Photoshop Retouching - settings questions

[Tim]

Two quick questions to do with image adjustments in Photoshop:

1/ If you adjust the Resolution in 'Image Size' but leave the 'Resample Image' unchecked, does that actually *do* anything apart from changing the numbers in Document Size - Width and Height?

2/ When opening the RAW processor, what is the difference between adjusting Exposure and Brightness?

Thanks, Tim

[Dave Humphries]

Hi Tim,

2/
From the Real World Camera RAW book I bought on Colin's recommendation;

"The Exposure slider controls the mapping of highlight tone values in the image to those in your designated working space, but it's first and foremost a white clipping adjustment"

whereas;

(The) "Brightness control is a non-linear adjustment that works very much like the grey input slider in Levels. It lets you redistribute the midtone values without clipping the highlights or shadows."

With both, if you overdo it, they can look similar and have undesirable effects elsewhere in the tone curve.

If a shot is under exposed, just bring it up with the Exposure control, the control is measured in stops. I think of it as amplifying the signal, just like turning the volume up on the radio. It'll make the white's whiter.

Brightness is fiddling with the greys, making (mostly) them, brighter or darker. It won't, within reason affects the white's.
That's my take on it.

I know less about re-sizing, so I'll let someone else answer 1/.

Cheers,

[Colin Southern]

If you adjust the Resolution in 'Image Size' but leave the 'Resample Image' unchecked, does that actually *do* anything apart from changing the numbers in Document Size - Width and Height?

Hi Tim,

In a word, no.

It's a bit misleading in my opinion, but I don't know how they could have presented it any differently (heaven knows that print resolutions cause enough confusion for people) (although I really don't know why - it's really not that hard to understand).

Probably easier to think of it as being more of a case of changing the image dimensions, and the change in resolution is the result. With Photoshop it doesn't have any real effect on what size the image displays -- it's really only a printing instruction. Some less sophisticated packages from days gone by though were a bit sensitive to image dimensions though.