Variable ND inducing softness and blurriness

In an attempt to achieve a shallow depth of field (DOF) with my Canon M-500 video camera, I purchased a Polaroid HD Multi-coated Variable Neutral Density (ND) Filter for that purpose.  The concept of the variable ND filter is to reduce the light, forcing the camera to open the aperture, reducing the DOF.

For regular ND filters, this is easy to do.  Put dark glass is put in front of the lens, cutting the light, the aperture opens, and the DOF drops.  There is no adjustment with these filters.  Really dark ND filters introduce a color shift, as the Hoya ND400 does, but it can be dealt with.

But with the variable ND filter, two polarizers are crossed and their relative position will determine how much the light is cut.  That’s the theory.  However, the variable Polaroid filter I chose makes the image blurry.  And not just a little bit but a lot.

Canon M-500 with Polaroid Var-ND
Canon M-500 with Polaroid Var-ND

At first I tried testing with video, as the above YouTube clip shows.  Once I realized the filter was making the video blurry.  It was still difficult to tell the extent of the problem, so I switched the M-500 to still mode to compare.  The problem was instantly evident.   The two photos show the problem.  Click on them to download and see for yourself.  Wow.

Canon M-500 no filter
Canon M-500 no filter

So, now it’s either drop $400 on a Singh-Ray Variable ND or just get a 3-stop ND for the M-500.  Considering the Canon video camera costs $400, it doesn’t make a lot of sense to purchase the Singh-Ray, as much as I want it. Buying a $1k camera with built-in NDs would be a better choice.

Here are some links to other discussions with the same problem:

Focus Problem with Cokin Variable ND

Variable ND filters (loss of sharpness)

Fader ND is killing my sharpness

Fader ND Softness

There seems to be a lot of non-uniform feedback on the problem.  This filter is something to be tested at the store prior to purchase if possible.  There’s nothing worse than getting home and having things not work.

Getting the technical moon shot

To get the moon shot using Ansel Adam’s oft-quoted exposure formula, used for his

Sailing the moon
Sailing the moon, Snow King, Jackson Hole

famous Moonrise over Hernandez:

Take the square root of your ISO – that becomes the aperture.

  • ISO100 = f11
  • ISO200 = f14

Then, take the luminance of the object.  In this case, the full moon is 250 cd/ft^2, relatively low on the horizon.  That becomes the shutter speed to put the object in zone V, 1/250 sec.  To bump up the moon to zone VII, a more desirable target to make the moon bright but not blown out, cut the shutter speed to 1/60 sec.

In the digital era, people probably don’t use the zone system too much any more.  But, being a former B&W photographer with a dark room, I still think that way.  And, it still works.

Moon exposure
Moon exposure

I have used this setting with proportionate variation to the ISO and aperture, to great effect over the years.  It’s much easier than trying to meter the moon.  Interestingly, the moon is the exact same exposure as daylight for zone V.  I’ve seen websites reporting luminance measurements that well exceed this calculation, yet it works well every time.  My Sekonic L-508c light meter does not have enough zoom to fill the meter area, as the moon is about a half degree wide and the meter area is one degree.

Also, a full moon is 250 cd/ft^2 when full.  The exposure drops quickly as the moon enters its gibbous, half and crescent phases.  Yet, the above shot is very close to the above calculation.

The shot was taken at f5.0 at 1/500 at ISO 200.  Lets see if the math works out.  My Nikon D300s was set to ISO 200 = f14.  Let’s just say the moon was full, so that’s 1/250

Moon exposure on D300s
Moon exposure on D300s

sec.  To get the moon to zone VII, I want to shoot at 1/60 sec.  (1/250 – 1/125 – 1/60).  Since I was shooting with a 180mm lens, 1/60 of a second would have gotten me a nice, blurry image.  So, I needed to shoot at a higher speed.  I chose 1/500 of a second, 3 stops above 1/60 (1/60 – 1/125 – 1/250 – 1/500).

That meant I had to open my aperture 3 stops to keep the exposure equal.  Lets Just fudge the calculated aperture to f16 for easier calculations for a moment. Drop the aperture to f5.6 (f16 – f11 – f8 – f5.6).  I wanted just a tiny bit brighter on the moon, so I dropped the aperture to f5.0.

Hence, the above shot was taken at 1/500 at f5.0 at ISO 200.  Conveniently, the sky metered just right to make a rich blue, so I just ran with what the camera gave me.  Had the sky been completely dark, the above calculations still would work.  My paraglider would have just been, had he/she been in front of the moon, a nice silhouette.


Over 70 years later, Ansel Adams was still right.  I always wonder where he got that equation from.  Probably an optics professor (or friend at Kodak) buddy of his.

One handy reference for shooting the moon is this site, Solar Calculator 2.2.  Find your location, click the moon tab and you’ll be able to see what the moon’s azimuth will be.  It’s pretty handy.

There are lots of phone apps out there to do this, too.  I’ve not figured out which one I’ll purchase, as they’re not cheap.  But once I decide on one, it will be posted here.

Is this camera good?

Last night one of my former coworkers asked me about a starter camera for his daughter.


She’s looking at getting into photography.  As with all kids, do you go all in and get something amazing or will it collect dust in the closet with the guitar, keyboard, science kit, etc?  That’s a parental prerogative question and for you to answer.

However, I’ll post the text of the email.  It’s low risk to start with a $130 camera and if your child gets into it, great, keep it, buy her a much nicer once to dramatically improve her photographs.  And, if she really gets into it, the choice will be easy.

Ultimately, you’ll want something with at least aperture control so you can take over depth of field.  Here’s the email text:


The Nikon L610 looks like a fun starter camera.  No guarantees on quality as I’ve not used it, though but it reviews well:

 The only negative on it is shutter lag.  Article here on how to deal with that:

 It uses AA batteries, so buy a pack of Eneloop batteries – love those things, as they’ll last a long time.  Alkaline will die immediately and Li are terribly expensive unless she’s going to a very cold place:

I use these batteries on my product shoots all day.  They don’t lose their charge sitting on the shelf like regular NiMH batteries, either.

I used this (gf’s camera)

in Antarctica – highly recommended, cannot recommend it enough.  It’s a lot more $ than the Nikon but it takes amazing pix in difficult conditions, has a great zoom.  It’ll take better shots than my DSLR without photoshop.  It’s discontinued, so when Amazon is out, that’s it, it’s gone.  It’s not discontinued because it’s bad, just a Sony thing I’m sure.  Maybe the Sony HV-50V is a good replacement.

But if you want to spend more $$ and get an awesome camera, the only one that’s better is the Sony RX-100.  If she doesn’t get into it and finds the L610 is not enough camera, then you have an upgrade path.  But, if she doesn’t get into it, you’re only out $130 with the Nikon.  Parental risk/reward assessment.

Let me know if you have a camera question – I’ll do my best to answer it!