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Condensation X - Prelude

1 exposure

scenes like this won’t benefit from HDR

Incubation II

 3 exposures

scenes like this may be made with 1 exposure but benefit from more

Antarctica CXXX

5 exposures

scenes like this require HDR

How many exposures do you need for HDR images?

It depends.

It depends on the contrast ratio of the scene you’re photographing.

And, it depends on how many corners you’re willing to cut.

There is a case to be made for rendering all images with bracketed exposures. If the best data in a file is in the top stop of the dynamic range of a camera, then making one exposure per stop of dynamic range in the scene, each weighted to the top stop pf the camera (ETTR), will give you ideal data in every stop of the rendered scene, once the exposures are merged. So, ideally, you’d make one exposure per stop of dynamic range in the scene. In your first exposure place the shadows in the top stop of the histogram (to the right), without clipping. Then in subsequent exposures reduce exposure in one stop increments, making a new exposure each time, until the highlights are placed in the top stop without any clipping. Then stop.

Practically, you don’t need to make one exposure per stop of dynamic range in the scene because detail rendered by data in the middle of the histogram, though potentially not ideal, is perfectly usable. Here’s where theory can overtake practice. Test this yourself and find out whether using many more exposures is really worth the effort. In my own tests, I haven’t seen enough difference to make this a regular practice. If you can’t see a difference, then the difference doesn’t matter.

If data in or above the middle of the histogram is good enough, then some scenes will have so little dynamic range (one, two or three stops) that you only need one exposure. Remember to expose to the right to get the best data. Files like this will look over-exposed until they are processed. Once again, for these types of images, using more exposures and processing them with HDR software routines may actually cause problems like posterization.

Surprisingly, some images that look ‘normal’ and don’t seem to need HDR can actually benefit from additional exposures; images where shadows are close to the left of the histogram; the last three stops to the left have dramatically less data to render tonal values and are prone to excess noise and posterization.

For scenes that exceed the dynamic range of a camera sensor and can’t be captured without clipping in a single exposure, the number of exposures needed to render them depends on the contrast ratio of the scene – some need two, some three, some four, some five …

How about making more even exposures and bracketing in half stops? Theoretically this would work. In practice, you’re likely to find that using too many exposures causes some artifacts like excessive midtone compression and posterization.

The number of exposures you need also depends on the number of stops of difference you choose between exposures. Using exposures one and a half stops apart usually produces results just as good as those made with one stop apart. Using exposures with two or more stops of difference between them may cause posterization, which is most visible in smooth gradations, like skies. Using exposures less than one stop apart usually does not produce better results. In a few cases using too many exposures can produce artifacts like excessive midtone compression and sometimes posterization.

In the end the number of exposures you use matters because if exposures are too close or too far apart results will not be optimal, nevertheless the final number of exposures you need depends on both the scene you’re photographing and the camera you’re photographing it with.

Read more on HDR techniques here.

Learn more in my digital photography and digital printing workshops.

Suffusion XV

 Workshop

Black & White Mastery

December 12-16, 2016

Find out more here.

Test the latest Epson printers, inks, and papers. They’re the best ever!

Learn the heart of Adobe Lightroom & Photoshop including the latest advances.

This workshop closely follows the content of my most popular workshop, The Fine Digital Print Intermediate, diving more deeply into black and white imagery.

The Fine Art Digital Printing workshop series offers the most advanced digital printing workshops available anywhere. You’ll learn more in one week than you learn in a semester in college.

Register Now!

Save 10% / $160 – Register By Nov 18

Alumni, save an extra 10% / $160

quotes_visualization

Enjoy this collection of quotes on visualization.

“Visualization is daydreaming with a purpose.” – Bo Bennett

“Visualization and belief in a pattern of reality activates the creative power of realization.” – A. L. Linall, Jr.

“Try out your ideas by visualizing them in action.” – David Seabury

“Visualize this thing that you want, see it, feel it, believe in it. Make your mental blue print, and begin to build.” – Robert Collier

“Having a mental snapshot of where you are, where you are going, and what you are moving toward is incredibly powerful.” – Sara Blakely

“The harder you work… and visualize something, the luckier you get.” – Seal

Read more

2016-cmca-auction-1

Don’t miss out! Browse + Bid on exceptional works by 36 leading and emerging artists. A great way to support The Center For Maine Contemporary Art / CMCA and contemporary art in Maine. Auction online through Paddle8. All proceeds directly support CMCA.

Participating artists include …
Bo Bartlett, John Bisbee, Katherine Bradford, Emily Brown, Tom Burckhardt, Tom Butler, John Paul Caponigro, Caleb Charland, Ann Craven, David Dewey, Lois Dodd, David Driskell, Betsy Eby, Inka Essenhigh, Linden Frederick, John Goodman, Ken Greenleaf, Peter Halley, Charlie Hewitt, Tanja Hollander, Yvonne Jacquette, Alex Katz, Rollin Leonard, Amy Lowry, Kayla Mohammadi, John Moore, Paul Oberst, Winston Roeth, Kate Russo, Peter Soriano, Aaron Stephan, Joyce Tenneson, Don Voisine, Todd Watts, William Wegman, Dudley Zopp

View the art works here.

calendar_201611

Alignment XIX

My free October Desktop Calendar features an image from Death Valley, California.

Download your free copy here.

Find out more about this image here.

Suffusion XV

Suffusion XV 

Check your inboxes!

My free enews Insights features an extended video on mastering black and white photography … plus more resources on optimum exposure.

Sign up here.

hdr_final_img_3327

hdr_3

How many shots do you need to make an HDR merge?

The most common answer is three.

The real answer is … it depends. First, it depends on the contrast ratio of the scene. Second, it depends on the exposure value (EV) increments you use between exposures. Third, it depends on the camera you use.

Many scenes only need 2 exposures. Most scenes need 3. Some scenes need 5. Only a few scenes need 7 or more.

How far apart in EV (exposure value) should separate exposures be?

1.5 stops. (Really any value between 1 and 2 stops.) While you won’t get better image quality if you use more shots separated by less exposure value (less than 1 stop), you also won’t compromise it. While you can also use higher increments (more than 2 stops) be careful – you may produce banding in smooth areas, particularly those with gradations.

Do you need to make HDR merges more frequently with some cameras and less with others?

Yes. Cameras that have a greater dynamic range can capture a higher contrast ratio and so don’t require HDR bracketing as frequently. While this can make a difference for images that would require two and occassionally three shots, for scenes with more extreme contrast ratios HDR merges will be necessary for all cameras.

What exposure mode should you use?

In a majority of cases, use Aperture priority mode (fixing aperture) to fix depth of field. If aperture changes dramatically between separate exposures, substantial changes in depth of field will most likely lead to a loss of focus in some image areas.

You can make exposures for HDR merges by bracketing ISO. Noise levels between exposures will be averaged. The final results will have more noise than the lowest ISO and less noise than the highest ISO.

You can also make exposures for HDR merges with shutter priority mode (fixing shutter speed). Try this when shutter speed drops so low that you can no longer eliminate motion blur, either because of subject motion or because you’re hand holding your camera. (But, use a tripod if you can.)

Do you need to use a tripod to make exposures for HDR merges?

No. By setting your camera to auto-bracket and making exposures in quick bursts you can eliminate the need to use a tripod for well lit scenes. Today’s HDR merging softwares do an excellent job of aligning separate exposures. However, in low light or when long exposures are desired using a tripod is usually necessary.

Read more on HDR techniques here.

Learn more in my digital photography and digital printing workshops.


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