ND Filters RCSTQ

FiShBuRn · Aug 21, 2023

I bought these ND filters for the Air 3 from RCSTQ on AliExpress.

I did some unscientific tests to see if there was any clear difference in IQ or any Colorcast.

ND16:

DJI CLEAR:

ND16:

DJI CLEAR:

I don't see any difference in image quality or any colorcast, maybe I'm blind, but I don't think there's a clear difference.

The filters don't have magnets like DJI's.

They cost 29€, of course I prefer another brand like Freewell but they're not on sale/available at the moment.

What do you think of it?

MS Coast · Aug 21, 2023

The ND 16 filter cuts out 15/16 of the light that would have reached the filter. That's 4 stops of exposure, meaning that it reduced the light by one half for four times. If you were shooting in auto mode, the drone just adjusted for the loss of light by slowing the shutter speed so the the shutter stayed open longer and let in 16 times as much light. You can see the shutter speeds by looking at the EXIF data for the files. The shutter speeds will be slower for the shots with the filter.

ND filters don't do much for photographs unless there's too much light for the drone to compensate with the shutter speed or aperture (Air 3 is fixed aperture.) or you want to blur something by leaving the shutter open longer.

FiShBuRn · Aug 21, 2023

I know what an ND filter does, what I'm talking about is image quality and colorcast....

MS Coast · Aug 21, 2023

FiShBuRn said:
I know what an ND filter does, what I'm talking about is image quality and colorcast....

What would you expect to be different? ND filters reduce the intensity of all wavelengths of light and have no effect on color rendition or hue. The EV (exposure value) for each pair of images is no different, just reached with different combinations of shutter speed, ISO, and ND value.

If anything, there's a greater opportunity for blurring with the filter and the slower shutter speed or greater noise from the increased ISO.

Also, any piece of glass you put between the subject and the sensor adds distortion.

ND filters do have value in videos for smoothing the motion thought the relationship between frame rate and shutter speed, but there's little motion in those videos.

FiShBuRn · Aug 21, 2023

Image sharpness and color difference since they are "cheap ND filters".

Any ND filter will reduce the shutter speed, the aim here was to see if there was any change in image quality, nothing more. That's why there are ND filters (same set) costing 30€ and others 100€. Maybe we pay for the brand?

I appreciate the replies, but it's not a question of "what does an ND filter do?"

MS Coast · Aug 21, 2023

Ok. so you were looking for obvious degradation of the image caused by the low cost ND filter? I understood that you were hoping that the ND filters were going to improve the image.

Someone with a professional grade monitor and shaper eyes is needed.

FiShBuRn · Aug 21, 2023

In video, the purpose of the ND filter is for the shutter speed be double of the frame rate. The overall Image maybe improve a little with the added motion blur.

Yes, but for ordinary mortals, there's not much difference!

MS Coast · Aug 21, 2023

FiShBuRn said:
In video, the purpose of the ND filter is for the shutter speed be double of the frame rate. The overall Image maybe improve a little with the added motion blur.

Yes, but for ordinary mortals, there's not much difference!

Right, as I mentioned in post #6. But I wouldn't think an essentially static scene with just some motion in the tree branches is a good basis for evaluating the effects of the ND filter.

Did you achieve the 2x ratio in all your samples?

SethB · Aug 22, 2023

FiShBuRn said:
In video, the purpose of the ND filter is for the shutter speed be double of the frame rate. The overall Image maybe improve a little with the added motion blur.

Yes, but for ordinary mortals, there's not much difference!

This is so dependent on subject motion, subject size in the image, and/or drone motion. For most people the combo of factors means they will rarely see a difference in motion blur with ND filters and a proper ratio of frame rate and shutter speed.

For example the moving cars in the OP’s test shots are moving rapidly, but are far away and small in the frame.

With drones flown far from the action and the wide angle lens that is typical we shouldn’t expect to see motion blur in most cases.

Until you do, of course. I’m not down on ND filters, I use them often.

Color casts and distortion are real issues with some inexpensive filters though. I’d think more about shooting a grey patches target and a regular grid target to show them. It’s hard to reveal these issues with most subjects.