THIS MONTH: IN- CAM­ERA PRO­CESING

What op­tions are avail­able for ad­just­ing the look of your pho­tos?

Digital Camera World - - BACK TO BA­SICS -

To con­vert this im­age, the raw data needs to be de­coded

QUITE a lot of things hap­pen very quickly when you press the shut­ter re­lease but­ton

on your cam­era. The light re­flected off the sub­ject is cap­tured by the lens and fed to the im­age sen­sor, where it’s recorded as an ana­logue elec­tri­cal sig­nal then turned into dig­i­tal data by the ana­logue/dig­i­tal con­verter.

All of this typ­i­cally hap­pens in a frac­tion of a sec­ond, but it’s really just the start of the process of cre­at­ing an im­age. Be­fore the file ends up be­ing tem­po­rar­ily stored in the cam­era’s buf­fer prior to be­ing writ­ten to the mem­ory card, the mas­sive amount of data cre­ated for each im­age you shoot has to be crunched. Dig­i­tal pro­cess­ing that’s car­ried out at this stage in­cludes ad­just­ment of the white bal­ance, colours and con­trast, along with lens cor­rec­tions, noise re­duc­tion and sharp­en­ing. How – or rather when – these ad­just­ments are ap­plied de­pends on the file for­mat se­lected on the cam­era. In the case of JPEGs or TIFFs, they’re ap­plied to the im­age be­fore it’s fi­nally com­pressed to cre­ate a smaller file size (in the case of a JPEG) and saved to the mem­ory card. If you’re record­ing im­ages as raw files, the pro­cess­ing data is saved as part of the file but not ap­plied. At this stage, a raw file is not an im­age at all: rather it’s a data file that con­tains the raw bi­nary code from the cam­era’s im­age sen­sor. To con­vert this in­for­ma­tion into a view­able im­age for­mat such as a JPEG, the raw data first needs to be de­coded. This is nor­mally done us­ing raw pro­cess­ing

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