Dipter Question with 12-24 Nikor behind Ikelite 8" dome?

[tx51210]

Anyone shooting with a 2+ diopter on the 12-24? Ikelite states in their onlline information that a diopter might improve corner sharpness.

Does a diopter help or is it avoiding the wider corners by changing the view?

 

[Mariozi]

It does help, but...

Ikelite should probably not have said exactly that.
When you arrange a dome-lens combination, you have mainly two big things to worry about:

1) Minimum focus distance: uw the dome works like a lens, and if you find your lens focused in an infinite subject, you will see (at the lens barrel) that she is actually focused in a "virtual" image 2-3 dome radius away... So if your lens doesn't focus that close, she won't be able to focus at all!!! You can fix it by doing 2 things, buying a bigger dome (or a better lens ) or fitting your lens with a positive diopter (close-up filter) strong enough to make the necessary changes in its focusing capabilities.

2) The other thing is dome-lens alignment, you need to make sure that the dome optical center, aligns perfectly with your lens frontal optical center... so that ALL the light rays entering your lens to form the image cross the dome at a 90 deg. angle. This sometimes gets very tricky with zoom lenses and it results in bad focusing/definition/color at the corners of the image. This is sometimes fixed with extension rings to adjust the dome-lens distance.

So, actually what you are saying is that you are trying to fix one problem with a remedy for a completely different problem... besides, the addition of a diopter in uw wide-angle domeport photography tends to deteriorate the depth of field, this deterioration is less noticed with lens with wider coverage and lower diopter filters. One other thing, dipoters doesn't change lens coverage (angle), it only changes focusing ability. And on a WA lens as the 12-24 can even produce some vignetting.

Hope it helps... but anyway you have to check everything uw, as even the dome thickness interferes in the math of the thing. This is one of the reasons that I do for thinking that the 12-24 is an AMAZING lens above water, but not as good as uw as it is above it. The 10.5 is exactly the opposite, AMAZING uw and a good option above it to shoot "out of the box".

 

[tx51210]

It does help, but...

Ikelite should probably not have said exactly that.
When you arrange a dome-lens combination, you have mainly two big things to worry about:

1) Minimum focus distance: uw the dome works like a lens, and if you find your lens focused in an infinite subject, you will see (at the lens barrel) that she is actually focused in a "virtual" image 2-3 dome radius away... So if your lens doesn't focus that close, she won't be able to focus at all!!! You can fix it by doing 2 things, buying a bigger dome (or a better lens ) or fitting your lens with a positive diopter (close-up filter) strong enough to make the necessary changes in its focusing capabilities.

2) The other thing is dome-lens alignment, you need to make sure that the dome optical center, aligns perfectly with your lens frontal optical center... so that ALL the light rays entering your lens to form the image cross the dome at a 90 deg. angle. This sometimes gets very tricky with zoom lenses and it results in bad focusing/definition/color at the corners of the image. This is sometimes fixed with extension rings to adjust the dome-lens distance.

So, actually what you are saying is that you are trying to fix one problem with a remedy for a completely different problem... besides, the addition of a diopter in uw wide-angle domeport photography tends to deteriorate the depth of field, this deterioration is less noticed with lens with wider coverage and lower diopter filters. One other thing, dipoters doesn't change lens coverage (angle), it only changes focusing ability. And on a WA lens as the 12-24 can even produce some vignetting.

Hope it helps... but anyway you have to check everything uw, as even the dome thickness interferes in the math of the thing. This is one of the reasons that I do for thinking that the 12-24 is an AMAZING lens above water, but not as good as uw as it is above it. The 10.5 is exactly the opposite, AMAZING uw and a good option above it to shoot "out of the box".

Thanks for the feedback. It just seems wierd to put a macro lens on a wide angle. I have really high hopes for the 10.5 and will have the 12-24 anyway so I got the adapter for it as well. I will try it both ways and see what happens.

Tried a couple of quick tests. The Canon 500D 2+ diopter does reduce my angle of view. I shot an identical photo with and without the diopter and the angle of view with this lens is slightly reduced and the performance is down as items are not as crisp with the diopter. Obviously, this lens is not designed to be used for this purpose (designed for 70-200 lens), but I wanted to see what happened with the 12-24 and I am unsure what other options are available for a 77mm diopter. Do other diopters behave differently than the 500D?


No Diopter


With Canon 500D

 

[Hidroj]

Hy Jeff!
Around the subject of corner sharpness and the Ikelite Domes, there's something a bit disturbing, at least in my opinion. What does Ikelite mean when thay say: "...some people feel a +2 close-up lens may enhance corner sharpness."?
May enhance?? Some people feel? Or it enhances corner sharpness or it doesn't! My conclusion is that photgraphers concerned about corner sharpness, probably find some difference, otherwise Ikelite won't say "some people feel" or won't write in such vague way.
This week I'll get the 5510.22 Body for the Nikon12-24mm, and I'll go to the pool to make some tests. Will post them as soon as I can.
Chears!
Jordi

 

[tx51210]

Hy Jeff!
Around the subject of corner sharpness and the Ikelite Domes, there's something a bit disturbing, at least in my opinion. What does Ikelite mean when thay say: "...some people feel a +2 close-up lens may enhance corner sharpness."?
May enhance?? Some people feel? Or it enhances corner sharpness or it doesn't! My conclusion is that photgraphers concerned about corner sharpness, probably find some difference, otherwise Ikelite won't say "some people feel" or won't write in such vague way.
This week I'll get the 5510.22 Body for the Nikon12-24mm, and I'll go to the pool to make some tests. Will post them as soon as I can.
Chears!
Jordi

My 5510.22 shows up tomorrow. It's a shame I will be out of town till late, but that will reduce the agony of watching the door all day. It will be good to see a couple of different reports to see how the system works.

 

[HowardE]

some people feel a +2 close-up lens may enhance corner sharpness."?
May enhance?? Some people feel?

Because its subjective

 

[Mariozi]

Dont worry, if you are into uw and topside photo you can never go wrong buying both of them. And it is great to be able to take a 12-24mm out-of-the-hat. For me I plan to add a 10-20 Sigma instead.

 

[f3nikon]

Thanks for the feedback. It just seems wierd to put a macro lens on a wide angle. I have really high hopes for the 10.5 and will have the 12-24 anyway so I got the adapter for it as well. I will try it both ways and see what happens.

Tried a couple of quick tests. The Canon 500D 2+ diopter does reduce my angle of view. I shot an identical photo with and without the diopter and the angle of view with this lens is slightly reduced and the performance is down as items are not as crisp with the diopter. Obviously, this lens is not designed to be used for this purpose (designed for 70-200 lens), but I wanted to see what happened with the 12-24 and I am unsure what other options are available for a 77mm diopter. Do other diopters behave differently than the 500D?


No Diopter


With Canon 500D

Shooting macro shots maybe a better test in this case to get a closer look at the image detail.

With the diopter lens the red flower on the far right seem a bit fuzzy when compared to the image without the diopter.

The less lense the better, the lense will bend the light, the more lenses you add the better the chances the light patterns will NOT converge at optimal point Canon designed it to be. That is the reason for prime, non zooming macro lenses.

Also check for contrast ie true black not a muddy grey and true white not a dirty white, adding lense will cause these to shift.

If you are taking pictures just to show friends how the U/W world is like and quality is not the issue, then all this does not even matter.