Neutral Density Filters

Iron Flatline · Aug 28, 2006

Hi all.

I've been considering doing some ND photography. It works well with architecture (a favorite subject) as the long exposures allow me to get a good image of a building as people move through without leaving much of an impression.

Can I get some guidance on NDs from anyone here who already has some experience? How dense? How do I gauge density vs. what I'm trying to accomplish. I assume this will be more than just a couple of f-stops. Is there a particular brand that has struck any of you as particularly avoidable or recommendable?

markc · Aug 28, 2006

They are rated by how many stops they reduce light. Just stack them if you need more light reduction. Just be careful not to occlude the view with too many rings.

Tiffen and B+W have 0.3, 0.6 and 0.9 ND filters for reducing one, two and three stops of light. Hoya, on the other hand, uses 2×, 4× and 8× to indicate reducing 1 (i.e. 2=21), 2 (i.e., 4=22), and 3 (i.e., 8=23) stops. The two ND filters come with Nikon's Coolpack are of ND4 and ND8 type, which means they reduce two and three stops, respectively.

From here: http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/filter/filter-ND.html

Iron Flatline · Aug 28, 2006

I guess my question is: how did he get this shot. I know he used ND filters, I'm just trying to guess how dense a filter he used.

Weekly Shot Submission

I don't want to link directly because it is not my shot. I've always been fascinated by abandoned urban landscapes. They are so unusual - we usually expect them to be full of people and vehicles.

markc · Aug 28, 2006

Not sure. We can play with some math:

Sunny 16: ISO 100, 1/125th, f16.
Change to f22 is 1 stop, so 1/60.
One ND8 filter is 3 stops, so 1/8.
A second ND8 filter is another 3 stops, so 1 second.
I don't think 1 second would be enough, so he either used a higher density filter, or even more filters. There's vignetting, so I wouldn't be surprised if he used three filters, for 8 seconds. That should be enough for moving cars.

Philip Weir · Aug 28, 2006

Hi "ironflatline" I like a challenge. What makes you think he used a ND filter ?? Is it just because you see no traffic ???

Iron Flatline · Aug 28, 2006

It came up in online conversation. I actually e-mailed him to ask him which filters he used, but haven't heard anything back in a couple of days. He might be traveling, or just not in the mood to share :er:

IT's not just a question of replicating one person's shot. I'm trying to learn as much about ND filters here because I know noone that's got them, works with them, or can help me understand. We have several very good photography store here in LA, I prefer Samy's, but even there the advice I would get on something like ND filters is going to be ultimately based on my sales person's experience with them. Before I go and ask there, I thought I'd tap the collective knowledge base of our community here.

Iron Flatline · Aug 28, 2006

But I guess if we're talking about Lumilux, let me link to the blog and the image at his site:

http://lumilux.org/2006/05/08/014886

The EXIF shows f/8 for 15 seconds at iso 200 (lowest for Nikon D70), so that's even denser than markc's calculation.

Again, this link here only to give credit where credit is due. I think the shot is cool. It would be fun to do Sunset Blvd. or Hollywood Blvd. early in the morning before cars really get bumper-to-bumper.

Just trying to learn, I guess.

EDIT: His equipment list says B+W ND 113 filter.

markc · Aug 28, 2006

From what I could find, that filer has a 4.0 density, so it's 13 1/3 stops. That's more than 4 of the ND8s stacked. Damn....

Alex_B · Aug 30, 2006

I have the feeling no ND was used ... maybe it was just some odd time of the day and hence long exposure .. or there was a football match on TV?

I think if this was in heavy traffic, even with a strong ND you would see traces of the many cars moving past. but I cannot see anything like that on the image.

Also, look at the odd colour of the tarmac, might be very early morning (??) with hence long exposure and then some tweaking with saturation of the digital data later? Just an idea.

Edit: just saw your edit .. so I take this back as he apparently used an ND ...

Anyway, I have a B+W ND 1.8 and an ND 3.0 .. they are supposed to be very neutral, but I have to start using them to find out myself (they just arrived this morning

)

Iron Flatline said:
I guess my question is: how did he get this shot. I know he used ND filters, I'm just trying to guess how dense a filter he used.

Weekly Shot Submission

I don't want to link directly because it is not my shot. I've always been fascinated by abandoned urban landscapes. They are so unusual - we usually expect them to be full of people and vehicles.

Iron Flatline · Aug 30, 2006

Alex_B, as I wrote in the thread you quote and in a different response within the same thread, I know that he used an ND filter. As I said, it had come up at a different forum, or possibly as part of one of his posts on Weekly Shot.

Not only have I since then communicated with him, he's actually a member of this forum and saw this thread before he ever had a chance to respond to my e-mail question about the filter.

I'll let him "out" himself.

It's a B+W ND 113 filter (4.0!), which was apparently designed for studying solar flares or just other staring-at-the-sun activity. It may have been discontinued.

Alex_B · Aug 30, 2006

yes, sorry, got confused here!

probably my lack of sleep

Wally · Aug 30, 2006

I use ND filters quite a bit, to play with long exposures. I often stack and 8x and a 4x to get 15 seconds of exposure in daylight. That is what I did with this shot

When stacking filters you have to remember to multiply not add. For example this is a 8x on top of a 4x. The 8x cuts 8 stops of light and the 4x cuts 4 stops. Together they do not equal 12 stops but rather 32 stops.

In this shot the model stood still for 5 seconds then moved around for 5 and then moved out pf the frame.

Alex_B · Aug 31, 2006

Wally said:
I use ND filters quite a bit, to play with long exposures.

That is in fact what I inted to do, not to get rid of cars and people in your image, but to get motion blur and half transparent people.

Wally said:
In this shot the model stood still for 5 seconds then moved around for 5 and then moved out pf the frame.

5 seconds is not that short, is it hard for the model to sufficiently freeze in her motion before she starts moving?

markc · Aug 31, 2006

Wally said:
When stacking filters you have to remember to multiply not add. For example this is a 8x on top of a 4x. The 8x cuts 8 stops of light and the 4x cuts 4 stops. Together they do not equal 12 stops but rather 32 stops.

As I understand it, the factor gets multiplied, but the stops get added. An ND4 is not 4 stops, but 2 to the 2nd power, so 2 stops. An ND8 is 2 to the 3rd power, so 3 stops. Mulitply 4 x 8 = 32 = 2 to the 5th power which is 5 stops = 2 + 5.

Digital Matt · Aug 31, 2006

Hoya makes a 9 stop ND filter.

Neutral Density Factor 2.7 / 400 x
Exposure Adjustment approximatly 9 Stops
Reduces ISO 1/500

http://www.adorama.com/HY77ND400.html