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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Rainbow striping on image

Thanks Bob - I'll try that. I can't remove the OLPF though ( its v2 and fixed and has warranty-void stickers on it - I am not sure if the replaceable system is out there yet). Will definitely let you know when we have a finished film. We've been shooting full time for 2.5 years now and the end is in sight!
 
Bob Gundu said:
I have not witnessed this on my Dragon, but on my friends it happened regardless of lens. We couldn't figure out what or when it would happen.
Click to expand...

Thanks Bob - did the issue ever get resolved?
 
Update:

I've had a brief opportunity to test further and this is what I am finding


1. It only seems to happen with my Optex/Nikon 50-300 PL conv.( I've not seen it with any other PL mounted lens I have : Century 2000 150-600, Tokina 11-16 or Zeiss superspeeds). I plan to test other Nikon lenses.
2. It seems to happen with whichever circular polariser I use on the lens - Hasselblad, Formatt, B+W.
3. I've used that lens / polariser combination a lot before with the MX sensor and never seen it.


So my thinking is that it seems to be something to do with that particular lens ( or its universal mount) and polarised light, interacting with the v2 OLPF and / or the photosite pitch of the Dragon sensor.
 
Does it show up on that particular lens without the POLA?

Battistella
 
Great to know you've pinned it down to lens/pola combo. I am upgrading to Dragon in couple months and always keen to see what everyone's experience is in order to troubleshoot things quickly if something odd shows up. Keep us posted if you find any other variables!
 
So - it continues...

Although I tried to recreate the conditions with other PL mount lenses and circ. polarisers in camp and couldn't, I took the camera out yesterday in exactly the same conditions and the diffuse vertical striping reappeared.
This time it was 6K, v2 OLPF, very bright ( think equator, midday, white dust /desert conditions) - all these were the same as before. The lens and polariser were different though - this time a PL mounted Tokina with a Formatt circular polariser. I had the same problem with diffuse rainbow banding ( most obvious was green and magenta) over the entire image. It wasn't as strong as with the 50-300 + pola but still obviously there.
I can only think that the circular polariser is somehow interacting with the OLPF or sensor to produce the striping.
 
Mark. One more oddball theory to throw you off your game. I guess it is unlilkely where you are but do you have any ND gel, even if it is lighting gel. If not, can you ND with mattbox filters, the lenses to a wider aperture, say f4 - f5.6. My notion is to put a piece of ND gel in the space behind the lens. If you do't have any gel, any old piece of shirt packet clear stiff plastic mayl make do for part of my theory relating to reflection and a secondary polarisation of reflected light which might be happening at the sensor.

Direct image from the lens passes to the sensor once. Reflected light between the sensor/OPLF and the rear of the lens or maybe a planar element within it has to make multiple passes, therefore should be attenuated if there is an ND between lens and sensor. Also, a piece of gel is not going to be a true planar surface so might also furthur disrupt any reflection going on.

My theory is on polarised light becoming furthur polarised by the sensor's individual pixels maybe while reflected forward and then projected back onto the sensor in the reflection as an enlarged or shrunken image consisting of the pixel grid pattern but with the rows per inch or milllemetre being of a different pitch.

It might not even need be in focus. Therefore, a moire artifact may be produced that an OLPF cannot deal with.

Attenuating the reflected light in the space between lens and sensor with a piece of gel plus disrupting the reflection path with two more non-planar surfaces of the gel, might make things look different enough to identify it as an internal reflection issue created by a polariser.

Is the light coming out of the rear of a long lens arriving at the sensor across its width with less angle of incidence. My imagining is that reflections off the sensor and returns to the sensor would be at lesser angles of incidence than with a wider-angle lens, therefore a reflected image of the sensor pattern itself may much closer to true scale, close enough for a moire effect to be generated.

I hope I am not sending you off on a goose chase.

Do you have hard skies over there this time of year and using the polariser to bring back some colour. I imagine you would need ND18 to get lenses down to f4-5.6 if your skies are like our Pilbara summers, sometimes almost white to about 30 degrees above the horizon.
 
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Rainbow streaking. We had the same problem in April with a Dragon. Red team were so patient and great coaching. They went back and forth, upside down, finally replaced the sensor even! Never, ever had this much support from a camera company in 30 some years!!!!
Bottom line, I put the darn Nikon circular polarizer on again and back it came. Primarily in the 18% grey / color tones! I have since switched to a linear polarizer: http://www.edmundoptics.com/optics/...ers/high-contrast-linear-polarizing-film/3435

I might add that for a feature film we are finishing, we used Davinci Resolve 11 color to diffuse the magenta streaking in order to obtain a 98% good clip color for these clips. A mask was produced to the four areas that were common place.

Hope this helps!

http://www.reduser.net/forum/showthread.php?116094-Dragon-is-a-field-of-Wild-Flowers!

Kennan & Karen Ward

COMING SOON, IT'S A WILD LIFE FEATURE FILM 88 MINUTES 4K 2.39 CINEMA!
 

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Thanks Bob - unfortunately we have none of that with us (just two of us in a fly camp at present) but I'll try and test when we get back to base. Both lenses show the same 3-4 vertical colour sequences - one a telephoto zoom (50-300), the other a wide angle zoom (11-16). Magenta seems to be the most noticeable, but I think the rest are there if I over-saturate, and pull down the exposure.


Keenan - thanks for all the info . I see the same artefact on your third image - much more subtle than we've been getting but the same striping, nonetheless. It is something I never saw with the MX sensor using the same lenses and filters, which makes me think it is either the new OLPF or higher pixel density or some other aspect of the dragon sensor.
Good luck with the feature, please post here when it's done. We are 2.5 years into shooting a wildlife feature on elephants...not quite there yet!
 
Mark,

Good luck with the new film and story! Karen and I know you will have a great film when you are finished! Thank you for keeping Elephants and nature in the hearts of everyone!

Finishing a six year feature film is kind of a transition, we would rather be back in the field creating instead of marketing. Hopefully Sundance will help us get the word out. We will post a teaser soon. Pm us when up for air, literally !

Best, Kennan
 
Mark, were you able to solve the problem? I'm having the exact same thing happen to me.
 
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