Be Careful Which Neutral Density Filters You Buy; They Could Do More Than Just Reduce Light

This was the scene I photographed.  I didn't have to worry about any of my subjects moving in the scene!  Lol.
The scene has blue, red, green, yellow, etc so it makes a good scene to compare exposure and color reproduction.
Fujifilm X-T2, 16-55mm f/2.8 lens @ 16mm; Aperture Priority @ f/8; ISO 200;
This was the "Control" image with no filtration applied.  I edited this RAW image for correct luminance and white balance,
then copied all the settings to fully normalize the other images to this "standardized" image.

I don't often have the occasion to use neutral density (ND) filters.  But when I need them, I need them.  Mostly, they stay packed in my camera bag in their original cases as I've found in other cases I've used, my filters have become dusty and clouded from out gassing.  The original cases are a bit more bulky but I've saved much time in not having to clean the filters before every use.  Only when an appropriate scene presents itself, do I dig in and grab an ND flter.  Otherwise, they are largely ignored.

I typically have carried two ND filters with 6-stop and 10-stop light reductions.  I find that combination takes care of every situation I've encountered in the past.  Some photographers carry a greater variety, but I've been happy with the light reduction using one or the other (or both) of those two.  If my desired shutter speed is still too great with the 6-stop, I'll put on the 10-stop.  If the shutter speed is a bit too slow with either filter, I'll increase the camera's ISO to get the shutter speed I desire.

Also, I've tried variable ND filters, but have not gotten the results I desired.  Variable ND filters, in my understanding, are basically two polarizing filters placed over each other with the ability to rotate the top one.  The more the rotation, the less the light passes through.  I first learned about cross-polarization many years ago when I was involved in scientific photography.  I used polarized light sources.  Back to the variable ND filters...

In some of my images, I could see the dreaded "X" pattern.  The "X" pattern is a result of the two polarizing filters and the effects they have on each other.  I found it interesting  as I had seen in it in some images but not others.  The problem is that when out in the field, you need to know your gear inside and out and not be surprised when you look at your images back home.  I felt I couldn't trust them to perform as expected.  Once you leave an area, there are no do-overs.  My variable ND filter stays in its case in the filter drawer.

I've always been a big believer in buying top quality filters.  I thought there was no sense in spending potentially over a thousand dollars US for a lens, then putting a cheap piece of glass in front of it.  A chain is only as strong as its weakest link, as an analogy.  I always bought B+W filters.  I always bought multi-coated filters and, when appropriate, the thin ones for my wide angle lenses.  B+W filters have been my "go-to" filter for at least the last 15 years, if not longer.  I've bought probably 20 of them over the years.  They are not inexpensive.  I buy the multi-coated versions of filters for the same reason your lenses are multi-coated—more light transmission and less flare.  

Almost two years ago, while I was photographing in Acadia National Park, I had the occasion to use my B+W ND filters.  As I said, I don't use them often, but when a situation presents itself where I need them, I put them on the lens.  A couple of weeks later, when I returned home and was looking at my images I noticed that the images I made using the ND filters were very warm in color.  Not even close to what the scene was.  The non-filtered images had great white balance.  Being that I shoot in RAW format, I color corrected them but made a mental note that the ND filters shifted the color of the scene quite dramatically and I needed to follow-up and check it out.  Of course, I forgot!

Using them again last December, I noticed the color shift seemed even more pronounced.  Again, I told myself that I needed to figure out what was going on with those filters and buy possibly some new ones, depending upon what I found.  Of course, again, I forgot about it.  I think it is a product of age, or at least I tell myself that.  Lol.

Two weeks ago, a friend and I were photographing together in Richmond, Virginia and I wanted to capture the water of the James River, which was running fast and dirty, with blur.  This time, when I pulled out the filters, I knew what I was going to get and kicked myself for not following up and buying new ones.  I made the images, color corrected them the best I could and, yes, I did buy some new filters.  Here is an example of one of the Richmond images color corrected as best I could.  This time I did some research on the Internet to figure out what filters are highly regarded and purchased new ND filters.

I decided to buy into the Breakthrough Photography filter system and I couldn't be more impressed with experience, not only using them in making images, but the attention from the manufacturer after the purchase.  Ever hear about registering your filters, using their individual serial numbers, so the 25-year guarantee can be honored?  Yes, 25-year guarantee!  How about an email from the CEO making sure you are happy?  Not usual.

I bought a 6-stop and a 10-stop filter.  They do sell more than one level of quality and the ones I bought are the: Breakthrough Photography 77mm X4 10-Stop ND Filter and the Breakthrough Photography 77mm X4 6-Stop ND Filter. I had a couple of gift certificates and I ended up buying one at B and H and the other at Amazon. The prices at both retailers are similar.  Of course, for now, no sales tax and no shipping at B and H.

When I received the filters, again, I was impressed.  Not only do they include a nice red lens cleaning microfiber cloth with each filter, the knurled edge of each filter has really deep knurling so it is easy to grasp and remove the filter if tight on your lens.  Ever have a filter stuck on a lens in the field?  I have.  There are lots of hacks to get them off.  I carry a wide rubber band that is used to bundle broccoli in the grocery store.  That has worked well for me in removing stuck filters.  I don't anticipate the Breakthrough filters giving me problems due to the deep knurling on the brass rings.

So...  After buying the filters I needed conduct an easy, non-scientific but informative, experiment to see what the actual differences in resulting images would be in light transmission, color shifts and potentially any reduction in sharpness under identical circumstances using both the old B+W filters and the new Breakthrough filters.  Conclusion: the difference was remarkable.  

I went out to a local cemetery.  I didn't want my subject moving around, (LOL) set up my X-T2 and 16-55mm f/2.8 lens on a sturdy Gitzo tripod, put the camera on daylight white balance, ISO 200 and aperture priority so any differences in exposure or white balance was due to the filtration.  The first image I made was a "control" image which would be used to compare all other images.  Also, I photographed an X-Rite Colorchecker Passport in some of the exposures so I could standardize the resulting images if necessary. 

I made my exposures and returned home.  I adjusted the brightness to reflect what I saw and adjusted white balance by using the white balance dropper in Lightroom on one specific spot on a particular headstone that looked pretty neutral gray.  After "normalizing" my control image, I applied the exact same settings to the images I made using each of the four filters.  Here are the results.  In a perfect world, all the images shown here should look identical.  But, as you can easily see, they don't.  The differences you see are due to the effects of the ND filters.

Control image as shown above for comparison

B+W 6-stop ND filter;  It should look like the image above it if all was as it
should be.

B+W 10-stop ND filter.  Compare the color and density to control image.

Control image again

Breakthrough Photography 6-stop ND filter attached to lens

Breakthrough Photography 10-stop ND filter attache to the lens

Then, I tried to match the images for exposure, color balance and vignetting containing the four filters to the control image, which of course, had no filter.  The first image is the control image once more so it is easier to compare.  That matching would then allow me to directly compare the differences in the exposure slider as well as the white balance slider so I can quantify how much effect each filter had on on image.

Control image one more time for comparison to below.
Lightroom Develop Settings;
Exposure +1.07
5250 K; +21 Magenta (which is slightly different from LR's daylight setting of 5500 K, +10 setting)
No vignetting compensation applied

This is the image with the B+W 6-stop filter attached matched (the best I
could in a reasonable amount of time) to the control image.
Lightroom Develop Settings;
Exposure +1.07
4200 K; +9 Magenta
+35 vignetting compensation applied

This is the image with the B+W 10-stop filter attached.  Again matched to the
control image.
Lightroom Develop Settings;
Exposure +1.07
5250 K; +21 Magenta
+10 vignetting compensation applied

Control image again.
Lightroom Develop Settings;
Exposure +1.07
5250 K; +21 Magenta
No vignetting compensation applied

This is the image with the Breakthrough Photography 6-stop filter attached
Again matched to the control image.
Lightroom Develop Settings;
Exposure +1.07
5250 K; +21 Magenta
+10 vignetting compensation applied

This is the image with the Breakthrough Photography 10-stop filter attached.
Again matched to the control image.
Lightroom Develop Settings;
Exposure +1.74
5650 K; +20 Magenta
+10 vignetting compensation applied

The upshot of my little non-scientific experiment is this:  

First, I didn't see any reduction in fine detail or image quality with either brand.  That is a very good thing.

To "normalize" the control image (make it look like I would want it to look), which is the one with no filtration applied, I added +1.07 to the exposure slider and the white balance was determined by using a very specific spot a very specific neutral looking gray headstone.  White balance was slightly different than Lightroom's standard daylight white balance of 5500K and +10 magenta.  The calculated white balance was 5250K and +21 magenta.  The increase in luminance as well as calculating white balance in the exact same spot was then applied to the other images so a valid comparison of differences made only by adding filtration could be compared.  No vignetting needed to be applied to the control image using the16-55mm f/2.8 lens.

The B+W 6-stop filter needed the color balance to be moved toward the blue by 1050k.  The magenta/green slider needed to be moved toward the green by 12.  The vignetting control needed to add +35 points to bring up the corners or the image.  The exposure was about the same as in the control image.  In other words the image was very yellow/magenta with heavy vignetting as compared to the same image with no filtration.

The B+W 10-stop filter needed the color balance to be moved toward the blue by 1350k.  The magenta/green slider needed to be moved toward the green by 1.  The vignetting control needed to add +56 points to bring up the corners.  The image was underexposed by 1/2 stop. In other words the image was underexposed and very, very yellow with heavy vignetting.

The Breakthrough Photography 6-stop filter needed no color correction and no exposure compensation.  The vignetting was insignificant and didn't need to be applied but to be fair, I tried to exactymatch the control image exactly so I added +10.  

The Breakthrough Photography 10-stop filter needed no color correction.  The vignetting was insignificant and didn't need to be applied but to be fair, I tried to match the control image exactly so I added +10.  The image needed about a 34 stop exposure compensation.

Since both the B+W and Breakthrough 10-stop filters underexposed significantly, I'm starting to think that the underexposure is a function of the camera's light metering.  I didn't change any exposure compensation in the camera for any of the images.

I don't know if the differences in light transmission, color quality and vignetting is due to the B+W filters being 20 or so years old or they are just aren't made as well as currently produced filters.  I didn't even think to check the effects the filters had on my images when I first bought them.  I know that in the last couple of years, I've noticed how badly they affected my images.  I think my love affair with B=W filters is now over.  I am a believer in Breakthrough Photography filters and plan to continue to give them my business in the future.

The lesson to be learned here is to research neutral density filters thoroughly as the good ones cost quite a bit of money but may still affect your images in more ways than just reducing light.  If I were a JPEG shooter and wanted to move my images using my B+W ND filters from the camera to social media while still in the field, I would be sending out really bad looking images.

Finally, I like to remind everyone on occasion, I don't get any gear for free or at reduced cost by any manufacturer or from anywhere else.  I pay what you pay.  I am not sponsored by anyone nor do I have any advertising nor click-through links to generate income from this site.  I write and share my experiences just trying to help others who love photography as much as I do.

Thanks for looking. Enjoy! 

Dennis A. Mook 

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