Use cre­ative edit­ing tech­niques

Take your im­ages fur­ther by cor­rect­ing in­con­sis­ten­cies and adding artis­tic ef­fects in edit­ing soft­ware

Digital Photograper - - Techniques -

The con­di­tions we ex­pe­ri­ence in the field when shoot­ing low-light and as­tro im­ages push our cam­eras to the ex­tremes of their de­signed ca­pa­bil­i­ties. The ab­sence of sig­nif­i­cant lev­els of am­bi­ent light presents is­sues re­lat­ing to dig­i­tal data gath­er­ing and there­fore the sig­nal-to-noise ra­tio, calling on the ad­vanced im­age pro­cess­ing al­go­rithms found in the lat­est cam­eras to re­duce chroma and lu­mi­nance pat­tern­ing. Fur­ther­more, the ex­treme con­trasts of ex­po­sure found in ur­ban ar­eas, as high­out­put ar­ti­fi­cial light sources are mixed with deep shad­ows, test the dy­namic range of the cam­era’s sen­sor. So while to­day’s DSLRs and ad­vanced CSCs are pre­ci­sion tools, the pho­tog­ra­pher’s tech­nique must be per­fected, since there is a fine mar­gin for er­ror. Post-pro­cess­ing is there­fore a use­ful buf­fer for cor­rect­ing mi­nor im­per­fec­tions and as­sist­ing the cam­era in ren­der­ing suf­fi­cient de­tail and tone.

How­ever, when work­ing with files con­tain­ing less in­for­ma­tion, con­flicts of ne­ces­sity be­come ap­par­ent, such as the need for greater ex­po­sure but at the risk of en­hanced grain, or the re­quire­ment for noise re­duc­tion at the ex­pense of fine de­tail. These as­pects are more eas­ily masked in day­light shots, so a con­sid­ered process is es­sen­tial. Many pho­tog­ra­phers be­gin their low-light pro­cess­ing work­flow with ad­just­ments to ex­po­sure, since the high con­trasts of­ten pro­duce the im­pres­sion of sat­u­rated colour – ne­ces­si­tat­ing hue and sat­u­ra­tion ad­just­ments af­ter work has been con­ducted on bright­ness. An in­crease in ex­po­sure can re­duce ap­par­ent sat­u­ra­tion and dark­en­ing an area of the frame can have the in­verse ef­fect. Visit the HSL (Hue Sat­u­ra­tion Lu­mi­nance) panel in Cam­era Raw or Light­room to ap­ply ap­pro­pri­ate com­pen­sat­ing ad­just­ments, af­ter mak­ing changes to global or lo­cal bright­ness.

The next area of fo­cus is cor­rec­tion of im­age ren­der­ing de­fects, from both the lens and cam­era body. Lens dis­tor­tion cor­rec­tion, vi­gnetting re­moval and noise re­duc­tion will ad­dress the most prom­i­nent de­fi­cien­cies of im­ages shot in poor or high­con­trast light­ing. Fi­nally crop­ping can aid com­po­si­tion, which can be com­pro­mised by un­sightly fall-off in ex­po­sure. Ar­eas of deep shadow can be over­looked in-cam­era, adding un­wanted empty space to the frame, but these can later be re­moved us­ing the Crop Tool.

1 USE LO­CAL AD­JUST­MENTS

When work­ing with scenes con­tain­ing ar­eas of deep shadow and ex­treme bright­ness, it is un­likely that all ar­eas of the frame will re­quire iden­ti­cal pro­cess­ing. There­fore ap­ply­ing lo­cal ad­just­ments us­ing the Ad­just­ment Brush in Cam­era Raw and Light­room, or us­ing layer masks in Pho­to­shop, will give a more cus­tomis­able edit­ing style. Lift shad­ows, mod­ify colours and en­hance mi­cro con­trast.

2 BLEND WHITE BAL­ANCES

As dis­cussed, mixed light sources make it chal­leng­ing to avoid un­wanted colour casts. Blend­ing files of vary­ing white bal­ance set­tings cre­ates a fin­ished im­age with the best of all colour ranges. WB can be brack­eted in-cam­era, although the fol­low­ing process saves card space by us­ing a sin­gle base RAW file.

2 . 1 CHOOSE A PRE­SET

Open your RAW file in a com­pat­i­ble edi­tor and se­lect a white bal­ance pre­set from the drop-down menu. Choose one that en­hances the cool tones in the im­age, such as those from blue neon lights or nat­u­ral light re­flec­tions.

2 . 2 AD­JUST GEN­ERAL SET­TINGS

Move the Ex­po­sure and colour con­trol slid­ers to im­prove the over­all tonal­ity. While these set­tings can re­main con­stant for all WB frames, ex­per­i­ment with mi­nor dif­fer­ences to com­ple­ment the cool or warm colours.

2 . 3 OPEN MUL­TI­PLE COPIES

Rather than open­ing an im­age as usual, hold down Alt/Opt and click on Open Copy. This will al­low you to re-en­ter your RAW edi­tor, se­lect an­other WB pre­set or Colour Tem­per­a­ture and open these var­ied files in Pho­to­shop.

2 .4 MERGE LAY­ERS

With all of your du­pli­cate files open, stack them as lay­ers in a sin­gle doc­u­ment and use layer masks to re­veal ar­eas of each copy. This will al­low both warm and cool tones to be main­tained in a sin­gle im­age, for bet­ter colour depth.

“Use De­fine to tar­get spe­cific noise types”

3 CON­SIDER MONO­CHROME

While not a genre that im­me­di­ately sug­gests it­self for mono­chrome con­ver­sion, with the right scene a black and white im­age can bet­ter fo­cus at­ten­tion on light and shadow. Con­vert­ing night street scenes gives a clas­sic and time­less feel to well-known lo­ca­tions. Con­sider us­ing a plugin such as Sil­ver Efex Pro from the DXO Nik Col­lec­tion.

4 CRE­ATE 32-BIT FILES

As an al­ter­na­tive to tone-map­ping for ex­tended dy­namic range, merge mul­ti­ple ex­po­sures into a 32-bit TIFF file in Pho­to­shop’s Merge to HDR Pro fea­ture. Just se­lect 32 Bit and use the de­fault set­tings. Then open the file in Light­room or ACR to ad­just shad­ows and high­lights. The file con­tains more in­for­ma­tion so there is more scope for re­triev­ing de­tail.

5 RE­MOVE VI­GNETTING

With strong light sources and min­i­mal am­bi­ent light, ex­po­sure di­min­ishes rapidly, mov­ing away from the source. This of­ten re­sults in edge vi­gnetting in low-light shots, ex­ac­er­bat­ing na­tive op­ti­cal dark­en­ing. Use the Lens Cor­rec­tion fil­ter to sub­tly lighten the frame pe­riph­ery, re­main­ing mind­ful of noise. Al­ter­na­tively, use the Ad­just­ment Brush with Noise Re­duc­tion loaded for si­mul­ta­ne­ous bright­en­ing and smooth­ing.

6 LU­MI­NOS­ITY SHARP­EN­ING

Long-ex­po­sure im­ages may of­ten need some sharp­en­ing, due to mi­cro shifts in cam­era po­si­tion across the ex­po­sure time. Sharp­en­ing on a new layer in Pho­to­shop and chang­ing the Blend Mode to Lu­mi­nos­ity will re­strict sharp­en­ing to de­tail, re­duc­ing ac­cen­tu­a­tion of colour noise and min­imis­ing halo ef­fects in high-fre­quency ar­eas. This al­lows more ag­gres­sive sharp­en­ing should it be needed.

7 NOISE RE­DUC­TION OP­TIONS

NR is al­ways go­ing to play a ma­jor role in fi­nal­is­ing a low-light im­age. While Light­room fea­tures ad­vanced re­duc­tion tools, an ex­ter­nal ap­pli­ca­tion like De­fine, from the DxO Nik Col­lec­tion, can pro­vide pre­cise tar­get­ing of spe­cific noise types and ef­fec­tive smooth­ing of grain, with min­i­mal dam­age to de­tail in­tegrity.

7. 1 OPEN THE IM­AGE

You can choose to ei­ther open your file di­rectly in De­fine, or from within Light­room or Pho­to­shop as a plug-in. In Pho­to­shop all of the DxO Nik fil­ters can be found in the Fil­ter menu.

7. 2 RE­DUCE LU­MI­NANCE NOISE

Min­imise the grain con­tent of the im­age us­ing the Con­trast Noise slider. This will add a blur to the im­age, re­duc­ing the tex­ture. Use this with care to re­duce sharp­ness loss.

7. 3 WORK WITH COLOUR NOISE

Se­lect Colour Ranges as the Method in the Re­duce tab. Then se­lect colours in the im­age that re­quire more work. This pro­vides a more so­phis­ti­cated style of NR to main­tain qual­ity.

7. 4 USE MASKING

Click the Brush but­ton to open in Pho­to­shop with a Layer Mask. This al­lows you to ap­ply lo­calised NR, to re­move pat­terns from the most neg­a­tively af­fected ar­eas while lim­it­ing de­struc­tive im­pact de­tail.

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