Using a 10-Stop ND Filter For a Long Exposure Shot

Last Saturday, I did a little fun experiment with the speed of the shutter on the flowing water while keeping the other exposure parameters, Aperture and ISO value, same. I had seen some really nice photographs on the Internet with the milky effect on the water which inspired me to try something similar on my own. I really wanted to try this on a big water fall where the water volume and the current is high but one of the such area I know nearby was closed due to the bridge construction. I am planning to go there again after the construction is finished. Meanwhile, I tried something similar in a little creek near my area. It was a bright sunny day and the only way I could achieve a long exposure shot was by using a Neutral Density filter. Here is the list of the tools I used for this setup. 1. Nikon D700 DSLR Camera 2. Nikon 16-35mm f/4 Wide Angle Lens 3. 10-Stop ND Filter (To stop the lights so that I can use the longer shutter speed to get the milky effect) 4. Shutter Release Cable (It is recommended for a long exposure shot to avoid any camera shake. If you do not have one, you can use the 2 seconds timer on your camera) 5. Tripod (It is a must have tool for a long exposure shot) 6. Exposure Calculator App (To calculate the exposure after applying a ND filter)

After setting up the camera on the tripod, I measured the correct exposure (in a Manual Mode) before using a filter and took a shot. I used the widest possible focal length (which is 16mm on this lens) and chose the minimum ISO possible to avoid any digital noise. And since it was a sunny bright day, I didn't need a higher ISO anyway. I turned off the VR on the lens (really don't need when you are shooting on a tripod), selected an aperture value of f/11 and manually focused the lens to the infinity to get everything in focus through out the frame. With an aperture value of f/11 and ISO 100, camera meter gave me the correct exposure with the shutter speed of 1/8th of a second. Here is the first shot with those camera settings.

 Focal Length : 16 mm     ISO : 100     Shutter speed : 1/8 sec     Aperture : f/11

Then, I applied a 10-stop ND filter on the lens and calculated the required shutter speed (using an app on the left side) to compensate the lights blocked by the filter. Since I left the ISO and the aperture values same, Exposure Calculator App gave me the shutter speed of 128 seconds as the right shutter speed to get the correct exposure. Most of the modern DSLR supports the shutter speed of up-to 30 seconds and if you need more than that, you have to dial into the BULB mode and open or close the shutter manually by pressing the shutter release button. But the cool thing about this app is that it gives you a stopwatch (at the right bottom corner) after you calculate the new shutter speed. When you are ready to take a shot, you can snap the shutter release button (with the shutter release cable) and then start the timer on the app at the same time. And when your timer goes to the Zero, you can release the shutter as well by releasing the button on the shutter release cable. When I took the second shot, I noticed that the shot was little bit underexposed. Then I took another shot without changing any settings but kept the shutter open for an additional 5 seconds than the app suggested. If you are shooting in a RAW, little bit underexposed image is far better than the overexposed because it is easier to bring the details from the shadow than from the blown out highlights during the post processing. The reason I got the underexposed image with the calculated time could be due to the changing light during the long exposure time or the filter coating variation or the programming on the app itself. Normally, I take the value given by an app as a base value and then play around few seconds left and right while monitoring the histogram chart on the LCD monitor until I get the correct exposure. Here is the second shot with the long exposure setting (notice the leaves movement and the person in a picture below which are the distractions).

Focal Length : 16 mm     ISO : 100     Shutter speed : 133 sec     Aperture : f/11

May be due to the amount of the water flowing in the creek and the current of the water, long exposure didn't produce very much dramatic effect that I was hoping for but there is some noticeable effect on the water due to the longer shutter speed. Some people prefer the first version with a shorter shutter speed and some prefer the second version. I am not sure which side of the aisle you are on but it doesn't hurt to try something new and out of the ordinary as long as you enjoy doing it.

What Is Hyperfocal Distance And When To Use It?

This post is a part of our Q&A section. If you want to submit your question, please use the form in the Contact page.

Rona (CA, USA) asked : I am very much interested in Landscape photography. Sometimes, when I shoot Landscape, it doesn't come out as sharp as I expect it to be. I have heard about Hyperfocal Distance and it's use in landscape photography but haven't used it yet. Can you please explain about it?

Hyperfocal Distance is the magical distance to focus on that gives you maximum depth of field (almost everything in the frame will be in sharp focus). Hyperfocal Distance differs with the focal length and the aperture of the lens. When you focus your lens on Hyperfocal Distance, the depth of field extends from half the Hyperfocal Distance to infinity. As you already know, for the maximum depth of field, you should always shoot with smaller aperture (large aperture value) like f/16 or f/22 for example. Most of the serious amateur and pro landscape photographers use Hyperfocal Distance for Landscape photography.

This short and brief introduction about Hyperfocal Distance may create more confusions and lead you to many more questions. You might be thinking what is the Hyperfocal Distance for the lens I have? How do I focus at Hyperfocal Distance? Which lens is the best for Landscape photography etc. In this article, I will try to answer these questions as clearly as possible.

How to Calculate Hyperfocal Distance?

Hyperfocal Distance can be calculated by using following equation.

Hyperfocal Distance Equation

Where, H is Hyperfocal Distance, f is Focal Length, N is f-number (Aperture value) and c is the Circle of Confusion

[Updated on 12/1/2015 after reading nev’s, one of our reader, comment. I did some research on the link he posted on the comment box below and also took some reference from Wikipedia as well and added the second formula]

But, for any practical f-number, the added focal length is insignificant in comparison with the first term. So, following formula can also be used to calculate H.

Hyperfocal Distance Formula

This formula is best suited if H is measured from a thin lens. But, for practical purposes, there is little difference between the first and second formula.

When you calculate Hyperfocal Distance (H) using any of the above equations, it comes in mm (millimeter) unit and you have to divide the result by 304.8 to get into the feet and by 1000 to get into the meter.

Hyperfocal Distance is a function of lens focal length, aperture value (f-number) and Circle of Confusion (CoC). In photography, the Circle of Confusion (CoC) is used to determine the depth of field, the part of an image that is acceptably sharp. A standard value of CoC is often associated with sensor type or size and brand of the camera. Every camera manufacturer has it's own CoC value for their different body types and sensors. Normally CoC for 35 mm or equivalent camera (FX format) is 0.030 mm and that of APS-C sensor (Nikon's DX format) is around 0.019 mm.

How do I focus at Hyperfocal Distance?

When you are in the field shooting landscape, you don't have to focus the lens exactly at the Hyperfocal Distance. It's best if you can focus on exact Hyperfocal Distance (you might want to use the measuring tape in that case) but even if you can't, there are different ways for work around. When you are not sure about focusing exactly at Hyperfocal Distance, experts recommend that you should focus it slightly beyond the Hyperfocal Distance. Let's say, for example, your Hyperfocal Distance is 4.6 feet, you should focus on 5 feet and then stop down aperture by one stop (from f/16 to f/22 for instance) to get a little more depth of field.

Why telephoto lens is not good choice for Landscape Photography?

Wide angle lenses are very much popular for Landscape photography. However, normal lens ranging from 50mm or shorter can also be used and works very well to adjust Hyperfocal Distance. Lenses having shorter focal length have relatively short Hyperfocal Distance when set to small aperture (larger aperture value). For example, the Hyperfocal Distance (using above formula) for a 14 mm lens set to f/16 aperture on a 35 mm or equivalent camera is about 1.43 feet. That means everything from 0.71 feet to infinity will be in focus taken with the lens focused at Hyperfocal Distance.

If you do same mathematical calculation for telephoto lenses, you will find the reason why telephoto lenses are not being used for Landscape photography. For example, the Hyperfocal Distance for 200 mm lens set to f/16 on a 35 mm camera is about 275 feet. That means everything from 137.5 feet to infinity will be sharp in a photograph taken with this lens focused at Hyperfocal Distance. Let's say if you have any subject near than 137.5 feet (half the Hyperfocal Distance), this lens will not be able to focus them. That's why such lenses with longer focal length are not considered useful for Landscape photography.

I hope I was able to answer your question to some extent. If you have further comments or questions, please do not hesitate to use the comment box below. Happy Shooting!