Polarizer filters and the Photographers Ephemeris

Drone on · Feb 4, 2019

We all know that polizer filters work best at 90 degrees to the sun.

There may be a location you want to film, but at the time that you want to film the location, the sun is not at 90 degrees to your flight path, so the polarizers won't work well.

An app called the photographers Ephemeris will show you when the sun will be at 90 degrees to the path you want to film in that location.

The time the sun is at 90 degrees to your flight path may not be at the civil twilight, or golden hour, but the quality of footage a polarizer can provide may compensate for that.

For some reason, the DOS desktop application is free (link down below - donations accepted - not me), but the IOS app is $10. I don't know about the cost on the Play store.

Being that this is a planning tool, you may not need the app in your phone. You may find the desktop application will suffice.

to use the tool, you locate where you want to fly, and in which direction. Then move the time slider at the bottom to to see when the sun will be at 90 degrees to your flight path at that location.

to get the most out of this tool, you have to play around with the various features, such as moving the red pin.

Note that you have to put in today's date. However, if you are planning a trip, this can help plan for that future date for many years (probably centuries as I'm sure it's based on something astronomical) into the future.

Hope this helps

A shot planned with TPE

zocalo · Feb 4, 2019

Drone on said:
We all know that polizer filters work best at 90 degrees to the sun.

The effect is strongest at 90 degrees to the sun, but it's much more subjective whether maxing out the polarizer is the best approach. In some cases that can result in almost black skies, which can be great for high-contrast mono conversions but a bit overpowering for something like the delicate colours of a carpet of spring flowers.

+1 on TPE though; I've been using that for stills photography for years. Some other good tools I use on Android (not sure if they all have iOS versions) are PhotoPills, Sky Map (I do some astro), SunPositionMap, Photo Tools Pro, and Windy. Where applicable they're purchased versions, so YMMV on free version feature sets.

Drone on · Feb 4, 2019

zocalo said:
The effect is strongest at 90 degrees to the sun, but it's much more subjective whether maxing out the polarizer is the best approach. In some cases that can result in almost black skies, which can be great for high-contrast mono conversions but a bit overpowering for something like the delicate colours of a carpet of spring flowers.

+1 on TPE though; I've been using that for stills photography for years. Some other good tools I use on Android (not sure if they all have iOS versions) are PhotoPills, Sky Map (I do some astro), SunPositionMap, Photo Tools Pro, and Windy. Where applicable they're purchased versions, so YMMV on free version feature sets.

Regarding the 90 degrees, I understand what you are stating. If the effect is strongest at 90 degrees, but not necessarily the best as it is subjective, what would be your recommendation as to how to set the polarizer?
Should we determine which orientation of the filter by facing 90 degrees, or the direction in which we plan to fly?

zocalo · Feb 4, 2019

It depends on what you are trying to achieve. If you want a high-contrast shot or to punch through reflections on water, then absolutely 90deg to the sun is the way to go. If you're dealing with something more subtle then it's down to previsualising the shot that you want to achieve and using experience of similar scenes to best guess the optimal angle.

To estimate the setting with the CP in your hand, you need to face the direction you intend to shoot at, e.g. keeping the same angle to the sun, then rotate the CP until you get the level of effect you want. Ideally, if you can do that with similar subject matter, and better still the actual subject, visible through the CP, then you should be able to nail it first time out.

If I'm still not sure, I'll do a quick recon flight with it set to 45deg, review the shots on my phone/tablet screen and make a judgement call as to whether they would benefit from more or less polarization. If I'm shooting from multiple angles, then I'll also make multiple flights - assuming I've got enough batteries for it!

You don't need to be perfect as you can still tweak the colour saturation in post, so just being in the ballpark is good enough, but the closer you can get the better. Even if you're doing a full 360 round a structure, three flights with it set at 0deg, 60deg, and 120deg will more than likely give you all the source material you need for post.