Free tool // Exposure
Exposure planner.
Lock what can't move, change what you want, and the rest rebalances itself to keep the same exposure. With flicker-free shutter angles for 50 and 60 Hz.
En español ↗Quick scenarios
Controls
Fix flicker
Finds the shutter angles that capture whole light pulses at the current fps. Tap one to apply it, with the exposure rebalanced.
How to use it
1. Reference: set the exposure the DP likes and tap “Set this as reference”.
2. Locked or free: whatever is locked never moves. By default fps and shutter come locked because they are creative decisions.
3. Change what you want: the control you touch locks itself, and the free ones compensate in this order: ND first (the cleanest), then light, then iris.
4. If it is not enough: it tells you how many stops are missing. Free another control or ask for more light.
Flicker: the safe angle comes from dividing the exposure time in milliseconds by the length of one light pulse (10 ms at 50 Hz, 8.3 ms at 60 Hz) and getting a whole number. That is why the classic 172.8° shows up at 24 fps with 50 Hz. Above about 100 fps with 50 Hz there is no perfect angle: it shows the ones that flicker least, and if it still shows you need flicker-free lights.
EI is left out on purpose: on an ALEXA, raising the EI does not give the sensor more light, only more noise.
Quick answers
What is a flicker-free shutter angle?
One where the exposure time holds a whole number of light pulses. On 50 Hz mains lights pulse every 10 ms, on 60 Hz every 8.3 ms. At 24 fps on 50 Hz that gives the classic 172.8°; at 25 fps, 180° and 90° are both safe.
How much light do I lose going from 24 to 100 fps?
About 2 stops at the same shutter angle (log2 of 100/24). The planner tells you where to get them back: ND first, then light, then iris.
Why can't I just raise the EI?
On an ALEXA the EI is a rating, not more light on the sensor. Raising it underexposes the sensor and adds noise, so the planner leaves it out on purpose.
Made by Adrian Alescio, DIT in Barcelona. Free tools, no sign-up, built for the set.