Tips for Using Neutral Density Filters for Cityscape Photography at Blue Hour

0Comments

Neutral density filters (ND filters) are essential tools when it comes to shooting cityscapes at blue hour. Even without an ND filter, you could shoot for a few seconds of exposure (using a small aperture like f/13) when the light falls towards the end of dusk.

But those opaque filters let you take even longer exposure photos (minutes, not just seconds), and create beautiful effects such as light trails, silky smooth water, rushing clouds, etc., by slowing down the shutter speed by a certain number of f-stops.

Singapore - Using Neutral Density Filters for Cityscape Photography at Blue Hour

This Marina Bay (Singapore) photo was shot with a 2-second exposure (at f/13) without using any ND filter. The sky looks good, but the water isn’t smoothed out at all, as that exposure is way too short to create silky smooth water effect that is seen in the photos to follow.

How ND Filters Make Your Exposure Longer

ND filters come in different strengths, some popular ones are 3-stop, 6-stop and 10-stop. The bigger the number, the darker the filter (i.e. the less light that is let through) and the longer the exposure will be.

For example, a base shutter speed of one second (i.e. when no filter is attached) can be extended to as long as 1024 seconds (over 17 minutes) with 10-stop ND filter attached, as each “stop” doubles the exposure time:

 

1 second > 2 seconds [1 stop] > 4 seconds [2 stops] > 8 seconds [3 stops] > 15 seconds [4 stops] > 30 seconds [5 stops] > 64 seconds [6 stops] > 128 seconds [7 stops] > 256 seconds [8 stops] > 512 seconds [9 stops] > 1024 seconds [10 stops]

 

It’s easy to calculate when a base shutter speed is a simple number like one second, but what about starting with, say, 1/15th of a second? This is where the Long Exposure Calculator app (for iOS) comes in handy and makes your life easier, as it automatically calculates a required shutter speed for you (look for an Android equivalent here).

ND filter and app - Using Neutral Density Filters for Cityscape Photography at Blue Hour

Neutral density (ND) filter (left) and Long Exposure Calculator app (right).

Using Different Strengths of ND Filters for Your Desired Effect

In this article, we’ll take a little deeper look at when to use which ND filter for your desired effect at blue hour.

3-Stop ND Filter

I don’t use 3-stop ND filter when taking cityscapes at a waterfront, as the strength is too mild to create a silky smooth water effect. Hence, my use of 3-stop ND filter is limited for scenes that have no water to be smoothed out, such as the photo below with light trails of moving cars, which doesn’t require a very long shutter speed.

Shanghai skyline - Using Neutral Density Filters for Cityscape Photography at Blue Hour

Shanghai skyline (China) shot with a 25-second exposure (f/8) using a B+W 3-Stop ND Filter (77mm). The base shutter speed was 3 seconds, ISO 100.

Singapore - Using Neutral Density Filters for Cityscape Photography at Blue Hour

Singapore skyline shot with a 10-second exposure (f/13) using the same 3 -stop ND filter. The base shutter speed was 1.3 seconds, ISO 100.

This mild strength 3-stop ND filter (i.e. not so long exposure) isn’t all bad, though. It allows you to take a number of photos during blue hour, unlike more dense filters like a 6-stop ND filter where you can take no more than a few photos due to a longer exposure time required per photo.

6-Stop ND Filter

I almost exclusively use a 6-stop ND filter when shooting cityscapes at a waterfront. To create silky smooth water effects, slowing down 3 stops isn’t quite enough, but a 10-stop one is way too strong. For example, a base shutter speed of 2 seconds (i.e. with no filter attached) gets extended to 15 seconds (with 3-stop ND filter), 128 seconds (with a 6-stop ND filter) and whopping 34 minutes and 8 seconds (with a 10-stop ND filter) respectively.

Shanghai - Using Neutral Density Filters for Cityscape Photography at Blue Hour

Shanghai skyline (China) shot with a 164-second exposure (f/11) using a B+W 6-Stop ND Filter (77mm) in order to achieve my desired effect of silky smooth water. Had I used a 3-stop ND filter, the water wouldn’t have been smoothed out this much (base shutter speed: 2.5 seconds, ISO 100).

Singapore - Using Neutral Density Filters for Cityscape Photography at Blue Hour

Marina Bay (Singapore) shot with a 163-second exposure (f/13) using the same 6-stop ND filter (base shutter speed: 2.5 seconds, ISO 100).

I typically aim to shoot with a base shutter speed of 2-3 seconds when using a 6-stop ND filter, which extends the exposure to 128 -192 seconds respectively. In order to create a silky smooth water effect, 2-3 minutes of exposure seems just right.

By the way, if you’re planning to buy only one filter for cityscape photography at blue hour, I’d recommend nothing but a 6-stop ND filter. I’ve probably photographed 90% of my cityscapes at blue hour using a 6-stop ND filter. It’s really a game changer if you are interested in doing this kind of photography.

10-Stop ND Filter

A 10-stop ND filter is a kind of special filter that lets you expose extremely long (longer than necessary in most cases!). Personally, I don’t really find 10-stop ND filter useful for shooting cityscapes at blue hour, as the exposure goes too long (even starting at a base shutter speed of 1/2 second gets extended to 8 and a half minutes), and digital noise caused by long exposure becomes too unbearable (even with in-camera long exposure noise reduction turned on).

So, this extreme filter’s use is rather limited to pre-dusk or even earlier in the day, not towards the end of dusk. In fact, one big advantage of a 10-stop ND filter is letting you take long exposure photos while the sky is still bright, which is something 3 and 6-stop ND filters aren’t up to the task of doing.

With a 10-stop ND filter, I usually aim to shoot with a base shutter speed of 1/4 or 1/3 second which is extended to 256 and 341 seconds respectively. I tend to avoid an exposure that exceeds 6-7 minutes, as long exposure noise starts to creep in.

Such a base shutter speed (1/4 or 1/3 second) can normally be achieved around sunset time or before, therefore you don’t really see deep bluish hue that’s typically seen at the prime time of the blue hour. Instead, your photo will have a surreal look that is very unique and distinctive to 10-stop ND filter.

Singapore - Using Neutral Density Filters for Cityscape Photography at Blue Hour

Singapore skyline shot with a 258-second exposure (f/8) using B+W 10 Stop ND Filter (77mm) with a base shutter speed of 1/4 second, ISO 100.

Singapore Using Neutral Density Filters for Cityscape Photography at Blue Hour

Singapore skyline shot with a 259-second exposure (f/7.1) using the same 10-stop ND filter (base shutter speed: 1/4 second, ISO 100).

Conclusion

I hope this post helps you get started with shooting cityscape photos at blue hour using neutral density filters. I’m sure that you’ll be hooked in no time and can no longer shoot cityscapes at blue hour without one!

If you have any questions or tips to share, feel free to do so in the comments below.

Read more from our Cameras & Equipment category

Joey J is a Singapore based enthusiast photographer primarily shooting cityscapes at twilight and dusk (a.k.a. blue hour). Get his free eBook Taking Your First Long Exposure Photos at Blue Hour. Or visit his website LASTLIGHTS.NET where he posts his best photos (from Singapore, Brunei, Southeast Asia, and beyond) and shares his experience photographing cityscape photos with long exposure at blue hour.

  • Daniel

    Great Article Joey! I find the 6 stop is the sweet spot for cityscapes too! I find my 10 stop gets used most for seascapes and nature long exposures, or if I’m doing black and white shots.

  • Thank you, Daniel! Yes, 6 stop ND filter comes in very handy for blue hour cityscapes. I’m experimenting with 10 stop ND filter more often lately. It can create epic shots if used well, I guess. 🙂

  • Md

    Thanks for the article …

    What is a base shutter speed !!
    So for a beginner,first you take a shot without any ND filter,which mode ( manual ) ?
    then you decide to use a 3stop ND filter ..
    How to know which f-stop ( 8,10,13 …… ) ?
    after attaching the filter to the lens how do you know how long you should keep the shutter open ?

    Thanks ……..

  • Hi there, a base shutter speed is just a shutter speed (when there is no filter attached). If shooting without any ND filter, Aperture Priority mode should be the easiest. You decide an f-stop (e.g. f/8, f/11), then let the camera decide a shutter speed. Manual mode is required only when your shutter speed exceeds 30 seconds.

    You can decide which f-stop to use. The bigger the f-stop number, the longer the shutter speed becomes (f/8 at 1 second of shutter speed equals to f/11 at 2 seconds of shutter speed).

    For your last question, please check where I’m talking about Long Exposure Calculator app. By setting a filter density (which ND filter you’re using) and a base shutter speed, this phone app automatically calculates a required shutter speed for you. Such a usual app!

    For more details, you may download and check my free eBook (http://lastlights.net/long-exposure-photography-ebook/) mentioned in the author bio.

    Thank you for reading my post. 🙂

  • Md

    Thank you for detailed answer ,,

Join Our Email Newsletter

Thanks for subscribing!


DPS offers a free weekly newsletter with: 
1. new photography tutorials and tips
2. latest photography assignments
3. photo competitions and prizes

Enter your email below to subscribe.
Email:
 
 
Get DAILY free tips, news and reviews via our RSS feed