What do you want to know about ND filters?

[msinger]

I have accumulated a collection of commonly used ND filters and am working on a review to compare them. What do you want to know/see?

 

[Air Ontario]

I'd say build quality and no color shift, or that one caused red tints another cast green, that sort of affect or not on color as a top of the line cut point.

 

[UpTo90]

Different weights of the filters and how the gimbal handles the change in balance? Is adding any weight beneficial for counterbalancing?

 

[Omniround]

plastic vs. glass. Generally glass lenses are of higher quality, but will weigh more. If you had a way to provide common lighting and then could do comparison pictures through each one, that might be helpful. By common lighting, meaning in an indoor setting where the ambient light can be controlled.You might also be able to hold them at an angle to see which ones are more or less reflective, i.e. anti-reflection coating. Thanks !

 

[msinger]

If you had a way to provide common lighting and then could do comparison pictures through each one, that might be helpful. By common lighting, meaning in an indoor setting

That's my plan. I'm not going to do any outdoor comparisons since there is no guarantee the light will be the same while testing each filter.

 

[PrecisionAeroworks]

AR coatings (if any).
I would be interested in comparative performance with a bright source out of frame.

 

[msinger]

I would be interested in comparative performance with a bright source out of frame.

What exactly do you mean by that?

 

[PrecisionAeroworks]

What exactly do you mean by that?

The goal would be to understand if there is a noticeable difference when the sun is at an extreme angle (i.e. nearly side-on). The effect is the lens flares, glares, or otherwise "lights up". Of course this only applies to "exterior" filters, as opposed to gels that go behind the stock UV filter.
Glass *should* perform significantly better than plastic. AR coated glass should perform even better.

 

[msinger]

Got any ideas as to how to reliably test that indoors?

 

[PrecisionAeroworks]

As straightforwardly as possible...
I would do something like this:

Point camera at target of choice in normal to dim indoor lighting.

Place a bright light to the side of the drone a foot or two away from the camera (maybe not all the way to the side, maybe 80-85 deg). A desk lamp or some other kind of lamp with a directional reflector would work. The more of a spot, the better. The "ideal" setup would light up the camera without changing the lighting of the scene. A desk lamp close to the camera should be good enough.

Observe scene and take image with lamp off. Turn on lamp. Observe scene and take image.
Change filter.
Repeat.

I'm interested in gross, observable differences between filters (and I would be surprised if there weren't some). It might take a little trial and error to find the best position for the lamp. You could possibly use in-camera metering or the histogram for some kind of quantitative comparison, but I think the images would do.

Or, maybe it won't work at all. But it's a pretty quick setup to find out. (Said the guy not doing the setup)

 

[msinger]

I'll give it a shot. It sounds like an interesting experiment

 

[Omniround]

That's my plan. I'm not going to do any outdoor comparisons since there is no guarantee the light will be the same while testing each filter.

something as simple as a room without light through the door or window. against a white sheet is best vs. offcolor wall. whatever the whitest lite you can come up with and then you will have a light common to all, if we know the color of the source light, we can accommodate for that when comparing.

Others have also mentioned the AR coating which I asked about, not mentioning that. Others have already provided some AR testing techniques. I think if you hold each lens at the same angle to a light source you will be able to see how much of that light reflects, ie. how bright the reflection is to use and that actually could be measured with a light meter.

 

[alokbhargava]

You would need a spectrometer to analyze the filters.

ND filters should not affect the spectrum but just reduce the intensity.

Also you need a good source of light with wide spectrum.

 

[alokbhargava]

I would like to know:

1. Quality of materials used
2. Weight
3. Material of lens
4. Spectrum consistency at any rotational angle

 

[Noodle]

Which one is the best bang-for-buck from your experience using them?

I have the 4-pack Taco-RC ND filters and I feel they are well-made and well-priced.

 

[Shaiful Rizhuan]

I want to know:
1. Weight. Till which point I can put the weight without adding counter balance.
2. Whether there will be any difference in quality between normal ND filter vs variable ND filter (at the same stops).

 

[Omniround]

What doesn't make sense to me is that the products like Polar Pro and Taco are charging premium prices for their filters without the normal "name" factor or anything to indicate the quality of the lenses. As a comparison, a known quality filter brand like Tiffen sells their filters for $16ea and you know what you are getting and you can see the specs on the lenses.

On the other hand, you can get a whole set of filters from lesser known companies like K&F for $26. A person who used them on an Inspire said they were too heavy which brings up that issue again.

I don't know what the Polar Pro and Taco ones are made of, but the resin lenses are going to be lighter but aren't the quality of a well ground glass filter.

The adjustable filters are going to be double lens which will make them all heavier than the single lens versions.

 

[Quafe]

Any updates on this? I'm looking for a filter set for my P3P and P4, and there's quite a few different brands to choose from.

 

[msinger]

I'm still working on it. I hope to wrap up my tests and post my findings this week.