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OM-D EM-5 Nauticam with 9-18 zuiko?


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#21 Storker

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Posted 18 February 2014 - 02:50 PM

Even with the +4 diopter, I was able to focus at infinity, however I lost some AOV due to the distortion correction. The third image is a composite of 1:1 crops of the center section of some distance shots, at f/4. From the top: +0, +2 and +4 diopters.



The fourth image is a downscaled composite of the full distance shots. From the top: +0, +2 and +4 diopters.

 

 

Attached Images

  • 20140218_9mm center.jpg
  • 20140218_9mm all scaled.jpg

Edited by Storker, 18 February 2014 - 02:49 PM.


#22 Storker

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Posted 18 February 2014 - 02:56 PM

Conclusion: I'm going to use the +2 diopter in the future when I'm using my 9-18mm behind the 4" dome port. The loss of AOV is rather negligible, and the improvement in corner sharpness is dramatic. While even f/11 gives noticeably poorer corner sharpness without diopter, the +2 diopter gives acceptable corner sharpness already at f/5.6 and pretty good at f/8. The distortion - and the CA - caused by the cheap closeup diopters can be handled quite acceptably by Lightroom.



#23 coroander

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Posted 18 February 2014 - 06:19 PM

Fantastic work!! I've always held off getting the 9-18mm and the 4" port because the corners were just too soft. That you can use a +2 diopter to sort this out is fantastic and the improvement is dramatic. Many thanks!



#24 Storker

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Posted 18 February 2014 - 10:44 PM

You're welcome.

 

It was a bit of an eye-opener for me, too. Just note that:

 

  1. I was using ordinary topside closeup lenses, not wet lenses.
  2. The overall quality of the pictures is rather crappy. Due to low light, I shot at ISO2500-3200, with shutter speeds of 1/30-1/10. The excellent stabilizing system of the E-M5 handled the low shutter speeds quite well, but some general softness due to high-ISO noise and slow shutter speeds is unavoidable. I didn't apply any noise reduction or sharpening except Lightroom's standard settings.

 

 

I'd like to know why the diopters improve corner sharpness. Are the edges of the virtual image too close to the lens, so the camera can't focus properly, or is there some other reason that I don't understand?

 

 

On a lighter note, it was an interesting experience. I brought some weights to help me keep under while shooting, but 8lbs wasn't enough to sink me with full lungs. The only way I was able to stay stationary at the bottom was by exhaling as I went under. It's quite interesting to lie still on the pool floor with empty lungs; the breath-holding experience is rather different from free-diving with full lungs...


Edited by Storker, 18 February 2014 - 10:47 PM.


#25 oskar

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Posted 19 February 2014 - 12:21 AM

Greit experiment!
 
So your conclusion is to always use the +2, right?  Part from the added distorsion, what are the drawbacks of the diopters?
 
 
What is the actual subject distance by the way?
 
How does the distortion look change with the diopters, more barrel-like?
 
 
Cheers
/O


#26 nudibranco

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Posted 19 February 2014 - 02:08 AM

Great results Storker!  I bought the diopters as well a few months ago but never went into the water to try them.  As soon as I can I will try with the 4.33" and 3.5" domes as well.   The results look good.  There has been an ongoing complaint for more than a year about softness on the edges with the 9-18mm lens open and the diopters do seem to solve the issue then.

 

+2 diopters does not even change FOV that much either it seems so it may be the optimal value.  I saw the +4 was not bad either and that may be a choice if you want a closer focus. The 18mm focal setting may  even allow getting some decent close ups (I never liked the fact that the 9-18mm does not have close focusing capability).

 

THANKS!



#27 Storker

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Posted 19 February 2014 - 02:12 AM

So your conclusion is to always use the +2, right?

 

Yep, at least for the time being and until I gather additional data on the subject.

 

 

 

Part from the added distorsion, what are the drawbacks of the diopters?

 

I think I saw some added CA, but it was quite manageable in Lightroom and could be almost completely removed. On a normal underwater subject, I doubt if it's very noticeable. And, of course, an extra layer of glass will decrease optimal sharpness and increase the risk of flare. However, with the much better corner sharpness, I'm willing to accept that tradeoff.

 

 

 

What is the actual subject distance by the way?

 

Somewhere around half a meter, maybe a little less. Just enough to fill the frame with an A3 size sheet at 9mm FL.

 

 

 

How does the distortion look change with the diopters, more barrel-like?

 

Pincushion. Very noticeable if the subject has straight lines close to the edges of the frame. For that kind of subjects, you need some correction, but as I said in one of the previous posts, LR (or PS/ACR or PSE) can handle it easily.

 



I bought the diopters as well a few months ago but never went into the water to try them.  As soon as I can I will try with the 4.33" and 3.5" domes as well.


Please do. I'll be looking forward to the results!



#28 nudibranco

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Posted 19 February 2014 - 02:15 AM

BTW I also noticed in my limited experience that correcting in SW for typical underwater pincushion distortion on the rectilinear lenses will improve the softness on the edges dramatically...



#29 chris_l

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Posted 19 February 2014 - 06:19 AM

This is the nauticam 4" dome correct?

 

I wonder if this translates to the the Zen WA-100 dome for the olympus PEN housings:

http://www.zenunderw...ts.php?prodID=5



#30 coroander

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Posted 19 February 2014 - 11:25 AM

The soft corners are because the curved virtual image that we are photographing has the corners much closer to the sensor than the centre. We rely on depth of field for the corners to be in focus (but it's often just not enough). I think that the diopters work by causing the image to appear further away to the camera (the camera focus changes from say 0.4m to 0.8m). This, of course, also allows you to get much closer to your subject because the minimum focus distance is now much closer than where the camera thinks it's focusing. By making the virtual image appear further away, the focus distance is also at a place where depth of field is greater and the corners can now be sharper. That's my take on it, i've never read why this works, but this seems reasonable.


Edited by coroander, 19 February 2014 - 11:43 AM.


#31 oskar

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Posted 21 February 2014 - 04:48 AM

Yes, + 1 on that it would be very interesting to see how the works with the 4.33" (+ some extensions)

 

Another useful piece of information would be to get the optical dimensions of the 4" port, as compared to the others.  

 

I suppose length from port mount to dome top would be useful for comparison. And dome radius. However I've heard that the 4.33",3.5" and 4" ports all have the same dome radius but I don't know if that is correct.

 

Great results Storker!  I bought the diopters as well a few months ago but never went into the water to try them.  As soon as I can I will try with the 4.33" and 3.5" domes as well.   



#32 nudibranco

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Posted 21 February 2014 - 05:46 AM

The 4" semi-dome certainly looks like a larger radius...



#33 breathless

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Posted 22 February 2014 - 06:09 AM

Long time lurker, first time poster. Inspired by the excellent work of Storker I tried the same trick with my setup - EM-5 in the Oly housing with Zen dome and adapter. Shots run through LR, tone adjusted with auto (sun kept moving behind clouds) and a quick distortion correction for the +2 and +4 diopters. I also shot freehand with the chart stuck to a pool wall so the same caveats around accuracy apply, however I think you'll agree the differences aren't subtle at the 9 mm end (corner crops):

slice.jpg

The +4 diopter didn't gain much on stopping down, the +2 caught up with +4/ f5.6 at around f10. The CA cleans up in LR nicely even on the +4, the diopters were cheap close up lenses I brought about 10 years ago so it may be nicer with more expensive glass (or maybe not). The corners were much nicer at the 18 mm end for all settings.



#34 Storker

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Posted 23 February 2014 - 10:44 PM

Good work, breathless!

 

I had my first real-life test of the +2 diopter inside the 4" Nauticam dome port yesterday, and those results pretty much confirm what my rather dull pool shots of a res chart told us (click image for larger version):

 

 

 

9mm @ f/5.6, 1/60 sec, ISO400, 4m depth:

12729486525_33e8977c91_n.jpg

 

 

 

18mm @ f/5.6, 1/20 sec, ISO400, 3.5m depth:

12729657653_659ab6d727_n.jpg


Edited by Storker, 23 February 2014 - 11:38 PM.


#35 nudibranco

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Posted 04 March 2014 - 01:49 PM

I quickly tried the 3.5" and 4.33" domes with a 30mm extension on the EM-5 and the 9-18mm and a good +4 topside diopter.

I did not upload the pictures but the findings:

- the 3.5" dome just sits too close (maybe a mm) from the lens and diopter.  The result is just unacceptable unless you close to F11 or so.

- the 4.33" dome is acceptable once you correct for distortions (both chromatic and focal). Good results at f8.  

However the 4" semidome still behaves better and for some reason it can focus much closer (like 20% or 25% better magnification). Good even wide open!

 

Maybe with 2 20mm extensions make the 4.33 worthwhile but at this point I do not see a reason to use the 3.5" or 4.33" domes with the 9-18mm.

The trials have shown that at least a +2 diopter will make the 9-18mm lens work well in the 4" semidome.  I wished I had known before as I have used this lens underwater very seldom....!

 

This port can now be used with good results for the 9-18mm, 60mm macro, and 12-50mm lenses.  A DIY macro adapter or the expensive flip holder would make it even more versatile.  I am thinking the 12-50mm in this port with the new SMC nauticam macro lens would probably be better than the same lens in the super expensive flat port offered by Nauticam  to use the lens macro function.  I never liked much the 12mm focal length behind a flat port and with an equivalent expensive 4" port and SMC macrolens you could get real macro and reasonable wide angle with this port.  

Has anybody tried the 12-50 with the powerful SMC lens?



#36 Alex_Tattersall

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Posted 04 March 2014 - 02:31 PM

Yes, my friend Doug did well with the SMC on the 12-50mm in uncropped splendour

 

11309183844_412d421225_z.jpg

 

11309113025_218daee4c6_z.jpg


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#37 oskar

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Posted 06 March 2014 - 04:10 AM

Ok thanks, as you seem to have found out the nodal points of the domes must be corrected with extensions to coincide with the lens' nodal point otherwise the results will always be bad.

 

So there could be hope for the 4.33" maybe?  Anyone that have a couple of 20mm extensions lying around to test?

 

Edit: could i ask you to measure the 4" port length from base to, say inside top of dome?   

 

I quickly tried the 3.5" and 4.33" domes with a 30mm extension on the EM-5 and the 9-18mm and a good +4 topside diopter.

I did not upload the pictures but the findings:

- the 3.5" dome just sits too close (maybe a mm) from the lens and diopter.  The result is just unacceptable unless you close to F11 or so.

- the 4.33" dome is acceptable once you correct for distortions (both chromatic and focal). Good results at f8.  

However the 4" semidome still behaves better and for some reason it can focus much closer (like 20% or 25% better magnification). Good even wide open!

 

Maybe with 2 20mm extensions make the 4.33 worthwhile but at this point I do not see a reason to use the 3.5" or 4.33" domes with the 9-18mm.

The trials have shown that at least a +2 diopter will make the 9-18mm lens work well in the 4" semidome.  I wished I had known before as I have used this lens underwater very seldom....!


Edited by oskar, 06 March 2014 - 04:12 AM.


#38 coroander

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Posted 06 March 2014 - 03:11 PM

Thanks nudibranco for trying out the 9-18mm in the 3.5 and 4.33" domes. These have much tighter optical radiuses and so results will never be near as good as with the 4" semi-dome.

 

Keep meaning to ask, nudibranco, if you could post results with the 8mm FE inside the 3.5" and 4.33" domes, particularly with regard to corner sharpness. I find that below f/8 with the 8mm FE in the 4.33" dome, that the corners get soft quite quickly. I'm wondering how the corner sharpness holds up with the 3.5" compared to the 4.33"??? Easiest to use the corner of the pool and use the tiles or place targets on two walls since the 8mm FE is so wide.



#39 Storker

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Posted 07 March 2014 - 09:41 AM

I find that below f/8 with the 8mm FE in the 4.33" dome, that the corners get soft quite quickly.


I know this is a bit OT, but would you mind expanding a bit on this? I'm considering the transition from rectilinear to FE, and I'm wondering if I should go for the 4.33" or the 3.5" dome


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#40 coroander

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Posted 07 March 2014 - 11:12 AM

Panasonic 8mm FE behind Nauticam 4.33" dome centre 100% crop at f/3.5:

8mmFE-4.33-centre-1.jpg

 

And the corners (100% crop, click image for full-size); note that the corner target was about equal distance from the camera as the centre (focus) target:

8mmFE-4.33-corners.jpg


Edited by coroander, 07 March 2014 - 11:22 AM.