Soft corners, dome ports and B+W +2 close-up optics

Hi

I've searched for a thread of this but cannot find much. I've read somewhere that using a +2 diopter on a 16-35mm lens will improve corner sharpness but at the cost of infinity.

Does anyone has an opinion on the Schneider Optics B+W +2 Close-up diopter - NL-2 that is available from Backscatter?  I know that they recommend it with wide angle lenses.

The questions I have are what would the difference between the +2 and +4 make?  I shoot with the 16-35mm F4 Sony lens.  What would be the min and max focus distance with either of these options? 

This article has information and a chart but I don't understand what its telling me: https://schneiderkreuznach.com/en/photo-optics/b-w-filters/filtertypes/nd-100-series/close-up

Anyone got any helpful guidance or perhaps a link to thread where this has been covered?

Cheers,

Duncan

Hi Duncan

I can't comment on the Schneider +2 but, in years gone by, I have used a Marumi +2 diopter with the Nikkor 16-35 and both an 8" domeport and then 9" on an FF camera (a Nikon D800)

Edges and corners were hopeless with the 8" with or without the +2 diopter. A 9" dome was significantly better especially when really stopped down. 

It's worth googling the Sea and Sea internal correction lens on the Wetpixel forums as the general consensus seems to be that this makes the most difference with a 16-35 lens on a FF sensor.

I used the  B&W +2 with wide lenses and domes in the past (I can sell you one second-hand!) They improved corner sharpness but reduced angle of view such that I was never sure whether a shot without the dioptre, cropped to the angle of view you get with the dioptre, would have been the same. My experience with the 16-35 behind a 230mm Nauticam glass port suggests you don't need the dioptre. The right extension is essential to get decent corners, somewhere between 70 and 90mm depending which dome you use. (With the +2 dioptre you can still focus on infinity underwater. I suspect the +4 won't focus on infinity underwater.)

If you are unhappy with the corners and you are using a large dome, check the position of the centre of curvature of the dome and the no parallax point of the lens and see if you can get them in the same place, or very close.

If this doesn't solve your issue, try the Sea and Sea correction lens which I haven't tried, but which people who I respect have used successfully. Kogia on Wetpixel for example. A couple of people have second-hand ones available.

Which dome and housing are you using?

There's a lot of old info on using +2 diopters with wide angle lenses online - mostly ancient history from older model wide lenses that don't focus close enough to focus on the virtual image of the dome.  If you can achieve focus with your current setup a diopter won't help you.  All a diopter does is allow you to focus closer than the lens can already focus alone.  The soft corners are a depth of field problem mainly not a close focus problem

The S&S correction is an entirely different type of lens but is only available in 77 and 82mm sizes I believe. 

Some questions on your situation:

• what format (FF or APS-C?)
• what size dome?
• what aperture do you typically use?

all of these have an impact on corner performance.  Similar questions have been asked here before and I can relay those experiences.

Here is a link to the S&S lens

https://www.bluewaterphotostore.com/sea-sea-internal-correction-lens

it allows you to shoot about 2 stops wider than you can without the lens. 

I used that filter (B&W +2 diopter) with my 16-35 behind a 230mm dome port for 4 years.   D810, then D850.   To be honest, I never noticed a difference with the diopter or without, and I was always disappointed with the corners.  I was resigned to cropping off the edges, until I got the Sea and Sea Internal Correction Lens.  HUGE difference.   Won't shoot without it now.  I think I'm using a 90mm extension, by the way.  I've heard the same rig used to be recommended with a 70mm extension.

I'm pretty happy now with the rig.    Had shot a lot with macro, but I'm learning to use wide angle to tell a story.  Or would, once travel is easier again.

Hi Duncan, was your questions answered?   Here's a couple of relevant threads talking about not needing diopters and how the S&S correction lens is a big help.  There are related threads on the Nikon 16-35 as well - same problem they are trying to solve as the SOny lens

View archived post in: Sea and Sea internal Correction Lens

View archived post in: Which Nauticam 9" dome with Sony 16-35gm?

In summary the ideal situation for 16-35 on full frame seems to be a 230mm dome plus S&S correction lens and stopping down adequately - probably f11-16 without the S&S lens closing down 1-2 stops with the lens.

Thanks for the info posted here. I had the sane question only for canon using the 16-35 and a diopter. 

4 hours ago, sharkbytesmatt said:

Thanks for the info posted here. I had the sane question only for canon using the 16-35 and a diopter. 

it's the same situation whether it's Canon, Nikon or Sony full frame with a 16mm or wider lens.

Using closeup lenses like the +2 and +4 is a carry over from the film days when zoom lenses would not focus as close as todays modern lenses will. Many older  zoom lenses would only focus to 18 or 20 inches so they were unable to focus on the virtual image in an eight inch dome port, the standard for those days. The CU lens has nothing to do with corner sharpness only the ability to focus inside the dome port. Closeup lenses only magnify therefore reducing AOV. You can do the same thing by taking a 16-35 zoom and shooting it at 18 or 20mm rather than 16mm which will improve corners sharpness.

The Sea & Sea 77mm and 82mm correction lenses don't magnify they are convcave on the front and convex on the rear to redirect and flatten light in the corners of the frame to improve corners. I have tested the S&S lens with domes from 170mm to 230mm and with a verity of lenses from 14mm to 18mm on the wide end. Regardless of the lens the smaller the port the worse the results just like without the S&S lens. I found that with a 230mm port on full frame at best you gain about two stops of light. Corner sharpness is subjective among photographers in my view just like barrel distortion with fisheye lenses. Some rave about fisheye lenses because of a perceived improvement in corner sharpness while others object to the distorted lines. The more interesting the subject matter the less concern one has for how the corners of the frame look.

The holy grail for both corner sharpness and barrel distortion going forward will continue to be the quality reasearched and developed water contact lenses like Nauticam WWL-1, WACP-1 & 2.