Exposure for night scene on Ursa Mini 4.6k

Hi there,

I’m planning to shoot a short film with a borrowed Blackmagic Ursa Mini 4.6k. This will be my first time shooting with a real cinema camera as I own the GH4.

I have a question on exposure, forgive me if it’s terribly basic. Most of the advice I’ve seen online involves setting zebras to 85% and exposing until the zebras appear then backing off a bit (only allowing them on headlights, chrome etc...).

How would this relate to a night time scene were I want it a bit dark and moody? On my GH4 I’d just use the built in exposure metre and know that I can be underexposed by 1 or 2 stops as long as the ISO isn’t too high. How would this work with the URSA?

I got a few minutes to play with the camera last night and just did a very quick test. However, I just ended up judging the exposure by eye to try and get the look I wanted. I’ve attached a screenshot of the end result. I’ve not really done a lot to the footage, I just applied FilmConvert. To me it doesn’t look too noisy but I’m sure you guys will have a much better method for judging exposure on night scenes.

I’ll be shooting UHD ProRes (rather than RAW).

Thanks in advance.

Matt

My first recommendation is to drop the zebra idea and start using false color. Generally you want to maintain a consistent exposure throughout a scene, and avoid the exposure roller coaster. Match skin tones throughout the scene, and your noise characteristics will match, and your grading will be a lot easier.

(There are those who disagree. In general, they're simply wrong, according to what the ASC cinematographers recommend, and they're in the ASC for a reason. I say in general because there are times when you simply don't have any option OTHER than to use ETTR to get an image, but that should be an exception and not a rule.)

For a night scene you should go for a bit brighter than your target, and pull the exposure down in in post. If the scene exposure is consistent, then that's VERY easy to do, and takes just a few seconds to dial in for the entire scene at once.

The most common newbie mistake is to make the scene dark, which has the effect of making the scene dark. Usually, the newbie then ends up raising the exposure to attempt to make the scene read like a film scene, which is to say to enable the viewer to see the actors' expressions, and the result usually ends up being to throw their hands up in the air and complain that their camera wasn't an Alexa or Epic, so don't go down that road, because it wasn't the camera's fault (duh).

Instead, light your actors, aim for fairly significant shadow to highlight ratios (this is one area where false color is enormously helpful). If you have lots of deep shadow in the scene, you can light your actors enough for the audience to see their expressions and still have a feeling of a dark scene.

I hope that helps!

Matthew, you may have read my earlier posts describing my use of 85% zebras. My camera is now set to 90% zebras but I rarely use zebras. As Rakesh mentions, false colour is your best friend. With BMD's implementation of false colour, pink is pretty on light skin, green is gold on dark skin ("middle grey"), and the medium grey between those colours may best suit skin tones between light and dark. There is some latitude to vary exposure there, but try to record with those values in mind and adjust exposure in post to suit the look you need.


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Hi Rick and Rakesh,

Thanks very much for the info, it's been a great help. I'll look to use false colour to get the correct exposure and adjust in post.

Thanks,
Matt

Use Rick's guidance for the right colors to look for on skin tones as a starting point; the colors are mapped differently on my camera. It's different on every field monitor also.

If you're planning on dropping the exposure in post, it might be a good idea to overexpose skin tones a little bit (a stop or two, ping Frank Glencairn for better guidance on this, he knows the UM 4.6K a lot better than I do), the most important thing being consistency. Figure out what exposure you need, e.g. where the brights of skin tone will be, and be consistent at keeping that one tone exposed the same way throughout the scene. The rest of the tones will be relative to that one; shadows 1, 2, 4 (for a night scene, probably 3 or 4) stops darker than the reference tone.

Good point, Rakesh. On my shoot yesterday I tried to follow roughly that technique so that my highlights were a very light grey and the shadows were sometimes pink but often light grey. I say roughly because I was shooting day exterior and the sun was a factor as the light levels changed up and down. It does make post a little less obvious to get the colour I want but I haven't got to that stage yet.


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Thanks Rick... that's exactly why I've been following your threads about NDs... I'm going to have to get a set at some point in order to accomplish the transition from a big mattebox (the Letus that I posted here) to a tiny portable one (the Bright Tangerine on that I ended up buying because of you ).

Changing light levels can certainly make things a drag. Having NDs on hand and paying attention to the false color saved me a lot of post work on some films I've worked on outdoors. I'll be temporarily without NDs once I sell my Letus filter kit, but I'll get another set; I'm going to trade off the vari-ND function for a significantly smaller kit. That I'll be able to use with my wino kit. (WineCountryCamera filter holder kit). With any luck I'll be able to sell my Zeiss CP.2s and get some Sigma Art lenses (smaller) and a follow focus kit, then as I build revenue again, start saving for Cooke and/or SLR Magic lenses down the road.

All good advice. If you are going to shoot 1-2 stops over (which I would recommend if you seek really clean shadows on the 4.6K), set up a test scene and then run some shots from neutral to a 4 stops overexposed. Find the exposure you prefer and note exactly where the shadows, skin tones and highlights fall on false color to use that as a reference to expose on set. Using a shot captured at your preferred exposure, grade it in Resolve for the look you want and export a LUT to load onto the Ursa Mini. That way, even without having to check false color, you can get a decent sense of how the shot will look in post on the camera LCD. Or, even better, if you have a color accurate calibrated external monitor, you can see on set exactly how the shot will look in post.

Thanks Rick... that's exactly why I've been following your threads about NDs... I'm going to have to get a set at some point in order to accomplish the transition from a big mattebox (the Letus that I posted here) to a tiny portable one (the Bright Tangerine on that I ended up buying because of you )... and get some Sigma Art lenses (smaller) and a follow focus kit, then as I build revenue again, start saving for Cooke and/or SLR Magic lenses down the road.

All good, Rakesh. I had just committed earlier today to order a full set of NiSi Nano 4x5.65" 4mm IRND filters tomorrow (statutory holiday here today)! So if you like, you can test them out when you come to Victoria for a visit. ND 0.3 through ND 2.1 apparently with virtually no colour cast according to Ketch Rossi (REDuser forum).

Remember these NiSi Nano filters are not IR Cut, they attenuate visible and infrared wavelengths equally. I'll still use them with the SLR Magic Image Enhancer Pro to reduce IR pollution. Still haven't been able to schedule another infrared test along with the SLR Magic APO prime comparisons, but now I want to wait until I have the NiSi filters here.


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The DSMC2 filter packs have IR cut, so I don't plan on getting IR/NDs. Plus I plan on eventually getting an IR filter pack for the camera so that I can actually capture IR images with it, so IR cut NDs would be counter productive for that.

I'm hoping that I can pay a visit to Victoria in spring, and also to Vancouver. Partly just to visit, and partly to look for a place to move to...

Congrats Rick on your new filters. They work grat, tested one of the two I have and compared it to the Lee Pro Glass filter, the results are not in yet, but on the PixE monitor they looked close. No added color cast that I could see. But need to put them up,on the computer for a real evaluation.
Cheers

Thanks, Denny, I'd like to see your results.


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Rakesh, looking forward to seeing you in Victoria! We have company next week, but most of the spring I'll be here. Private message me when you have some possible dates. I can put you up here if you like if you can cope with the four females that run this place!


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Rick, do you use Drop Box? I could send you the files, they are very short takes, like 15-30 sec. each.
Cheers

Thanks, Denny, I'd like to see your results.
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Yes, I use Dropbox.


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Rakesh, looking forward to seeing you in Victoria! We have company next week, but most of the spring I'll be here. Private message me when you have some possible dates. I can put you up here if you like if you can cope with the four females that run this place!

Will do!

If ever you had met my possessive furry princess, you wouldn't be worried about that

OK, will see if I can get it loaded up.
Cheers

Yes, I use Dropbox.
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There's no princess quite as 'entitled' as a furry princess! Sorry I won't be meeting her.


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Hi,

Just wanted to say thanks again to everyone for all the great advice on this.

Matthew

Hi,

I’m going to shoot some more tests. One quick question, how do you tell on the URSA the number of stops under or over you are? On DSLRs and mirrorless there is a meter that shows you whether you’re at zero or a certain number of stops over or under but I don’t see this on the URSA, unless I’m missing something.

I think I understand about using false color to expose skin correctly but a few people mentioned being x number of stops under or over so I presumed there was some kind of built in light meter but I can only see the histogram, zebras and false color.

Thanks, and sorry for all the questions.

Matt

Matthew, not sure if this will satisfy you, but easy enough when using false colour. Let's assume you have the pink colour on a light-skinned face and you are exposed using ND 1.5 for example. Switching to ND 1.2 will then make you expose a stop over. Or easier if it works for you: properly exposed pink at T5.6, so adjust the iris to T4 to be a stop over.


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Hi Rick,

Thanks for getting back to me. That makes sense. I'll try this method.

Thanks again,
Matt

Hi,

I’m going to shoot some more tests. One quick question, how do you tell on the URSA the number of stops under or over you are? On DSLRs and mirrorless there is a meter that shows you whether you’re at zero or a certain number of stops over or under but I don’t see this on the URSA, unless I’m missing something.

I think I understand about using false color to expose skin correctly but a few people mentioned being x number of stops under or over so I presumed there was some kind of built in light meter but I can only see the histogram, zebras and false color.

Thanks, and sorry for all the questions.

Matt

The most trusty tool I use for my lighting is a light meter. That's how I judge my lighting ratios. I use false color to expose the sensor. Pink on false color is 1-stop over middle grey.

If you've ever used a light meter to expose motion picture film you'll understand exposure better when working with digital. It's possible to light the scene using a light meter without looking through the camera's viewfinder. A great skill to build.


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