Process version is the technology that Camera Raw uses to adjust and render photos. Depending on which process version you use, different options and settings are available to you in the Basic tab and when you make local adjustments.
Process Version 5
New images edited in Camera Raw 11 use Process Version 5. PV 5 features improved high ISO rendering that helps remove purple color casts which are sometimes visible in the shadows of lower light images. PV5 also features an improved Dehaze slider. With this, you can easily add haze for creative reasons when you move the Dehaze slider to the left.
Process Version 4
Images edited for the first time in Camera Raw 10 use process version 4. PV 4 adds support for the Range Mask feature and an improved Auto Mask that handles image noise better. PV 3 (2012) images will be automatically upgraded to PV 4 when they do not have any Auto Mask adjustments applied.
Process Version 3 (2012)
Images edited for the first time in Camera Raw 7 use process version 3. PV 3 offers new tone controls and new tone-mapping algorithms for high-contrast images. With PV 3, you can adjust Highlights, Shadows, Whites, Blacks, Exposure, and Contrast in the Basic panel. You can also apply local corrections for white balance (Temp and Tint), Highlights, Shadows, Noise, and Moiré.
Process Version 2 (2010)
Images edited in Camera Raw 6 used PV 2 by default. PV 2 offers improved sharpening and noise-reduction from the previous process version, PV 1.
Process Version 1 (2003)
The original processing engine used by Camera Raw versions 5.x and earlier.
To take advantage of the newer processing, you can update previously edited photos to the current process version.
To update a photo to the Camera Raw 10 process (PV 4), do either of the following:
To apply an older process version to a photo, go to the Camera Calibration tab and choose Process
> Version 3 (2012), Process > Version 2 (2010), or Process > Version 1 (2003).