GH2 Strange Color Grading of Sky - see video

I

iflight

Active member
http://vimeo.com/20286076

This was filmed in Creative Movie mode, on the P (ie auto) exposure setting, with 14-140mm HD lens, 1080, 24p- HQ, ISO 160.

Notice the strange color bands in the sky - this is greatly exaggerated with my ND filter.
 (this video is without any filters)

What's more, everything looks great in the EVF untill i hit record...then I see the same problem in the EVF. I've tried serveral different film modes (ie. cinema, standard, ets), but it's the same thing.

Anyone else getting this?
What could it be?
Thanks.
 
Here's another example of the effect, this time with my ND filter on - the effect is more pronounced. http://vimeo.com/20283513.

Again, this is not caused by the ND filter, it just seems to be exaggerating something that happens without the filter as well.
 
Vari ND filters are basically polarizing filters. Buy a 2 stop and 3 stop true ND filter and you wont have that problem.
 
iflight said:
The first video was without any filtration - why is this happening without a filter?
Click to expand...

I believe that this is because the encoding is 8 bit. There is not enough room to store information such as gradients like these.
 
That is strange- I haven't seen noticeable banding like that before- can you try another lens and see if you get the same result?
 
The two videos on this thread were shot with two diff lenses: 1) vid @ top of page with 14-140mm (no filter)and 2) vid in 2nd post was with with 50mm FD + Vari ND (CPL + LPL)
 
sorry- missed that one- This looks quite odd. I havent been able to get such a strong effect on the gh2- It reminds me of doing an 8-bit to 8-bit recompression.
Just a whim, try other settings (M) and various picture profiles- Maybe even a factory reset & pixel refresh.
 
hunter richards said:
sorry- missed that one- This looks quite odd. I havent been able to get such a strong effect on the gh2- It reminds me of doing an 8-bit to 8-bit recompression.
Just a whim, try other settings (M) and various picture profiles- Maybe even a factory reset & pixel refresh.
Click to expand...

OK. Just to be clear - I see this in the EVF - when not recording, everything is clear. as soon as i hit REC, the effect shows up in the EVF as well. Does that say something about what's happening as well??
 
Total guess!
but how did you get the over all image darker, did you stop down or increase the shutter speed?
For some reason I feel stopping down instead of having a high shutter may help prevent this...

don't know why... probably wont help but maybe worth a try.

jc
 
iflight said:
The two videos on this thread were shot with two diff lenses: 1) vid @ top of page with 14-140mm (no filter)and 2) vid in 2nd post was with with 50mm FD + Vari ND (CPL + LPL)
Click to expand...

Without other information, I'd agree that the banding is due to codec 'squeezing' too much out of the data, and representing it as 8 bits. You will see this on your flatscreen display as well, if the media is so compressed, or the screen 'bit depth' is less than 10-12 bits per R, G, B.

This is most noticable in smooth, or 'gentle' gradients, such as the transition between blues to light blues in sky. (As a note you can also see dust on the sensor under these conditions as well). Whereas on image that has lots of detail, etc. both gradient problems and dust almost 'vanish'...

Looked at the second clip. I'd still think the effect is due to compression artifacts. But I think the ND filter unfortunately accentuates the effect by placing the values of the pixels in a more 'obvious' range.
 
Last edited:
You must log in or register to reply here.
Back
Top