{"id":185,"date":"2020-08-20T20:11:46","date_gmt":"2020-08-21T00:11:46","guid":{"rendered":"http:\/\/wordpress.forensicpath.us\/?p=185"},"modified":"2020-09-04T11:28:38","modified_gmt":"2020-09-04T15:28:38","slug":"using-hdr-methods-for-photomicrographs","status":"publish","type":"post","link":"https:\/\/wordpress.forensicpath.us\/index.php\/2020\/08\/20\/using-hdr-methods-for-photomicrographs\/","title":{"rendered":"Using HDR methods for photomicrographs"},"content":{"rendered":"

I’ve been playing around a little with some HDR software to see if it might be useful in photomicrography.\u00a0 My results have been mixed.\u00a0 I think it may be useful, depending on what you are trying to show with the photomicrograph.\u00a0 For those who don’t know, HDR imaging stands for “high dynamic range” imaging.\u00a0 The idea is that sometimes details that are very dark or very light are sometimes obscured in regular photography because they all get coded into very few light or dark values.\u00a0 Let’s say I have a series of pixels that are 0 1 2 10 50 200 300 500 900 1000 1001 1002,\u00a0 and let’s say that we can display values between 100 and 900.\u00a0 In the photograph that can display values from 100 to 900, the result will be 100 100 100 100 100 200 300 500 900 900 900 900, since all the values below 100 are set to 100 and all the values above 900 become 900.<\/p>\n

So, you take multiple photos at different exposures.\u00a0 Say we take three.\u00a0 One is regular exposure.\u00a0 One is overexposed, so that everything is slid upwards.\u00a0 In that case, the values would be 100 150 300 600 900 1400 2000 3000 3100 3200 3300, which, with the same limits on the image, become 100 150 300 600 900 900 900 900 900 900 900.\u00a0 Similarly, you take an underexposed image that, when encoded, ends up as, say 100 100 100 100 100 100 100 200 300 400 500.\u00a0 In the underexposed image, the bright objects have good separation, but everything else is bunched towards the bottom.\u00a0 In the overexposed image, the dark objects are easily seen, but the brighter objects are washed out.\u00a0 In the regular exposure, the broad middle looks good, with a little bit of things getting lost at both the dark and light edges.<\/p>\n

Then you combine them so that you get the best discrimination for each object in the photo.\u00a0 The good news is that you have enough information that you should be able to do that.\u00a0 The bad news is that you still have a limited number of levels you display, so whatever method you use to combine the images, the result will not be entirely realistic.\u00a0 Also, as you might expect, there are a lot of possible strategies for combining the images.\u00a0 Some of these focus on preserving color, some focus on enhancing contrast, others focus on luminance issues, etc.<\/p>\n

This technique is often used in landscape photography.\u00a0 The results are often pleasing but just a little bit unrealistic.\u00a0 You can look at some examples here. <\/a>They are all very pretty, but somewhat unworldly.<\/p>\n

So, let’s see what happens with photomicrographs.\u00a0 Here are three photos of a liver section, one regular, one light, one dark.<\/p>\n

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I made these simply by changing exposure time on my camera.<\/p>\n

Now, let’s combine them.\u00a0 Here’s the results of two methods.\u00a0 I used “LuminanceHDR” on a laptop running Fedora 32 linux.<\/p>\n

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The results are certainly not quite what I see through the scope in terms of color, but some of the features really seem to pop out.\u00a0 In any case, it may be worth giving a try.<\/p>\n

There are a number of free applications that will allow different ways of combining images to create HDR photos.<\/a>\u00a0 A number are available for Linux<\/a>.\u00a0 As I noted, I use Luminance HDR for the most part, but sometimes use Raw Therapee.\u00a0 I am not familiar with most of the Windows apps, since I’m a Linux guy.<\/p>\n

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I’ve been playing around a little with some HDR software to see if it might be useful in photomicrography.\u00a0 My…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[27,24,25,28,26],"class_list":["post-185","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-image-processing","tag-imaging","tag-microscopy","tag-pathology","tag-photomicrography"],"_links":{"self":[{"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/posts\/185","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/comments?post=185"}],"version-history":[{"count":4,"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/posts\/185\/revisions"}],"predecessor-version":[{"id":194,"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/posts\/185\/revisions\/194"}],"wp:attachment":[{"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/media?parent=185"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/categories?post=185"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wordpress.forensicpath.us\/index.php\/wp-json\/wp\/v2\/tags?post=185"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}