{"id":767,"date":"2009-11-21T08:56:55","date_gmt":"2009-11-21T16:56:55","guid":{"rendered":"http:\/\/ralphnordstromphotography.com\/wordpress\/2009\/11\/21\/hdr-tip-1\/"},"modified":"2018-09-09T19:10:58","modified_gmt":"2018-09-10T03:10:58","slug":"hdr-tip-1","status":"publish","type":"post","link":"https:\/\/ralphnordstromphotography.com\/wordpress\/2009\/11\/21\/hdr-tip-1\/","title":{"rendered":"HDR Tip #1"},"content":{"rendered":"

I shoot a lot of HDR.\u00a0 That\u2019s where you take multiple images at different exposures so that you capture the full dynamic range of the scene in front of you.\u00a0 Many people consider HDR to be unnatural and you can definitely get a surreal effect.\u00a0 But HDR is the only way you can capture certain challenging scenes and make the results look like what you see, not what your camera sees.<\/p>\n

I had a talk with my good friend Andreas Waldeck who works for HDRsoft, the creators of Photomatix.\u00a0 This is the premier software for doing HDR.\u00a0 Andreas shared some things with me that were real eye-openers and I\u2019d like to pass them along to you in a series of HDR Tips.\u00a0 So let\u2019s get started with the first tip.<\/p>\n

This tip has nothing to do with Photomatix or any HDR software for that matter.\u00a0 But it\u2019s probably the most important tip of all.\u00a0 It applies to when you capture your images in the field.\u00a0 As with all photography, the exposure is critical and it\u2019s the same with HDR.\u00a0 But this time there\u2019s not a single exposure that you have to get right.\u00a0 There are multiple exposures that, taken together, all have to be right.<\/p>\n

The aim of HDR is to capture the entire dynamic range and then some.\u00a0 Those last three words, \u201cand then some\u201d are very important.\u00a0 The histogram is the key to getting the proper number of exposures and the proper range.\u00a0 You will have an underexposed image that captures the highlights and an overexposed image that captures the shadows. In between you will generally have one or more exposures.<\/p>\n

The trick is to get the underexposed image underexposed enough and the overexposed image overexposed enough.\u00a0 And the histogram is the best tool to make sure you\u2019re getting what you need.<\/p>\n

The underexposed image should be underexposed enough so that there is plenty of room between the right tail of the histogram and the right edge.<\/p>\n

\"histogram_underexposed\"<\/a>The example above is about the\u00a0 minimum clearance I like to see.\u00a0 I\u2019d actually like a bit more.\u00a0 A good rule of thumb is for the right tail of the histogram to end about 20% short of the right edge.<\/p>\n

This is just the luminance histogram.\u00a0 You also need to be sensitive to the RGB histograms.\u00a0 Your\u00a0 luminance histogram may look like you have a comfortable margin but your RGB histogram may show that you have clipping in one of the channels.\u00a0 If that\u2019s the case you need to underexpose even more.\u00a0 You don\u2019t want clipping in any of the RGB channels.\u00a0 I find the red channel particularly problematical, especially photographing all the beautiful red rocks in the American Southwest.\u00a0 Blue clipping can be tolerated sometimes, especially if it is coming from the sky.\u00a0 There\u2019s no detail in the sky.\u00a0 But when the red clipping comes from the rocks you\u2019re loosing detail in the most important channel.\u00a0 So I always make sure the RGB histogram is displayed on the LCD and check it after every exposure, especially when shooting HDR.<\/p>\n

The considerations are a bit different when evaluating the overexposed histogram.\u00a0 In this case the luminance histogram tells the whole story.<\/p>\n

\"histogram_overexposed\"<\/a>I follow the same rule of thumb; that is, I like the left tail of the histogram to be about 20% from the left edge.\u00a0 This example is find but a little more clearance would be just a bit better.<\/p>\n

You really want a full exposure in your shadows.\u00a0 This\u00a0 will guarantee as much detail as you will ever want without any noise.<\/p>\n

If you really want to be safe, spot meter the brightest highlight in your scene.\u00a0 This becomes the underexposure setting.\u00a0 Then spot meter the darkest shadow in your\u00a0 scene.\u00a0 This\u00a0 becomes your overexposure setting.\u00a0 The next question to resolve is how many exposures you will need between the overexposed and underexposed settings.\u00a0 Photomatix suggests intervals of 2 stops.\u00a0 So if the overexposed exposure is 1\/8 at f\/11 and the underexposed exposure is 1\/500 at f\/11, the entire dynamic range is 6 stops.\u00a0 If your exposure interval is 2 stops you would take the following exposures (all at f\/11) \u2013 1\/8, 1\/30, 1\/120, 1\/500 or four exposures.<\/p>\n

Many experienced photographers advocate an exposure interval of 1 1\/3 stops instead of 2.\u00a0 This would give you proportionately more exposures.\u00a0 I personally use 1 1\/3 stops.<\/p>\n

There are a few more quick tips for shooting in the field.<\/p>\n