Blackmagic and tungsten

[dbp]

Is anyone else struggling with Blackmagic cameras in tungsten lighting? I find the pocket looks brilliant in daylight and even florescent, but it's always a struggle to pull something nice out of tungsten.

RAW is usually doable with some work, but Pro Res is even worse. It's been a struggle because a lot of events (weddings etc..) have big parts of the day under tungsten lighting.  

[shijan]

For tungsten use RAW and get 80A filter. The only side effect is that you loose 1 stop of the light with it. Without 80A filter even in RAW you loose a lot of color information, washed and shifted colors if balance back to 5600 white point.

[tupp]

Blackmagic cameras are sensitive to IR, and tungsten sources emit a high percentage of IR.  So, you might want to try an IR cut filter.

[shijan]

if someone still interested, here are two frames from my early tests of BMMCC done with Hoya UV-IR filter+Hoya 80A and with Hoya UV-IR filter only. As light source i used 500W halogen lamp. In Resolve i adjust WB by the grey Color checker patch (third from the left). Color conversion done with custom generated LUT in LUTCalc app (output gamma Alexa-X-2, output gamut LC709). 

To my opinion 80A filter makes some things better but it is not too perfect. It rises color temperature but also adds cyan-green tint to the image which eats saturation in greens when you try to adjust image to netural grey balance. As opposite warm temperature light souse without filter produce very low saturated and noisier yellows for same reason. 

Probably all those color shifts can be corrected with more complicated color correction but this is another story...

[tupp]

10 hours ago, shijan said:

if someone still interested, here are two frames from my early tests of BMMCC done with Hoya UV-IR filter+Hoya 80A and with Hoya UV-IR filter only.

Thanks for doing this test!

 

10 hours ago, shijan said:

As light source i used 500W halogen lamp.

OP is shooting weddings/events, so OP might often encounter incandescent tungsten which starts at less than 3200K (with a higher percentage of IR), and which is likely further dimmed (further increasing the percentage of IR).  I don't know if your 500w halogens are 3200K, but using a full CTB correction (80A) probably helps OP color-wise and IR pollution-wise.

 

However, with a full-CTB/80A filter, brightness will suffer a 1 1/2-stop to 2-stop hit, so it might be better to use a 1/2 CTB (80C?) correction.

[tupp]

11 hours ago, shijan said:

To my opinion 80A filter makes some things better but it is not too perfect. It rises color temperature but also adds cyan-green tint to the image which eats saturation in greens when you try to adjust image to netural grey balance.

Not all 80A filters are created equal.  You might try one from another manufacturer.  Same with CTBs and CTOs (lighting color temp correction gels).  Also, filters can fade with age.

 

Nevertheless, your corrections on the test are well within almost anyone's tolerances.  Good job matching the two images!

 

11 hours ago, shijan said:

As opposite warm temperature light souse without filter produce very low saturated and noisier yellows for same reason.

I don't see a huge problem in your test (yet I do see a slight difference), but If one finds oneself without correction filters and if one is also concerned about slightly noisy channels, one can often overexpose 1/2 stop (depending on the subject/scene).

 

On the other hand, with well-lit sets, I have never encountered noise problems shooting raw with tungsten and only IR cut filters and ETTR.

[shijan]

9 hours ago, tupp said:

Not all 80A filters are created equal.  You might try one from another manufacturer.  Same with CTBs and CTOs (lighting color temp correction gels).  Also, filters can fade with age.

 

Nevertheless, your corrections on the test are well within almost anyone's tolerances.  Good job matching the two images!

 

I don't see a huge problem in your test (yet I do see a slight difference), but If one finds oneself without correction filters and if one is also concerned about slightly noisy channels, one can often overexpose 1/2 stop (depending on the subject/scene).

 

On the other hand, with well-lit sets, I have never encountered noise problems shooting raw with tungsten and only IR cut filters and ETTR.

Yes, maybe there is a reason to experiment with less stronger filters (80B or 80C). Also maybe i do a test with warmer light source closer to 2800K to see how it works.

Beside different saturation I notice only only chroma noise difference in some colors, it can be easy fixed with noise reduction or chroma blur. BTW these test images are with chroma noise reduction applied, thats why the color patches are pretty clear as you can see.

[dbp]

On 2/6/2017 at 0:09 AM, tupp said:

Thanks for doing this test!

 

OP is shooting weddings/events, so OP might often encounter incandescent tungsten which starts at less than 3200K (with a higher percentage of IR), and which is likely further dimmed (further increasing the percentage of IR).  I don't know if your 500w halogens are 3200K, but using a full CTB correction (80A) probably helps OP color-wise and IR pollution-wise.

 

However, with a full-CTB/80A filter, brightness will suffer a 1 1/2-stop to 2-stop hit, so it might be better to use a 1/2 CTB (80C?) correction.

Agreed, thanks for the test. Very interesting. You did a great job with matching, but it's neat to see the subtle differences in hue/saturation for each color.

And yeah, the more I test... the more I realize the issue isn't classic tungsten per se, but the incandescent type that you see, which typically sits in the 2850K range. Dimming increasing IR makes even more sense. It's a worse case scenario for the pocket, but and unfortunate reality for most venues at night. The filter isn't really an option because the pocket already *barely* gathers enough light in these scenarios as it is. 

Just did a similar event with a mix of RAW and prores in the same room. It really surprised me how much easier raw is to deal with. The pro res was bad and nothing I did could really salvage it.

I'll get an IR cut soon and hope for the best. I've been surprised that this issue hasn't come up more, but I guess people aren't using the pocket as an event cam, LOL.  

[tupp]

23 hours ago, dbp said:

The filter isn't really an option because the pocket already *barely* gathers enough light in these scenarios as it is. 

Of course, you could gain over a stop by using a focal reducer or by using the Metabones BMPCC speed booster.

[shijan]

Done some outdoor tests with same 50 mm Yashica lens few days ago. All shot in RAW, but processed with slightly different LUT than images earlier posts (LUT generated in LUTcalc as usual but it is more color netural than all those Amira709, Alexa-X-2 and LC709). As you can see 80A filter produce almost 100% correct colors and can be used as reference.