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Alex Healing Adastral Park Photography Club, 11 th February 2010

HDR Photography

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Alex Healing Adastral Park Photography Club, 11 th February 2010. HDR Photography. What is Dynamic Range?. For a scene : ratio between the brightest and darkest parts of the scene.   - PowerPoint PPT Presentation

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Page 1: HDR Photography

Alex HealingAdastral Park Photography Club, 11th February 2010

Page 2: HDR Photography

What is Dynamic Range?

For a scene: ratio between the brightest and darkest parts of the scene.  

For a camera: ratio of saturation to noise. More specifically, ratio of the intensity that just saturates the camera to the intensity that just lifts the camera response one standard deviation above camera noise.  

For a display: ratio between the maximum and minimum intensities emitted from the screen.

The luminance of starlight is around 0.001 cd/m2, that of a sunlit scene is around 100,000 cd/m2, which is hundred millions times higher

Source: http://www.hdrsoft.com/resources/dri.html

Page 3: HDR Photography

What is High-Dynamic Range Photography?

Post-processing technique where multiple exposures are combined to create a single image with higher dynamic range.

They are 32-bit images (96-bits per colour pixel) with an infinite set of values each pixel can take (floating point). Standard RAW images are 12-bit and JPEG are 8-bit.

In order to reproduce the dynamic range on low dynamic range displays or prints, the ranges are compressed using by tone mapping.

Page 4: HDR Photography

A ‘bit’ of conversion

12-bit RAW

12-bit RAW

12-bit RAW

8-bit

32-bit HDR 8-bit HDR8-bit

8-bit

RAW Conversion(optional)

Exposure Blending

Tone Mapping(Dynamic

Range Compression)

Page 5: HDR Photography

Normal Exposure(full-frame metering)

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Exposure Bracketing

+1

0

-1

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HDR Image

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Not entirely new

Gustave Le Gray, (1820–1884)

Source: http://en.wikipedia.org/wiki/Gustave_Le_Gray

Page 9: HDR Photography

Why HDR?

“well… you really had to be there…” Film/CCDs are not eyes

we are under a patchwork illusion all the time (but ignorance is bliss)

Realistic Surreal Increases your photo-taking possibilities

e.g. eliminate need for fill-in flash for indoor/outdoor hybrid shots, direct sunlight, …

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What you need

A (digital) camera Preferably capable of auto exposure

bracketing Ideally a tripod

(I’ve never used one!) HDR software

Some free, some commercial Lots of other optional tools

Photoshop …

Page 11: HDR Photography

HDR Software

Source: http://wiki.panotools.org/HDR_Software_overview

Page 12: HDR Photography

Taking the photos

Preferably use a tripod

Use Automatic Exposure Bracketing (AEB) where possible

Shoot in either JPEG or RAW. HDR software can handle several RAW formats.

Source: http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=1646

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Preparing the photos

Be aware of any moving subjects can remove before to avoid ghosting or

do in a single step after the HDR image is created

HDR software may be able to avoid ghosting but there will always be cases where it fails

Page 14: HDR Photography

Combining the photos

HDR software may have integral image alignment for handheld photos.

The combined image will not display well on your monitor however until you tone map to compress the 32-bit image into something renderable.

Page 15: HDR Photography

Tone mapping

Depends what effect you want but if realism is what you’re after then you have to be very careful. Potential unwanted effects include halos,

tone reversals, noise and sometimes just too much colour!

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Tone mappingSource: http://beforethecoffee.wordpress.com/photomatix-tutorial/

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Surreal HDR

Photo by welshbaloney http://www.flickr.com/photos/welshbaloney/

Photo by aicizz http://www.flickr.com/photos/aicizz/

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True Tone HDR (TTHDR)

Photos by ojaipatrick http://www.flickr.com/photos/ojaipatrick/

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Some of my shots…

… and the reasons for why I shot them

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Blown-out Skies

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Silhouetted Foreground

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Silhouetted Foreground

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Nothing right

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Outside from inside

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Direct Sunlight

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Direct Sunlight

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Direct Sunlight

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Direct Sunlight

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Moving Targets

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Moving Targets

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Moving Targets

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Moving Targets

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Where are the colours?

Page 34: HDR Photography

Where are the colours?

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A dull day?

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A dull day?

Page 37: HDR Photography

Exposures and how many?

Spot metering on the highlights and shadows, note the exposure times.

Multiply exposure time for highlights by four successively (stop spacing of 2 EV) until you pass the exposure time for the shadows.

Three exposures with 2 EV is typically good but you may have to go to full manual depending on your camera model.

Page 38: HDR Photography

Remember your settings

Settings should remain constant for all the images in a series Focus Aperture (set small) ISO (set as low as possible, particular if

using tripod) Auto white balancing (beware but impact

minimised) Custom white balance or shoot in RAW

Page 39: HDR Photography

RAW ‘HDR’

Not strictly HDR but using a good RAW converter you can create fake exposures which sometimes squeeze more data out than you would otherwise with a single image. Due to good noise reduction

Dynamic range is essentially the same though as you’re simply splitting the dynamic range of a single RAW image (12-bits per colour) into slices and then recombining.

Page 40: HDR Photography

HDR Panorama

Panorama first, then HDR same effect across whole image

Page 41: HDR Photography

Post-post-processing

Re introduce originals to make more realistic and get rid of any ghosting.

De-noising further.

HDR software can be very powerful but there may be times that you’d prefer touching up further with what you’re familiar with.

Page 42: HDR Photography

HDR in conclusion

Diverse: ultra-realistic to shockingly surreal Personal taste but think about what your aims

are Don’t use for the sake of it

If the scene lends itself to higher dynamic range, otherwise many other post-processing techniques that might be more suitable

Go play, either casually or more seriously Doesn’t take long to get results and there is an

element of exploration and discovery in the tone mapping process in particular

Page 43: HDR Photography

Thanks!

http://www.flickr.com/photos/alexhealing/tags/hdr/

http://www.hdrsoft.com/resources/