2. HDR for grown-ups

Treat HDR as it was in­tended – a way to han­dle a high dark-to-light range

NPhoto - - Nikopedia | Freeman On -

HDR was in­vented to archive light, but got hi­jacked and cor­rupted. Here we re­turn to what it’s re­ally all about – skil­fully cre­at­ing im­ages that span the range of light with­out get­ting over-ex­cited. The HDR part of the process is dead sim­ple: you shoot a range of iden­ti­cal frames with dif­fer­ent ex­po­sures, suf­fi­cient to cap­ture ev­ery­thing, and then one-click soft­ware turns them into a sin­gle im­age file.

What many peo­ple and man­u­fac­tur­ers call HDR style isn’t that at all. The style of re­veal­ing ev­ery tone in the scene (and then some) is down to tone-map­ping, which is the set of al­go­rithms for dis­play­ing the im­age in a view­able way on a screen or in a print. There’s a hard-to-re­solve is­sue here: you have an im­age file that con­tains ev­ery­thing, but your screen or print­ing pa­per can show just a frac­tion of it. Your eyes, on the other hand, which work quite dif­fer­ently from a sen­sor, can take in any amount of dy­namic range. So, there has to be a com­pro­mise, and in pro­fes­sional work that usu­ally means tak­ing tra­di­tional pho­to­graphic val­ues as a base – and not stray­ing too far from them. The ar­gu­ment is that af­ter a cou­ple of cen­turies we’re happy with a pho­to­graphic ‘look’, even if it in­cludes flare in the high­lights and dense blacks. The aim with re­al­is­tic HDR shoot­ing is to stay within those view­ing bor­ders of tol­er­ance.

There are many ways of do­ing HDR, but the fol­low­ing (shown below) is at least one solid and re­strained way to pro­duce a nor­mal-look­ing im­age. The key is to cre­ate a 32-bit float­ing point

TIFF file at the first stage, when you com­bine the dif­fer­ent ex­po­sures, in Pho­to­shop or other soft­ware. Then you con­tinue the pro­cess­ing in Adobe Cam­era Raw (ACR, the nor­mal RAW pro­cess­ing en­gine). The ex­pe­ri­ence at that point is no­tably dif­fer­ent, and the ex­am­ple here shows the steps. Nor­mally you would shoot a range of ex­po­sures two ƒ-stops apart, that go from dark enough to hold even the bright­est high­light, to bright enough so that even the dark­est shad­ows are ren­dered as mid-tones. In this case, a Thai in­te­rior shot en­tirely in avail­able light on a very bright day, I var­ied the shots by 1½ ƒ stops, and needed five frames to archive all of the light.

This method starts with mak­ing a base over­all ad­just­ment to gather the bright­est and dark­est tones, and be­cause I’m deal­ing with what you could think of as a su­per-sen­sor, I do what I would never con­sider nor­mally: take the High­lights and Shad­ows al­most to ex­tremes, then raise the Con­trast. Or­di­nar­ily, this would pro­duce the kind of hy­per­ac­tive re­sult I want to avoid, but with a 32-bit file it stays re­al­is­tic. The real work is then done with ra­dial fil­ters. Here we need re­straint. You can pull out any­thing from this file, so it’s es­sen­tial to keep in mind what you want to get from the im­age, and go no fur­ther.

The in­ten­sity of trop­i­cal mid­day sun­light gave a high dy­namic range to this Thai in­te­rior, which needed a six-stop range of ex­po­sures to cap­ture ev­ery tone

An at­mo­spheric tea room with late af­ter­noon sun­light stream­ing in, at the Wis­taria Tea House in Taipei, Tai­wan

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