9 stop ND questions

[goodoneian]

I have a Hoya 9 stop ND filter that I've been messing around with since Christmas, and so far I like using it a lot. The only thing I don't really understand is why when i take and exposure without the filter, the colors come out warm as you would expect, but when the filter is on and i adjust for the 9 stop difference in shutter speed the colors come out very blue and washed out?

And I know the pictures aren't perfectly exposed, but in every situation I use the filter, I have the same problem, sometimes it's more obvious than others though. I just did these real quick before it starts to rain, and shot in cloudy white balance which is what i almost always have it set to in camera.


Examples: (left is no filter, right is with filter)

Also, on a kind of related note, I made the big mistake of cleaning my 3 stop filter with some sort of alcohol based lens wipe, and I still cannot get the streak marks off it it. I've tried just using the lens paper but to no avail, so if anyone could offer any suggestions up that would be cool too

 

[Montana]

In the top set of photos, the color looks more correct (to me ) with the filter on. Must be a wb issue. You relying on AWB? What camera body you shooting with?

THe bottom set, the colors again look more accurate, but less contrast. What brand of ND? It appears an easy fix in post regardless, but without the filter (to my eyes) the camera is producing grossly warm colors with that WB setting.

 

[brianT]

Do you use automatic white balance? Perhaps the ND filter is confusing the camera's white balance setting. Just shoot RAW and tweak the white balance later.

As for cleaning, I use a Lens Pen and it works well.

 

[KmH]

To clean the filter just huff your breath on it for some moisture and use a lens tissue.

If you're using a cloth, it's very possible the cloth is contaminated. How many people wash a lens cleaning cloth, toss it in the dryer and add one of those Bounce fabric softner sheets? Not good, as the bounce thing puts a coating on everything in the dryer.

Oh, the coating is very flammable too, so don't use those things on your kids clothes.

I only use lens cleaning solution from Nikon as a last resort if a huff of breath or a damp lens tissue won't do the job. Also, I probably clean a lens 1/40th as often as most people do. But I brush my glass and the insoide of my lens caps, all the time.

I avoid cloths, lens pens, and anything else like the plague. I've seen to many people waste to much time and effort using 'high tech' cleaning methods.

 

[goodoneian]

For both who asked what brand filter/ white balance I was using, as I stated in the post, it's a Hoya filter and the white balance was set to cloudy, so the white balance isn't changing. I have heard ND filters can cause some color tint but can it be that drastic? I know the colors are far less than desirable, it just made me curious as to why the colors come out so much different with the filter on/ off

And as far as cleaning the filter, I'll give the breathing thing a try. I Never use a cloth, the wipe i was used was in a sealed package as a one time use

 

[Iron Flatline]

Nine stops is a lot, the light is burning onto to the sensor in ways that wasn't expected by the engineers who designed it. You will have to do some post-processing to get the colors corrected. It's coming out a little cool/bluish, that's to be expected.

 

[Garbz]

One thing you need to understand is that a 9 stop ND filter is incredibly difficult to manufacture. When you're filtering out so much, trying to keep the filter perfectly wavelength neutral is a challenge. Even the type of ND filters used in optical experiments which cost $80 for a slide of glass that's only 25mm in diameter aren't perfectly linear (often there's a bump in spectral response around the 400-500nm [green] mark).

Shoot RAW, and correct the white balance in the camera.

 

[goodoneian]

Yeah, it seems like it could be a pretty tricky thing to make, since it only lets in like 1% of the light or something extremely low like that, possibly even lower I can't recall. I always shoot raw and it's very easy to fix, I just wanted to see what you guys had to say about it

 

[Garbz]

2^-9 = 1.9E-3 = 0.19% which should make you respect it even more