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BTM_Pix

My Prototype Electronic Variable ND Filter

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2 hours ago, Robert Collins said:

True enough of waterfall, river and seascapes - I often take a 10 stop ND filter with me But it isnt strictly necessary. This shot was taken without an ND. About 20 shots (equivalent to 95%) taken at 1/8, f16, iso50 and then 'mean averaged' in photoshop....

Nice shot.

It isn't necessary if you want to do it in post, no. 

2 hours ago, Robert Collins said:

Headlight streak shots dont usually use NDs, they are a function of 'night time' plus 'low iso' resulting in a long shutter speed.

It is more usual to get ND for free as it were by using low ISO (though I have used NDs for twilight traffic shots with wider apertures to get the exposure down to get effective streaks) but NDs can still often be necessary if you want to avoid diffraction if you have to step the lens down too far to make the exposure.

2 hours ago, Robert Collins said:

Well you could use an ND for this but it wont turn out that well because you will tend to get 'ghosting'.

The standard method is to take multiple shots on a tripod over a reasonable period of time and 'median average' in photoshop.

The standard method now might be to use Photoshop but I'm an old git ;) 

The ghosting is dependent on just how long you are prepared to make the exposure and I've seen some that are measured in minutes rather than seconds where its imperceptible. It throws up a load of other problems with trees and clouds of course which they then have to fix in Photoshop anyway so.....

3 hours ago, Robert Collins said:

A very minority case with modern cameras. My fastest lens is an 85 1.4. There are over 1200 images (keepers) from my 85 1.4 in my Lightroom library but only '1' image was taken with the maximum shutter (1/8000) with the aperture stopped down (to F2.) (And I live in Thailand.)

Agreed that it is becoming less of an issue with more recent cameras but I still have quite a few cameras in my collection that don't go beyond 1/4000th though and even those that do can't always make the exposure without some ND.

Case in point even from yesterday is the SD Quattro for the DNG that @mercer wanted where I was also using a 1.4 lens but couldn't open it beyond 2.8 because of the light here in Spain and the camera maxing out at 1/4000th. This would've been your second 1/8000th at f2 shot :) and I think I only posses one camera that could've made a 1.4 exposure in that light (albeit with electronic shutter) which would be the X-T2 so while we've gained recently on the one hand with faster shutters we've lost on the other with faster lenses and a thirst for shallow depth of field. 

Of course I didn't follow my own advice and happily wandered out of the house without an ND filter (or sunscreen) ;)

Having said all that....

I wouldn't buy my own device for stills either as it is sledgehammer to crack a nut when there are enough existing cheaper and more appropriate solutions.

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8 hours ago, buggz said:

Wow, you are the man!  Very talented indeed.

I will take a 4x4 one.

Is it available to be variable?  Or just in stops?

Since it is digital, there is always steps/stops as it isn't analog...

What I was referring to regarding the stops was measured stepping between values.

If you want it to be user variable (there are 256 steps of adjustment) then it can be like that but from a control point of view it makes it easier to use if those steps are divided between stops as tied to the exposure you are setting on the camera using the controller.

So if you set your base setting of f4 at 1/50th then when you changed to f2.8 or f5.6 it would automatically turn the ND up and down to maintain the same exposure.

I'll give some thought to the interface for a standalone on regarding variable control. Probably a small joystick (like the controllers on a PSVITA) would work best I think.

3 hours ago, tellure said:

I love the functionality of this device and hate messing with my manual variable ND while shooting video.  I hate to say though that I probably wouldn't buy one unless it was almost as small as a variable ND.  Maybe a bit bigger radius and thicker but not nearly as big as the prototype there.. it would need to be small enough to fit into a camera bag while attached to a lens.  I'm a hobbyist shooter though, I could maybe see a dedicated crew shooting with something that large.

No, the box its in is purely to hold it while I was developing the code to control it. Its actually a cut up cardboard box from a USB power bank with a Cokin flat filter adapter grafted on to get it on to a lens as they were what was within my eye line when I was doing it!

The filter itself is as thin as a regular filter.

As a standalone unit it will obviously need some electronics to drive it so it will all be contained within a frame but it will be nowhere near as big as what you can see on the, erm, carefully constructed and lovingly sculpted housing its currently in.

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My ultimate use for this would be to have it be integrated into the camera and have the camera vary it continuously instead of the other parameters.

This would mean that you can set it to 1/50th, F4, Auto ISO and Auto ND and it will control the exposure for me while I still have control over SS and Aperture.  Then I never have to think about exposure ever again but I still get the advantages of 180 shutter and controlling DoF.

It's unlikely, but are you able to make a deal with a manufacturer perhaps?  Having this thing as part of the sensor stack, or maybe as a switchable ND (so the camera just moves it into the light path or out of it) would be perfect.

At the moment I can either have the camera control the exposure, OR I can have full creative control, but not both at the same time.

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2 hours ago, kye said:

My ultimate use for this would be to have it be integrated into the camera and have the camera vary it continuously instead of the other parameters.

This would mean that you can set it to 1/50th, F4, Auto ISO and Auto ND and it will control the exposure for me while I still have control over SS and Aperture.  Then I never have to think about exposure ever again but I still get the advantages of 180 shutter and controlling DoF.

This will get you far closer to that as it will track the aperture (and shutter speed if you wanted it to I suppose) and you then set a conservative limit on the auto ISO so it will constantly be doing the offset without large changes in the ISO.  You would deliberately set the base exposure to be a stop or two away ISO wise from the limit you'd set for the auto ISO so it had some range above and below to work in.

For example, if your base exposure is 1/50th, f4 and ISO640 then you'd set up the ND to add enough to make that exposure at ISO320 instead and set the auto ISO limit to be ISO800. That will take care of a reasonable change in light as the auto ISO can range above and below that point and the ND will track the changes from the aperture point of view to keep that initial base exposure constant as far as the auto ISO can see.

It depends on how much swing you expect to have within a single shooting scenario but configuring it like that would take away a lot of manual intervention. 

It can be done exactly like that now with any ND either fixed or variable but the difference is in the tracking of changing aperture which would otherwise require a manual change in ND level.

Otherwise you'd be looking at a Sony FS5 which will work in full auto mode as it has a built in variable electronic ND.

2 hours ago, kye said:

It's unlikely, but are you able to make a deal with a manufacturer perhaps?  Having this thing as part of the sensor stack, or maybe as a switchable ND (so the camera just moves it into the light path or out of it) would be perfect.

No, what I've done here isn't groundbreaking or original so manufacturers are able to do this themselves if they want and, as above, cameras like the FS5 already do.

This is more about being able to add that style of functionality to any camera, especially when integrated with my controller, and at a reasonable price.

3 hours ago, kye said:

At the moment I can either have the camera control the exposure, OR I can have full creative control, but not both at the same time.

As I say, it depends on how changeable conditions are going to be within the same shooting period but I think its possible to get pretty close with an ND filter that can track aperture changes.

Or take the full creative control option and buy an FS5 ;) 

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Super excited to hear that a compact version is possible; I'll definitely be in for buying one when you kickstart it.  Given the size constraints most camera mfrs are working within it seems like it might be a long time until variable ND's appear inside the body of consumer mirrorless camera lines, so your approach of an external solution seems like it will serve this need really well.

Any chance of a smartphone app to control it instead of another dedicated device?  Would love to avoid having to carry another piece of hardware.

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1 hour ago, tellure said:

Any chance of a smartphone app to control it instead of another dedicated device?  Would love to avoid having to carry another piece of hardware.

It will use Bluetooth LE to communicate with my controller so a smartphone app could equally be used.

My personal view of that though is that its a bit of an overkill way to do it, especially considering the size and cost of the smartphone even though you might already have it. 

Using something like a small Bluetooth LE controller (a keyfob sized remote control similar to smartphone shutter release for example) is, to me at least,  a better way to control it as the beauty of doing it that way is you don't have to fire up an app on the smartphone so its a bit more instant, not to mention tactile ?

There'll be options for both though.

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Stop bumping it you buggers, I'm working on 50 different things as it is without being guilt tripped that I haven't finished this one ;)

I'll put up a pic of a new iteration of it next week hopefully. It will of course be in an elecrtic blue case as I still haven't changed that spool on the printer.

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How is it possible to change ND sensitivity on there?! It seems to me like a "small outside - huge inside" concept from the 29th century. 

Don't you need physical space to have on/off positions?

And the glass has to be top notch, which is very very expensive, but there is no shortcut on that anyway.

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35 minutes ago, Kisaha said:

How is it possible to change ND sensitivity on there?! It seems to me like a "small outside - huge inside" concept from the 29th century. 

Don't you need physical space to have on/off positions?

And the glass has to be top notch, which is very very expensive, but there is no shortcut on that anyway.

Its actually really simple to vary the amount of ND just by changing the voltage that you feed to it from the controller.

That control can be done in numerous ways such as with switches on the controller for defined steps, a pot/fader for absolute position control or remotely by bluetooth.

I've been having some thoughts this morning regarding this development and whether I currently have the bandwidth to commercialise it in the nearish future.

The short answer is I probably don't in terms of how I would want to do it with a much larger filter, sourcing different glass and everything else manufacturing wise that is involved in a fully commercial product.

It doesn't mean I won't do just not right now but I was wondering whether there would be any interest in a build-along thread for people to make their own?

I have had a re-think about a controller that would be more suitable for a project version rather than a commercial one and I would be provide you with the code and how to make it amd how you could enhance it.

The parts will be inexpensive and readily available and the collaboration might be fun.

Would this be something anyone would be interested in? 

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1 hour ago, BTM_Pix said:

Would this be something anyone would be interested in? 

I would absolutely be interested!

I just had a thought, and I'm fairly sure it's stupid and won't work, BUT.... Would there be a way to power this through an XLR plug with phantom power? And if so, could (in theory at least) the volume knobs adjust how dark the filter goes? Or do the knobs only adjust the signal between the XLR socket and the camera?

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1 hour ago, BTM_Pix said:

Its actually really simple to vary the amount of ND just by changing the voltage that you feed to it from the controller.

That control can be done in numerous ways such as with switches on the controller for defined steps, a pot/fader for absolute position control or remotely by bluetooth.

I've been having some thoughts this morning regarding this development and whether I currently have the bandwidth to commercialise it in the nearish future.

The short answer is I probably don't in terms of how I would want to do it with a much larger filter, sourcing different glass and everything else manufacturing wise that is involved in a fully commercial product.

It doesn't mean I won't do just not right now but I was wondering whether there would be any interest in a build-along thread for people to make their own?

I have had a re-think about a controller that would be more suitable for a project version rather than a commercial one and I would be provide you with the code and how to make it amd how you could enhance it.

The parts will be inexpensive and readily available and the collaboration might be fun.

Would this be something anyone would be interested in? 

Go on!

Still I am not aware of the technology of changing the voltage - increase ND, what I know is that to vND something with glass, is very very expensive, and my 100euros ones do not worth a dime. One has to go to Breakthrough Photography, or more, to have what you have to have from a vND!

another option could be to find an "easy" and standard way (let's say 72mm to be the most for a lens's diameter) and try indie go go it, or something.

People are funding all kind of crazy ideas, and this is something really practical that is missed by the community, and especially the "lower" tier (GH5/S, P4K, Z cam, all hybrids) which are not going to "invest" on a C200, just because it has internal ND. 

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44 minutes ago, Anaconda_ said:

I would absolutely be interested!

I just had a thought, and I'm fairly sure it's stupid and won't work, BUT.... Would there be a way to power this through an XLR plug with phantom power? And if so, could (in theory at least) the volume knobs adjust how dark the filter goes? Or do the knobs only adjust the signal between the XLR socket and the camera?

If you put 48v through it you'd be picking shards of glass out of the wall for a while ;)

It only needs 3v through it to reach full reduction and this is supplied by the controller which itself is powered by a small lipo or 3 AA batteries.

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