Sunday, March 17, 2013

Las Vegas and Neutral Density Filter

Las Vegas Blvd
Las Vegas taken from the back side of the main strip during sunset using an ND filter at 2min exposure, the lights from oncoming traffic was too bright so using an ND filter helped reduce the cars bright lights while giving a chance for the lights on the buildings to shine thru.

Supposedly PANSTARR was to be visible on the skyline at sunset on this pretty evening but I could not see it. so I decided to try some long exposure using a B&W ND 3.0 filter which is 10 stops. The trick to using a neutral density filter is to take an exposure reading first, say f16 and the camera says it'll shoot it at 30s, now apply your filter to the lens, then use a chart or an iphone app which helps you figure out how long to keep shutter open, my advice is try not to go over 30s because that greatly adds noise to image. ND filters can be fun to play with as they can really create unusual images, they are good fort scenes where you want to create light trails, smooth waterfalls and add blur, combining them with a flashgun can add drama.
ND Filter Chart

I'm not going to go into great detail about all this because its been done to death on the internets but you can google it. Its fairly simple and in some cases I do trial and error, i've been doing it for a while now, that by looking at my cameras exposure I can sort of tell how long I need to shoot for now. The chart above assumes the following. without the nd filter on, take a reading, make note of the exposure (shutter speed) look at chart, now apply your nd filter, put camera in manual mode, dial in the proper shutter speed value, connect a remote trigger if going over 30s or use self timer with exposure delay and fire away. But what I do wish to say is don't use cheap filters reason being, the glass is inferior. I now have a collection of these filters, ranging from $15 all the way up to $250 and I can assure you the B&W filters are top of the line and hence produce a much better result.
How not to use ND Filter
So a friend asked me recently what should I buy? I told him since you are just getting into it don't buy the most expensive and dont get the cheapest one. He said? why are they not all the same? is glass not glass? my flat out reply to this is NO. its about quality and how the glass is made and what went into it. Above is a perfect example of this. This image is exact same shot as the first one but using a Variable ND filter that goes from 2 to 8 stops. I wanted to see if this $15 Variable (meaning you can rotate to adjust the amount of light it lets into the camera by simply turning it) ND filter could compare to the B&W 10 stop filter, aka Black Glass. The variable ND filter had some sort of odd reaction when i pushed it to the limits at 8 stops and it some how bent light. now would this happen with a regular cheap 8 stop filter, most likely no. The notion of simply caring with you one ND filter is nice especially if you can adjust how many stops you want problem is the more stops you use the worse the image gets in some odd distortion, so in reality this kind of filter is good for a few seconds, going past 30s will get ya ugly results. But I simply wish to emphasize, you get what ya pay for. So the N-ND filter could not match the B&W but I think if you just used its to reduce a few stops you would get decent results. I've not had much good experience with the V-ND filters so i recommend getting an ND filter kit, something that you can buy that comes with usually 3 to 4 filters, a CPL, than 1,2, and 3 stop nd filters.

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