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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 :)

Purple Blacks IR in Forrest

Martin Preiss

Martin Preiss

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I know this was already posted here, that you need ND filters with Hot Mirror IR Pass filter. But my situation is different. I have purple black without any NDs infront of lens. Default setting on camera and default settings of everything.

I think that the leaves of forrest are acting as ND filters, cos chlorophyll in leaves working as stopper of visible light and producer of IR (there is photosynthesis in progress in trees, so they will produce some small heat, crazy idea I know but like it ... :bleh: ) but more probably they letting most of the warm light (IR) pass through as they using the visible light and UV.

So need the IR pass filter all the time. Should be packaged with every camera :shifty:
(unfortunately there is not many, if some, in Europe.)

First picture is camera 4K to 2K in RedAlert, at the picture is our sound guy in his black shirt...NO ND at camera! Interesting about the dyes of fabric is that his baseball cap remains black!

Second is director Karel Janak as seen by my Canon Ixus (top) and photo of HD display from camera (bottom)

Third picture shows what histogram looks like, where there is no lens and the RED cap is covering the PL mount. Why there is a peak in histogram when there is no light at all falling at chip?
 
Ed Blythe said:
Freaky.

Did you do a black balance?
Click to expand...

Yes with every camera update.

About the peak...maybe I understand that all the information are in black...and maybe i'm stupid I asked :clown2:
 
I have the same histogram peak in my lens cap/cavity cap covered B16.

Interesting enough it changes with the meta data.

So if I crank it up to 2000asa the curve, hill, meat (what ever you wish to call) of the histogram grows with it.

It seems as if it is catching the noise and showing it.
 
Frzendreams said:
I have the same histogram peak in my lens cap/cavity cap covered B16.

Interesting enough it changes with the meta data.

So if I crank it up to 2000asa the curve, hill, meat (what ever you wish to call) of the histogram grows with it.

It seems as if it is catching the noise and showing it.
Click to expand...

we need a little Nattress wisdom here ...
 
Biba said:
No lenses on test picture .
Click to expand...

He means lenses for the purple issue. Well don't remember if on our Canon 300mm was the same as on our two sets of Zeiss Utra HiSpeed Lenses...and that's not bad lens...and it's not changing with t-stop...if there will be error in coating of lens it will significantly change with T-Stop...

Will try tmrw but i think will be same on all lenses...
 
issic said:
He means lenses for the purple issue. Well don't remember if on our Canon 300mm was the same as on our two sets of Zeiss Utra HiSpeed Lenses...and that's not bad lens...and it's not changing with t-stop...if there will be error in coating of lens it will significantly change with T-Stop...

Will try tmrw but i think will be same on all lenses...
Click to expand...

We had problem with MP 37mm in one scene with white background and one actor. We had purple circle in the middle - maybe some strange kind of flare. Circle size was dependend on f-stop.

RED 18-50 helped us and worked fine.
 
Laco Zamba said:
We had problem with MP 37mm in one scene with white background and one actor. We had purple circle in the middle - maybe some strange kind of flare. Circle size was dependend on f-stop.

RED 18-50 helped us and worked fine.
Click to expand...


If you had a purple circle in the middle of the white it sounds more like the "black sun" issue.
 
Purple is the "NEW" black!

Get with the times guys.
 
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