Assessing the necessary lighting gear during a tech recce

[Anzer Sizov]

Hello friends,

It might have become second nature to many of you, but I'm puzzled.

How do I calculate which lights exactly I should be using in a certain space, aiming for a certain exposure? 

I mean, is this at all common practice to calculate this way?

For instance, we enter a room during the recce.

Let's say I measure the light by the window, in the middle of the room and also in the darkest corner. 

And also outside, where the background is, obviously.

And I like the way it falls off the further you get from the window.

I just need to triple the quantity to have proper exposure inside along with some background, too.

How do I proceed, so that ultimately I would end up having enough light but also saving some money? 

I've been in situations when I brought in big lights and eventually, it was way over the top. 

When I really needed them the next time, I could not afford them. 

I feel that the distance is important and the inverse square law might also step into play. 

But how does it all come together?

Any piece of advice would be much appreciated. 

A.

[David Mullen ASC]

You'd probably have to work with photometric data of lamps based on foot-candles. Inverse square law comes into play; unfortunately one aspect of lighting through windows is that the natural slow fall-off of natural light is replaced by the faster fall-off from artificial lighting outside the window, which cannot be as far away are the sky and sun.  But obviously the bigger and farther you can get, the slower you can make the fall-off rate.

I'm afraid that practically what tends to happen is that you get the largest lights you can afford and can rig, even if they are not enough. Yes, experience sometimes tells you when something will be overkill.

[Abdul Rahman Jamous]

Good day to you brother and hope that you are doing fine.

I also used to struggle with the concept of lighting, but reading this book was an eye opener

https://archive.org/details/mastersoflightco0000scha_b9t3

Well,,,, yes in this forum there are a lot of legends who would happily answer your questions, but perhaps you should attend as many shootings as possible and feel free to know the standards of lighting in your country or region and then try at the beginning stealing those lighting technique and then bit by bit you come up with your own style of lighting. Or may be you can go to rental houses and examine their equipment and get yourself familiar with lighting till it becomes 2nd nature, or perhaps when it comes to the technical aspect of the job you may rely on a gaffer you trust. 

Beside being a DOP I also recommend you to accept getting hired as an operator, being an operator would help you grasp the technical aspect of the craft.

[Anzer Sizov]

On 9/4/2023 at 7:33 PM, David Mullen ASC said:

You'd probably have to work with photometric data of lamps based on foot-candles. Inverse square law comes into play; unfortunately one aspect of lighting through windows is that the natural slow fall-off of natural light is replaced by the faster fall-off from artificial lighting outside the window, which cannot be as far away are the sky and sun.  But obviously the bigger and farther you can get, the slower you can make the fall-off rate.

I'm afraid that practically what tends to happen is that you get the largest lights you can afford and can rig, even if they are not enough. Yes, experience sometimes tells you when something will be overkill.

Hello David, 

Thank you for taking the time to respond. I've always felt rather reluctant to dive way too deep into the technicality of the lighting process. Even though I understand that it's a part of the craft and do understand quite a bit, my focus always shifts onto the story itself, the atmosphere, where to put the viewer (i.e. where to put the camera) etc. So, your advice seems simple, straight-forward and reassuring and I guess I'll follow along. Thank you.

A.

[Anzer Sizov]

On 9/6/2023 at 8:21 AM, Abdul Rahman Jamous said:

Good day to you brother and hope that you are doing fine.

I also used to struggle with the concept of lighting, but reading this book was an eye opener

https://archive.org/details/mastersoflightco0000scha_b9t3

Well,,,, yes in this forum there are a lot of legends who would happily answer your questions, but perhaps you should attend as many shootings as possible and feel free to know the standards of lighting in your country or region and then try at the beginning stealing those lighting technique and then bit by bit you come up with your own style of lighting. Or may be you can go to rental houses and examine their equipment and get yourself familiar with lighting till it becomes 2nd nature, or perhaps when it comes to the technical aspect of the job you may rely on a gaffer you trust. 

Beside being a DOP I also recommend you to accept getting hired as an operator, being an operator would help you grasp the technical aspect of the craft.

Hello Abdul,

Thank you for your detailed response and all the thoughts and suggestions you've kindly shared. It's obviously good to learn the best practices from the more experienced craftsmen. To be able to apply them adequately, to combine, to reinvent etc. But ultimately it's about one's own way of thinking and interpreting. That what makes us all different, hopefully. As filmmakers and as human beings alike. Thank you for the book, too!

A.

[Adam Richards]

Hey Anzer, first time poster here! 

I've been through the same situation as you. I work a lot with very stringent budgets and small crews and have to justify every light I need, which is fine when you've done something similar before, but when I want to try something new or bigger I need to be sure!

My solution was an Excel spreadsheet. I would input a light's published photometric data into a column, say 1m = X fc/lux. Then using the inverse square law I would use that to extrapolate the foot candles at all different distances. I then had another column that converted that foot candle measurement to camera stops.  As an example, an Aputure 300dii open face at 3m, gives about 120 fc. The spreadsheet calculation works that out as T83 (assuming 25fps, 1/50 shutter, and iso 800). That’s the starting starting point for me. So on a recce for example I would determine my light would likely need to be 10m away, and I'd know I'd want a key stop of T4. Using the table, I can see that the Aputure open face at 10m gives T27 - quite a bit under what I’d need. 

Though to be honest, it's not really that elegant and quite time consuming, and the formula for converting footcandles to camera stops is complicated. If you're mathematically minded there's a few websites out there that can help. I'm not, so I had to ask a friend to help. It also doesn't take into account a lot of other factors (diffusion, existing ambient, spread etc). In it's favour, you do get a good idea of a unit's falloff over distance which is useful. 

And despite having all this data, real world experience beats it all, as the others said, get to know a rental house, try out some lights, and makes notes about your fixtures on every shoot Hope that helps!