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Tips & Techniques
Neutral Density Exposures the Easy Way! PDF  | Print |  E-mail
Tuesday, 24 June 2014 21:29

Artistically blurring moving elements in a photograph can offer a new way to represent familiar scenes.  A ten stop neutral density (ND) filter renders a wonderful softness to waves, waterfalls, and moving clouds.  It's also effective with tall grasses blowing in the breeze.  Car lights passing in a busy street scene are transformed into glowing lines slicing through your composition.

Avalon Pier 5641

As its name implies, ten stop ND filter will reduce the light exposing your image by ten stops.  So, for example, working at dawn, if the proper exposure without the filter is 1/4 second, it'll require an additional ten stops of exposure with the filter.  That's 4 minutes at the same aperture and ISO.  There's a phenomenal difference in the look of an image at 1/4 second and that at 4 minutes.

But using this filter presents some challenges.

If you hold a ten stop neutral density filter to your eye, you will not see through it.  Same problem when you put it on your lens.

Using a solid tripod is a must.  Not only must you hold the camera steady during long exposures, you'll find it necessary to hold the composition stable as you work with the filter.  A shutter release cable will permit you to hold open the shutter without shaking the camera.

Work in manual mode while the ND filter is attached.  In most cases, your camera's meter will not get enough light to meter properly, so your exposure automation will not be reliable.

Since you can't see anything through the filter, neither you nor the camera will be able so focus.  The trick is to focus without the filter on the lens.  After obtaining focus, switch off auto-focusing so the camera does not try to refocus.  Work carefully so you do not upset the sharp focus you just obtained.  If you accidentally shift the focus, remove the filter, refocus, and again disable auto-focus.

Before you attach the ND filter, you must decide how to determine the exposure.  Here's three ways.  Two are cumbersome, one is super easy.

Cumbersome Way #1 - Calculate it in your head
Determine your exposure without the ND filter.  You can do this either with exposure automation on, or in manual exposure mode via the meter in your camera, or by making test exposures and checking your histogram.  Insure that you aren't clipping any important highlights, and have as many of the shadows as possible inside the histogram range.  Once you are satisfied with the exposure, note the shutter speed.  Switch to manual exposure.  Carefully attach the ND filter, being careful not to upset the focus.  Now, multiply the shutter speed, in decimal seconds, by 1024.  (1024 is 2 to the 10th power, for math geeks.  Ten stops!)  Multiplying by 1000 instead of 1024 is close enough.  Set that for your shutter speed.  You may have to go to bulb setting. 

Using our previous example, 1/4 of a second is 0.25 seconds (in decimals notation), multiply that by 1000, and you get 250 seconds, or 4 minutes and 10 seconds.  (We have a little rounding-off error here.  A ten second discrepancy in four minutes is not noticeable.)  Yes, it works.  But you may get brain blisters from all the math.

Cumbersome Way #2 - Use a Neutral Density Calculator App
Determine the correct exposure as above.  Switch to manual exposure.  Carefully attach the ND filter, being careful not to upset the focus.  Use an ND Calculator smartphone app, enter the exposure, the number of stops in your ND filter (we've been discussing 10, but there are other densities available), and read out the new shutter speed for when you use the ND filter.  Apps include ND Filter and ND Filter Calculator for Android, or ND Filter Calculator and LongTime for iPhone.  Not as cumbersome.  But there's an easier way.

The Easy Way - The ISO 6400 trick
Be sure you are in manual mode.  Attach your ND filter, being careful not to bump the focus.  You are going to do the exposure determination and the final shoot both with the ND filter attached.  For exposure testing purposes only, turn your ISO up to 6400, and determine the correct exposure by making test shots and checking the histogram.  Note the shutter speed in seconds.  At ISO 6400, these photos will be noisy, not what we want for a final image.  Turn the ISO down to 100.  The shutter speed you noted in seconds at ISO 6400 is the shutter speed in minutes at ISO 100! Set that shutter speed in minutes, possibly needing to use the bulb setting, and make your final exposure.  Under the lighting conditions of our example, with a ten stop neutral density filter attached, and ISO at 6400, the shutter speed would be 4 seconds.  Turn the ISO to 100, and the correct shutter speed is 4 minutes. 

If you are going to make a mistake here, it will probably be forgetting to turn the ISO to 100 before making your "real" shot with the ND filter, so pay attention to that.

You may be tempted to use exposure automation to make the ISO 6400 exposure determination.  I've found that the meter is less accurate with such severely subdued light coming thru the lens because of the ND filter.  If you get your ISO 6400 exposure in any way that relies on the meter, you may find that your final exposure is off.  And since ND exposures can range into minutes in some cases, you don't want to take more of those than necessary trying to dial it in.  If you use test shots and check the histogram, it's WYSIWYG - what you see is what you get!  You are determining exposure by what the camera actually recorded, rather than by what the meter thinks the camera will record.

Note that this ISO 6400 trick is completely independent of the ten stop density of the filter we're discussing.  It can be used with any strength ND filter, even a variable ND filter.  It has nothing at all to do with the filter!  In fact, this trick is just as useful for any low light exposure determination.  The key is the relationship between ISO 100 and ISO 6400, and between minutes and seconds.  The difference between ISO 100 and 6400 is six stops (100, 200, 400, 800, 1600, 3200, 6400 - six steps.)  The difference between 1 second and 1 minute is also six stops (1 sec, 2 sec, 4 sec, 8 sec, 15 sec, 30 sec, 60 sec - six steps.)  So, holding aperture constant, the correct exposure in seconds at ISO 6400 is also a correct exposure in minutes at ISO 100.

What if your camera only goes down to ISO 200?  Figure the exposure at ISO 100, and use one half that time at ISO 200.  That's double the ISO sensitivity, one half the amount of time to expose.  A one stop change of each.  Again using our example, at ISO 200 the shutter speed would be 2 minutes.

Try a strong neutral density filter, such as a ten stop ND, to open exciting creative possibilities.  Find new ways to record moving items, turning the movement itself into compositional elements.  And use the easy, fail-proof ISO 6400 trick to determine the exposure through that nearly opaque, but magical piece of glass.

Thank you to Boston-based photographer Paul Treseler http://paul-treseler.artistwebsites.com/ for sharing this technique with me.


The photo accompanying this article was made about 10 minutes before sunrise, using a ten stop ND filter.  Using the ISO 6400 trick, I determined that the ISO 100 exposure at f/16 would be 25 minutes.  With the sun about the break the horizon, the light was changing too quickly to allow a 25 minute exposure.  So I bumped the ISO by three stops to ISO 800, and shortened the shutter speed by three stops to 3 minutes.  This rendered the sky and water perfectly.  However, the underside of the pier was far too dark.  The range of tones in the scene exceeded the sensor's ability.  So, I made a few bracketed exposures at the same ISO and aperture, but without the ND filter.  The underside of the pier was nicely recorded at 1/2 second, but it blew out the water and sky.  I combined the images in the digital darkroom to create the image as I saw it in my mind.  Avalon Pier, Kill Devil Hills, on the Outer Banks of North Carolina.

Last Updated on Wednesday, 25 June 2014 18:36
 
Quality of Light PDF  | Print |  E-mail
Thursday, 25 November 2010 17:20

"Quality of light" is a term I've used in two recent conversations.  One use, with one of my early photographic mentors, went without question, completely understood by both parties.    Another, sent the conversation off on a puzzling tangent about the benefits and drawbacks of living in our remote edge of the earth, the Outer Banks.  It was only later that I realized that she misheard my saying "quality of light" as "quality of life."

Sun rising thru fog in the SmokiesLike "quality of life", the term "quality of light" can be used in both a positive or negative way.  But photographers usually use the term in its positive context, describing light that flatters our subject.

Depending on the subject, the most desirable qualities vary.  Light can be hard and direct, casting deep contrasty shadows.  Or it can be soft and indirect, wrapping light around our subject, filling shadows.  A portrait photographer may prefer harder light to show the character lines of a wizened elderly man, or the soft light to complement the soft features of an innocent girl.  The portrait photographer may use unmodified light from his flash units to get direct light.  He may limit the spread of the light with a honeycomb attachment called a "snoot."  Or he may purposely soften the light by directing it through a diffuser, or bounding it off a soft reflector.

In the outdoors, photographers are much more at the mercy of nature and the environment.

In the sun under a clear midday sky, the light will be hard and directional, casting hard shadows.  If the sky is hazy or softly overcast, shadows are cast, but softened by reflections off the moisture in the atmosphere.  If completely overcast, the light appears to come from all of the sky, making the lighting nearly shadowless, with all the atmospheric reflections filling any shadows from the weakened direct lighting.  All are qualities of light.

In clear air, the sky is blue and there's detail in the foreground and off toward infinity.  In fog, the level of detail drops with distance.  Very different effects.  Which is right?  What is the effect you are after?

Light also has direction.  If light skims across a surface, it emphasizes the texture of the surface by creating numerous highlights and shadows.  It the light is 90 degrees from the surface, such as at high noon over a plain, the only shadows are from items that reach up from the plain at an angle different from that of the sun.  Texture is minimized.

Early or late in the day, the sun cuts tangentially through the atmosphere, and the high frequency bluish components of the white sunlight are filtered out, leaving noticeably warmer colors of red, orange, and yellow. At midday, there is less atmospheric filtering due to the direct and shorter path through the atmosphere.  The color is noticeably bluer.  The colors of the light, and the colors reflected off the objects we see, are qualities of light.

A glance through the images in Outdoor Photographer or a similar magazine, typically portray landscapes being glanced by golden sunlight at the beginning or the end of the day.  The "quality of light" differentiates these images from the more mundane shots made in the harsher light of midday.  The favorable quality of light invoke favorable responses to the image.  Outdoor photographers are in place before the sun rises, and eat very late dinners, all to get that low golden quality of light.

When a photographer gushes about the quality of light, he has found the conditions that flatter the subject in the way he wants to portray it.  That could be hard or soft, low or high angle, warm or cool.  The quality of the light is open to your interpretation.


Click the photo for more info.

 

Last Updated on Monday, 30 May 2011 13:24
 
Making Neveria Alicia PDF  | Print |  E-mail
Tuesday, 08 September 2009 21:39

Photograph: Neveria Alicia 1253 by Daniel J BeauvaisHere's a fun way to create a tasteful interpretation of a photograph, requiring some moderate Photoshop skills.

This photograph of an ice cream parlor on Isla Mujeres, off the shore of Cancun, uses a combination of two effects to achieve the final image.  Here's the basics of how I did it.

Layers used to make Neveria Alicia photographIn Photoshop, I copied the original background photo onto two additional layers, and labeled them "Watercolor look" and "Line drawing."  (See the Photoshop screenshots)

I selected the "Watercolor look" layer, and temporarily turned off the visibility of the other two layers.  I applied Topaz Adjust plug in filter, tweaking the controls until I found a pleasing smooth painterly effect  You may find that some of the standard Photoshop filters may give you another pleasant effect.

I then selected the "Line drawing" layer, and temporarily turned off the visibility of the other two layers.  At this point, it looked like the original photo.  I applied the "Find Edges" filter (Filter > Stylize > Find Edges), getting a colorful line drawing.  To turn the line drawing to black, I used Image > Adjustments > Black & White.

To put it all together, I restored the visibility of the "Watercolor look" layer, then changed the blending mode of the "Line drawing" layer to "Darken."  In this way, the "Watercolor look" layer showed thru except where the "Line drawing" layer had dark lines.  I saved the result.

Hint:  If you try this technique, and you may find that the line drawing is not bold enough.  If so, select the "Line drawing" layer, apply some Gaussian Blur to it (Filter > Blur > Gaussian Blur) to fatten-up the lines.  Use Levels (PC: Ctrl-L, Mac: Command-L) to keep just the darkest parts of the fat lines.

I used Photoshop CS4 and Topaz Adjust 3, however, any recent version of these programs will suffice.

Give this idea a try with some of your own photos, and have fun!

Prints and gifts containing this image are available in my gallery.

 

Last Updated on Thursday, 25 November 2010 16:44
 
Most Valuable Photo Accessory PDF  | Print |  E-mail
Wednesday, 10 June 2009 22:47

Mother and sons searching for seashells at sunrise on Pensacola BeachI added one simple item to my photo gear that doubled the number of keepers I get when shooting in golden light.  Without this item, fully half of all available golden light was not visible to me.  The best part is, that the least expensive of these items is as effective as the most expensive.  If I should forget to bring this item when I travel, a replacement is available at almost any store, but there's most likely a very serviceable one in my hotel room.  I can even substitute my cell phone for this photo accessory.  A few people don't need this, but I, and most others do.  The item?  My alarm clock!

Closely related is my 5AM filter.

Thanks to Boston-area photographer Jacob Mosser (http://www.psaphoto.org/gallery/mosser.htm) for the clock quip, and Hatteras Island photographer Scott Geib (http://www.lightkeepergallery.com/) for the 5AM barb.

A larger view of this image, and print and gifts are available at here.

Last Updated on Friday, 26 November 2010 11:56
 


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