ND - internal vs external filters

[Petter Flink]

I have a 3 stops internal ND on my GY-HM150 which quite often isn't enough without closing down aperture. I've tested to stack an external ND 3 stops ND (hoya/kenko) as well but experienced really poor picture quality.

Do you prefer the internal one or do you always go with an external variable ND?

[Glen Vandermolen]

I have an FS100, so I have no choice but to use an external ND filter. I definitely prefer internal NDs, even though my external variable ND gives me more control.

I'm surprised you're getting too much exposure using full ND on a 1/4" CCD camera. I would think you'd be wanting more light.

[Don Bloom]

I too prefer internal and am also surprised that you don't find the internals of the HM150 to be enough. I use an HM700 and an HM100 and find the internal filters to be more than enough unless you're trying to go with a wide open iris all the time to try to get some shallow DoF.
As for bad quality with external filters, yeah that can happen. You need really top notch filters since you're adding another piece of glass and it's darkened. Not saying yours aren't good, just saying that maybe you've got too much glass on the lens. Maybe use the internal and a less "heavy" external.
Depends on what you are trying to accomplish.

[Petter Flink]

I shot outside on a snow covered lake in bright sunlight. :)

The effect with both NDs looked as if some parts of the colour spectrum was filtered out.
Anyway I'll get an eclipse variable and see how that works and try to avoid using both internal and external filters. Will compare the two and see. The internal do look ok when used stand alone.

[Tom Hardwick]

It can be a problem that the cheaper neutral density filters aren't neutral, and they can indeed give a colour cast to your footage. You say you 'experienced really poor picture quality' and this sounds to be a colour shift. As the 150 only has an on/off internal ND, I'd be tempted to shorten the shutter speed (when and if needed) rather than fit external ND.

tom.

[Trevor Dennis]

Just wondering how you attached the external ND filter? Even if using a mattebox, flare can be a problem if light can hit the filter slot on top of the matteboax, and it helps to have a strip of dark cloth to cover the slot. I you are using a Cokin/Lee/Formatt type rectangular filter without a lens-hood, then perhaps rig up a French flag, or even hold a bit of dark card in place with your hand. I've resorted to using my hat at times.

Regarding the use of quality filters, this article from the Lens Rentals guys makes the point very nicely:

LensRentals.com - Good Times with Bad Filters

[Don Bloom]

Petter,
Snow in bright sunlight...in Sweden? Hard to believe! ;-)

OK I get the reason now but again, maybe it's the quality of the filter so trying a different one might well give you the answer or just slow the shutter speed down if you're on a tripod and no real movement going thru the frame!

I still can't get over having BRIGHT sunshine and SNOW in Sweden! ;-) (a truly sarcastic comment)

[Petter Flink]

@trevor

I used a screw in Hoya/Kenko ND with a large hood attached. No extra flags or barn doors used.
Did both shots with sun in my back as well as into it to provoke some flaring which I got.
I got the feeling that the two NDs did not that well together.

Will get a Genustech eclipse and see if it works better then my combo.

@Don

Haha.
True most of our winters are close pitch black all day but when spring is closing in and the sun appears we are like flies on a pile to get some. :)

[Pedanes Bol]

I combine two external B+W ND's many times and the results are very good. I recommend B+W filters.

[Allan Black]

^ +1.

Cheers.