Neutral density filter question

KevinfromUK · Jun 8, 2015

It seems a lot of people are wanting to fit a neutral density filter to the cameras of their P3s because they say it improves the image quality.

I just can't figure out how such a filter could do this - can anyone enlighten me please?

JayB · Jun 8, 2015

I have only learnt this recently so will try and explain.
The camera has a fixed aperture of 2.8 which means it can only control the exposure by varying the ISO and shutter speed. The ideal shutter speed to give you smooth yawing footage is approximately double the frame rate, so at 1080p 60fps you are looking at a shutter of around 1/120, obviously on a bright day if you manually dial in these settings the image will come out over exposed and if you set it to auto the shutter speed will be way higher than 1/120. The only way you can reduce the amount of light entering the lens in this situation is with ND filters. Also I believe that by reducing the shutter speed you can also eliminate the effect of jello.

Bob Publicover · Jun 8, 2015

I've had the same question for months and it has never been answered better than JayB. The next question is, Does one by a $20. filter or a $100. filter? I see a lotof filters being offered on the web. Some make od "glass" and some made with "gel" paper.
Once again, Thanks to JayB for getting me to the next step

craig4855 · Jun 8, 2015

I recently ordered the 3 filter pack, from PolarPro. There are 2 ND filters, and a polarizing filter, (great for shots over water" They are "REAL" filters, that replace the UV filter, already attached. They are made of glass, not gel.
Here is the link
http://polarprofilters.com/shop/shop-by-activity/quadcopter-multi-rotor

JayB · Jun 8, 2015

Bob Publicover said:
I've had the same question for months and it has never been answered better than JayB. The next question is, Does one by a $20. filter or a $100. filter? I see a lotof filters being offered on the web. Some make od "glass" and some made with "gel" paper.
Once again, Thanks to JayB for getting me to the next step

I ordered 2 sets of the Gel filters from Data which for the money, $5 per set of 2, were great value, even after paying $10 carriage to the UK. They are quite delicate and on location could be a bit fiddly especially as you want to try and keep them clean from dust and fingerprints. I haven't had a problem with this so far but I could understand peoples concerns. Each filter gives you 3 stops and you can combine them, so 2 = 6 stops etc. I've combined 2 but I'm not sure if combining 3 or 4 would effect the picture quality. I will more than likely invest in a set of the Polar Pro or similar when they are available from a UK dealer, as they are imo a more permanent solution but I will have more options combining them with the Gel filters, so money well spent.

jlo · Jun 8, 2015

craig4855 said:
They are "REAL" filters,

Care to explain what constitutes a "REAL" filter? Is it that it screws on and is made of glass? Does that make it "REAL"? You know that glass filters are typically gel sandwiched between glass, yeah?

loganboyd · Jun 8, 2015

When shooting video, you should have a shutter speed no faster than 1/2 the frame rate. If frame rate is 24fps or 1/24th sec then your shutter should be 1/50th (cameras don't have 1/48th). If you're shooting 30fps then use 1/60th and for 60fps you can use 1/60th or 1/125th (cameras don't have 1/120th).
Videos inherently have blur because they are capturing motion. If you don't have an ND filter then even with an ISO of 100 in bright light you will get a shutter speed of about 1/500th - 1/1000th on the P3 camera. This fast of a shutter speed freezes each frame and produces a very sharp image without motion blur and when put in sequence in a video you get a stuttering effect instead of smooth motion.
The ND filter with a 3 stop effect will take a shutter speed of 1/500th and drop it 3 full stops to (1/250th, 1/125th, 1/60th) and give you the right shutter speed for 30fps video.

loganboyd · Jun 8, 2015

craig4855 said:
I recently ordered the 3 filter pack, from PolarPro. There are 2 ND filters, and a polarizing filter, (great for shots over water" They are "REAL" filters, that replace the UV filter, already attached. They are made of glass, not gel.
Here is the link
http://polarprofilters.com/shop/shop-by-activity/quadcopter-multi-rotor

i ordered these as well plus I have the ND100 filter from RageCams on the way.

spankybear · Jun 8, 2015

jlo said:
Care to explain what constitutes a "REAL" filter? Is it that it screws on and is made of glass? Does that make it "REAL"? You know that glass filters are typically gel sandwiched between glass, yeah?

Do you have a link to how glass fliers are made... and I am talking the nicer ones.. I find your claim hard to believe

jlo · Jun 8, 2015

spankybear said:
Do you have a link to how glass fliers are made... and I am talking the nicer ones.. I find your claim hard to believe

There are no doubt different process to make them. Hence 'typically'. The point is that suggesting that a gel filter is not a "REAL" filter is patently false. Many would argue that gel is better because there are less reflective layers in play and the fact that they are incredibly thin, they retain better optical quality.

Both have their merits, and both are "REAL" filters.

spankybear · Jun 8, 2015

jlo said:
There are no doubt different process to make them. Hence 'typically'. The point is that suggesting that a gel filter is not a "REAL" filter is patently false. Many would argue that gel is better because there are less reflective layers in play and the fact that they are incredibly thin, they retain better optical quality.

Both have their merits, and both are "REAL" filters.

I'll take glass thank you.... WAY easier to clean the fingerprints off of... and more durable...

Prylar Bek · Jun 9, 2015

True. The Polarpro filters are FANTASTIC. High quality and the threads are clean and perfect. highly recommended. First class and well worth the $

snerd · Jun 9, 2015

Prylar Bek said:
True. The Polarpro filters are FANTASTIC. High quality and the threads are clean and perfect. highly recommended. First class and well worth the $

Is the CPL filter turnable? I've never seen one that isn't. How do you adjust it to the scene if it doesn't turn? In the upper listing, it says the weight of the ND filter is 3.75 grams. In the lower description, it says it's 6.7 grams. Which is it? I'm asking because they are very tempting to me lol!!

craig4855 · Jun 9, 2015

spankybear said:
Do you have a link to how glass fliers are made... and I am talking the nicer ones.. I find your claim hard to believe

Google "how glass fliers are made"

craig4855 · Jun 9, 2015

snerd said:
Is the CPL filter turnable? I've never seen one that isn't. How do you adjust it to the scene if it doesn't turn? In the upper listing, it says the weight of the ND filter is 3.75 grams. In the lower description, it says it's 6.7 grams. Which is it? I'm asking because they are very tempting to me lol!!

They are listing the difference, in weight. The polarpro is approx 4 grams heavier than the included UV filter

craig4855 · Jun 9, 2015

craig4855 said:
They are listing the difference, in weight. The polarpro is approx 4 grams heavier than the included UV filter

I do not believe that it turns. I will have to check

jadebox · Jun 9, 2015

craig4855 said:
I do not believe that it turns. I will have to check

No, it doesn't turn. I think you can adjust it by how much you screw it into the camera.

I haven't used a circular polarizer on a quadcopter, so I am not sure how practical it is. Unless you have a really tall ladder, you will have to adjust it on the ground for the conditions that you expect in the air.

-- Roger