Best dome port for the Olympus m4/3 9-18 lens

[Interceptor121]

At f/4 even on a 4:3 the dof is too little for a dome it so small
At the end I think the issue is that he adjustments you have to do to correct fringing apply to the whole image so if your close up lens is not high quality you deteriorate the whole frame when you correct it
I have the same problem for macro I don't have an achromatic diopter that is 3 or 6 so i need to ensure the corners are dark or blurred so I don't correct at all
When I do the image also deteriorates in the centres as It works on hues

 

[Furnari]

What would be a good quality diopter to purchase? Most of the stuff on Amazon seems to come in a kit for 10-20 bucks- as cheap as I am, I would have thought I'd have to spend more than that...

 

[Interceptor121]

http://www.bhphotovideo.com/c/product/87487-REG/Canon_2821A001_52mm_500D_Close_up_Lens.html

+2 achromatic is what you want

 

[Storker]

Heh, from a general POV I was going to recommend either a lens from one of the reputable filter producers (B+W, or Hoya), or from one of the big camera producers (Nikon, Canon etc.). If you want to add extra glass in front of your lens, it should be good.

That Canon lens looks sweet. Do you know of any other producers who make closeup lenses of comparable quality? Nikon don't make a +2, only +1.5 and +3.9

EDIT: I found a page listing various achromatic closeup lenses: http://fuzzcraft.com/achromats.html

 

[Interceptor121]

Looking at that list the only 52mm +2 is kenko

---------- Post added December 19th, 2014 at 11:49 AM ----------

Kenko number 2 costs more than canon

 

[Furnari]

Apologies for hijacking, but if a google search finds this thread, we might as well have as much info as possible I use a 62mm step up ring in place of the Oly shade ring- is there any difference optically with using a bigger diameter achromatic diopter?

 

[decidedlyodd]

What would be a good quality diopter to purchase? Most of the stuff on Amazon seems to come in a kit for 10-20 bucks- as cheap as I am, I would have thought I'd have to spend more than that...

I wish I could find the reference now, but I read somewhere (think it was here on wetpixel but maybe somewhere else?) that the cheap diopters often work better than the expensive ones when used to improve corners behind a dome underwater. Something about cheap diopters producing a more curved focal plane which tends to work better for dome optics but worse above water while the expensive diopters produce a flatter plane with the opposite effects.

 

[Interceptor121]

I wish I could find the reference now, but I read somewhere (think it was here on wetpixel but maybe somewhere else?) that the cheap diopters often work better than the expensive ones when used to improve corners behind a dome underwater. Something about cheap diopters producing a more curved focal plane which tends to work better for dome optics but worse above water while the expensive diopters produce a flatter plane with the opposite effects.

A cheap diopter is single element so the lens will have issues in the corner outside water too.
An achromatic diopter will have two elements positioned so that the aberrations cancel each other this may not work 100% but will definitely be much sharper in the corner as you can see from the link storker posted
In water single element diopters are completely useless and even two elements work poorly. In fact the best underwater diopters have 3 elements so they present a curved front but due to the two air spaces are virtually free of aberrations. You don't need such lens in air and in fact in air those lenses don't do well
So I would be curious to see why a cheap diopter would work better than a double element one?

 

[nudibranco]

A +2 diopter at those focal lengths might give you better corners but will surely degrade overall quality and also prevent the camera to focus at infinity. Corners are corners nobody looks into that unless they are really poor don't bother

I used the single lens diopter so it will not vignette. There are some nice achromat lenses from Marumi Amazon.com : Marumi 52mm 52 DHG Macro +3 330 Achromat Achromatic Close up Lens / Filter Japan : Computer Internal Raid Controllers : Camera & Photo
or others that do cost more but probably get rid of the fringing noise. Maybe I should try one and see if it vignettes however, for the pics I like and select, I generally go in and fix so that is an easy solution for me. However it will focus even at +4 just fine.
I attached some pics with a +4 (but do not know how to improve size quality of it here so i attched on flickr below links). First is an original one with chromatic noise. Second one is with some chromatic noise fix. These are F/11. I also attached better one which is actually at f/5 after some easy fix...

https://www.flickr.com/photos/34875224@N07/15941144208/in/photostream/lightbox/
https://www.flickr.com/photos/34875224@N07/15941282560/in/photostream/lightbox/
https://www.flickr.com/photos/34875224@N07/15942488369/in/photostream/lightbox/

Sometimes some lens correction will also help overall image.

 

[Storker]

Had my first shoot with the achromatic Canon +2 instead of the cheap-a$$ Vivitar diopter I've used until now.

The conditions weren't the best, with really low light giving the camera h€ll finding focus and needing a large aperture get any ambient light at all in the background, plus clouds of silt drifting over from other divers, but I'm looking forward to check the pictures anyway. A quick&dirty check on a small laptop screen without any post-processing at all indicated that the IQ might be better with the Canon than with the cheap Vivitar diopter.

---------- Post added December 28th, 2014 at 11:01 PM ----------

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