Kenko 1.4xTC + Nikkor 8-15mm Intermittent Dark Images

Hi,

Has anyone run experienced intermittent dark images, like 4-stops dark, when using the Kenko Pro300 DGX 1.4x with a Nikon 8-15mm fisheye on a D850?

Some background, the the intermittent dark image never occur on land, only underwater (Nauticam housing) and only with the 1.4xTC. I have tired two copies of the TC, and both act the same. The dark images metadata reports a 7mm lens and two stops brighter. For example, with the same camera settings for two images taken in succession: dark image is f/9.0 and 7mm; normal image is f/11 and 20mm.  (20mm is with 1.4x on, of course, and the camera reports the lens correctly to be 8-15 f/3.5-4.5 in either case). The intermittent issue occurs every dive, more frequently near the beginning, and, of course whenever the shot requires lengthy setup and much waiting for the fish to be preciously in best position!  

TIA for any feedback, Mike

Just to clarify you have shot the 8-15 outside the housing with the 1.4x attached and it doesn't produce the dark images?  Have you tried shooting on land with the camera sealed in the housing?  Are you always at the same zoom setting, is the ISO and shutter speed the same in Metadata?

Something electronic would have to be the cause you would think.  If you are shooting at f11, the lens probably only stops down to f22 which is only two stops darker.  Are you on manual flash?  TTL? or ambient light only?  Changing some of those variables might narrow down the potential cause.  The Metadata gives a clue that data communication might be an issue - but why do you have errors only when diving?

Hi Chris,

No issues on land, in or out of housing with this setup.  

Yes, same zoom setting, and metadata for ISO and shutter speed same between normal and dark images. 

I judged darkening by matching normal and dark image in Lightroom with the exposure adjustment. 

Always manual flash, no TTL. For the few times without strobes at depth, I don’t recall if there was an issue. 

Mike
 

I’ve seen this quite often. It is an intermittent communication issue - caused by the connectors through the TC. I’ve not found a solution, other than using a different combination of body, TC and lens (the TC being the easiest to change). Alex

Glad to hear I’m not the only one!  Thanks, Alex, and it sounds like I should source a 3rd TC from your experience. 

As an aside, I am still undecided on whether one gets better results using a 1.4 Kenko with an 8-15 or 10-17, or just cropping the image later.

1 hour ago, Draq said:

As an aside, I am still undecided on whether one gets better results using a 1.4 Kenko with an 8-15 or 10-17, or just cropping the image later.

With a D500 I don’t think you can see a great difference in image quality between the 8-15 and 10-17 plus Kenko. I’ve tried/used both. 
 
I’m not sure cropping will give you quite the same perspective.

I don’t have experience with the 10-17, but find myself often cropping the 15mm to get a bit closer. The 8-15 with 1.4x is perfect, plus small dome for travel. 

Although i never really noticed any issues, Kenko warns that  "Proper work and accuracy of AF mode only when the lens has a resulting aperture of f/5.6 or faster. If the resulting aperture is greater than f/5.6 manual focus is strongly recommended.

I use autofocus, and never use 5.6 or larger, so apparently, I am living dangerously when I have the 1.4 TC on..

4 minutes ago, Draq said:

I am living dangerously when I have the 1.4 TC on.

If you're not living on The Edge, Draq, you're taking up too much room..... Be Bold 

Can't say I have ever noticed a problem. 

10 hours ago, mchiado said:

Hi Chris,

No issues on land, in or out of housing with this setup.  

Yes, same zoom setting, and metadata for ISO and shutter speed same between normal and dark images. 

I judged darkening by matching normal and dark image in Lightroom with the exposure adjustment. 

Always manual flash, no TTL. For the few times without strobes at depth, I don’t recall if there was an issue. 

Mike
 

Sounds very strange that it happens underwater only.  If it's a communication issue I'm wondering if the zoom gear places a strain on the lens/TC connection as that should be the only real difference between inside and outside of the housing.  I'm wondering if giggling the zoom knob or zooming to desired point then backing off a little might help.  Only speculation but may be worth trying. 

1 hour ago, ChrisRoss said:

Sounds very strange that it happens underwater only.  If it's a communication issue I'm wondering if the zoom gear places a strain on the lens/TC connection as that should be the only real difference between inside and outside of the housing.  I'm wondering if giggling the zoom knob or zooming to desired point then backing off a little might help.  Only speculation but may be worth trying. 

Interesting thought, Chris, or even using without zoom ring for testing. I will try next trip (April). I also ordered a 3rd TC. Since I now have multiple TCs I’m going to disassemble one for any insights. 

3 minutes ago, mchiado said:

Interesting thought, Chris, or even using without zoom ring for testing. I will try next trip (April). I also ordered a 3rd TC. Since I now have multiple TCs I’m going to disassemble one for any insights. 

Yeah, I can't see how just being enclosed in a box causes the issue.  It might be worth fiddling with the zoom gear to see if it's possible to cause the problem on land - you might be able to adjust the fit a little bit to compensate.  You could do this with dome off perhaps to see what is going on.

1 hour ago, ChrisRoss said:

Yeah, I can't see how just being enclosed in a box causes the issue.  It might be worth fiddling with the zoom gear to see if it's possible to cause the problem on land - you might be able to adjust the fit a little bit to compensate.  You could do this with dome off perhaps to see what is going on.

Yes, good advice, thanks Chris.