Measuring Skyreat ND Filters just for fun

[vindibona1]

I'd just received a set of Skyreat ND filters. I had not had a chance to use them on my M2P yet, but I was contemplating an easy way to determine which one to choose. So I decided to see how close they were to "spec" and realized I had the perfect measurement tool; a Minolta Flashmeter IV with a flat disc dome. And so I found an area at home where I could lay the meter down and the filters on top. The filter area was almost the perfect dimension to cover the entire flat disk. I dialed the meter at ISO 100 and them found the shutter speed that would put my ambient meter at f16. I measured the meter with no filter, then measured again with each filter laying across the flat disk. Each filter appears to be in tolerance within 1/10th f stop, which is really, really good. I've not tested for even-ness across the image nor color of image. I have not tested the polarizing filters yet and doubt I will use them much.

FWIW, they weigh 2.12 grams (ND4)- 2.15 grams (ND16) while the Hasselblad clearfilter weights 1.83 grams, weighed on a jewelry scale that can measure differences of 0.01 grams. I'm curious as to the weight of the PolarPro filters. Anyone have them and a fine enough scale to weigh them?

 

[BadWolf1]

It's intereting but I'm not sure the pictures and captions match show what the text says.
It looks like
No filter - shoot at f/16
ND 2 would be f/11
ND 4 - should be f/8 but meter shows f/5.6
ND 8 - should be f/5.6 and is
ND 16 should be f/4 and shows f/2.8

I have smaller ND + Polorizing filters for the mini. I can't see the polarizing effect by looking through a filter and turning it (I'd expect the sky to get more saturated at some angles than others) but holding one filter in front of another and rotating it blocks all the light out, suggest both are indeed polarized. I can't see any polarizing effect on the shots, if there's any effect on colour the drone white-balance handles it, and I can't see an vignetting - but I haven't tried anything approaching a scientific test - I probably could using my phone camera as a light meter.

My back-of-an-envelope sums say my mini has a fixed f/2.8 aperture so using the "sunny 16" rule, at ISO 100 I'd shoot 100th @ f/16 on a bright day. To get to 100th @ f/2.8 needs an ND32 and to the get 1/50th (which would be ideal for video) I need an ND64. I lost my ND32 and the replacement is in the post, and I added a 64.

 

[vindibona1]

It's intereting but I'm not sure the pictures and captions match show what the text says.
It looks like
No filter - shoot at f/16
ND 2 would be f/11
ND 4 - should be f/8 but meter shows f/5.6
ND 8 - should be f/5.6 and is
ND 16 should be f/4 and shows f/2.8

I have smaller ND + Polorizing filters for the mini. I can't see the polarizing effect by looking through a filter and turning it (I'd expect the sky to get more saturated at some angles than others) but holding one filter in front of another and rotating it blocks all the light out, suggest both are indeed polarized. I can't see any polarizing effect on the shots, if there's any effect on colour the drone white-balance handles it, and I can't see an vignetting - but I haven't tried anything approaching a scientific test - I probably could using my phone camera as a light meter.

My back-of-an-envelope sums say my mini has a fixed f/2.8 aperture so using the "sunny 16" rule, at ISO 100 I'd shoot 100th @ f/16 on a bright day. To get to 100th @ f/2.8 needs an ND32 and to the get 1/50th (which would be ideal for video) I need an ND64. I lost my ND32 and the replacement is in the post, and I added a 64.

I appreciate your comments. I did not translate stop reduction into actual stops as folks with different drones would have different "transpositions". In the case of the M2P it has different apertures settings so it might have been a little confusing for some. At some point I might buy a set for my Mini. I would advise anyone doing photos/video to get a basic grasp on aperture/shutter speed interdependence and understand how they work together as well as in conjunction with ISO.

I did not do the same testing with the polarizing filters as without knowing the specific rotation setting any examples would probably have been invalid. They are heavier than the Skyreat. And for some reason my M2P doesn't like the Skyreat filter when I have a lens hood attached, which I use mostly for (whatever) protection in the event of a collision anyway.

Edit: For those with fixed aperture (i.e. f2.8 on Mini), here are corresponding shutter speeds in 1 stop increments.

1/1000......1/500...... 1/250...... 1/125...... 1/60...... 1/30...... 1/15...... 1/8...... 1/4...... 1/2...... 1sec (note that DJI drones have shutter speeds in between those listed. use the nearest shutter speed based on your selected frame rate).
For your convenience, note that each step up or down is the equivalent to +/- 1EV (exposure value).
Instructions for selecting proper ND density: 1) Set drone to "manual" exposure mode) 2) Find proper shutter speed (and aperture) exposure for the scene (hint: use histogram). 3) Note the shutter speed for the given aperture and count down the number of steps (stops) between your unfiltered exposure and your preferred shutter speed. 4) Select the appropriate ND filter to achieve the desired shutter speed. Re-meter-and adjust shutter speed.

 

[jag32266]

My experience was different, to be expected though, as I have both a different bird AND filters- I have the Polar Pro ND filters. But, honestly though, I was hoping for something closer to a standard being set by these companies. I was also more interested to see if they measured up to professional filters where the ND-number correlated to the f-stop power the filter had in stoppage. SLR cameras use ND filters but are labeled to show how many F-stops to expect from the filter thereby you know what you are doing before you put the filter on the camera. Such as ND-2 would be 2 stop difference between a bare lens and using that filter. Nd-4 a four stop difference etc...

Though my memory may be off somewhat that is what I recall to be the gist of the matter,.

So I pull out my spot-meter to check the stop difference in the filters, and I'd done this some time ago when I first purchased the filters so I don't recall the exact numbers (a year or two ago). They didn't coordinate at all with what they are labeled is what I do recall. There wasn't a 'standard' that, I as a old photographer, could coordinate with F-stops. As I recall the first ND was a half exposure difference, the 2nd stepped filter was maybe 1.5 steps difference and the 3rd filter, after I measured was so different I just put the meter away as I couldn't make sense out of any kind of pattern to the filter logic. I'd be happy to re-do if you'd like but it wasn't a sensible pattern so I just dropped it, so to say.
And the filters are labeled 4, 8, 16 so one would be prone to think what maybe 2,4 ,8 (6) stops difference?

Meters- the difference between what vidibona1 used is a reflective meter measuring ambient light coming into the meter.
The spot meter measures the subject and the light reflecting off of it. So there are going to be a difference in the measurements taken as the meters are of a different nature but they are still both very accurate.

Please note: not meant to be an argument. Just to note the difference in what he found and what I did. It could also be a difference in manufactures. I look forward to your thoughts...

 

[vindibona1]

My experience was different, to be expected though, as I have both a different bird AND filters- I have the Polar Pro ND filters. But, honestly though, I was hoping for something closer to a standard being set by these companies....

Though my memory may be off somewhat that is what I recall to be the gist of the matter,.

So I pull out my spot-meter to check the stop difference in the filters...

Meters- the difference between what vidibona1 used is a reflective meter measuring ambient light coming into the meter.
The spot meter measures the subject and the light reflecting off of it. So there are going to be a difference in the measurements taken as the meters are of a different nature but they are still both very accurate.

Please note: not meant to be an argument. Just to note the difference in what he found and what I did. It could also be a difference in manufactures. I look forward to your thoughts...

I'm not going to argue with you and agree with you that the ND system is mega-confusing. I made my living as a photographer for 30 some years and never had a call to use ND filters. It was usually the other way around, looking for more sensitivity in low light situations. I had to look up the ND values in terms of stop reduction, which is one reason I posted the images, so others might get un-confused too... But that's the way I remember it always being in spite of never having to use an ND filter before.

One small but important correction. The meter I used is an INCIDENT METER with a flat disk dome, not a reflective meter, though it has an attachment for that too which I rarely used. You can see the diffuser on the head in the first image. BTW... It is a Minolta Flashmeter IV which ceased to be made after Sony bought Minolta. That meter was the best meter you could buy in 1987 and cost $500 back then. It replaced my Gossen Luna Pro, (a terrifiec meter in its own right at the time) which sits in a case in a storage locker. You can't really get consistent results with a reflective meter because you have to rely on consistent light and the consistency of the subject area you're metering. With an incident light meter the only thing you have to make sure of in tests like these is that the light is consistent and in between filter changes I made sure that the open meter continued to read f16 on the nose.

 

[vindibona1]

I'd just received a set of Skyreat ND filters. I had not had a chance to use them on my M2P yet, but I was contemplating an easy way to determine which one to choose. So I decided to see how close they were to "spec" and realized I had the perfect measurement tool; a Minolta Flashmeter IV with a flat disc dome. And so I found an area at home where I could lay the meter down and the filters on top. The filter area was almost the perfect dimension to cover the entire flat disk. I dialed the meter at ISO 100 and them found the shutter speed that would put my ambient meter at f16. I measured the meter with no filter, then measured again with each filter laying across the flat disk. Each filter appears to be in tolerance within 1/10th f stop, which is really, really good. I've not tested for even-ness across the image nor color of image. I have not tested the polarizing filters yet and doubt I will use them much.

FWIW, they weigh 2.12 grams (ND4)- 2.15 grams (ND16) while the Hasselblad clearfilter weights 1.83 grams, weighed on a jewelry scale that can measure differences of 0.01 grams. I'm curious as to the weight of the PolarPro filters. Anyone have them and a fine enough scale to weigh them?

View attachment 110335

I SCREWED UP! THE ILLUSTRATION I INITIALLY POSTED WAS WRONG! Editing option had expired.
Below find the correct illustration with an addition of the reduction for an ND32. Sorry about that.

So, to follow this up on a practical basis, assuming it was a bright sunny day and the "sunny 16 rule would apply", with an ISO of 100, the rule would tell you to set your shutter at 1/100 and aperture at f16. But in the case of an M2 or Mini if you're goal is 1/2 the frame rate, assuming 24fps (for simplicity of calculation), then the unfiltered setting would be f22@ 1/50 sec (or it's equivalent EV). If your aperture needs to be f4 you need to reduce by 4 stops so you'd need an ND16. If you have a Mini with a fixed f2.8 then you need a ND32 to reduce 5 stops.

 

[jag32266]

Like I said-" Please note: not meant to be an argument. Just to note the difference in what he found and what I did. "

sorry to have said anything. Thx

 

[vindibona1]

Like I said-" Please note: not meant to be an argument. Just to note the difference in what he found and what I did. "

sorry to have said anything. Thx

Why be sorry? Discussion is how we all learn. Please don't confuse discussion with "argument". And if you think about the true meaning of the word "argument" is really nothing more than a discussion of different viewpoints- nothing more. If I may pontificate for a moment... I think the problem with society today is that many are too ready to shut out opposing viewpoints rather than analyzing them and thinking them through, and sadly miss important learning opportunities for themselves- preferring to look to solidify their erroneous theses through unchallenged misinformation.

I've only been flying drones for two months (?) and if it weren't for the discussion of this group I'd still be in the beginner stage (and maybe I still am) and wouldn't know 1/10th of what I know because of the kind folks here.

 

[BadWolf1]

I did a quick test holding mine over my phone camera. Whites remained white, and the change in the cameras shutter speed (aperture is fixed and I fixed the ISO) is within about 1/3 of a stop of where it should be. The ones with a prominent brand name are that little bit more exact.

 

[vindibona1]

I did a quick test holding mine over my phone camera. Whites remained white, and the change in the cameras shutter speed (aperture is fixed and I fixed the ISO) is within about 1/3 of a stop of where it should be. The ones with a prominent brand name are that little bit more exact.

Isn't the phone susceptible to change the color balance having AWB built in? What is the "prominenet" brand name mentioned?

 

[jag32266]

Why be sorry? Discussion is how we all learn. Please don't confuse discussion with "argument". And if you think about the true meaning of the word "argument" is really nothing more than a discussion of different

" I'm not going to argue with you and .."
That to me doesn't sound like a good way to have an open discussion. Instead, it sounded combative and that is the very reason I stated what I said- that I wasn't trying to argue. I appreciate you clarifying your intent in you reply. Thx

 

[BadWolf1]

Isn't the phone susceptible to change the color balance having AWB built in? What is the "prominenet" brand name mentioned?

I could fix a white balance and see if the phone picks up a shift, but it's reasonably academic, if there is a small shift which auto handles it doesn't matter.
I bought 4 filters (4, 8. 16, 32) with Sunnylife emblazoned along the edge. I lost the 32 (took it off tucked it in the watch pocket of my jeans and it wasn't there when I went to get it later). And figured I needed a 64 as well. The new 32 and 64 came from the same place but are unbranded.

 

[vindibona1]

Update: [See image]
I got to do an initial test of [one] Skyreat filter, the ND16. It was mid-day with sun shining. So I put the color balance on sunny, where I tend to leave it most of the time and went for a fly. I was curious to see how true the density and color consistency was with the filters. I probably should have used the custom WB and probably set it at 6500°K

I first measured the light with a light meter out in the open sunshine and determined that the ND16 was appropriate for ISO 100/f4/ 1/50sec. For the most part it was accurate, though I didn't think it through entirely and depended on screen brightness rather than histogram, but the moments, based on caption information, that the setting was correct.

In both stills and video the consistency across the filter was excellent. I didn't see any gradations or odd shading. It is my impression that a few points of red are added, but I didn't have a true gray reference to test that. I did pull up a JPG in Photoshop and dropped an eye-dropper on 4 locations in the image; the street, one gray roof a lighter driveway and a darker driveway. Based on what I can tell numerically there isn't a enough color shift to make a difference and could be in the "sunny" white balance setting instead of 6500°k. I included some metadata in the image as well. It may be important to note that when I did an "auto correct" in Photoshop it wanted to brighten the image, might coincide with the difference in the set shutter speed (1/80 sec) where 1/50 might have been appropriate or a lightly more open aperture. To have an appreciation of the image it is best to view the image on a calibrated monitor, which my Photoshop/Editing monitor is (and it looks different from the monitor I'm using to type now).

Without a full scientific approach I think I am satisfied enough to call, the Skyreat filters (at least this one) at least acceptable and perhaps "within spittin' distance" of any other brand regardless of price. Would the PolarPro brand fare much better? Perhaps... but IMO not 2x the price better.

 

[Deleted member 103366]

Such a pity Minolta are gone, and now Oly are quiting too!

 

[vindibona1]

Such a pity Minolta are gone, and now Oly are quiting too!

That Minolta meter and I have seen a ton of action together. Probably around 500 events plus 10+ years of commercial jobs thereafter. There was a time when I considered buying a new meter and Calumet Photographic (here in Chicago and sadle OoB) had Sekonic meters on display. I brought my Minolta in to see how accurate the Sekonics were compared to my Minolta, which had been calibrated. Needless to say, I didn't buy a Sekonic. 33 years after purchase my Flashmeter IV it is still going strong, though the case is getting a bit worn .

I'm sure you know, Minolta was bought by Sony, which was a very smart move on their part, and now Sony is one of the leading companies in digital imaging. If I didn't already have Canon lenses I think I'd be looking at Sony cameras going forward. FWIW, those Minolta Rokkor lenses from the 70's were every bit as sharp and contrasty as the Zeiss and Leica Summicron lenses- head and shoulders above Nikon, which I had at the time.

 

[LifesShort]

That Minolta meter and I have seen a ton of action together. Probably around 500 events plus 10+ years of commercial jobs thereafter. There was a time when I considered buying a new meter and Calumet Photographic (here in Chicago and sadle OoB) had Sekonic meters on display. I brought my Minolta in to see how accurate the Sekonics were compared to my Minolta, which had been calibrated. Needless to say, I didn't buy a Sekonic. 33 years after purchase my Flashmeter IV it is still going strong, though the case is getting a bit worn .

I'm sure you know, Minolta was bought by Sony, which was a very smart move on their part, and now Sony is one of the leading companies in digital imaging. If I didn't already have Canon lenses I think I'd be looking at Sony cameras going forward. FWIW, those Minolta Rokkor lenses from the 70's were every bit as sharp and contrasty as the Zeiss and Leica Summicron lenses- head and shoulders above Nikon, which I had at the time.

I thought we could be friends until you made that disparaging remark about Nikon lenses! ???

 

[vindibona1]

I thought we could be friends until you made that disparaging remark about Nikon lenses! ???

I still have a whole collection of Nikon lenses from my eary days with my Nikkormat and my F3 (I still have em all)... and now Canon lenses as well as several legacy Hasselblad lenses. But those Rokkor lenses man... My friend had a SRT 101 and compared to the images I was getting with my Nikkormat FTN there was no comparison. Minolta was so under-rated back then.

 

[LifesShort]

I still have a whole collection of Nikon lenses from my eary days with my Nikkormat and my F3 (I still have em all)... and now Canon lenses as well as several legacy Hasselblad lenses. But those Rokkor lenses man... My friend had a SRT 101 and compared to the images I was getting with my Nikkormat FTN there was no comparison. Minolta was so under-rated back then.

I've been using Nikons since I got my Nikon F way back when, and still use them on my film cameras quite often. I have switched over to Fuji for digital, but quite often use Nikon manual focus lenses on it. I've never shot a Minolta lens, but will have to check into it.