{"id":234,"date":"2008-11-29T08:48:55","date_gmt":"2008-11-29T16:48:55","guid":{"rendered":"http:\/\/ralphnordstromphotography.com\/wordpress\/?p=234"},"modified":"2008-11-29T09:01:51","modified_gmt":"2008-11-29T17:01:51","slug":"high-dynamic-range-processing","status":"publish","type":"post","link":"https:\/\/ralphnordstromphotography.com\/wordpress\/2008\/11\/29\/high-dynamic-range-processing\/","title":{"rendered":"High Dynamic Range Processing"},"content":{"rendered":"

High Dynamic Range or HDR has become a standard and often used tool when I’m in the field.\u00a0 For example, a few weeks ago when I was shooting sunrises in Bryce Canyon we would arrive well before sunrise.\u00a0 Generally I would start shooting when it was light enough to get a good exposure at 30 second,\u00a0ISO 100 and f\/16.\u00a0 That’s a good 20 to 30 minutes before the sun peeks over the horizon.\u00a0 In that wonderful pre-sunrise light the dynamic range is very low, maybe a total of four or five stops.\u00a0 There is no need for HDR because under those circumstances I can get a good 8 and if I want 9 stops of dynamic range from my sensor.<\/p>\n

But as soon as the sun is above the horizon all that changes.\u00a0 The dynamic range jumps to at least 8 stops, probably more.\u00a0 (I don’t take the time to scintifically measure the dynamic range because things happen so fast in those first few minutes.)\u00a0 I don’t want to take any chances with that incredible light so I switch to HDR, just for insurance if nothing else.<\/p>\n

Recently I’ve started shooting 5 HDR shots, varying the exposure by 1 1\/3 stops.\u00a0\u00a0 Yes, I know that PhotoMatix Pro, the utility I use exclusively to process HDR, recommends 2 stops.\u00a0 But I have it on good authority that something less than 2 stops is more optimum.\u00a0 So I vary the exposure by 1 1\/3 stops and adjust the base exposure compensation so that the left end of the most overexposed image histogram falls at least 20% above the minimum.\u00a0 The same goes for the most under exposed image.\u00a0 The right end falls at least 20% below the maximum.\u00a0 In a recent post I explained how I configure the camera shutter and drive to take advantage of mirror lockup.\u00a0 You can read about it in\u00a0New Shooting Technique<\/a>.<\/p>\n

I do all my HDR processing in PhotoMatix Pro.\u00a0 This tool permits a fantastic amount of control.\u00a0 That’s the good news.\u00a0 The bad news is that it permits a daunting amount of control.\u00a0 So it can take a while to get this high performance thoroughbred under control.\u00a0 But once you get it you have a powerful, expressive tool.<\/p>\n

One of the things you must take into account when shooting HDR is the extent to which your subject is moving.\u00a0 Ideally you want a subject that is stationary – totally stationary.\u00a0 You don’t want leaves blowing; you don’t want people walking through your shot; you want everything to stay put.\u00a0 You can usually achieve this by being patient, sometimes very patient.<\/p>\n

On the morning in question, however, the clouds caught the pink early dawn glow against a baby blue sky.\u00a0 A test shot indicated the dynamic range was to great so I opted for three shots at +\/- 1 1\/3 stops.\u00a0 The light was still very dim and the total time for the three exposures took anywhere from 25 to 30 seconds.\u00a0 This introduced the serious possibility of cloud movement in that period of time, something that could prove significant even though I was using a wide angle lens.\u00a0 Additionally, there was only time for two series of shots before the light began to fade.\u00a0 Talk about things happening getting a bit hectic at sunrise.<\/p>\n

So back in the digital darkroom I was eager to see how these images turned out.\u00a0 I ran the two sets of images through PhotoMatix Pro 3.1 in batch mode. \u00a0(I have to use batch mode because of the size of my raw images – around 25 MB.\u00a0\u00a0But batch mode is a lot more convenient because you can set up the process and let it run – all night if you have a lot of image to process.)<\/p>\n

When processing a set of images in Photomatix Pro the first thing\u00a0it does\u00a0is create an HDR file.\u00a0 This is a file with 32 bits per pixel, sufficient to capture the most extreme dynamic range.\u00a0 Normally the files we work on are 16 bits per pixel and for good reason.\u00a0 At 32 bits per pixel our monitors are incapable of displaying the image.\u00a0 In fact, when Photomatix Pro creates the HDR image and it is displayed on the screen it looks horrible.<\/p>\n

So the second step is called ‘Tone Mapping.’\u00a0 In this step the 32 bit image is mapped down to 16 bits.\u00a0 But I’ve gotten way head of myself and a bit off the point.<\/p>\n

When generating the 32 bit HDR file Photomatix Pro gives you a number of options, one of them being ‘Align source images.’\u00a0 This is great if you happen to be shooting hand held HDR, something Uwe Steinmueller refers to as ‘Capture More Light<\/a>.’\u00a0 Each shot will be off by just a little and Photomatix Pro will attempt to line up the images for you.\u00a0 It does a good job of it too.<\/p>\n

Another option\u00a0is ‘Attempt to reduce ghosting artifacts.’\u00a0 These occur when something moves in your scene between shots.\u00a0 This may be leaves blowing or people walking through.\u00a0 When this happens one image may record the leaf, for example, in one location and the next image may record it in a slightly different location.\u00a0 When the images are merged you get a little ghost around the leaf.\u00a0 Photomatix Pro does a pretty decent job of handling this too.<\/p>\n

I wasn’t sure if I should use ‘Align source images’ or ‘Attempt to reduce ghosting artifacts’ on my dawn photographs so I turned them both on.\u00a0 The results were not successful.\u00a0 You can see for yourself.\u00a0 There are strange shape in the sky.<\/p>\n

\"Bryce<\/a>
Bryce Sunrise with Artifacts (Click to enlarge)<\/figcaption><\/figure>\n
These two options didn’t work so well in this particular situation.\u00a0 So I tried it again, generating the HDR files without these options selected.\u00a0 The results were exactly what I as after.<\/div>\n
\n
\n
\"Bryce<\/a>
Bryce Canyon without Artifacts (click to enlarge)<\/figcaption><\/figure>\n<\/div>\n<\/div>\n
What’s the lesson here?\u00a0 Photomatix Pro is a versatile and powerful tool.\u00a0 Not all of the options it presents are intuitive and getting control of this thoroughbred is going to take some effort.\u00a0 But the effort is well worth it.<\/div>\n
Oh, how did the photograph turn out?\u00a0 Stay tuned; I’m still working on it.<\/div>\n

(578)<\/p>\n","protected":false},"excerpt":{"rendered":"

High Dynamic Range or HDR has become a standard and often used tool when I’m in the field.\u00a0 For example, a few weeks ago when I was shooting sunrises in Bryce Canyon we would arrive well before sunrise.\u00a0 Generally I would start shooting when it was light enough to get a good exposure at 30 … Continue reading “High Dynamic Range Processing”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[64,6],"tags":[175,66,187,15,190,21,43,188,20,189],"class_list":["post-234","post","type-post","status-publish","format-standard","hentry","category-how-to","category-journal","tag-bryce-canyon","tag-hdr","tag-high-dynamic-range","tag-national-park","tag-photomatix-pro","tag-southwest","tag-sunrise","tag-sunset-point","tag-utah","tag-winter"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p9Nl7-3M","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/posts\/234","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/comments?post=234"}],"version-history":[{"count":13,"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/posts\/234\/revisions"}],"predecessor-version":[{"id":249,"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/posts\/234\/revisions\/249"}],"wp:attachment":[{"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/media?parent=234"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/categories?post=234"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ralphnordstromphotography.com\/wordpress\/wp-json\/wp\/v2\/tags?post=234"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}