Removing Hotspots 1

[fwbaumann]

I'm copying thousands slides (Scanner takes much too long) using a digital camera and slide projector. Of course the center is hot and the corners are dark. I want to take a picture without a slide, invert it and use it to correct only the brightness. (Non-linear) I don't want to add pixels or blend images. Is there anyway of burning the center and dodging the corers based on the negative no slide image.
Just overlaying the image and reducing the opacity is not sufficient.

 

[rickwells]

Make an alpha channel from your 'no slide' image. Open up each picture and drag into the canvas wich has the alpha channel ( holding down the shift key at the same time will put the image centre of the canvas ). Command/Click on the alpha channel to make a selection. With your slide pic layer active use levels or curves to adjust centre. Invert selection to adjust the corners. Record an action to speed up the process.
(AppleMac keystrokes)

 

[fwbaumann]

Rick:
Thanks, but I'm a little under experienced in this area.
The "no slide" is actually a picture of the lens fall off.
That is, it has dark corners and a light center. (Black and white) I can then invert it so the corners are light and the center is dark. What I need to do is apply the inverted picture as a brightness control to the slides I've captured. In this way I've compensated for the lens fall off. The center of my slides will be darkened and the corners brightned. I don't have to make any other adjustments to the original captured slide.(such as level curves)

I tried making an alpha channel of the of the black and white mask, but just darn I don't know how to apply it to the captured slides. I got a book in one hand and a mouse in the other...I just can't get there from here. I just haven't worked much with alpha channels. Help!

 

[mscallisto]

If ther're not too personal, can you post a pic someplace where we can take a look?

 

[rickwells]

Okay, the principle of using the "no slide" image is right. Please note that my instructions are for applemac keystrokes. With your "no slide" image open, go to the Channels palette and drag any one of the channels down on to the document icon at the bottom. This will give you a new ( alpha ) channel. Click on this channel to make it active and open your Levels controls. You may want to adjust the black to white densities. The black represents solid colour and the white represents transparent. Greys give you varying degrees of transparency. Click back on to your composite channel. Now drag one of your slide pics into your canvas creating new layer. Either hide or delete your "no slide" image. With your slide image layer active, put your cursor over the alpha channel, hold down Command and then click. This will make a selection which is in effect a mask. Using levels you can alter the strength of colour to the shape of your original "no slide" image. Invert the selection to do the inside or outside.