Exposure adj. in PS = exposure adj. on camera ??

[caesars0331]

Basically, I've just found that if I save as RAW and browse in PS at the pics, I can preview them and adjust the "exposure" slide bar. Is this adjustment equal to adjusting the exposure of the lens prior to shooting the pic?? If not, how "real" is this adjustment?

Thanks,

Alex

[kawter2]

i think you can adjust about 1.5 stops either way in RAW with out loosing any image data. I will probably be corrected because this is just off the top of my head

[chris.bailey]

From what I have read, as long as you adjust so you do not clip data off either end of the histogram you can adjust as far as you like.

A further trick is to do two conversions with a left and a right biased histogram and sandwich them.

[maderito]

Adjustment of exposure through camera settings vs. using exposure compensation (EC) during RAW processing is different - sometimes very different.

Image data has noise approximatley proportionate to exposure. Thus dark tones have more noise (relative to the dark tonal values) than light tones.

If you take an underexposed image and move all the shadow tones into the midtone region, you bring the noise along. So the midtones now have more noise than they would if you had exposed the image properly in the first place.

Moreover, if you clip highlights (overexpose) or block up the shadows (underexpose), some of the image data may not be recoverable by EC.

There is the additional issue of "exposing to the right" which means setting camera exposure so that the histogram just kisses the right edge of the highest tonal value (255 in 8 bit images). That's another story for another thread, which has been preceded by countless others.