View Full Version : Photos and F-Stop in photoshop

02 February 2004, 06:54 AM
Ok I was wondering if I take a picture that is set at an apperture of f5.6 but I want to make it look like it was taken at f2.8 or f8 what % would I darken or lighten the picture in photoshop for each f stop? Any one any ideas is there a set of actions or present I can download?

02 February 2004, 07:53 PM
well surely the steps would vary to do with the type of lens and the ISO used....could be anything.

02 February 2004, 10:35 PM
Sometimes you simply can't since there is no information to be recovered there.

See ya!

02 February 2004, 01:08 PM
Changing the aperture on a camera by one full stop will increase the amount of light into the camera by a factor of two or reduce it by half, depending on which way the aperture ring is turned*.

So if your camera was set to full manual setting and the correct expsure was 1/125sec at f5.6, opening the aperture to f4 (but keeping the shutter speed the same) would over expose the image, and stopping it down would under expose it.

The following settings would give the same exposure though:

f4 @ 1/250 (with a reduced depth of field)
f5.6 @ 1/125
f8 @ 1/60 (with an increased depth of field)

*As most modern cameras change aperture electronically now, this is merely a turn of phrase.

02 February 2004, 04:24 AM
I just installed Photoshop CS. I happened to look at the pro tips in the intro screen. There was a way to do it. I want to give credit to the author, Bruce Fraser.
Duplicate your image layer for darkening, set the mode to multiply and set the opacity to 38%. for lightening set the mode to screen at 38%. Then he suggests using masks to fix the overly light/dark areas. He also gives % for 1/2 and 1/3 stop adjustments.

It was adapted from "Real World Photoshop".
Again this was written by Bruce Fraser and is part of the expert tips and tricks of PS CS.

note to mods, this is my first post, so if this is inappropriate, please delete the post and PM me.

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