Photoshop problem

I recently took a course on Photoshop and am trying to replicate several techniques I learned during the course. While doing so, I ran into a problem I have never seen before and I hope someone can help me. When I want to darken an image, I will create an adjustment layer (usually levels, but I have also used curves with the same result) and then set the blend mode to multiply. This darkens the entire image by about 1 stop. From there I adjust the layer's opacity until I like the darkening effect. The problem I am having is that when I set the layer opacity to anything other then 0% or 100%, I get a series of verticle lines running across the image. The same thing does not happen if I set the blend mode to any other setting (screen for example). I have no idea why this might be happening and appreciate any suggestions on how to fix it. Thanks.

Chris, not sure about the lines, but the method you suggest works globally. There are various methods you can use to selectively apply lightening and darkening to specific areas.

Try this one

Make a new layer above the image. Set the blend mode (simpler to choose it on top next to opacity in the layers palette) to Soft Light. Type D on the keybord to set the Default fore/background to B&W. Typing X will switch the two. Select the brush tool, with a feathered edge brush, and make the opacity 10% or less. Painting over the image with black will darken, and white will lighten the area painted over. Since it is all done on a transparent layer it can be altered at will.

Using the history brush with levels will also allow selective darkening or lightening, you need only make two different snapshots, one for each of the effects desired.

Best,

Chas

Chas,

Thanks for the quick response. While I haven't used the particular method you recommend, I have used serval different methods for selective dodging and burning (50% gray layer set to overlay for example). While I can work around it, I have found using multiply to be a quick fix for global changes. now I just need to figure out how to get it working again. Thanks for the tip.

Chris, YES, (50% gray layer set to overlay) is another wonderful tecnique. PS has many ways to get there, it is only the end result that matters most .

However, I still cannot duplicate your problem?

Chas

The vertical lines are very strange. The first thing I would do is to reinstall the video drivers - actually updating them might even be better by going to the website of the manufacturer of your video card. Then I would kill the current Photoshop preferences file and start over. PS7 is very prone to preference file corruption and when it does, all sorts of strange things start happening. Here is how to do it:

http://www.naturescapes.net/phpBB3/viewtopic.php?t=486