find them online for $200. The only info I have found on the difference between the -01 and the -02 is the external size or shape.
Mfg page: Fantasea Line Water Sports Photo Products & Accessories- FWAL-01 Wide Angle Lens
Specs: .54x, 4 group, 4 element, 200ft, 320g, 80mm x 45.9mm

Ikelite makes the W-20 6420.46, 46mm native, available online for $300.
Mfg page: IKELITE W-20 Wide-Angle Lens
Specs: .56x, 4 group, 5 element, 200ft, 630g, 100mm x 60mm, green/blue filters available

Epoque makes the DCL-20, for $235 online.
Mfg page: Epoque DCL-20 Wide Angle Conversion Lens
Specs: .56x, 4 group, 5 element, 200ft, 650g, 99.4mm x 59.5mm, green/blue filters available

Can anyone comment on the relative quality or differences between these? The specs appear to make the Ikelite and Epoque very similar, while the Fantasea has one less element, half the weight and a bit smaller size than the other two.

The application would be on a Ikelite housing with a TBD Canon digital P&S with 28mm equiv, for taking 720p video & stills while wreck diving in lake michigan and vacation diving. I have a 35w HID for video lighting and just ordered an Intova ISTR strobe.

Are the Ikelite & Epoque comparable in quality?

Are they both significantly better than the Fantasea?

Would vignetting be a problem on any of these?

Any other lenses to consider in this price range?

I've searched the forums and I just haven't found much info on these lenses, and nothing comparing them. If it's not obvious from my questions, I'm a newbie to photography

Rob

 

[Nemrod]

IMO among the lenses you mention you would be better off with the 67mm threaded Ikelite.

The 67mm lenses will have a larger rear element, at least the ones I have seen compared to my Inon 100WAL 67 threaded Type II. This reduces the likelihood of vignetting. In addition, the fact you mention a 28mm lens on your "undecided" Canon makes me say this, choose one with a 35mm native lens. Also, if you get a camera with a 28mm native lens it will probably vignette so you will have to zoom to the equivalent of 32-36mm for optical alignment. That is my bet.

Let me add, the reason you read little about them anywhere is most people don't know why they need them or what they would do with them or want to afford them or in any way have a concept of what they are or what they do.

N

 

[mmakay]

Yeah, get the larger adapter size. (67mm) It's easy to step-down a wet-mount, but you can never step up without vignetting. This isn't likely to be the last housing you use that lens on. Consider it an investment in future flexibility.

Quality-wise, all the lenses are likely to be very similar. Any problems I've heard or seen are more from housing/lens incompatibility than the lens itself.

 

[robzr]

Thanks for the info guys, I found a used 67mm Inon IWL-100 for $240, from what I've read and seen, it's a great lense, at least on par with the Ikelite.

Nemrod, I am a novice here, the reason I was planning on 28mm is twofold. 1) use out of the water/housing, I have a 28mm SD870IS now and I'd hate to go back to anything less wide, although there is no reason I can't keep the 870 for use out of the water, so maybe a non-28mm camera would be a better choice.

2) My primary interest is wreck penetration video footage in the great lakes here, from my limited experience and from what I've heard, "the wider the better" (especially in low vis, and especially in a wreck). But as you point out if its vignetting at the wide settings and I have to zoom to get rid of that, getting a 28mm lense would be somewhat counterproductive.

Rob

 

[Nemrod]

I hope that was a Type II Inon 100WAL.

Don't use your underwater camera but for underwater--problem solved.

For what you want I think the Canon 590, 720 and Fuji F60d are your best P7S bets, JMO.

For the widest possible view you will need the dome converter for the 100WAL.

To complicate things, there are the Inon 28AD series lenses which are intended for native lenses of 28mm but try putting that on a housing, good luck, I could do it but what a PITA that manufactures choose to put threaded ports on cameras that should have the Inon 28AD bayonet mount.

N

 

[robzr]

Yah, it is a Type II for 67mm threads and not one of the proprietary bayonet mount ones... The camera that I am really curious to see some sample video on, is the Canon SD960IS because it does h.264 1280x720 @ 30 fps video, and has a 2.8" widescreen LCD. If the video looks as smooth as my current SD870IS 640x480 @ 30 fps, then it's going to be hard to resist that camera.

The models you mentioned are all 640x480 video, so about 1/3 the pixels as the 720p video. I'm sure I'll be compromising still picture quality, but I'm willing to do that. And a dedicated 720p underwater camcorder setup is probably $$$, very large, and would suck for stills.

But you have me thinking, the SD780IS will be worth looking at as well, as it has 33mm equivalent on the widest setting, although the LCD is 4:3, so that wouldn't be as ideal.

Inon apparently rates the UWL100 as needing a 31.5mm equivalent focal length to avoid vignetting, so the 33mm on the 780is would be just about right.

Is my math correct:

28mm * 1.33x (flat port underwater) * .57x (mag. of UWL100) = 21.2mm (35mm equivalent focal length) = 80.7 degrees horizontal FOV (as per http://www.tawbaware.com/maxlyons/calc.htm)

? Is FOV usually expressed as horizontal, if not specified? I tried using the formula with the CCD size, actual focal length (2 * arctan ( ccd / (2 * f)) but it wasn't jibing with the #s I get from the webpage; although with an arctan I'm guessing that is diagonal FOV?

Sorry for all the questions here, I'm trying to learn, and it is a bit confusing to say the least

Lastly, I was wondering if in my calculations, I would need to know the distance between the end of the lense, and the end of the port on the housing, or if that does not affect the overall FOV?

Rob

 

[Nemrod]

The measurements for FOV are usually diagonal field. Since most digi-cams have a 4/3 format and 35mm is 5/3 when people express lens focal lenghts in terms of a 35mm equivalent it is an approximation.

Yes, your math is essentially the same thing I am doing except I added to it by also taking actual measurements of various lenses and cameras and then doing some optical hand solving via geometry I learned years ago making a few astronomical telescopes.

The distance between the lens elements does effect the vignetting issue, they need to be very close, there is an optimal distance which varies with the specifics of the camera, housing and particular wets lenses. As little as a 1/32 inch can have a significant effect upon severe vignetting. I am still fighting it with my custom modded Ikelite/AD mount.

Thank you for being so studious.

N

 

[Nemrod]

Ikelite does not yet make the housing for the 960/780. I can see how as a video camera it would be preferable to the units I suggested. They have manual control but since you are doing mostly video clips for u tube etc I see your interest.

Back to the figuring, the wet lenses are optimized almost universally for approximately a 35mm equivalent lens behind a flat port with one known exception, the Inon 28AD which are for 28mm lenses behind a flat port but have a bayonet mount as you have learned.

N

 

[robzr]

Back to the figuring, the wet lenses are optimized almost universally for approximately a 35mm equivalent lens behind a flat port with one known exception, the Inon 28AD which are for 28mm lenses behind a flat port but have a bayonet mount as you have learned.

N

Hey Nemrod - your earlier point about 5:3 aspect vs. 4:3 aspect got me thinking. The video (what I'm most concerned about) will actually be 16:9, so if my math and assumptions are correct, 33.3% would be cropped from the vertical (16.6% from the top, and 16.6% from the bottom) of the 4:3 sensor.

I wonder if all the vignetting that would occur by using 28mm focal length with the Inon lense would occur in that cropped 16.6%. I'm at a loss as to where to begin this math, maybe I'll blow the dust off my trigonometry books, do some research, thinking and sketching and give this a shot, but I'm curious if you have any quick thoughts.

I got the Inon lense in the mail today, it looks like a real well made piece and seems like it's in great shape. I don't have anything to thread it onto yet, but I stuck it up to my eye and peered at my co-workers which was kind of fun. I can't wait to get this setup going, it's gonna be a real nice step up from my current P&S setup...

Rob

 

[Nemrod]

Hey Nemrod - your earlier point about 5:3 aspect vs. 4:3 aspect got me thinking. The video (what I'm most concerned about) will actually be 16:9, so if my math and assumptions are correct, 33.3% would be cropped from the vertical (16.6% from the top, and 16.6% from the bottom) of the 4:3 sensor.

I wonder if all the vignetting that would occur by using 28mm focal length with the Inon lense would occur in that cropped 16.6%. I'm at a loss as to where to begin this math, maybe I'll blow the dust off my trigonometry books, do some research, thinking and sketching and give this a shot, but I'm curious if you have any quick thoughts.

I got the Inon lense in the mail today, it looks like a real well made piece and seems like it's in great shape. I don't have anything to thread it onto yet, but I stuck it up to my eye and peered at my co-workers which was kind of fun. I can't wait to get this setup going, it's gonna be a real nice step up from my current P&S setup...

Rob

It might cut out most of the vignetting. Your question is a good one and it has occurred to me as well. Of course you realize that as you go to the 16:9 mode you loose a large portion of the sensor. Most of the A Series Canons have a postcard mode and a 16:9 mode, each crops more of the sensor off to produce the "widescreen" effect. You could do the same thing in Photoshop.

I have done all of the sketching and trig and measuring I can given my limited resources but I cannot answer for every camera and housing other than just as a general guideline. I suspect a good portion of the vignetting would be eliminated by cropping the sensor in the camera at the 16:9 mode. I don't like loosing so much of the picture myself.

N