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Ikelite 8" Dome

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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!

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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???  :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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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.

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

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.

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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.

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: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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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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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?

 

Thanks

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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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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

 

20D + Ike housing, Canon 10-22 EF-S, Tamron 28-75, Nik V yada yada yada.

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There is an improvement in image quality.

 

The article is done but I don't know how to post it on the new Wetpixel. Here's a photo of the back side of the dome that should explain a lot:

 

domeback.jpg

 

And this is what the different extension rings look like:

 

extring.jpg

 

That one is super-long. The one for the 10-22 is much shorter.

 

Cheers

James

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Thanks James, that makes things clearer.

 

I was figuring no extension rings, like the other Ike ports, but obviously that's not the case.

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James, could you bring the different extensions that you have on the Shark Trip? I only have the one that came with the dome...I'd be intereted in trying different ones

 

Karl

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Gee, I dunno Karl, these are kinda heavy. And after the wetsuit incident...:-)

 

J/K OK, I'll bring them.

 

Cheers

James

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Thanks James....I'm still embarrassed about the wetsuit :D:(

 

Karl

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Thanks James for posting this info.

 

So it looks like the extension sustem is on the ikelite end. So what is the chance that the 10.5 can be used in this port if you had the proper extension?

 

I really think its critical that you can use the 10.5mm in this port. Since I already own ports for every other lens there really is no motivation for me to spend an additional $400 unless:

 

1) I can reduce my packed volume for the 4 lenses I plan to use in domes by carrying the appropriate extensions (10.5mm 15mm, 12-24mm and occasionally 60mm)

 

2) I can use it for split levels with the 10.5mm and/or 15mm

 

3) I can justify the cost since I already need to buy the port for the 10.5

 

4) Of course if there is a significant increase in quality then the whole equation changes.

 

So what's the deal, will this work with a 180 degree FE or not? I expect it won't be too long before Sigma or Canon offers one for Canon as well so the problem isn't going to be isolated to Nikon users for long.

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It will not work with the 10.5mm....vignettes badly :D ....don't know about the 15mm.....

 

Karl

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Per Ikelite site, "Dome is positioned for the new zoom lenses like 12-24mm Nikon and 10-22mm Canon. Small wide angle lenses in the 10mm to 15mm range can not operate with this placement. Lenses that utilize our #5503.50, #5503.55 and #5503.80 ports can utilize this 8" dome.

 

Mounting system placing the dome closer to the housing will also be offered. "

 

http://www.ikelite.com/web_pages/bigdome.html

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Thanks Peter and Karl,

 

I guess its just that I've just received my Nikon rebate and its burning a hole in my pocket!

 

From the statement on the Ikelite website, it looks like this may be accomplished with a different extension ring.

 

James, it looks like for now just one of these is available? The one for the 12-24mm and Canon 10-22?

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Improvement in image quality is an understatement! Look at the vignetting behind the small dome! THe corners are black!!!

 

I might also add that there is much more vignetting on the brick shots than I would expect from L glass on a 1.6 body. Agree?

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Kasey

 

I see no more vigntting behind the small dome than I see in the brick wall test. Are you talking abou the left hand side of the frame? To me the left side looks more like not lit by the strobe than vignetting....

 

Yes a L lens on a 1.6x body would be better than that. Perhaps thats why the lens isnt L. And I would expect that all EF-s lenses vignette much worse than a full frame lenses when both are used on crop cameras.

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Ignore what looks like vignetting in the photos - that is just bad strobe aiming on my part.

 

Have you guys actually used the 17-40L? It probably vignettes more (on full frame) than the 10-22 vignettes on 1.6x crop. The 10-22 is excellent - and it's a $650 lens to boot...

 

Cheers

James

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Holy Moly! I definetly have never, ever, not even once, got any black corners like that in any of my images taken with the 10-22mm even at 10mm. Now, of course, shooting in tropical waters I seldom shoot more open than f8. But NO, please anyone who looks at those shots, please do not conclude that if you get the Ike dome you will end up with pictures with black blobs in the corners because that definetly has NOT been at least my experience.

 

On the above, I wonder what else plays in. I think trobe placement (like James already mentioned) is a big one. Was the port turned correctly (with the shade petals inthe right locations)?

 

Seriously: You really need to be very careful when you present info collected in this manner as "evidence" or this type of ad hoc testing as scientific or correct. It's one thing to do it in your backyard pool and discuss with your friend down the street, quite another to bring iot out on the internet like this. Wetpixel is a great site, it has grown alot and you have a good part of the uw photographer population checking in here. So what you say or claim might have a pretty significant impact on the company whose products you are 'testing". I am saying this with the disclaimer that I do very much believe in an open forum for discussion without pressure from brand x,y or z. And were not out to "cover up" for anyone. However we cannot just go out and make claims about soemthing and base that on shaky evidence. But just keep in mind that while heresay is easy to dismiss, ppl might be less critical of something you pass off as a "test". When you do that, you really do have take reponibility for your methodology and conclusions.

 

Sooo...Now that we have had the "wiseman report", I would be interested in, to get some balance to this discussion, to get more info about Ike's tests. I don't know if they have actually conducted these or not, but if they have, and from their site it sounds as they might have either done tests or have some other empirical material, it would be wonderful to hear from them as well.

 

We have heard some less than scientific claims (Sorry Kasey, just putting the dome to the sun and eyeballing the light, doesn't seem to drop 1/3 stop light when I look thru my dome. Could be that your eyes are more light sensitive than mine, who knows). Those claims could be right or wrong, but until tested in a controlled situation where you have all factors controlled and are able to measure them, they are not proven one way or the other.

 

James did write in conclusion that it is hard to draw conclusions from his report. Good. But in his post he wrote that there is a difference. Hmmm...

 

Marjo

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