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f-stop settings in Photoshop 6

Mark Lee , Sep 08, 2003; 10:14 a.m.

I have just begun to get more serious with my photography and would like to do more post exposure refining in Photoshop 6.0. I was wondering if there are settings people have found for pushing or pulling an exposure per f-stop. I tried to take a 2 second exposure of a waterfall and knew that it was going to be overexposed by 4 stops. Is there a formula where I can plan to overexpose or underexpose a picture and than set up photoshop to correct it by knowing how many stops I need. Thanks

Responses

Jim Vanson , Sep 08, 2003; 11:52 a.m.

Film latitude.

There are three common, basic categories of film. Slide film, traditional silver halide B&W Print film, & Color Print film. Of those, slide film has the least latitude. Next is conventional B&W followed by color print with the most latitude.

Within those three categories films latitude will also vary. One thing is a given with them...you can not consistently under or overexpose any film by 3 or 4 stops and then think you can repair it in P/S...the information you need just isn't there.

What I suggest you consider is visiting various film web sites and looking for spec's. That will give you some idea what the film is capable of.

Neil Lupin , Sep 08, 2003; 12:18 p.m.

not sure what's happening here - my replies keep getting deleted, but Jim is right, you need to learn to use the camera metering system properly, then you won't need to do the impossible in PS...

Will Hammond , Sep 08, 2003; 12:52 p.m.

Another rough approximation of lightening or darkening by one stop in Photoshop is the following:

Duplicate your background layer and put the duplicate layer in Multiply mode. This will create the effect of lowering your f stop by 1. The effect is more like taking 2 slides and stacking them on top of each other, then looking through them together.

Duplicate your background layer and put the duplicate layer in Screen mode. This will create the effect of raising your f stop by 1. The effect is more like take 2 slide each in a projector and aiming them both at the same spot on a wall.

Hope this helps.

Regards,

Adobe CTT Photoshop


Left>Normal, Center>Multiply, Right>Screen

Mark Lee , Sep 08, 2003; 03:15 p.m.

Additional Info

I mostly use Kodak color print film. So the most you can fix exposures on PS is about 2-3 stops? I know tht if I try and over expose or underexpose my film too much I will either blow out too much info, or not enough will record onto film to try and correct. does anyone have any good websites that can help me with these kinds of techniques? thank you for all of your responses so far. One last thing, has anyone used "Photoshop for Photographers" by Martin Evening? if so has it been useful for these kinds of questions?

Will Hammond , Sep 08, 2003; 04:18 p.m.

I'm not sure I understand WHY you are under/over exposing your film and then fixing in Photoshop. In the waterfall example you gave earlier, you mentioned that you did "a 2 second exposure that you knew was going to be overexposed". Was this after the fact or before you took the image? Are you not familiar enough with your camera equipment or are you trying to salvage some otherwise lost images? Or could you simply not stop down any further?

An excellent resource is "Photoshop Retouching and Restoration" by Katrin Eismann. It is published by New Riders, an outstanding manual on digital imaging repair.

Regards

Steve S , Sep 08, 2003; 08:50 p.m.

Let's say that you wanted a 2 second exposure of the waterfall to get that soft water effect, and you can't or don't want to stop down your lens any further...
I think the best solution would be a neutral density filter to lower the level of the light...this way you get the effect you want and a good exposure that you don't need to 'fix' in photoshop...
I have ND filters in 2x, 4x, and 8x for just this sort of thing...
Cheers

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