ND filters (8 replies and 2 comments)
- Stacking 2 or more ND filters, bad idea, I presume? Never really tested it myself but I've read about it.
- I like to control my exposure only using ND filters, keeping the iris consistently wide open; I shoot at the wider spectrum of lenses and I love the subtle separation it creates on medium shots (feels a bit like large format photography). At the moment I can get a way with the internal filter of my camera but I discovered that they cause very bad artifacts. I'm done with internal ND filters. Maybe it's just the bad design of my camera but I seem to believe that the area between lens and sensor is extremely delicate, even more so than front of the lens. So if you're going to put anything in there.. no matter how well designed it is, it is going to affect the image. The way it ruins high contrast edges in my images has become unacceptable; I never, ever want to use it again.
- ND filters are expensive, but I need my own set. I like light weight and speedy workflows and I shoot using full frame 35 photography primes, using a customize-able lens hood/shade that attaches to the lens. So right now I'm thinking about getting a large set of circular photography ND filters designed for digital imaging which I can directly attach to the lens hood/shade.
- One drawback: screwing on the filters: time consuming, too fiddly and it's hard not to get fingerprints on the filter.
But this is essentially easily solved using a magnetic contraption:
- How many ND filters? Should I just get every 1-stop increment all the way up to 8 or maybe 10 stops? Or could I get away with specific filter for specific lighting situations? For example: for sunny outdoors: 8-stop & 10-stop reduction; for overcast: 2-stop & 4-stop reduction? Or would it be safer to just get them all, all the way up to the brightest natural light I can possibly encounter: white clouds or ambient sky, illuminated by direct back/sunlight.
- I know that photography filters might not be directly compatible in situations where I'm using actual cine glass.. but if I would, I would probably use those small cooke lenses or the old zeiss super speeds. I think they have a filter thread and if they don't, I'm sure I could find a screw-on filter adapter so that I could attach the magnet system and lens hood/shade on to those lenses as well.
What do you think? Am I crazy?
You can stack two filters or more but there always is a danger that you might get some artifacts from doing so. If the filters are optically correct they should not diminish the image quality by themselves but I think there is a limit to just how many you can stack up together without doing so. I use two in front of the lens sometimes but the Alexa has a behind the lens system that allows me to put one behind the lens and another that is more easily changeable in front.
Thought about trying an ARRI Varicon? Was used by Khondji on Se7en I believe.
Though, this gives you a very specific look, I'd say. Depending on how you use it.
wow, never even knew that thing existed!
From my limited understanding it seems more like a variable contrast filter though, no?
Also a bit bulky.
Roger, do you find anything wrong with the image when using a filter behind the lens?
And what are the artifacts from stacking multiple in your experience? Like softening of the image, chromatic aberration or just multiple reflections/flares when pointed towards bright objects?
I use the Arri behind the lens system and I have not had any real issues with that.
All of those things can be a problem when using a filter in front of the lens. Flares are the chief problem and you can also get an interesting 'moire' type pattern when filters are at different temperatures.
The Varicon system is ARRI's version of a partial mirror system invented by cinematographer Jerry Turpin in the UK. It is really an in camera way of flashing the negative rather than a way of controlling the light level going to the negative. As it is in effect a partial mirror the light affects the deepest shadows first. Jerry Turpin used it to add a green hue to the shadows of 'Young Winston', if my memory serves me well.
Now that you mention it, yeah. The Vericon only adds exposure overall as opposed to blocking the light coming in like say a polarized filter. It's great for adding a certain look to your film, but I suppose this is obsolete now that this look can be replicated in post using editing software.
If you like baking in certain effects though, like green color tones etc., I can see how this would be a useful devise.
Here's Mr. Rob Draper giving a brief explanation (for those who are interested):
I have a question about behind the lens ND filters.
The filter have two parallel flats and some refractive index. For this reason convergent light rays should shift the thickness of the filter. Does Arri behind the lens system have compensation for that? And if so does it mean that you should use clear filter if you don't need ND?
Yes, there is a clear filter.
Depending on the camera and filter, couldn't IR become a problem when using ND?
Yes, IR can be a problem and there are filters to counter this.