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Ikelite 8" Dome


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#41 echeng

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Posted 10 March 2005 - 03:10 AM

You can get away with crop-sensor cameras, full-frame WA lenses, and diopters. But I find that slapping a diopter on a wide angle lens connected to a full-frame camera is disaster. So I shoot with a big dome and do not use a diopter.
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#42 Kasey

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Posted 10 March 2005 - 03:36 AM

I was already wondering if PC is some english short term for "Acrylglas" (what it's called in german). So PC=polycarbonat.

<{POST_SNAPBACK}>


Marjo used the term PC and it stuck for the duration of the discussion. I don't pretend to be an expert in materials engineering, I just prefer glass to acrylic after maintaining both.

In regards to light transmission - hold your glass dome up to the sky and look thru, then do the same with an acrylic. It doesn't take a light meter to see the difference! Looks like 1/3 stop or more. Not so significant for digital, but shooting velvia I'll take all the light I can get!
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#43 Jolly

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Posted 10 March 2005 - 03:46 AM

yes, I've picked up PC as well assuming it's the material Ikelite Dome's are made of.

agreed, yes, I prefer the contrast and clearness of glass as well. Even with digital :-) I consider this as image quality as well and the theoretical refraction index advantage of acrylic doesn't outperform the other items.

Julian
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#44 mexwell

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Posted 10 March 2005 - 04:31 AM

Hi Julian,

I you want to buy Ikelite stuff import it directly from the states. I did it and saved big times without any hazzles. What Werner Voelker and ProSub are doing is absolutly ripoff! Both need to be avoided by any means!!!

I recommend Ryan or bhphoto.

Best regards

Chris

But the Ikelite 200% German price philosophy and the absence of a bigger dome for fisheye (split) work weakened my interest and I kept using my film camera with the Seacam port system a little longer.

Julian

<{POST_SNAPBACK}>


Best regards

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#45 Detonate

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Posted 10 March 2005 - 04:43 AM

If I house up my camera and take it out in the back yard.

Set the exposure in manual mode and take 2 pictures.

One with a Acrylic port, and one with NO port attached and set to the same exposure, how many people here claim they will be able to take the pepsi challenge?

#46 Kasey

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Posted 10 March 2005 - 04:55 AM

If I house up my camera and take it out in the back yard.

Set the exposure in manual mode and take 2 pictures.

One with a Acrylic port, and one with NO port attached and set to the same exposure, how many people here claim they will be able to take the pepsi challenge?

<{POST_SNAPBACK}>


Great Idea!!! Be sure to use a pro quality lens or prime!
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#47 Jolly

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Posted 10 March 2005 - 05:05 AM

Christian,

thanks for the information. If I would have chosen Ikelite I would have tried B&H.
I guess warranty is covered when you send it in to the USA? Ike? Could you please confirm?

ProSub is ridiculous. Nothing in stock, could give me absolutely no product information. I asked how I could confirm that an intended setup works. They said they don’t know and I have to try it out. But if the combination doesn’t work/fit, they told me right away “We won’t take back any of the accessories in general, you have to keep it even if it doesn’t work”.

In my opinion they do nothing more than moving closed shipping boxes. But they increase the price to over 200%. The few times I had called them I always had the feeling of disturbing someone. And an 10D housing only price of 2500 US Dollars was not my taste.

A German dealer told me that ProSub has had some kind of exclusive contract for Ikelite distribution in Germany – but the contract would end very soon. I don’t know if the rip-off will continue?

Julian
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#48 Jolly

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Posted 10 March 2005 - 05:12 AM

Great Idea!!!  Be sure to use a pro quality lens or prime!

<{POST_SNAPBACK}>


one wide open for drop off demonstration please. and another one stopped down to see possible dust/reflections, etc. :blink:

Kasey, don't forget someone taking a pic when cleaning your glass. :)

Julian
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#49 Marjo

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Posted 10 March 2005 - 06:29 AM

I understand the logic, but as an observer it makes a statement to the precision of Ike's port system.

??? :blink: ??? You were the one who recommended I go with Ike instead of that other brand... Hopefully you like what you recommend :)

Anyhow, I am happy I did go with that recommendation, because I have been very happy with Ike's gear. I have not had problems with scratching, besides the already discussed, in which case Ike shone with his brilliant service, replaced the port and changed the recommendation on their site. I do not think this incident is any reflection on precision of Ikelite gear. I have heard of other brands having problems with xyz. I do not know of how those brands react on complaints besides what I have read on this board in other threads. What i DID learn from this incident was how Ike responds to events, which is promtly, openly, and with outmost concern and diligence.

Granted, I only dove with this system about 160 dives (about one year), and the system has only been on one "rough" overseas trip, but my shoredives are not "gentle" either, climbing on rocks and rolling in the surf happens... I have not had problems with foggig or "swirling", and I certainly have no problem with cleaning the port of keeping it clean and clear. The only little thing I would change if I could would be to get a bigger viewfinder, but I wouldn't be ready to pay another 1k for it.

#50 Marjo

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Posted 10 March 2005 - 06:37 AM

Ps. Kasey, I'll take a pic of you cleaning your glass this weekend, and thereafter I can take a picture of you cleaning MY Poly...sorry.. Acrylics, and then we can make a scientific study :blink:

#51 craig

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Posted 10 March 2005 - 07:18 AM

In regards to light transmission - hold your glass dome up to the sky and look thru, then do the same with an acrylic.  It doesn't take a light meter to see the difference!  Looks like 1/3 stop or more.  Not so significant for digital, but shooting velvia I'll take all the light I can get!

<{POST_SNAPBACK}>

Yes, exactly. I don't know how much the difference is in stops but there is a difference. How often do lens designers use acrylic instead of glass? The dome is just one more element and it doesn't make sense to skimp on it after spending $1000 on the lens behind it.

Only once have I hit a dome hard enough that it would have damaged a glass part. It was acrylic though and it was ruined. I don't think there's ever been a time when I was better off having an acrylic dome except when I wrote the check. Wish the glass parts were lighter.
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#52 Kasey

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Posted 10 March 2005 - 07:29 AM

???  :blink: ??? You were the one who recommended I go with Ike instead of that other brand... Hopefully you like what you recommend :)


I'm glad you mentioned that - I really believe that Ike offers a tremendous value. Further, by adding the 8" dome option, an even better value.

I was disappointed with the dome system that was recommended with the drebel, and curious about the optical correctness of the recommended combinations. As I stated before, however, it is unfair to judge the system based on one mistake.

Frankly, for a new uw photographer, Ikelite would still be one of my 1st recommendations. Especially now that they offer the big dome! Their service is the best in the industry, and their products are rock solid.

Every system has compromises, and I feel that the acylic dome is a compromise - and a reasonable one considering the cost of big glass. To argue that small acrylic is better than big glass, however, doesn't sit right with me. To argue that it is acceptable and provides a good value - I would agree with that!
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#53 Ryan

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Posted 10 March 2005 - 08:29 AM

Marjo, you do more dives in a year than many of the "experts" here do in four or five. Your feedback is very valued and appreciated.

founder of Reef Photo & Video
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#54 Detonate

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Posted 10 March 2005 - 10:14 AM

To argue that small acrylic is better than big glass, however, doesn't sit right with me.

<{POST_SNAPBACK}>

Is that what you think I've been saying? Please go back and re-read my posts.

My arguement is that I don't believe you will be able to SEE a difference. And to justify spending $500 on a dome vs $200 on a difference I can not see does not make any sense.

#55 Marjo

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Posted 10 March 2005 - 12:52 PM

Thanks Ryan, you are very sweet :blink:

I think everyone has a point.

I agree with Kasey. Ikelite certaily provides a great price/quality ratio.

I also completely agree with Detonate. I personally wouldn't pay what to me is Lotsof$$$ for some difference that I with my own eyes cannot see.

Being new to UW Digital photography, maybe there are finesses that I simply cannot fully appreciate yet. And sure, if I was as wealthy as some of the other posters on this site, and money was no object whatsoever, then I would go for the top $ gear, you know the stuff made of alumini..no lets make it titanium, glass and of course I would get a BLACK camera (because we have been told that you aren't really a photographer unless your camera is all black).

But, alas, I am just a poor IT troll who slaves with the puters all week for a meek little dry bread and water, just grateful to get to take my very own little camera in a watertight box onto the reef... and this being the case, my only option is just to [gasp!] focus on actually finding great compositions and subject matter, since I cannot seem to impress anyone with my gear alone. And, did I mention, I am a Girl after all, you know that species that just can't fully understand or fully appreciate anything more technical than a toaster. And if I do come across a bit frumppy, we'll that's probably just me suffering from PMS.

#56 whitey

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Posted 12 March 2005 - 01:36 AM

:D :( :( (That's me looking very sad after reading Marjo's post...)

OK, hi folks. So Ike has an 8 inch dome port, but Ike says it's optically no better than the little itty-bitty Ike ports?

Based on all the previous threads where we've discussed dome port optics, wasn't the conclusion that

1/A larger dome would provide more margin for error in terms of nodal point
and
2/You still want nodal point in the right place for a given lens - and the Ikelite 8 inch doesn't have extension rings to allow this. So it's pretty much hit and miss whether your new expensive 8 inch dome is correctly positioned.

I haven't been stoked with the combination of the little Ike port and 17-40L I've tried in terms of optical performance esp corner sharpness. So I'd quite like to try the 8 inch dome - but if it's poorly positioned optically for this lens, I may be no better off.

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#57 Jolly

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Posted 12 March 2005 - 02:30 AM

Hi Rob,

You have to distinguish between two basic dome problems causing image quality issues:

1. Improper dome setup
2. rectliner lenses focus on a flat surface. The dome’s virtual image is curved.

Item 2 is much worse for rectlinear wideangle lenses. Fisheye lenses focus in a matter the virtual image is shaped (curved, closer edges). Therefore they perform much better behind dome ports in general. Getting a good corners performance with a fisheye in comparison to a wide rectlinear lens does not say anything about item 1.



There are two main issues causing corner performance decrease as stated earlier in this thread (see quote):

Basically a big dome in terms of big diameter doesn’t help at all if the radius is the same. Assuming the full radius is actually used in both cases.

As item 2 is the worse one and visible with EVERY dome I would not blame your Ike dome too quickly.

In other words: your 17-40 lens offers maximum 77° FOV on a 10D. It might not help too much buying a dome with (almost?) 180° curvature. Only the centre of the dome would be used by the lens. Theoretically you could cut down the 8” dome to the required centre surface and you would end up with a piece of glass you already have right now?!

To determine this you could check your current dome and its position according to the lens.
Even if the dome is positioned absolutely correct you will experience soft corners with any wideangle (see above).

Julian
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#58 Kasey

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Posted 12 March 2005 - 03:03 AM

Whoa! WOn't there be an extension system to complement the Aquatica dome? I'd assumed this... No wonder there is no promised optical benefit to the 8" dome!

One question - do the different domes out there yield slightly different FOV with the same lenses? For example - a fisheye lens behind my superdome vs behind a 180 degree fisheye port. Does the FOV change slightly?

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#59 Jolly

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Posted 12 March 2005 - 03:27 AM

yep, different FOV. As long as the curvature is equal or greater and the setup is accordingly, the FOV is theoretically untouched.

If the curvature is smaller than the lens's FOV: the dome has to be placed closer and you loose some degrees of effective FOV.

A 180° Fisheye behind the superdome looses some minor degrees. Of course the FOV is still much bigger as the dome's angle of curvature but a bit smaller than the lens' topside FOV.
That's why Seacam Austria doesn't call it a fisheye Dome as many other manufactures would do it. They officially recommend the SuperDome für 14mm and above wideangles. But it's clear that many use the SuperDome successfully for fisheyes as well. Especially for split shots it is unbeatable.

As the SuperDome feature a really huge radius it's absolutely non critical to use it with a fisheye as many other manufactures do it in general with even smaller domes. Often it even provides better corner results than normal wideangles.

Julian
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#60 Spinner

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Posted 12 March 2005 - 07:58 AM

Has anyone else tried the recommended Ike small dome (5503.50) with the 10-22 mm? I'm getting very soft corners. From reading all the info on these forums, I understand I need some extensions to match the optics, but I can't find any such extension on the website (Ike?).

Eagerly awaiting James' report on the 8" dome to see if it improves, but Ike's website says that there's no improvement in quality.

Confused,
Ben

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