RAW proti JPG:streljanje za tiskanje

Pred mesecem dni sem pisal o nekaterih mitih in napačnih predstavah o razlikah med formatoma RAW in JPG. In na koncu tega članka sem RAW vprašal:"Je kakovost res boljša?" Nadaljujte z branjem, če želite izvedeti, kaj sem se naučil. Odgovor vas bo morda presenetil.

Želel sem videti, če je kaj opaznega razlika v kakovosti med sliko RAW in sliko JPG, ki jo ustvari fotoaparat. Postavil sem testno sceno in jo dvakrat posnel s stojala:enkrat z uporabo formata RAW in enkrat z nastavitvijo najvišje kakovosti JPG. Nastavitve obdelave v fotoaparatu so bile nastavljene na:ton +1, ostrina +1, izboljšana nasičenost. Slika RAW je bila obdelana s programom Nikon Capture NX. Za slike ni bila uporabljena nobena dodatna ostrina ali zmanjšanje šuma.

Preizkusni prizor

Konvencionalna modrost pravi, da odpiranje JPG in njegovo ponovno shranjevanje zmanjša kakovost. To je zato, ker datoteke JPG uporabljajo obliko stiskanja, ki dejansko zavrže nekaj informacij o sliki (torej stiskanje z izgubo). Zanimalo me je, kako slabo je pravzaprav v praksi. Tako sem kot tretji preizkus desetkrat odprl in znova shranil JPG fotoaparata z uporabo nastavitve stiskanja JPG najvišje kakovosti.

Vse tri slike so bile nato poslane v isti laboratorij (ezprints.com), ki je zame izdelal tri mat odtise velikosti 11×14. Vsaka od spodnjih slik prikazuje optično prebran vzorec v polni ločljivosti (300 ppi) vsakega od natisov. »RAW« je slika v formatu RAW, »Camera« je različica JPG v fotoaparatu in »10-gen« je JPG, desetkrat odprt in ponovno shranjen.

Preverite, ali lahko opazite razlike.

Conclusions

It’s clear from the examples that the RAW image provides superior sharpness and resolution. It’s most noticeable in areas of fine detail like the feathers but the RAW image also appeared to provide better definition and contrast, especially in darker areas of the photo.

But what’s it like looking at the actual print? When viewing these at a distance of about 5 feet they are completely identical . I think that’s important because it applies to how most people will view prints like this in real life. Most people aren’t going to get out loupes and examine them as closely as I have in this article (especially if they’re hanging on a wall).

At closer than five feet, I can spot the RAW print but I still can’t distinguish between the JPG prints. I have to bring the prints to within about 20 inches to distinguish between all three.

I asked a few non-photographers to look at all three prints as well. The first impression from everyone was that I was trying to trick them. They thought they were identical. I had to tell people exactly what to look for and let them examine all three prints side by side before they could find any noticeable difference.

It’s clear to me from this test that RAW does provide better sharpness and detail than an in-camera JPG. If you absolutely must have the best possible print then you must shoot in RAW. Most people, however, can happily shoot in JPG mode without worrying about any noticeable difference in print quality.

As an added bonus, I was pleasantly surprised to find that the lossy JPG problem isn’t nearly as bad as it sounds. Despite the compression, JPG files can tolerate a number of generations before any quality issues arise.