What to choose 16 bit PNG or 8 bit PNG if post processing in Photoshop needed later?

I found that some people recommend to render sequence of images as 16 bit png if later this animation will be edited in photoshop? Once i render my animation i will export sequence of images in photoshop and apply dust and scratches filter to my animation (to remove some speckled type of noise) and also will use animated mask inside of the photoshop to define area of influence for this filter. Also maybe a bit of color correction. So for that should i render in blender my sequence as 8 bit or 16 bit and how render time will be increased?

Using 16bits is always better of course, this is a requirement if you plan to do some grading. If you only apply dust and scratchs and nothing else, then you can use 8 bits.

On a side note, Photoshop 16bits is integer, so it’s pretty useless for grading 16 bits half float images.

Thanks. But render time will be increased as well?

Not at all, the rendering is always done in 32 bits float, the only thing that will increase is the space on disk of your image sequence.

No, it only affects saving the final image. The render itself is always in 32bit float.