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by Bart Arondson

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I would like to take a picture of a street during the day to depict how much traffic and cars there are on the street. Is there anyway to do this with a long exposure photograph? I have a Nikon D90 and I set the f stop down to 1/16 (the lowest of my lens) and set the time to 2 seconds. Doing this, the exposure is almost saturated when taken around 5pm with the sun setting behind a tree. Doing this, the cars passing by were very hard to make out against the stationary background, being visible as a blur in the color of the car.

Perhaps this is not possible and I should just do this at night where the cars lights are much brighter than the background.

Please suggest how else I might depict the traffic in a photograph? Are daytime long exposure photographs even possible?

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Note - A neutral density filter is the obvious first answer here, but after reading into your question a bit more, I don't believe that is what you are quite looking for. –  dpollitt Sep 27 '13 at 2:29
1  
Are you confusing "time lapse" with "long exposure"? Time lapse is usually a series of photos taken at intervals, which is then assembled into a video to speed up something that happens slowly - eg a seed germinating. It sounds more like you a looking to achieve a longer exposure - such as would show vehicle light trails at night. However, note that if you use too long an exposure then passing traffic will effectively disappear completely from the photo, leaving an empty-looking street. You could try a slow-ish exposure, and add a pop of second curtain flash to try and highlight a car. –  John Sep 27 '13 at 8:12
    
@John I've corrected the question to use the correct term. –  WilliamKF Sep 27 '13 at 14:48

4 Answers 4

up vote 2 down vote accepted

One of the photographers that I find most interesting in the area of long exposure is Michael Wesely (yea, the website doesn't really do anything to show his photography).

His images include

enter image description here

enter image description here

The first one you can see the date on it... it was shot from May 4th, 1997 through March 6th 1999... almost two years. The tracks in the sky are where the sun traveled each day (or actually, two days for each track).

From a two second exposure, its "only" five stops to a one minute exposure, and then about ten stops to a one day exposure... and a week is only three more stops beyond that.... two more stops for a month...

So yes, you certainly can take a long exposure during the day time.

What you need is a stack of neutral density filters... although you can make your own that will give you quite a few stops by using cross polarizers. You can either buy these (they're often called VariND or VND filters) or make your own using a pair of polarizer filters (note: you need the outer filter to be a linear polarizer, not a circular polarizer.

Look at that second photograph from Wesely and note that with a long enough exposure, you won't see the car itself, though you might be able to get some hint of its lights.


For capturing traffic, you are going to want something that isn't quite as extreme as the photographs of Wesely. You'll want to see about a properly exposed 1 second photo and then work from there. There are many factors that play into this - the distance from you to the traffic, the focal length of the lens (field of view), the speed at which the vehicles are moving... all that plays into trying to capture the proper image.

Note that often the most striking photographs of traffic come at dusk when you can get the cars with their lights on (white in one direction, red in the other, and maybe even some yellow blinkers). This will also aide in getting the long exposure.

Consider the image on this post. A small section of it follows:

A snippet of long exposure

If the cars are moving at 30 mph, and the duration of the exposure is three car lengths (about 60 feet), this is 1/88th of a mile. 30 mph is 2640 threeCarLenghts/hour. 1/2640th of an hour is 1.3 seconds.

This isn't necessarily saying that this is the right exposure for your setting... but it gives you a starting point and the tools to work out about what exposure you are looking for.

Once you work out what duration of exposure you want for your scene, you can then work out the rest of the exposure to figure out how much neutral destiny you will need. If you are doing a 1 second exposure in daylight at ISO 100 at f/16, the rule of thumb gives me 1/100th of a second. To go from 1/100th of a second to one second you will need about six and a bit stops of neutral density (closer to seven). (1/100 . 1/60 - 1/30 - 1/15 - 1/8 - 1/4 - 1/2 - 1)

And from this, you'll be able to go and get an appropriate set of neutral density filters to try to capture the image.

I'll also point out that dusk is about six stops from full sun.

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You are achieving somewhat long shutter speeds of 2 seconds. But the problem is the result of this is that the moving objects are not captured for long enough in the same position to get the desired effect. What might work best is to stack images. You could capture shorter frames of the cars moving, maybe 1/15th of a second for example, multiple times, then combine those images in post production to form a pleasing result. This might require many frames as well as experimentation of how long the shutter speed is. We have some previous questions that might help you with image stacking knowledge as well:

You might also be interested in another way to capture timelapses without using such a narrow aperture. See: What are neutral density filters and how do I use them to create long exposures in daylight?

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An ND filter can help you take longer exposures during daylight. This is what people use when photographing things like those blurred shots of running water.

An ND filter is like sunglasses for your camera - its only effect is to reduce the amount of light entering the lens, allowing you to take longer exposures with the same aperture, or widen up the aperture with the same shutter speed.

You can get ND filters that reduce the light by 1 stop, 2 stops, etc up to 10 stops. Sometimes they are marketed according to the reduction factor, so 2x means one stop, 4x means two stops, up to 1000x which is, more or less, 10 stops.

A 10 stop ND filter would allow your 2 second exposure to become a ~2000 second exposure (about 33 minutes). Or, it would allow you a 5-10 minute exposure with a more comfortable aperture of say f/8.

Such extreme ND filters are not as useful for everyday use as, say, a 3-stop filter, but can be useful in niche situations like this.

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I have tackled a very similar situation, the problem with doing this during daytime is that the car exists particular area of the image for a very short time compared to the background. If you get 0.5 seconds of car and 20 seconds of background the car is going to be very washed out compared to the background.

for this reason long exposures of motion tend to look very washy and unimpressive.

The solution I came up with was to shoot a large number of short exposures and produce two image stacks in Photoshop. For the first I set the blending mode to lighter colour and one with the blending mode set to darker colour.

This gives you one image with the darkest version of each pixel and one image with the lightest version of each pixel. More importantly you will guarantee that a car will show up in one or other of these images.

You can either do a simple average of the light and dark image, or if that doesn't look good you might have to selectively blend them together.

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