full decision/control over aperture/depth of field using ND filters (3 replies)
New to the forum. Amazing that this resource exists. Thank you Mr. Deakins for providing this space!
For a long time I had confusion about how to approach a scene wanting full control over the depth of field per setup, and keeping accurate exposure consistency.
I know some people want to never change the T/F stop but I want to decide and not be held hostage to that. I want to decide exactly how much depth of field there is per setup because i think it frames the idea of that shot best.
then it dawned on me. setup for all setups of ONE scene:
- Decide the MOST in focus (most closed) aperture that will exist in a scene. For an example, T8. And knowing that I'll want to zero in on objects all the way down to T2.8 (3 stops more open)
- So if your lighting works at that T8 and no ND filters, when you go into other coverage and want to decisively "focus" the background (aka adjust aperture for your desired depth of field), you drop in NDs to compensate for opening it up.
- Master shot at T8 no NDs. Another setup at T5.6 (drop in a .3 ND - 1 stop). Another setup at T4 (drop in a .6 ND - 2 stops), Another setup at 2.8 (drop in a .9 ND - 3 stop).
- This means you can DECIDE your depth of field, and it doesn't force you to relight for setups.
maybe that many stops is extreme in one scene but... it seems like as long as you have quality NDs and the actors can take the amount of light, this is kind of an awesome way to be able to decide your depth of field precisely.
Maybe this is common knowledge? Maybe I'm whacky thinking outside the box against "never change your T stop in a scene" but.. hey... I've been trying it out, and it's exciting for me.
Just wanted to share incase that gets someone else's creativity going.
Hello Joseph! I'm not Mr. Dakin of course (not even remotely) but if I can I would to talk with you about your post.
I think your "formula" could be good and as I learned from Mr. Deakins advice's on this forum, there is not one specific rule.
If you consciously want to have that kind of control of your focus fall-off I think it's correct (but of course Mr. Deakins or Mr. Mullen can be more specific).
The problem, I think, could be about your "need" to have enough light always to expose an interior like a T8 (about your example).
Sometimes could be possible, but when you are not able to have a lot of light for your set-up, maybe the aperture shift may have to be more narrow and near a "base" stop that you have to deal with.
I think the method to stick with a constant T value is related in a way to "simplicity" during a busy day. Lighting a set with a certain stop that you have in mind for a scene could help you to not apply math for each shot related to the .nd that you have to add or leave.
But this is only my thought, of course, there are a lot of wise and talented DP's here that can give you their thought.
Have a nice day,
Yes, your understanding is technically correct, the reason ND exists is to allow you to set use an aperture that is too wide for a scene on the stock you’re using.
on the other hand as Max says, unless shooting natural light the brighter the scene you’re lighting the higher the cost to production and often the more time it will take, so you do have to consider if it’s right and necessary for the scene.
Also as has been said many times, aperture is not the only tool for controlling the depth of field, distance from camera and focal length will have an effect too, so simply wanting to have a certain shot with very deep focus is not enough to say you absolutely have to light at T8, for example a 24mm lens @ T2.8 will allow you to keep 11ft to infinity in focus.
Thanks both of for your replies. Good info!